MadModder
Gallery, Projects and General => Project Logs => Topic started by: awemawson on January 08, 2014, 01:37:08 PM
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Its been an ambition to have a 4th axis on my CNC mill for several years, and to this end I've been collecting suitable bits. Frequently people adapt manual rotary tables, in fact I did one myself many years ago using a stepper motor and a 4" table, but to be properly integrated into my Beaver Partsmaster it needs to be servo driven.
The other issue is that standard rotary tables end up on the left side of the mill table so that the motor sticks out forwards - as I have an automatic 16 station tool carousel on that side my 4th axis needs to be a mirror image
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I thought I'd cracked the problem when I 'caught' a Nikken 4th axis positioner on ebay a few years back - but when it arrived it proved to be stepper driven not servo although it is 'handed' correctly :bang:
Never mind, prompted by the success of Jim McCracken on the CNCZone forum getting his working I've decided to put a servo motor on the table of the Nikken
So this is what was there originally:
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And here are the bits that together hopefully will drive the table in future:
a/ SEM HT 30H4 -44 with ROD450B 125 count sine wave encoder and integral tachometer (more about the encoder later!)
b/ Bosch Servo drive card rescued from a Bridgeport Interact
c/ Bosch special choke for servo card from same source
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So far I have removed the stepper motor and started dismantling the rotary table. The table has a pneumatically operated locking brake, and it had jammed in the on state. Fighting my way into the mechanism proved to be anything but simple, and has required making some special tooling, but I'll leave you to ponder on this shot of the bit that had me stumped for a couple of days, while I go and have my supper :ddb:
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Ok so what's the big deal?
Well firstly from the top there is little indication what you are dealing with, and there seems to be two concentric threads and a retainer with two forms of locking. The retainer has been slit so that a hex headed bolt pinches the slit gripping the thread, and also there is a grub screw bearing on an almost detached 'crescent' of thread to press it into a locked state. They really didn't want that to come adrift!
The grub screw was in a most inaccessible place and didn't seem to have a standard hex socket - I ended up grinding the end off a 3 mm one so it was short enough, then gently reducing its a/f size a few thou with a diamond file.
The retainer is bored for a pin wrench - so first of al I applied my Facom adjustable pin wrench. The retainer won and I sheared the pin on the wrench - lucky they screw in ! :bang:
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As the retainer is recessed the Facom was not really getting where it was needed. So then I realised I'd have to make something to fit - I made a pin wrench out of a bar end and counter bored it 3/8 for a tommy bar I had lying arround
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You guessed it - the tommy bar ended up like a banana :bang:
Time to get serious - if only that pin wrench I'd made could go on my air impact wrench. Well it can if you cut a 1/2" square in the end. Lucky I fixed that EDM machine :ddb:
So let's make an electrode:
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You guessed it - the tommy bar ended up like a banana :bang:
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Ouch!
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You'll notice that the lump of copper I used had had an odd multi-pointed star shape in the other end, and a little broke through - never mind it won't affect anything
So here is the result:
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Now I don't like using masses of force to dismantle things - things tend to break :lol:
So I set my air impact wrench to it's lowest setting and had at it. Nothing, no movement. Well I went through the four power levels, and at last on the highest setting off it screwed - relief :ddb:
Now I could see what was inside, and here it is:
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As you can see, there is a cast 'shoe' on the shaft that is pulled up against the wormwheel to lock it. The shaft has an acme thread onto which a gear threads, which engages with a rack which is pulled up by an air cylinder triggered by a solenoid valve - simple really :bugeye:
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OK now I'm in so far at least hopefully the rest of the mechanical side should be reasonably straight forward. Currently I can only rock the worm and wheel about two degrees - I suspect that a bit of the broken brake pad has got between them - so they'll have to come out for cleaning.
Watch this space . . . . . . . . :thumbup:
Andrew
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Hi there, Andrew,
There you are, you see. That wasn't so difficult, was it?!?! (To share it with us, I mean.) :D :D :D
Seriously, congratulations on your tenacity and ingenuity - I'm pleased you got a result and I hope the way forward is complex enough to be interesting but not so awkward it's frustrating. :thumbup: :thumbup: :thumbup:
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Thanks Pete,
So quite a bit of progress this morning. Objective was to free the worm 'capsule' so that it could be swung out of engagement with the worm wheel.
First I attacked the drive end, removing the gear that engages with the servo motor, then a cunning micro backlash adjuster, and loosened the various locking devices:
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Then I attacked the other end of the worm shaft. Turns out that the cover has an oil sight glass I'd not spotted before. It was all pretty gungy in there - obviously water based coolant had got in. When I managed to locate all the various locking devices, (and realised that some of the grub screws were two to a hole !) the worm capsule rotated nicely away from the worm wheel.
At this stage the worm would turn freely but the table was still only turning a few degrees, so obviously not foreign matter between the worm and wheel.
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This allowed me to gently tap the table with worm attached out of the casting to reveal the very nice end thrust race and top thrust race.
The construction reminds me of a swivelling tank turret :ddb:
The side thrust race deposited all its rollers on the bench - all eighty of them - but all were located and put in a tote bin for cleaning.
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Those rollers look pretty grotty, but an initial inspection shows that they measure spot on 4 mm, so it is more discolouration than wear.
I'd replace them if easily available - anyone know a source of roller bearing rollers in various diameters?
So far I'm pretty pleased with progress - I need to get it re-assembled then work out just how I'm going to mount the servo motor, as its fixings are bolts into its end bearing plate, whereas the original stepper had a mounting flange with externally accessible bolts. It needs proper planning as the mesh of the gears is set by moving the motor, and if the motor has to be fixed before the cover goes on, there is no way of adjusting it :ddb:
I'd hoped that I could make a dummy flange, but the sizes don't allow that :loco:
. . something will occur to me hopefully :lol:
. . .watch this space,
Andrew
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Hi Andrew
Its looking good, a good clean and new oil. together with your new actuator, should last for ever.
Interesting project
Cheers David
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Andrew
Is this what you are looking for
http://simplybearings.co.uk/shop/index.php?cPath=c23_5043
Stuart
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Stuart, yes many thanks, Google got me there as well, but their 4 mm rollers are either too short at 4mm or too long at 11.8 so I decided to use the originals.
So onwards and upwards! I removed the vertical and horizontal thrust races. The Horizontal one has 80 solid 4 mm rollers all of which were ok measurement wise so they went back as is.
The vertical one on which the weight of the table and work is taken comprises 36 hollow rollers of 8 mm diameter, one of which was broken :bang:
However I now think that this was why the table was jamming. I was surprised to find they not only were hollow, but had really quite thin walls. I've come across hollow rollers in bearings before in for instance the Gamet headstock bearings of a Colchester Student, but they were quite thick walled. So what to do?
Options - a/ Leave a roller out b/ Try and source one c/ Make one. I opted for c/ on the grounds that although it probably would be perfectly ok leaving one out, it's not very professional, and I was unlikely to be able to find just the right roller. I turned a piece of silver steel to just oversize in the hard state using carbide tooling, then lapped to size. I decided to leave it solid as no doubt the flexibility of the steel would be totally different to the original.
So here we have the broken roller with it's replacement, and the bearing back in situ:
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Look carefully at the picture and you can see the new roller at 'ten o'clock'.
So on to the side thrust bearing. This has 80 little rollers all of which need to stay in their places as the table / worm wheel assembly is re-fitted. The usual trick is to smother them in grease, and this I did, but needless to say it was 'fun' as they kept sticking to my fingers and coming off again :bugeye:
However we got there :
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And not only that, but I got the table on and it's hold down keeper fixed. :ddb:
AND The table is now free to turn :clap: :clap: :clap: :clap:
Hoo- flipping - ray !!!
So I am now sure that the jamming was that broken roller.
. . more to come later . . . watch this space :lol:
Andrew
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Hi Andrew
Well done. It's coming along nicely.
The hollow rollers are unusual and I wonder whether there's a reason. I wonder if it's to prevent shock loads from denting the bearing surfaces by making them a bit springy. It seems unlikely as I'd expect them to be too hard to spring much.
Russell
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Andrew
Well done. I love to follow along as you take it apart so you can figure out why it doesn't work as it should. As you have found out some times it can be a very small piece that has caused all the problems. You keep fixing them and I'll keep watching and cheering for you. :D
Cheers :beer:
Don
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Thanks Russell and Don,
So a bit more progress: The table is back on and turning so I've started re-assembling the end bearing assemblies for the worm shaft. First the drive end:
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Then of course the other end. This cover is oil filled within, but there was no gasket or other sealing, so it went back with a smear of Blue Hylomar which is usually pretty good stuff
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Next in sequence needs to be the brake assembly, so I can't put off deciding what to do with the broken bit. I think that it is probably a steel forging - could be cast possibly but it's steel not cast iron.
