Titivating A CNC Plasma Table

[awemawson]

All rather frustrating, as I'd thought that as soon as that relay arrives and is fitted, I can wack a 12" hole through the welding shop wall, and start using the table. In fact to speed up the process I ordered an exhaust cowl for the outside wall rather than bend one from Zintec, but now it looks like I have a bit more to do before that can happen.

So today the relay and cowl arrived, but I've still not worked out how I'm going to mount better covers. Having to remove the end plates of the gantry may well help, as I can possibly bend something up to fit round the profile of the end plates.

... ah well, onwards and upwards, at least I've fitted the E-STOP relay and wired it all up and it tests out OK.

Incidentally the OMRON relay that I thought I'd ordered turns out to be an ONROM relay - sneaky cunning naming intended to confuse I'm sure, OMRON are a well respected brand - never heard of ONROM - but it works OK

[awemawson]

OK time to sort out the gantry issues - I started the day intending to draw up the shape of the end plate in cad to aid me in making an all embracing cover but it got so complicated missing all the bits that needed missing, and covering the bits that needed covering I changed track. I decided to make just belt covers, as the original owner had done, but this time with 'joined up corners' and not mounted at that odd jaunty angle.

The covers for all three axis are identical apart from the brackets, so I've bent up three boxes, and I will sweat brackets on to match the existing holes in the gantry.

To get reasonably sharp bends in the 1.2 mm Zintec sheet that I'm using, having laid it out and notched the corners I ran a 1 mm cutting disk lightly down the fold lines before bending in my Edwards Box and Pan folder. Then I soldered the corners using lead free solder, as it takes to the zinc coating nicely, and is significantly harder than plumbers lead containing solder.

The boxes came out pretty well and will get an obligatory coat of blue paint before being fitted.

Next job is to remove the end frames of the gantry and drill holes for the HiWin sliders in the right place - hole spacing on the end plates is 45 mm whereas the sliders are 40 mm - not sure how that happened, as I said before perhaps a different rail system has been used previously 

I intend to remove the ends one at a time, replacing the one I've worked on before starting the next to stop the gantry getting out of control. To this end I've made up a wooden packing piece and wedge to secure the cross beam during the operation.

End plates come off tomorrow hopefully.

[hermetic]

 at last! someone has found something that lead free solder is actually good for!, Thanks Andrew, I will remember that one. Can't wait for the demo video, she's nearly there!

[awemawson]

You and me both Phil, this should have been done and dusted by now.

I found the usefulness of lead free solder with Zintec when I was making boxes and panels for the Traub lathe - funny how these things accumulate as 'handy fixes'

[Pete W.]

Hi there, Andrew,

It's looking good!

Regarding the lead-free solder - did you use a gas torch or a smouldering iron?  And what flux did you use? 

[awemawson]

Propane Gas torch Pete

For years I've had a blue bottle of butane and a torch on a length of tubing - if fact I've installed central heating with it in five houses! But I got fed up searching for a lighter and wanted a 'click to light' one.

I thought that I was being extravagant buying a "Rothenberger Super Fire 2" torch kit complete with a 'hot bag' to keep it all in but it has been amazingly useful in the workshop - ready to hand - instant lighting - focused flame - idea for soldering box corners 

[awemawson]

This morning I bent up a pair of fixing brackets for the belt cover for the left hand side of the gantry, and sweated them onto the box. This allowed me to mark hole positions on the pinion swinging plate, to be drilled and tapped when it is removed.

Then with slight trepidation I started dismantling the left hand end of the gantry assembly. In practise it went quite well. I started by removing the stepper motor and limit switch and associated wiring, then releasing the spring tension on the pinion I was able to unbolt the rest of it and pull it apart.

Having the main bracket plate off allowed me to mount it up on the milling machine, pick up the location of the holes that were being used, and with that as a reference place correctly located ( 40 mm away) holes so all fixings on the HiWin sliders can be used. As the incorrect holes were at 45 mm spacing, inevitably I had to form a slot rather than a hole.

After a quick check that the new holes were in the right place, it was a case of cleaning up a couple of nasty welds and re-making them, a good rub down and a coat of Ford Tractor Blue.

All together quite productive, but I will have to repeat all this on the other side when I've re-assembled what I've done today, but that will have to wait for the paint to dry. Very glad I made up that wooden gantry support - it made the job much easier 

[awemawson]

OK paint dry enough to handle, so I've re-assembled the left hand gantry end.

The T5 timing belt is unbelievably tight even at the slackest adjustment, and is showing signs of fatigue - it's 5/8" wide 5 tooth per inch and every time I count the teeth I get 71 which seems an unusual number to choose. I'll replace it (them) with a 72 or even 73 tooth to get the adjustment in the centre of it's travel.

Then it was a case of 'rinse and repeat' - I've stripped the right hand gantry assembly, relocated the holes, cleaned it up and given it a coat of paint which will hopefully dry overnight.

[awemawson]

It seems that these belts are metric specification 5 mm pitch 16 mm wide with 71 teeth and a "T5-355" which gives the belt length. I've ordered three "T5-365" which have 73 teeth so hopefully will put the adjustment about right.

