Titivating A CNC Plasma Table

[millwright]

Same here,   your glad someone is following Andrew? With nearly 2000 reads on this project I'm sure we all are as usual.
John

[Will_D]

You are an inspiration to a retired old Welsh Git

Following closely!

[AdeV]

  Me too!

Andrew, your posts are always informative and entertaining - and some of them are damn useful! OK, maybe not so much the flail mower (still a great thread & highly entertaining, but how many of us really need a mower that big...)

Now as for this project... well, I fancy making my own CNC plasma table from scratch, I'll need to make a solid holder for my existing plasma torch, so I can disconnect it for freehand use.... but this thread has already shown me loads of useful tips & tricks - like the curve supports for example, I'd never have thought of that one!

So, a big thumbs up from over here 

[kayzed1]

Me to, sitting here taking it all in and trying to keep a record in my head of all the tips and tricks.
Thank you Sir...
Lyn.

[awemawson]

Don't make me blush chaps 

I'm just a retired old fart who enjoys tinkering in his barn and if I see a bit of engineering that I reckon I can do better I'm too big headed not to get stuck in 

However very happy to have you all along for the journey, it makes it all worthwhile 

[AdeV]

I'm too big headed not to get stuck in

Nowt wrong with that! I mean, who did I think I was designing and making a dry sump for a highly-stressed race engine? Me, with no engineering credentials whatsoever....? IMHO belief is a big part of what we all do here, and having a large book of excuses to hand is a useful back-stop if it all goes wrong 

[awemawson]

Ade, it was your dry sump thread that tempted me onto / into the forum 

So today's task - and so far it's gone pretty productively - is to work out how to mount the very powerful extractor fan. After all most of this re-build has been aimed at achieving 'down draught extraction' through the slats.

First issue - the rear cross member of the frame obstructs the line of the duct were it to go horizontal. I'd originally intended that the fan sat on the floor and was connected by flexy duct, and it would work fine like that, but I wanted to integrate the fan. (Mainly as it is going to be stopped and started under program control from Mach3).

So I decided to replace the cross member with one at a lower level, and also form a 'hanging cross member', and let the fan straddle the pair of them, with it's rubber anti-vibration feet sitting in 'cups' to stop it falling off.

The output from the duct that I had made will connect to the fan by a short length of 12" circular flexy ducting, and the exhaust from the fan will go outside via a yet to be made wall plate.

So before breakfast I had all the bits cut to size (oh I love my Pedrazzoli cold saw !) and then after porridge I set too gluing them all together with the MIG.
 
That all went pretty well, and left me time to give them a good degreasing and a blow over with Ford Tractor Blue. The 'Plasma Perch' and the trunnion got a coat at the same time, so now it's wait for the paint to dry time 

[DICKEYBIRD]

I KNEW IT!:doh:  Your plasma machine is called "Blue Peter" which is the super-secret military code name of the RAC's hyper-speed simulation tunnel for testing advanced top secret aircraft models.

Harrumph, down-draft  extractor fan my sweet grannie's arse!  Oh yeah, how's that new "tractor shed"  coming along? (Wink-wink, nudge-nudge)

[awemawson]

 

[awemawson]

The newly blue trunnion and 'plasma perch' and gallows bracket got returned to their rightful places and I set too fixing the new rear cross member and forward hanging support for the fan.

Then I cut out the original rear cross member - as expected the rear legs moved a bit and will need clamping when I fix the replacement.

[awemawson]

Tywrapping the hanging support allowed me to determine the correct height for the new rear cross member, so when that was clamped up tight, I could then adjust the fore and aft position of the hanging fan support rail.

That done I had a trial fit of the fan to check that the measurements were correct, and all was well 

Then it was a case of drilling and tapping to permanently fit the rails in place. Getting the flexible trunking over the lip on the fan was a nightmare - it's just too tight - it's 'on-ish' but I'm not happy with it - looks like it needs a slightly fatter trunking.

Powering up the fan it caused a huge draught in the workshop which I stunk out holding a smoking paper roll over the table to track the down draught. It's excellent apart from the extreme corners, which is perhaps not surprising.

On the subject of the fan - it's making funny noises for all the world as though its speeding up then slowing down. The rating plate says 2,800 to 3,300 rpm which I'd assumed was for 50 or 60 hz but just maybe it's a universal motor with some sort of speed monitoring. Normally if you block a pump or fan it's load (slightly against instinct) decreases. This one draws more current (1.7 amps as opposed to 1.5 unblocked) and the speeding up / slowing down stops - odd. It claims to shift 65 cubic metres of air a minute, which is quite possible from the blast it produces 

[awemawson]

Today has hopefully seen the last of he 'mechanical' side of things - I've been pondering how and where to mount the monitor and keyboard - it's not possible to put them on an adjacent wall, and really I want this table to be self contained and able to be moved about without too much hassle.

I obtained a wall mount monitor / keyboard swively thing which is not ideal but was a good starting point. Clamping some flat plate to the frame of the table I experimented with various positions trying to  find somewhere that would clear all the moving bits, and yet still swing out of the way allowing plates to be loaded onto the table.