I decided to silver braze it first - if it proves not to be strong enough the fall back plan is to turn off the end, axially drill and tap it, and bolt a cheek on the end. Bally awkward thing to clamp. I ended up 'buttering' both parts with silver braze, holding one in the vice and the other in pliers and putting them roughly together, letting it cool a bit, then clamping them together with extended mole grips and re-melting. It's important to not only keep the alignment but minimise the thickness of the joint. The silver braze will absorb some of the steel and alloy with it if thin enough.
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Although the brazed joint is nice and even, the operating 'face' of the shoe isn't perpendicular to the shaft as it should be. The part must have bent before it broke. I'll skim the face tomorrow - the intermittent cut will show if it's just stuck on with flux or has properly brazed :lol:
. . so onwards and upwards !
Andrew
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So up early and skimmed the brake shoe. Happily the brazing stood up to the intermittent cut - ended taking about 45 thou off both sides. Remains to be seen if it stands up to working conditions !
Andrew
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So - now to re-assemble the brake and see if it works.
Here's the assembly:
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And here's where it has to go:
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Ah . . it won't go in as an assembly - needs assembling in situ :bang:
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So that WAS all good fun :lol:
Now did it work ?
No - it broke first time I actuated it :bang:
I'm not entirely surprised, so we'll have to revert to plan B :clap:
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So first make a suitable disk
chosen from the extensive stocks of quality traceable bars made from a handy bar end :clap:
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Trim it roughly to size by taking big gulps with a beefy end mill, then fettle it a bit so that it fits. (by heck it was TIGHT !)
There is presumably quite a torque on the brake shoe when operated, so before I loctited the screw in, I welded the 'heel' of the sector to the shaft. Then it was a case of re-assembly in situ AGAIN !
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:ddb: :ddb: :ddb: Well I'm pleased to say it works :ddb: :ddb: :ddb:
I've re-assembled the air actuator rack and cylinder, and am operating it blowing air from an air duster in the appropriate port for 'brake' or 'release'
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There is a solenoid valve that fits on the end of the cylinder that diverts the two ports so one releases when the other operates (otherwise the inactive side of the cylinder would be blocked shut). I've not mounted it yet as it's coils seems to be 110 V and I need to operate on 24 V . I will probably re-wind the coil - it's all a bit of a mess currently :
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So with a few ups and downs at least this phase of the build has had a happy ending :thumbup:
. . .lots more to do yet on this project. Probably the motor mount is next on the list
Andrew
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A bit of playing around with CAD and some careful measurements showed that it was just possible to make a flange to convert from the end fixing SEM servo motor to the flange mount with external screws needed to be able to adjust the 4:1 gear train mesh for minimum back lash. The original stepper motor relied on oversized holes to get some movement, but as I was CNC'ing the flange I opted to give the hole a slot form with a 2 mm 'travel'
So first we have a CAD drawing and a 20 foot long bar of 100 mm x 20 mm bar stock
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Now in an ideal world that flange would have been 110 mm square, but you use what you have :lol:
So all we need do is slice a 100 mm chunk off in the Pedrazzoli cold cut off saw, and remove the bits we don't want - how hard can it be :ddb:
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There that was easy wasn't it :thumbup:
Well yes, but I confess that is the third flange I made :( First one I broke a 6 mm carbide end mill as it was starting the hold down slots and it left too much mess to re-use. Second one was perfect except when I revised my careful measurements of hole centres and did an average of hole to hole spacing, although my figure was correct I put the wrong one in the CAD drawing :bang:
Still, third time lucky and now we have a flange that fits and looks reasonably presentable. Here it is as a mock up with the motor balanced on top in it's eventual home. Not bolted on yet as I'm awaiting some 5/16" UNF cap head bolts to hold it on.
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Your shop seems to be well stocked with tools... I like how you take this problem and solve it taking all issues in stride with a matter of fact attitude.
Eric
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Thanks Eric, hills are there to be climbed :lol:
Now I reckon that there is an oddity there :scratch:
If you look carefully there is a horizontal cap screw that used to bear on the original stepper motor flange to adjust gear mesh, but it is pushing the gears OUT of mesh, not as I would expect, INTO mesh. Presumably a pair of gears will tend to separate if anything when they are under load and running, not pull into each other, so I would have expected that adjuster to work the other way. I may bolt something to the side of my flange to take a screw with a pad on the end that would allow uncrewing the adjuster to pull the assembly to bring the gears further together. All suggestions welcome.
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So the next thing to sort is the fitting of a suitable pinion to the SEM motor shaft. The original stepper motor had a nice accurate 16 mm shaft, and a 20 tooth 1.5 mod gear fixed by 5 mm key and a grub screw, with the grub screw trapped by a circlip. I would have liked to re-use this gear, if only for economy, but the SEM motor shaft is a rather under sized 5/8" resulting in a 4 thou slop.
I had considered that perhaps Loctite would bridge the gap, but better sense prevailed and I bought a replacement with a 'pilot bore' from HPC gears. Loctite say up to 1.5 thou gap and mine would be 2 thou circularly. Incidentally let me pour praise on HPC. A phone call at 15:30 on Friday resulted in the postman bringing me their parcel on Saturday morning - how fast is that ! They also were able to provide some drive pulleys and a belt that I need for the encoder, but more of that later.
So I need to mount the gear in a collet, bore it to the rather arbitrary motor shaft diameter, and slot a key way to match the 1/8" key in the shaft.
I've also decided to fit a single lip oil seal to the shaft of the motor, as the gears run in an oil bath.
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This morning I've bored the gear hub to size, broached it's keyway, and drilled and tapped for a 6mm grub screw to line up with an existing and convenient flat on the servo motor shaft
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I can't mount the motor yet as those 5/16" UNF cap screws haven't arrived, so time to investigate the ROD450B/125 encoder and it's mount.
The TNC355 Heidenhain controller can only accept either 18,000 or 36,000 counts per rotary table revolution. Now my table worm has a ratio of 90:1 and the gear train has a ratio of 4:1 and the encoder gives 125 count per rev. Multiplying up we get 90 x 4 x 125 = 45,000. Divide 36,000 by this and we get 0.8, or a ratio of 20:25.
Somehow I need to gear the servo motor to the encoder, slowing the encoder by a factor of 20:25
Here are the bits we are dealing with
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The current plan is to mount the encoder at the side of the servo motor on a specially milled housing allowing me to run a timing belt between them. The servo motor will have a 40 tooth pulley, and the encoder a 50 tooth one. Mounting the encoder facing the other way will shorten the whole assembley which is a 'good thing'
Masking tape mock up below :ddb:
Andrew
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This morning's job was to make an adapter for the ROD450B encoder. It was to allow movement on slots to tension it's drive belt, and to bring the shaft position to the same axial point as the SEM servo motor.
Only two little 'funnies' during this process:
Firstly we had a power cut as I was downloading the G code file to Heidenhain controller from my PC, it wouldn't have been an issue, but I'd not saved the CAD drawing of the cut outs - no big deal as it's only a few minutes work to re-do it
Secondly, for some reason Featurecam refused to cut one of the adjusting slots, claiming that the tool was too big despite using the same tool for the other identical slot. I had to lie to it !
So here we are:
a/ the blank adapter cut from another bit of that (was) 20 foot plank of 100 x 20 aluminium - the notch is for clearance on the servo motor
b/ same thing holding the encoder
Andrew
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Today the Postman brought me the oil seal for the Servo Motor shaft, and the 5/16" UNF cap screws, so I've been able to mount the motor and try the gear mesh, which seems ok. No doubt it'll sound better when filled with oil - it's just lightly oiled at the moment as I'm not convinced the original housing flanges are oil tight and while it's on the bench I don't want it dribbling everywhere !
The servo motor is 140 volts 26 amps peak, so I was surprised how it runs quite well on 24 volts at less than an amp for testing.
Now I'm working on the CAD for the housing that holds the encoder onto the back of the servo motor, fighting tangent snap modes in Featurecam :scratch:
Andrew
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How does the machine Interface with the 4th axis drive electronics Andrew? Do they simply both comply to a standard?
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The Heidenhain TNC355 (which is very similar to the TNC150/151/155 ones) outputs an analog signal in the range +10v to -10v representing the motor speed and direction. This goes to the Bosch servo driver card that beefs it up to the 140 volt max and 26 amp absolute max peak that the motor will take. Into the Bosch servo card goes the tachometer output that is integral to the motor (7 volts per 1000 rpm).
At this point the TNC355 has no idea if the motor has moved at all so it takes in signals from a rotary quadrature encoder (also made by Heidenhain so conforming to the same spec) fixed to the servo motor (in my case through a belt drive as I need to change the ratio) giving it 36,000 counts round the 360 degrees of table rotation. Also on the table is a 'reference point' switch. When the controller is first switched on, all axis, including the rotary one, have to transverse across their reference points. From then on the TNC355 keeps count of where the table is.
The servo card has some more sophistication in that it has a form of 'three term control' (proportional, differential and integral) that when set up right allows it to respond to, for instance, a step function increase in speed without either overshooting or approaching too slowly.
All this is ahead at the moment until the mechanicals are sorted :lol:
Andrew
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You will have a very hot motor if you manage to stuff 26 amps into it !
IIRC the peak current value is the maximum the motor can tolerate before de-magnetisation occurs - continuous stall current is 4.4 amps for an MT30 H4-44, which I think is the one you are using ?
Regards,
Nigel B.
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Yes that's the one Nigel. I am amazed that at 5 volts on a psu that limits at 1 amp it is turning the table, and while it's doing that (remember the encoder is removed) I cannot stall it by grasping the rear end of the shaft with my fingers - the current just goes up from 250 mA to about half an amp. Incredible torque.
Presumably the Bosch servo driver limits the current to a safe level ?
Andrew
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Pulleys and belt for the encoder reduction drive came in the post this morning, no time to fit as we have guests for lunch
Andrew
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There should be some method of adjusting the current limit on the drive. I am not familiar with the Bosch drives - I've tweaked them & swapped one or two, but can't recall the setup - usually I was just fine tuning the standstill offset or the speed to get the trailing error correct. It maybe a potentiometer, where you set a voltage on a test pin to a particular value for a particular current limit, but some drives require a resistor changing to set the limit. Most of the Bosch drives on Bridgeports would have been set up for the axis motors, which were 3.5 or 4.5 Nm, so the current limit will probably set much higher.
If you Google the Bosch drive part number, you may be able to find a copy of the installation / set-up manual.
HTH
Nigel B.
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Thanks Nigel. There is a pot on the servo card to set the limiting current when stalled and a full 10 volt command input is applied. I have had the manual on file for a few years as this project has been long in gestation :lol:
Andrew
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So this morning I've finish off the CAD drawing for the reduction belt drive to the encoder. Now I just need to work out how to hold the stock when machining. (Stock is 200 mm off that long plank of 100 mm x 20 mm aluminium) As I want to cnc mill it at one setting I obviously cannot just grip it in the vice, and there are no convenient lands to put bolt in from underneither that won't finally be cut away. :scratch:
Any suggestions welcome :wave:
Incidentally you can see on the rendering that in an ideal world this would be cut from 110 mm stock, but as I've said before, you work with what you have :med:
Andrew
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Any suggestions welcome :wave:
Andrew
Buy a laser, find an old plywood packing case and start off with this.
(http://www.stevenson-engineers.co.uk/files/hoffman3.jpg)
A bit of PVA and here's one I made earlier :ddb:
(http://www.stevenson-engineers.co.uk/files/hoffman4.jpg)
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SNIP
As I want to cnc mill it at one setting I obviously cannot just grip it in the vice, and there are no convenient lands to put bolt in from underneither that won't finally be cut away. :scratch:
Any suggestions welcome :wave:
SNIP
Andrew
Hi there, Andrew,
Surely, it's OK to design in features that facilitate manufacture, even if they don't have a function once the component is in use?
How about a boss between the two holes with one or two tapped holes in their underside? Is there room between the pulleys?
Drill and tap the holes as stage #1, then screw the blank to a holder-plate. (Studiously avoiding the terms 'jig' and/or 'fixture'!) :lol: :lol: :lol:
Turn the sandwich over and clamp down via the holder-plate.
Then, stage #2, machine the part according to your drawing (but leave some meat round the tapped holes).
Agreed, this would require two sessions of machining, but .......
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OK John, I KNOW I made a masking tape mock up, but a plywood mount is going too far :lol:
Peter, Yes I'm going to have to make some form of jig to hold it and do it in two sessions. I did try tentatively using a longer (*) piece of stock clamped with four hold downs on a sacrificial piece of contiboard. Needs the clearance for the 22 mm profiling cutter to pass round the ends. I put double sided tape between the contiboard and the aluminium to try and reduce vibrations on the finishing cuts, and reduced the through bores by 0.5 mm to leave a solid base to hold things in place. However it let go :bugeye:
I'd already reduced the feed to 50% of programmed rate and had my hand on the E Stop button so it wasn't too dramatic, but that length of aluminium won't now be the finished item :(
However as I'd drilled the holes to mount on the Servo motor and the holes to mount the encoder at least I was able to use it as proof that I'd got my hole locations correct :ddb:
I'm being dragged to a nieces wedding in Bath this weekend so progress will be delayed
(*) I've not yet found how to define 'keep out' areas in Featurecam so I need a fair space between the work and the clamps.
Andrew
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Hi Andrew I may be able to help you on the plug for the 4th axis ,pm sent ,
Peter
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SNIP
I'm being dragged to a nieces wedding in Bath this weekend so progress will be delayed
SNIP
Andrew
Hi there, Andrew,
:offtopic: :offtopic: :offtopic:
I've seen adverts for clockwork feeders for domestic cats and dogs - do they make them of a size to suit your livestock? :lol: :lol: :lol:
Joking aside, I hope the sun shone on the bride. :D :D :D :D :D :D
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Well Pete, happily a good neighbour has been dealing with the stock while we were away, but my brother in law told me this weekend he had modified a timed cat feeder to supply his dog between visits from the dog walker while he was away for this wedding !
Now we are returned so perhaps I can get on with things, but I have 600 hedging plants arriving either Monday or Tuesday to plant a new 100 metre hedge across the field where we moved that mountain of earth last year, so that's going to hold things up :(
Andrew
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What are you going to do hire a petrol post-hole drill?
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Should just be 'insert spade, wiggle it, drop in bare root whip, fit rabbit wrap, insert cane, tred in . . next '
Andrew
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Progress :thumbup:
I decided to mill the inner form of the belt drive housing, then make some hold down disk and mill the outer profile as a second operation on a spoil board.
So:
a/ Slice another slab of stock
b/ A few passes with the roughing cutter and finishing cutter
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Then make some heavy duty hold down disks and re-tram onto the correct location
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And go at it again with the roughing and finishing cutters
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It'll do, but there's a bit of hand blending needed where the stock wasn't quite wide enough. Next thing is to get it mounted on the servo motor and fix the encoder so that I can decide how much dishing the cover will need to accommodate the thickness of the pulleys.
Bit of a delay tomorrow as all those hedging plants arrived today and need planting -it's a BIG heap :(
Andrew
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Nice :thumbup:
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Thanks Pete.
Not much done today as I was planting hedges - a 100 metres of 'em :(
However I've bored and reamed the pulleys and test mounted the drive enclosure on the back of the SEM servo motor, and fitted the encoder thus proving that the allowance for belt tension is ok. But is also shows me I need to bore a hole to let me fix the encoder pulley's grub screw. I'll tap it and seal it with a larger grub screw when the settings are finalised.
Andrew
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Hi there, Andrew,
I'm confused! :scratch: :scratch: :scratch: :scratch: :scratch: :scratch:
You seem to have mounted the larger pulley at the smaller end of the casing. Is that because it's just a trial assembly? Or have I missed something?
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Pete,
Yes you ARE confused! :lol:
The housing has it's two circular ends the size that they are to accommodate the existing mounting holes for the SEM servo motor (larger end) and the Heidenhain encoder (smaller end). However the encoder needs to be slowed down to give 100 counts per motor rev, and not the 125 that one revolution of the encoder gives. Hence the encoder has a 50 tooth pulley, and the servo motor has a 40 tooth one.