Ended up with a reasonable compromise which suited 'stand up typing' so I went ahead and fabricated a weldment - really a darn great bracket

[awemawson]

Now although this weldment is made from 6 mm plate I was expecting some tilt or twist, and sure enough there was a bit too much to tolerate. My fall back plan was to incorporate a 'torque tube' made from heavy 40 mm box welded on the back to resist the twist.

Worked well and made things very rigid. So it was a case of drilling mounting holes, clamping it in place and drilling and tapping the table frame.

Then of course the obligatory coat of Ford Tractor Blue to add a bit of bling - well in all honesty actually to slow the rust down   

[awemawson]

This morning I attached the monitor bracket gizmo and cut a bit of melamine chip board as a keyboard / mouse table (hate the stuff but it was all I had to hand.

The table is looking more and more like an oil rig out of the water, with all sorts of things hanging off it 

... anyway this means no more procrastination, I need to get on with drawing up a wiring schedule of the current set up, so that when I pull it all apart and mount things in the new cabinet I stand some chance of getting it right 

It's not that complicated, but as the various settings are already up and running I want to keep things 'as is' rather than re-invent the wheel.

Over the next few days I will go through the rest of the original wiring documenting it and try and decide how to implement the limit switches he currently ignores (he's only wired one on X, one on Y, and one on Z and I suspect that only -Z is actually used by the software) and also how to build in an eStop in a sensible fashion.

First thing - try and identify the stepper motors. X, X-slave, and Y are all the same - "Astrosyn MY259RE" and quote 0.8 ohms 4.3 amps on the case - can't find details of them on the web but they seem to work. The Z stepper carries no markings what so ever 

So far I have traced the stepper motor wiring from each motor back to the appropriate AM882 driver in his box of tricks, and also traced out the limit switch wiring back to the break out board and drawn out tables as a record. Initially it puzzled me that X and X-slave were wired differently, then I realised, as they face each other they must rotate in opposite directions 

It seems he has implemented all limit switches as normally closed, with the exception of Z- which is wired normally open, but held closed by gravity assisted by a spring, until the torch touches down for height setting purposes.

I've attach the tables but really only to keep a record, pretty boring for anyone else !

[awemawson]

I  >>>THINK<<< I've completed documenting the existing wiring to the extent that I can pull it apart and start re-locating the various modules into their new places .... time only will tell if I've forgotten something 

Anyway the document has grown to 8 pages and I attach it here for reference, but it's pretty dry stuff 

[awemawson]

So I've decided to rip out all the stepper motor and limit switch wiring from the table and re-run it, and that's today's job. The master plan is to re-wire, then temporarily hook up to the existing controller box to prove all OK before pulling the controller box to bits, thus cutting down on fault finding (hopefully)

Firstly some little things to overcome:

a/ Z-Down limit switch is only fixed by one screw and has no cover as everything is very inaccessible

b/ How to run the wiring from the (missing) X-Far limit switch as it's a long way from the 'power chain' ducts

c/ How to connect to the stepper motors as present chunky car type plugs and sockets are not acceptable

d/ Best position to move the power chains to for threading, as as soon as I start removing wires I can no longer move the carriage about 


Starting with the Z-Down limit switch, I decided that the best course of action was to carefully measure up and drill a pair of access holes, allowing a screw driver to access the M4 mounting screws. Having done that and removed the single screw currently fixing the switch it turns out he's not drilled or tapped the hole for the other screw 

Now M4 needs a 3.3 mm tapping drill, and a standard 3.3 jobber drill is far too short to reach the plate that needs drilling. It just so happens that when I was rebuilding my Dominion Super Elliot Woodworker I'd had the same problem and had made an extended 3.3 mm drill - result 

But what about an M4 tap 100 mm long - well extend one ! Across the 'points' of the square shank of the tap I chose measured 3.85 mm, so I drilled a 3.7 mm hole in a bit of 6 mm mild steel rod and used the lathe to press the tap into the undersized hole - worked a charm and ensured that they are concentric - problem solved 

As for the X-Far limit wiring, having thought about drilling the frame and threading the wire through I've come to the conclusion that it might as well be Tywrapped.

The power chain issue I think is OK as one side has 'open fingers' to allow wires to enter

Now the stepper motor connections call for a neat little 4 way junction box that can be fixed to the body of the motor - not sourced any yet and would welcome suggestions

[awemawson]

Right-ho, that's all the wiring off the table 

Cropped off the original ends at the stepper motors so that there can be no confusion which core is which on replacement, but unscrewed the limit switches individually. For some reason best known to himself the wires had been stripped for about 2 inches and wrapped round the terminals about 10 times  They will go back with crimped on 'boot lace ferrules' with about 6 mm sticking out !

Removing the cable from the gantry, I realised that he'd left the angle iron support in bare metal and it was already getting rusty, so another job - remove, clean and paint - which I did. It's fixed into the slotted extrusion of the gantry with Tee nuts of the type that you can put in and twist - handy, but he's spaced it down about 1/2" using a pile of 6 washers on each bolt - so it looks like I'm turning up eight spacers this afternoon !