Thus one 'table revolution' gives x90 (worm wheel ratio) x4 (gear train ratio) x100 (encoder pulses per motor rev)
so 90 x 4 x 100 = 36,000 which is the count the TNC355 controller needs to give the required accuracy of 100 turns counts per degree
Andrew
Andrew
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Thus one 'table revolution' gives x90 (worm wheel ratio) x4 (gear train ratio) x100 (encoder pulses per motor rev)
so 90 x 4 x 100 = 36,000 which is the count the TNC355 controller needs to give the required accuracy of 100 turns per degree
Andrew,
Shouldn't "100 turns per degree" be "100 pulses (or counts) per degree"?
Phil.
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Phil yes it was a typo,
The TNC355 requires either 18,000 or 36,000 encoder 'counts' per 360 degree 4th axis revolution (set by parameter) - I've settled on 36,000 as it makes the gearing easier. So there are 100 encoder counts per degree.
To turn the table by one degree takes one revolution of the servo motor.
:coffee: I keep re-working those figures but I >think< that's right :scratch:
Andrew
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So I've finished the CAD for the cover, drilled an access hole for the encoder pulley Allen key, all I need now is to work out how to hold the cover when machining - the perennial problem :scratch:
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So I cracked on this afternoon and got the belt drive cover made.
First I cut the inner shape so it sits nicely with a lip
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Then I reversed it and sliced 10 mm off it's thickness using the CNC mill 'sort of manually' :ddb:
Then I screwed it down to a scrap chunk of aluminium for profiling:
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And when that was done clamped it to the main body, and transferred the holes though with a 4 mm transfer punch and drilled and tapped them
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Then just for devilment I thought that I'd reverse the cover to see how symmetrical it is. It was drawn symmetrical, but I've not allowed any tolerance on the screw holes. 4 mm screws in 4 mm holes and I measured the screws as 3.93 mm.
I was quite amazed that it reversed with no problems at all :ddb:
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OK enough mucking about, get on with it :hammer:
So hopefully this is the last 'trial assembly'
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In all I'm quite pleased with it. If I were doing it again I would probably have not stuck so rigorously to the diameter of the servo motor, and reduced the curve of that end to the size of the stock to avoid those two flats. I'll probably blend them on the belt sander before the final 'put together'
Also I must try and get my hands on some corner rounding cutters - the cover would look far better with a radius on it's outer edge.
Making the four elements of the mounting using CNC have made me much more confident in going from a CAD drawing to something tangible, and I've also gained confidence in the use of the Heidenhain probe, allowing me to break down work, and re-set it with some confidence that it's accurately placed. The 'reversal exercise' is also useful in that there are occasions when I'll want to reverse a symmetrical part to machine it, and the 'reference point' will thus move.
Andrew
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Nice looking job Andrew!
You must have a whole barn full of 'projects to be got round to - you seem to own 'one of everything but it needs fixing' :D
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Nice looking job Andrew!
You must have a whole barn full of 'projects to be got round to - you seem to own 'one of everything but it needs fixing' :D
Thanks Pete for the kind words.
Projects : yes well I've been saving them up :ddb: When we moved here not much got done engineering wise as we had rather a lot of sorting of the domestic buildings, and actually building the workshop, but now those things are on an even keel I'm going through them ticking off the list. However it's a long list :)
Need to sort the foundry, need to cast some aluminium billets :ddb:
Andrew
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:ddb: Today officially is MY LUCKY DAY :ddb:
I recently won a reasonable quality 200 mm chuck on eBay that was nice and local.
First task today was to draw up a converter plate to mount the three jaw chuck on the 4th Axis table. Table has four main slots and four auxiliary smaller ones. As the face mounting chuck has three holes at 120 degrees and the slots are 90 degrees nothing matches - hence an interposer plate.
Then I looked at the extra four tapped holes someone has added to the table - hey just maybe two of those line up with the chuck and the third goes in a Tee nut in a slot. Tried the first pair and they were close but not quite right by about 3 mm. Tried the second pair - spot on, exact, bullseye :clap:
I'll need to round the end of a Tee nut to slide further into the short slot, and no need for an adaptor plate - yipee !
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Then the second bit of good luck today:
I wanted to sort the air solenoid that drives the 4th axis table brake - it needs to work off 24 v DC and the original is 100v AC. I fired it up via the variac, and although it works it hums like an angry wasp. Pulling the coil off it, it became obvious that it wasn't viable to re-wind the coil as I had intended as it was a sealed unit :( I considered using it via it's own transformer arrangement, but I really don't want 100 v AC in the environment that it will have to live in with coolant and swarf flying everywhere.
:scratch: So what to do. Well it's obvious really - chuck it out and start again. Now the original sits on the end of the operating cylinder, and the valve ports directly link to the cylinder so unless I was VERY lucky and found a similar one, I need to make a simple adaptor to clamp on the cylinder end to take normal push fit pipe unions, and use a standard air valve.
ebay provided me with a brand new one with 24v DC operation for the princely sum of £9.99 including postage :ddb:
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Today was really a day for plotting and scheming.
Firstly to decide on how to get cables in and out of the unit. The encoder has an umbilical cord which I don't really want to re-make, and the servo motor, inbuilt tachometer, in built thermal alarm, coil for the brake solenoid, and magnetic sensor that says the piston has moved, along with the reference micro switch takes 12 cables, however due to some being common we need a ten pole connector. So I will make up a second umbilical cord and have a box mounted on the machine with chassis mount sockets. Decided on the Amphenol '97' series connectors as I already had the plug, just need the chassis mount socket. Order placed with RS components promised delivery Monday.
Secondly, how to adapt the end of the pneumatic brake cylinder to give me a standard 1/8" BSP port where previously the solenoid valve mounted.
A bit of poking around convinced my the easiest way was just to clamp a suitable adaptor on the end using the existing mounting screws and gasket.
So adaptor turned up out of a convenient aluminium bar end:
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Then I needed to decide how things like the new pneumatic valve, cable clamps and covers would be mounted. First off I set too cleaning up the original mounting bracket so I could see what was what, and how the original cover was retained.
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I will probably retain the original bracket, cutting a few bits off where it fouls the encoder cable, and extending it to give more support for a far larger cover and the cable clamps.
The original cover is far too small. I want it to extend over the rear to afford protection to the encoder and servo motor, and be stout enough not to suffer when the 4th axis is lugged about. It is a VERY heavy beast, and it's hard to be delicate moving it. :ddb:
I'll probably use the existing cover as the start of a pattern to develop the new one. Knowing how, when the machine is in full flight, chips go absolutely everywhere and coolant gets splashed over everything, it needs to be all embracing, but with an open bottom for anything that enters to fall out :lol:
Can't do much more to this until the new pneumatic valve arrives, as the bracket and cover need to be designed to fit round it.
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Hi there, Andrew,
That project looks to be coming along fine.
Have you decided what sort of a test-piece you're going to set it all to to try it all out?
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Well Pete that's a good question and perhaps one for suggestions from the forum :scratch:
I'll be very pleased to see it under servo control and being able to shift it back and forth using the TNC355 controller - I expect it'll be simple hex or the usual coarse square screw thread, though I was watching some cylindrical engraving on Youtube that set me thinking . . . . need to read up on that :coffee:
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A little bit of progress over the past few days:
I've been researching the power side of the servo system. In the Bridgeport Interact where the Bosch Servo driver card and SEM servo motor originate, there is a whacking great 3 kW auto transformer with enough tapping to confuse a Bletchley Park decrypter:
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Now I don't like autotransformers at the best of times, as they offer no isolation, and that number of tappings is silly :scratch:
Going through the Bosch manual for the drive, what it needs is two 180 volt windings aranged 180-0-180, and a further 200 volt winding added to one of the 180's to give 380 volts. The main power is taken by the 180 volt windings, and the 380 volts uses a measly 10 VA, and feeds an internal transformer generating 15-0-15 volts DC and also it uses this winding to get the synchronisation of the thyristor drives.
Searching around there were no suitable transformers 'off the shelf' or available second hand, so I'm having one wound. But what power? Well in a Bridgeport Interact it would feed three axis's and potentially a 4th axis rotary drive, and was 3 kW. Pro-rata that means that my 4th axis only needs 750 VA, and I reckon that's probably over stating it as the main axis drives will take more than the 4th axis.
I've simplified the secondaries to just the three needed ones, but have added a 415 v primary for isolation, with a 240 volt tapping so I can drive it off mains on the bench for testing. I upped the 200 volt winding to 50 VA so that they don't use stupidly thin wire.
As a 1 kVA transformer was not much more than a 750 VA that's what I plumped for:
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Meanwhile I've got on with the physical mounting of the Bosch servo board and it's twin wound choke. Nothing too complicated, just a bit of a pain as the space is a bit tight. Back panel of the enclosure is 2 mm steel, so everything is mounted using 6 mm hank bushes as 2 mm although it could be tapped and would be ok for first mounting, would strip after a few 'ins and outs'
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The X, Y, and Z axis are driven by Indramat AC servos - it would have been nice to use one for the 4th axis, but they fetch telephone number prices even second hand
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So now I'm waiting for the transformer to be delivered - (expected middle of next week) and also the air solenoid for the brake operator, which should be here already but isn't :(
. . . getting impatient in my old age :lol:
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I have a couple of 12v air solenoids left over form a project. Got some random servo/stepper drives too I'll be selling soon. You could have had one of the soleniods for your project Andrew.
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Pete that is very kind. The requirement is pretty specific - 5 port with 1/8" bsp tapping and 24 v DC coil, also physically small. Hopefully the post man will bring it today !
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Well time goes by - I've made quite a bit of progress, but some has been up blind alley ways :bang:
Firstly, in the picture above where I've mounted the Bosch servo card with it's associated choke just below it - I've had to re-locate the choke, as I found a tiny little paragraph tucked away in the Bosch manual saying that the servo card must be at least 300 mm away from transformers and chokes - it is presumably susceptible to magnetic fields. I'm sure that they are closer than that in Bridgeport Interacts !
I wanted to have the 4th Axis with it's cables easily de-mountable, so have placed a termination box on the machine right hand side where the Encoder, and two Adaptaflex covered cable forms will plug it. This also has a rotary enable / disable switch
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Now getting wiring to that point was a bit of a b****r to say the least. There is a semi-protected way in which the power for the machine light runs in armoured cable, but although protected by shields, it is in the 'wet' part of the machine and chips do fly under the shield. I am running two Adaptaflex IP54 rated 20 mm flexible conduits in this channel, but pulling them in took much ingenuity and messing about. The chassis sockets on the termination box have to be soldered in-situ, so to avoid soldering upside down in a confined space have minimum length tails to reach a table on which I could do the soldering, they then will be coiled up and put inside the box.
Fortunately I'd made a dummy test plate before I drilled the box, so used this to keep things at the right spacing.
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Having traversed the front of the machine the 20 mm flexible conduits terminate, along with many others, in the wall of the electrical cabinet.
From there for now they stop on a DIN rail mounted terminal strip, from whence they will be wired to the rest of the machine. Exceptions being the Heidenhain encoder, that goes directly to the TNC355 controller in it's rather special 4 pair twisted screened cable, and also the tachometer output which goes directly to the Bosch servo card in screened twisted pair
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At long last the pneumatic valve has arrived allowing me to make up a bracket and mount it. I'm glad to say that the brake works very well. In the relaxed state the cylinder is releasing the brake, and when powered it is applied
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I then could start planning how to physically fix the ends of the umbilical flexible conduits that lead from the 4th Axis to the termination box.
I decided that the easiest thing was to replace the SEM servo motor termination box with a much larger one that could take the Adaptaflex fittings, and also the air fitting, so went too and made a new box:
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Now that all went very well, I was pleased with the result . . . until I realised that due to the minimum bend radius of the flexible conduit the 4th Axis could not be layed down in 'rotary table' mode :bang:
Now I'm unlikely to want to use it as a rotary table, but will want it sat that way for initially mounting chucks and the like, so a re-think was needed. I could have brought the cables out on the rear of the box on the narrower side, but that would have made the 4th Axis too long and the cables would foul on the enclosure door.
I fell back to using the original SEM termination box with the cable emerging 'backwards' so that the curve could be accommodated, and making up a bracket for the second conduit which I had to reduce to 16mm to clear the body of the motor
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The transformer to drive the Servo motor and card has arrived, and this and that 'wandering choke' will now be mounted alonside the original transformers on the base of the electrical enclosure
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I still need to mount a contactor for the 4th Axis power, with it's associated MCB, a brake operating relay, and a '4th Axis enable' relay' - these relays are on order and should arrive during next week - but so is the new puppy, so that may delay progress a bit :clap:
Watch this space . . . . .
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Well the relays arrived today, as did another coil of Adaptaflex, but so did this chap, so no more progress for a few days I expect, especially as we are replacing the oil boiler in our holiday cottages tomorrow (Tuesday). This'll be the third (and hopefully the last) boiler I've replaced since we bought this place. (That's the house, the workshop and now the cottages )
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Hi there Andrew,
I don't know whether this is :offtopic: or not:
My lovely but shy assistant suggested, at 50% confidence, he's a Vizsla. (My confidence regarding the spelling is much less than 50%!! :lol: :lol: )
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I have seen Andrews other two dogs, absolutely gorgeous, like stroking velvet, unlike that shaggy mad dog I own.
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Yes Pete, Hugo is a six week old Viszla and is being spoilt rotten on my lap as I write this.
John, sadly Max our 5 year old Viszla, the larger one of the two you saw, died very suddenly in November. So Hugo is here to fill a big gap and has a lot to live up to.
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Andrew,
So sorry I didn't know. It's always a wrench and you say you won't have another but you always do.
We are on No's 9 and 10 of the Old English Sheepdog rescues.
But No 9 is doing my head in, play for England 25 hours a day, mind you if truth be known he plays better than England............
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Hi there, Andrew and John,
This is definitely :offtopic: but here goes,
This is 'Unity', she's a retired guide dog, twelve years old and has been with us just two years and one month.
(http://i1342.photobucket.com/albums/o770/Pete_W73/Cats%20and%20Dogs/Image14Nov2013303_zps78cfecbe.jpg) (http://s1342.photobucket.com/user/Pete_W73/media/Cats%20and%20Dogs/Image14Nov2013303_zps78cfecbe.jpg.html)
She's successor to our previous GSD who we lost at six and a half years of age, it took us a while to get over that loss.
We meet several Viszlas while dog-walking in local venues, one of them is wire-haired.
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I'm pleased to say there has now been lots of progress on the 4th Axis.
I decided that the side exiting wiring was a no-no, and that the use of the original SEM termination box was messy, so I re-made the motor box with rear exiting cables that have to emerge 'upwards' to avoid fouling other things. I also gave the mechanics a lick of paint, that no doubt will all be removed in use !
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I then wired up the various relays needed:
a/ 4th Axis enable
b/ 4th Axis brake
c/ 4th Axis ESTOP
Wired up the servo card and finished off the external termination box
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At this stage I was then able to start testing. The system worked, amazingly, but I couldn't get a decent speed out of it without generating 'Gross Positioning Errors' Fairly obviously the servo card needed tuning, and some parameters tweaking in the control. However the good bit was that the gearing and encoder interface was working correctly to give me 360 degrees for a full turn as it should.
I went through the Bosch manual MANY times following their procedure, and try as I might couldn't get the main servo motor spinning more than about 700 rpm without errors - it's max speed is 3100 rpm and I'd initially set it up to max on the servo at 2000 to be on the conservative side.
Many people offered help, both from this forum and others and I thank them profusely, but the break through came the other day, when by chance I was put in touch with a local chap who had installed this type of servo card many years ago.
Long story short - he came round yesterday, and after four hours of tweaking, un-tweaking and head scratching we got it to a very acceptable performance. Servo motor is now reliably able to spin at 2500 rpm giving 2500 degrees a minute on the table.
So to celebrate, last night and this morning I made up the swarf cover and am ready to put it on the machine table and try it for real. That won't happen immediately due to family commitments
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Wow Andrew,
That looks very nice. Anxious to see the results of all your hard work.
Eric
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Hi there, Andrew,
Your project is coming along nicely, exciting stuff. :thumbup: :clap: :thumbup: :clap: :thumbup: :clap:
:offtopic: How is Hugo?
:offtopic: I've actually been cutting metal myself this afternoon, I may get some photos on my thread later.
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Thanks Eric and Pete for the kind words - it's been quite a journey getting to this point, much more than I'd have expected, but I'm happy so far with the result.
Pete, Hugo is now at least 2 1/2 times the size he was when we got him and he's only 12 weeks now - took him round our field this morning as things are drying out nicely. His 'sister' Cleo decided to swim in the stream, and he plunged straight in. Fortunately he seems to do a good doggy paddle :ddb:
Off to the abattoir early doors tomorrow (it's half an hour away and I have to be there by 7 am having cajoled the sow to get in, then have to go to the bank regarding some trustee business for my niece so I'l be lucky if I get any play time by the time I've hosed out and disinfected the stock trailer and concreted in the bolts for the new gates (replacements for the ones we lost in the storms) and adjusted the hinges. Hard work this 'retirement' :lol:
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At least it will keep you away from the white paint - Yuk
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At least it will keep you away from the white paint - Yuk
Grumpy old git :lol:
It's actually a tasteful shade close to magnolia that was colour matched to the rest of the machine, but it's not a brilliant match !