[awemawson]

So after lunch an off cut of 19 mm hex aluminium was turned into eight spacers - much nicer to handle than a pile of washers !

Waiting for paint to dry - already touch dry but pushing my luck to mount the chain support until the morning. At the moment I'm thinking I'll just use crimps to couple the stepper motors - much rather use a small junction box but every thing on the market seems to be far too big. I'll try and leave enough cable in the system that I can re-terminate in the future if anything suitable turns up.

... so it looks like re-wiring can't start until tomorrow ... 

[awemawson]

Late on Friday afternoon I located some small clip together boxes on Toolstation - not ideal as they aren't sealed, but definitely functional. Ordered on line and they arrived first thing this morning - pretty good.

I re-fitted the 'power chain' support now the paint has dried.

[awemawson]

So I was able to start the wiring - so far the four stepper motor cables are pulled through, as are the six limit switch cables. The motors and limit switches are all connected and the controller ends brought back to the cabinet in flexy conduit awaiting drilling the cabinet bottom plate - a job for tomorrow.

Another job tomorrow is to finish off securing cables with 'P Clips', and binding the various bundles with spiral wrap.

[awemawson]

This morning I bored out the right hand base plate for the electrical enclosure to take the four 20 mm flexible conduits that take the motor and limit switch cables, and also holes for the two connectors that interface to the Hypertherm plasma cutter. While I was at it I put an extra 20 mm entry, blocked by a blind grommet, as a just in case provision as it's much easier to do it at this stage than later.

Then I mounted the base plate, attached the flexible conduits and was then able to dress them to their final position with tywraps. The tidying up of the wiring continued by applying 'spiral wrap' to the cable bundles to keep them neat and out of danger.

Finally I temporarily lashed up the motor drive cables to the AM882 driver modules to prove I'd not accidentally interposed wires somewhere - glad to say it all worked as it should 

Initially I didn't bother with the limit switches (he'd only wired in three) - interestingly MACH3 wouldn't 'go to X0 Y0' which is a software point not a home position and currently is miles away from the limit switches. Then I realised that as they are normally closed, but not wired, MACH3 was seeing the table as on limits. Quickly lashing the three switches in and it homed to X=0 Y=0 just as it should. 

[awemawson]

So to finish the cabinet / electrical enclosure I made up the left hand base panel - rectangular holes for clip in IEC plugs and sockets - I don't like cutting rectangular holes 

Anyway, a bit of chain drilling and hand filing and an acceptable result - that's one IEC inlet socket, linked to three outputs (PC, PC Monitor, and a spare) and one separate IEC outlet socket which will be relay controlled for the extraction fan.

Round socket is a 'feed through' CAT5E which is the only connection from the PC to this control. I like ROUND holes 

[awemawson]

Today's task: strip out all the modules from the original controller, and physically mount them on the cabinet back panel.

Rather than use nuts and bolts, as I want all modules to be removable from the front, I've drilled and tapped the cabinet panel with about 10 million M4 and M3 holes 

Took forever but if a module fails it'd be a pain to have to remove the entire panel to get it out, and the panel is 2 mm which is as thick as an M4 nut anyway.

Not started the wiring yet as that needs a fresh mind probably tomorrow, but I did do a trial fit - took a bit of jiggling, but it did go in nicely - be almost impossible without those handles.

The majority of the wiring will be done on the bench, with just final connection of inputs and output actually fixed in the cabinet.

[Homebrewer]

Looking great so far! 

Sent from my SAMSUNG-SM-G900A using Tapatalk

[awemawson]

Thanks Libby 

I spent an anti-social day today locked away in the workshop doing an intense wiring session - very productive 

A/ I've completed the AC mains wiring distribution

B/ I've completed the DC power supply wiring and distribution

C/ I've completed the wiring for the four AM882 motor drivers, from the ports on the BOB to the AM882 and onwards from the motor driver outputs to the X, X-slave, Y, and Z DIN terminals

(I've yet to decide how to lash the cables down that feed the AM882's - they look a mess as they are. A possible solution is to use 'sticky pad Tywrap saddles', but they tend to come unstuck over time. I may have some with provision for a screw.)

D/ I've cut the capping for the trunking

E/ I've added a further six DIN terminals for the Torch Height Controller (which I'd forgotten  )

F/ I've added the 12v DC driven contactor for the fan as it was delivered this afternoon

All in all a very productive day.

The DC power leads to the torch height controller originally passed through a ferrite ring - presumably to cut down on noise coming from the plasma arc. Not sure if it's needed, but I've incorporated it and hidden it inside the trunking !

Yet to complete:

A/ The Limit switch input wiring

B/ The Torch height wiring

C/ The Fan relay wiring

D/ The CAT5E ethernet cables to the interface and the torch height controller - they just plug in but I'll probably need to make custom lengths.

(Then of course there will be another big session fitting it in the cabinet and making off all the input and output cables )