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Well after a bit of a struggle I managed to get the unit up onto the milling table. By heck it's heavy. I fitted a bar in the chuck as a handle, moved enough junk out of the way to get my hydraulic pump up table closish, and used a bridge of 18mm mdf to slide it into place.
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So now it's on the table it needs holding down - I need to make some clamps
If you look closely at this picture, I've added a rear 'brace' to the swarf cover that picks up three of the bolts on the encoder belt box. This was to make it a little more rigid and stop drumming
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However its not going to happen immediately as these four little piggies that I picked up this morning need dealing with
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OOooo goody, sausages........
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OOooo goody, sausages........
I've approx 100 kGs of sausages coming back next week from the demise of Martha the sow if you need sausages . . . . :ddb:
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Bacon? Yup, yup, yup :)
&t=4m55s
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Well today went pear shaped from the start !
Cut a long story short, but because of some early arrivals that weren't expected until the end of the month, no time for clamp making so I bought these
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So what were the early arrivals? Two Ewe lambs and one Ram Lamb
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So the 'Lambing Tent' that was scheduled to be put up during the coming weekend had to be put up today in a hurry. This is an ex Chinese Army inflatable Field Hospital that is stored in two pallet mounted boxes, and needs a road compressor to put it up.
We got it up after a few setbacks and the sheep are at least now safe from the foxes.
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Cor, you molly-coddle your sheep. On the Falklands, where I lived for a few years, the sheep only come inside for shearing and slaughter!
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I seem to remember that there are no foxes on the Falkland Islands. We'd loose too many lambs to the little b****rs otherwise.
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You're absolutely right, and there are vultures to get rid of any stillborn ones!
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Flash bastard, anyone else makes do with a taup draped over a tractor.
I'd be a bit careful putting that up where you live.
You are very close to the tunnel and next thing you will have 567 Romanian families kipping in there and nicking everything not welded down.
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:lol:
Flash bastard, anyone else makes do with a taup draped over a tractor.
I'd be a bit careful putting that up where you live.
You are very close to the tunnel and next thing you will have 567 Romanian families kipping in there and nicking everything not welded down.
:lol: :lol: Isn't that just another type of new arrivals?
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The clamps I ordered arrived today and I managed to find five minutes to fit them
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They work and certainly hold the 4th axis securely, but in the long run I'll probably make up a custom clamp as these are a bit chunky as a semi-permanent fitting.
To celebrate I mounted a bit of 1" bar and mandraulically milled a square and a triangle, really just using the 4th axis as an indexer. Although the brake is fitted and worked well, I've not yet run compressed air to a convenient point, so this was done with no braking. No sign of chatter what so ever so for many things I probably don't need the brake - but I will run the air anyway.
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That's wicked Andrew.
I have a idea for some mirror mounts for my bike that would require 4-axis milling. Any chance you could do a small job for me when you have the air piped in?
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Do you have a sketch or drawing ?
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No, but I will have soon!
The problem is I do a lot of filtering through city traffic so I probably fold my mirrors in a dozen times a day or more. This causes them to be loose, and self-folding above about 50mph. I have an idea to cure it but no idea how to machine it manually.
I'll do a sketchup or something.
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So the next task is to sort out a tailstock for use with the 4th axis.
I picked up this one, which is bored 2 MT and really intended for a dividing head, as it's a tilt and height adjustable one:
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The 80 mm diameter plastic hand wheel was smashed, and it was a bit of a mystery how it was fixed, until I turned the remains off carefully on the lathe. This revealed that it was an 11 mm shaft with loctite and a taper pin. Ebay kindly provided me with an identically shaped handle (but black not grey!) however the mounting was an M10 thread. So the 11 mm shaft got turned down and threaded thus:
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I will need to bore a hole aligned with the axis of the barrel to allow knock out of the morse taper using a tapping rod, as there is no other provision. I strongly suspect this is how & why the original handle was broken.
This mornings job was to make a stepped key for the base. The milling machine has 18 mm Tee slots and the base of the tailstock is grooved 16 mm, so a bit of milling this morning produced this:
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I am a little concerned that automatic tool changes may take tools ever so close to the tailstock, so at the moment I'm seriously considering making a cardboard mock up of the size of the tail stock and performing a few tool changes to prove that there is clearance. It's remarkably difficult to see during a tool change cycle exactly where in space things are as there's no real reference point for the eye to latch onto !
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Hi there, Andrew,
I am a little concerned that automatic tool changes may take tools ever so close to the tailstock, so at the moment I'm seriously considering making a cardboard mock up of the size of the tail stock and performing a few tool changes to prove that there is clearance. It's remarkably difficult to see during a tool change cycle exactly where in space things are as there's no real reference point for the eye to latch onto !
Maybe Wax would be better then Cardboard?
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No Pete I want something that will just be swept away without damage - it's my Heidenhain probe I'm most concerned about. It's pretty well the longest tool in the crib, and definitely the most delicate as the ruby is mounted on a thin ceramic tube that would easily break if it hit wax. Whereas a thin card mock up would probably not damage it before I leap for the ESTOP button.
I may be able to find a parameter in the control that slows the motion down during tool changes, and thus be able to avoid the Blue Peter modelling approach :lol:
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.....ah...... a solution has presented itself :ddb:
It turns out that although the feed rate over ride control on the panel will not allow traverse speed to be increased during tool changes, it will allow it to be decreased :clap:
I knew that the over ride control was over ridden during tool changes but I thought that it was both for increase and decrease. But no, I can slow it to a crawl and watch and measure as in the fully slowed position it can be stopped - result !
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Hi there, Andrew,
Fair enough and I'm glad you have a way forward.
:offtopic:
I thought I'd set up my profile to display the time at my longitude but I'm posting this at 16:20 GMT and your message says it was posted at 16:47. :bang: :bang: :bang:
What am I doing wrong? :scratch: :scratch: :scratch:
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As far as I know I've never set anything up for longtitude on the forum other than put the country as UK. I've just had a poke around my profile and found a setting to have an offset from 'forum time' with an auto-detect feature that says it is to display local time. Clicking this gave a four hour offset so maybe this post will bear UK time.
Later edit - Nope shows 4 am ish !!!!! unless the 24 hour clock is wrongly implemented and it means 16:00, but it shows as 04:.. which is early hours in the dark even though it SAYS PM !
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The new knob for the tailstock arrived today, and promptly had an extra hole drilled in it to allow the use of a knockout bar to remove the No 2 Morse centre.
Whatever the plastic they made the handle from is filled with it's abrasive stuff - took the edge off an end mill in no time short !
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Now the eagle eyed amongst you will notice that the clamping bolts have their nuts on the 'wrong side' for placing the tailstock on the left hand end of a milling table as I must. The pair of bolts used to clamp it at a particular elevation and tilt, once set, should not need adjustment, however the clamp for the barrel will need to be 'got at' every time it is used. It would be easy just to remove the centre section and assemble it the 'other way round' but it would be nice to have ALL the locking bolts on the same side.
Then I suddenly realised that all that stops me putting the bolts in the other way round is a small groove milled to take an anti-rotation peg that is part of the bolt head
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All I had to do was mill a matching 3/16" slot on the other side and I could assemble the bits the other way round !
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Hi Andrew, the plastic knob is is very likely to be made of a glass filled plastic as many structural plastic components are(PA 66 maybe?).
It is very abrasive and dulls most tooling very efficiently....OZ.
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As far as I know I've never set anything up for longtitude on the forum other than put the country as UK. I've just had a poke around my profile and found a setting to have an offset from 'forum time' with :D :Dan auto-detect feature that says it is to display local time. Clicking this gave a four hour offset so maybe this post will bear UK time.
Later edit - Nope shows 4 am ish !!!!! unless the 24 hour clock is wrongly implemented and it means 16:00, but it shows as 04:.. which is early hours in the dark even though it SAYS PM !
Andrew
Local Time:March 18, 2014, 05:57:21 PM (copied from your profile)
Local Time:March 18, 2014, 01:58:21 PM (copied from my profile)
Note the difference of 4 hours between your profile and mine. If you right click on my profile and compare it to yours you will see that there is a four hour difference which will be the reverse of that shown above.
Hope this helps Andrew, now back to those servo drives and sheep and whatever else may come your way. I know all about this retirement thing. I don't know how I ever had time to work. :D :D
Cheers :beer:
Don
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Hi Andrew,
I am very impressed with your 4th axis upgrade. I know this is an old thread, but I am about to do something quite similar. I have the choke, the servo card and a J&S 4th axis. Before I start putting all the bits inside my BP Interact 1Mk2 I thought I'd try to get the encoder at least working first . I can get the IVth axis to display on the TNC151, and I can tell it to display encoder outputs for inhibited axes, but my spare working encoder does not work in the 4th axis. It works if I swap it into the X encoder plug if the X axis is inhibited. Is there a set of Machine Parameters someplace that I can set to check the IV axis encoder? Currently using MP72=9, MP75=0, MP76=1. Not really sure what I am doing to be honest.
Regards, Hazel
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Hazel,
I'll pop over to the workshop later tonight and see how those parameters correspond with mine
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Thank you very kindly. :thumbup: If you can think of a way to test the 4th axis encoder without the rest of the 4th axis attached, that would also help me out a bunch, I've spent all day today trying to get this encoder to run.
-H
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Hazel,
I assume that you have a manual with a list of the parameters and their make up? If not it's freely downloadable from the heidenhain.de web site.
I've just checked my parameters against those you list:
MP72=9, Mine = 0
MP75=0, Mine = 0
MP76=1, Mine = 0
I've just dumped all my parameters to file and I attach a copy. Remember - mine is a TNC355 not a TNC151. I think that the lower numbered parameters are the same but best to check
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Hi Andrew,
thank you, thank you, thank you! I do have all the 151 manuals from Heidenhain, which are kind of sparse. Installation/Interface, Service Instructions, operators book, plus all the Bridgeport stuff. Your MPs being zero makes sense, as none of your axes are inhibited. I'm right in the guts of my TNC151 analogue board, tracing through the 11uA buffers to a bunch of comparators, which I can only guess is some sort of ADC to do the phase-quadrature interpolation. Next step is to power up the analogue board with an encoder and check the comparator outputs to compare Z and IV. Maybe I should save up for a 355 control...
Regards, Hazel
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Some photos of my Mad modding:
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I think that logically this bit of the two controls is the same, although the implementation is different. IIRC the encoder inputs on the 355 wire directly to custom lsi modules just onboard from the connectors - when I had a 151 I never pulled it apart :)
On my 355 in it's Beaver Partsmaster there is a user parameter (165 I think) that enables / disables the 4th axis - let me have a poke around in my hard - drive ....
... no I was wrong - it's parameter 158 - copy of decode attached
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Ooo that is interesting. All the 151 blurb says is "MP158=Setting of 16 markers to binary number" which isn't so very helpful. The User manual simply says to activate the 4th axis from the user parameters. I've sent an email out to a repair company to see if they do an exchange on the board, as it may save a month of my life :)
H
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They are probably machine specific - Heidenhain just provides the facility for manufacturers to have 'flags' that the user can set that are (usually) used as inputs to the PLC ladder logic
Somewhere buried in the parameters is one that sets the count per rev of the encoder - iirc I harp on about it in the pages above when I'm making the belt drive for my encoder to change from 125 to 100 pulses per motor rev. If that hasn't been set and left blank it may explain your problem. There are only two permissable values and in my case it was 100 x 4 x 90 = 36000 pulses per table rev. I think 18000 is the other one
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Hi Andrew,
Sadly nothing in the TNC151 documentation directly says how many counts the rotary table should be. There is an option (MP15) to change the interpolation of the 4th encoder between 10 and 20 divisions , and another (MP90) that says to display the 4th axis as 0 to 359.999 for options A,B & C . So I guess that would be the 36000 and 18000 options. ? One of the documents also mentions that the 4th axis reference end position be tied to 24V, yet my rotary table does have a normally closed index switch - how is this supposed to be wired then?
regards, hazel
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Hazel,
I've pm'd you some info I got when I was struggling.
Also picture below is of my home switch wiring - note it does ref pulse inhibit and home on one c/o switch
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Hi Andrew, again, many thanks. My BP Interact 1.2 only uses the reference end positions for X,Y. Z and I think it uses e-stop if you go over the end of the ref point.
I've given up trying to get the Heidenhain repair places to return my emails. Instead I squandered my time wiring up the Analogue PCB to the appropriate Voltages, and stuck a SEM motor into each axis to see the voltages. I managed to trace it down to a little red module, which I think is a capacitor array or maybe a transorb input protector array?
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Okay, in for a penny so to speak, I decided to repair the module, seems to be SM capacitors. Reassembled and all the front end 4th encoder amps now work the same as the others!
So, now to reassemble the mill...
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Well done that girl :bow:
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So now I've put the TNC151 back in the mill, connected an encoder to the 4th axis , and after the usual referencing I now get counts in the 4th axis, and sure enough they go from 0 to 359.999
Yay. Of course I still have to figure out the axis home signal, and put the choke, servo card and amphenol connectors into the cabinet, oh and repair the encoder in the 4th axis, which has a dead bulb. I also have to put the spindle bearings back in as I had a large amount of play while I was trying to calibrate my home made touch probe. Seems like a long time since I had any chips on the garage floor and in my hair... :nrocks:
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Hazel, do you have a particular 'thing' that you need to make, or is it, (like me) the journey that you enjoy ?
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I do have a project in mind - A 5 cylinder radial engine, which will require some accurate placement of lifters to get the sound I want. :drool:
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Hi Andrew,
I'm just installing my Z15 Servo card, and just discovered that the card does not have screw terminals on it, but takes another connector with screw terminals on it. I found something in Farnell, but the pins are much thinner than the other ones in by axis cabinet, which are more like 1.5mm thick. The farnell ones are only 0.9mm thick according to the datasheet. I don't suppose you recall where you got yours from?
(http://i773.photobucket.com/albums/yy19/alfahaze/Bridgeport%20Interact%201%20Mk2/IMG_4079_zps0b826a58.jpg) (http://s773.photobucket.com/user/alfahaze/media/Bridgeport%20Interact%201%20Mk2/IMG_4079_zps0b826a58.jpg.html)
I Just realised the same connector system is used on the rear of the TNC151. Which is anooying, as I removed the interface PCB and ribbon cable to avoid disturbing the cabling - and all I needed to do was pull the connectors out - D'oh... Oh well I only did that about a dozen times while I was repairing the 4th axis encoder interface.
(http://i773.photobucket.com/albums/yy19/alfahaze/Bridgeport%20Interact%201%20Mk2/TNC151J4IMG_3921_zpscb48c8c5.jpg) (http://s773.photobucket.com/user/alfahaze/media/Bridgeport%20Interact%201%20Mk2/TNC151J4IMG_3921_zpscb48c8c5.jpg.html)
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Hazel,
I used these from Rapid:
http://www.rapidonline.com/Cables-Connectors/CamdenBoss-CTB1050-12-12-Way-24A-90-Interlocking-Terminal-Block-5mm-Pitch-21-4625
They are not a perfect match, and infact I have put a dab of 'hot melt' glue bridging the male and female housings to ensure that they don't vibrate loose. They've proved ok in practise.
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Ah, those are the same as I discovered in Farnell. I think my plan is to get some of the 5mm pin header stuff which has 1.5mm diameter pins and solder it to one of the Camden thingies. Many thanks ! Now I have to wade through all the din terminal blocks to find some 35mm rail ones to fit the 3R3 motor brake resistor. Fun Fun Fun!
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Well it's been a LONG time in the gestation, but at last, as it hasn't stopped raining for days, I've found a bit of time to sort out a suitable 'Post Processor' to allow me to engrave text on the outside of a cylinder mounted in the 4th Axis. :ddb:
So what's the issue :scratch:
Well, if you use a CAD/CAM set of programmes to generate the bits you want to make on a CNC mill or lathe, the program has to spit out code that meets the specification of the controller that drives the machine. So most CAD/CAM set ups use an intervening set of definitions and code that take in the symbolic actions, and translate them to actual code that the controller can understand. Once defined and installed, from then on the CAD/CAM should (hopefully) produce the right stuff for the controller.
Now there wasn't a 'standard' Featurecam Post Processor suitable for the TNC355 controller in my mill that understood the 4th axis. There were ones that drove 4th axes. And there were ones that were close to the TNC355 (as the TNC150/151/155 is very similar, so it was a case of making a Frankenstein version, with a few tweaks of my own.
It didn't help that some of the 'standard' Post Processors made mathematical errors when wrapping stuff round a cylinder :bugeye: All sorts of Gotcha's appeared - like the one that made moves all the way round the bar backwards to get to somewhere close to where it started, cutting a nice groove as it did it :( Anyway much :coffee: :coffee: and rather a lot of :med: got me there in the end.
So what are we talking about: well the first picture below is a screen shot of a very small fraction of the program like structure of the Post Processor, and the second picture is code suitable for my Heidenhain TNC355 to obey
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Now there is still quite a bit of tidying up to do to generate more compact code - but hey - it works :clap:
The 32 mm bar in the picture below has been engraved with my initials 'AWEM' using a diamond 'drag engraver' - quite hard to photograph curved surfaces but I'm sure that you get the general idea.
If you look at the over view picture, you'll see several failed attempts along the way :bugeye:
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Pretty cool Andrew.
Lot of effort to ID-mark your stock though :)
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Well Pete what got me re-started on this was working out how to engrave a calibrated collar for the infeed screw of my Dormer 108 drill grinder. Then I remembered that I'd never sorted the Post Procesor for the 4 th axis :doh:
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Fix a tool to fix a tool - Doc Smith would have been proud!
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Andrew,
All would have been a lot easier if your 4th axis were to accept g-code.
I wrecked my diamond drag engraver by forgetting to set Z and running out of spring travel.
I ground a 120 degree point on a broken 4mm carbide end mill and have used it to do a lot of engraving on stainless steel and anodised aluminium with no signs of wear. I'm not bothering replacing the diamond now. I have made a 90 degree one to try on harder material.
For those running a 4th axis on a machine which understands g-code there's a wonderful free utility called g-code ripper which can convert flat (x&y) g-code to wrapped around a diameter and swapping either x or y for the 4th axis. It can also split g-code into smaller sections if you want to machine parts bigger than the travel of your machine as well as rotate or scale.
Phil.
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Phil, it will accept G code just by altering one parameter in the TNC355. But as the good post processors for the TNC controllers generate the Heidenhain conversational code I tend to use that
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Hi Andrew
I replied to this post even though its old .
I'm looking at adding a 4th axis to my TNC355 (Denford quatromill).
Silly question
The fourth axis that's on input X4.. In which case its a sine wave encoder ?
X5 is quadrature square wave .
What encoder did you use on your system , I see it has to be 180000 or 36000.
I'm in s wales by the way and do get to sussex from time to time
Peter
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Peter, if you are passing do pop in and have a look.
My encoder came from the late lamented good chap John Stevenson, it was a sine wave Heidenhain off a Bridgeport Interact and I'll see if I can find any numbers - hang on . . . .
. . . worryingly my entire directory not only describing this build, but also all my data on the Beaver Partmaster for which it was built seems to have vanished from my hard drive :bugeye:
. . .but all is not lost, as it is detailed and pictured in reply #2 of this thread - it's a ROD 450B :thumbup:
(Later Note: for some odd reason the entire 'lost' Beaver Partmaster directory had become a sub-directory off my Ingersoll Rand Drier directory so just needed moving back - but why did that happen :scratch: :scratch: )
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Hi Andrew
I would love to next time I'm in sussex . My mother in law lives in Blackboys near uckfield.
Do you have the numbers after the Rod 450B as they say what the number of pulses is. I find the Heidenhain numbering system confusing .
Pete
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If you read the thread I'm sure that there was long discussion regarding counts per rev and belt ratios, however I do have a picture of the encoder (also embedded in this thread) of the encoder with numbers - here it is again:
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Thanks Andrew
I can't see the number of pulses on that picture but I just order a ROD 456 1800 02S09-04 Sinusoidal Rotary Encoder.
This will be a 1800 pulse (i'm assuming 1800 is the pulse per rev .. Again not sure of their numbering system) so I can gear it to give 36000, as it was a reasonable price.
The RI+/- signal confuses me and I can't find any info anywhere .
Is it a once per rev ? And needs selective gating so it can only appear during a specific angle range ?
I think I same something about gating in th thread so I will work back through it .
Peter
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Hi all
I also pulled out all the param settings for others for the 355
all the tuning params etc are there.
Peter
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I worked through all the relevant settings
summary
Andrews settings
MP 3 : 2500 - 4th axis rapid
MP 7 : 2000 - Manual feed 4th axis
MP 11 : 1800 - approach speed approaching ref marks 4th axis
MP 15 : 2 - sig eval input x4 x x interpolation
MP 19 : 0 Traverse direction approaching marks ( 0 positive)
MP 23 : axis IV ref pulse inhibit active/inactive
on connector X10
0 - Ref pulse inhibit
2 - Ref pulse inhibit active
A ref mark is traversed every full rotation of the sensor .
If there are multiple pulses the pulse inhibit can be controlled by a cam switch or similar.
MP 27 : 0 Polarity Positive with traverse dir
MP 31 : 0 Integral factor (set to 0 ?)
MP 35 : 1.000 Differential factor set to 0 ?
MP 39 : +0.000 Backlash compensation
MP 43 : +0.000 Linear compensation factor (keep to 0)
MP 50 : +30000.000 software limit switch range +
MP 51 : -30000.000 software limit switch range -
MP 59 : 14 ZYX IV ref mark approach seq
MP 72 : 0 P all axis set to non inhibit
MP 90 : 0 axis designation of 4th axis 0 = A
MP 166 : 500 Feed speed for 4th axis for param 126-156
MP 180 : 2.000 4th axis KV factor value 0.1-10
MP 189 : +0.000 datum for 4th axis position block for M92
MP 256 : 0 allocation of encoder inpit to 4th axis
0- Standard allocation
4- Encoder x4
MP 299 : 0.250 4th axis accel
MP 302 : 9.000 4th axis rapid traverse voltage
Partsmaster 355 option param 158
Notes on setting to enable 4th axis
param 158 needs to be 16
1 = air conditioner
2 = flashing lamp operated with m22 / m23
4 = flashing lamp on when program run is stopped
8 = swarf conveyor
16 = 4th axis present
32 = feedrate effective in toolchange
64 = high speed spindle
128 = override spindle stall
256 = no toolchanger
add up value & enter into param 158
On my Denford Quatromill it already has 128 set for override spindle stall
so its 128 + 16 = 144 to enable 4th axis / 128 disable 4th axis
It appears a 1800 count.. Count is strange as its a sin/cos but then with the basic interpolation of x5 on the TNC355 then a 4 fold in the signal evaluation parame gives the full 36000 with no gearing.
As to enable / disable 4th axis I have yet to test bit it looks like its
either MP72 8 = IV axis inhibited / clear to enable
MP158 +16 enables 4th axis (on denford quatro it would be 128 = No Ivth axis .. 144 Ivth axis enabled)
I will update when I test.
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"Later Note: for some odd reason the entire 'lost' Beaver Partmaster directory had become a sub-directory off my Ingersoll Rand Drier directory so just needed moving back - but why did that happen"
Andrew:
If you have a tremor like I do, your fingers probably twitched on the mouse as you were scrolling past that directory. I lost my entire Machining Favorites folder for several days, and that's the only way I can figure it could happen. I about had a heart attack the next time I tried to go on-line to one of those Favorites. Like you I finally found the folder as a sub-folder in one of the adjacent Favorites folders.
Don
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. . . a tremor . . . Well Don only after a few too many Harvey's Best Bitter or Glen Fiddich's :clap:
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Hi Andrew could I ask a couple of questions
1/ What did you do for pulse inhibit etc ? Did you do it the same way as hazle ? Simple switch arrangement.
2/ Is there a way to tell the machine that the 4th axis isn't present without changing parameters ?
I almost have all the information sorted now .
Peter
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Peter I'm a bit tied up at the moment but a quick glance tells me that's covered round about reply #150 to this thread
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OK to answer the inhibit part of the question.
MP23 is for axis IV on connector X10
0 - Ref pulse inhibit
2 - Ref pulse inhibit active
A ref mark is traversed every full rotation of the sensor .
If there are multiple pulses the pulse inhibit can be controlled by a cam switch or similar.
I'm lucky enough to not need that as my encoder will give 1 ref pulse per rev, so I don't need pulse inhibit.
Peter
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Hi Andrew
I added to reply #156, so I hope that quote contains most of the info in one place to help others .
Peter