All three original belts (X, X-Slave and Y) are the same, have the same over tension issue and are showing signs of distress 

[mattinker]

Andrew, 71 teeth for regular wear? If it's not to long, a 73 rather than a 72 tooth.

Just got back, haven't unloaded the saw yet!

All the best, Matthew

[awemawson]

Glad you are safely back Matthew. It seems 73 is the next standard size so that's what I've ordered

[awemawson]

I re-assembled the right hand end of the gantry and tested it - all ok.

As I've gone so far, I'll try and pull off the Y drive and clean it up and give it a coat of paint this afternoon - it's box cover is already done.

Then I need to sort out what's causing the lower bearing for the Z ball screw to tilt at such an alarming angle 

[awemawson]

So fortified by a spot of lunch (Pilchards in mustard sauce on lightly buttered toast - yum  ) I cracked on and started dis-assembling the Y stepper motor mount. This is very integral with the Z slide, so all came off and were dismantled, cleaned, the odd weld splatter ground back, and - you guessed it - yet more Ford Tractor Blue paint.

Hence there is now yet another box of odd shaped bits to re-assemble tomorrow when the paint can be handled. I've decided to leave the peculiar alignment issue with the Z ball screw until I put the Y stepper mount back. There were shims tilting the slide mount, and I think perhaps we've got compensating errors somewhere. I will re-build it as though starting from scratch - it's only a case of getting the torch held reasonably perpendicular and the Z slide also moving perpendicular - how hard can it be  (famous last words  )

There is a 'mini slide' on a short length of HiWin rail that is used to touch down, operate the Z-Down limit, and hence find where the top of the piece being cut is. Dismantling the mount I jolly nearly had the slider off the rails, which I assume would shed ball bearings in every direction The eagle eyed amongst you will notice some brown electrical tape wrapped round it to prevent a repeat performance.

[awemawson]

"Scope Creep" -  uncontrolled changes or continuous growth in a project's scope. This can occur when the scope of a project is not properly defined, documented, or controlled. It is generally considered harmful.


Well it obviously happened on this project - I've just found myself ordering six 6003-2RS bearings - the assembly that holds the  gear wheels that engage with the racks on the machine each have two of these bearings - and at least one set feels notchy. Easy enough to change, silly not to really, but ........... 

[hermetic]

 Scope creep be damned, do it once, do it right, never have to do it again! (at least thats the theory!) Cracking job Andrew, absolutely no point in leaving notchy bearings in a project.

[awemawson]

Well things might just get a bit delayed this morning. I was walking across our field coming back from taking the dogs for an early walk when I spotted one of the Ewes on her own with two large black crows next to her. Getting closer I realised that those 'crows' were black lambs that had just been born 

Now the ewes aren't due to lamb until late March / early April, and this particular Ewe, a Dorset Down, certainly shouldn't be producing black lambs having been tupped by a Hampshire Down which should produce white(ish) lambs. So I reckon that there's been early hanky panky involving the Jacobs ram 

[awemawson]

I managed to get it all back together between sheepy things - sorry only one picture. The Z axis ballscrew lower bearing assembly, that was on a cant was squiffy for several reasons:

a/ The vertical plate that it mounts on was bent where it mounts

b/ The mounting surface of the bearing assembly wasn't at right angles to the axis of the bearing

c/ The (knackered) bearing was squiffed in the bore that it fits.

I reckon that it has had a significant crash at some time, that bent the plate and mangled the bearing (which is a 6000-2RS)

I re-machined the mounting face of the bearing assembly, bent the vertical plate as best as I could with a rubber hammer and much violence, and replaced the bearing. As it happened I had a 6000 bearing (26 mm o/d 10 mm i/d) with metal shields which should be fine.

(NB Ewe and Lambs doing fine. Mum is eating well and offspring are both up and suckling  )

[Pete W.]

Hi there, Andrew,

When I saw the photo of that ewe in your earlier post, I thought to myself 'That ewe's got ATTITUDE'!          

[awemawson]

She's saying 'watch it mate - I'll protect my lambs whatever comes at them' mean while in the back ground I'm trying to stop the dogs eating the afterbirth 

[nrml]

Couldn't you have put the vertical plate in your hydraulic press? It did an outstanding job on the flaps of your flail mower. Yet another amazing rebuild. Thanks for taking us along on the journey.

[awemawson]

I was being lazy and didn't want to dismantle all the gubbins on the plate

[awemawson]

The six 6003-2RS bearings arrived this morning by post. No point in fitting them yet as the belts aren't here yet and it's much the same dismantling to change either.

Belts promised for tomorrow, but as it's Friday the 13th who knows what might happen 

[mattinker]

Andrew,
I wish there was a like button! I follow your posts with pleasure!

All the best, Matthew

[awemawson]

Thanks Matthew, good to have you along 

The new slightly longer belts arrived late this afternoon. I only had time to fit the Y drive.

First I pulled off the T5 pulley and the pinion bearing assembly and rebuilt it with new bearings, then it was just a case of putting it all back together and adjusting the belt tension. Previously the belt had been 'murder tight' even with the adjustment at it's slackest. At least now I can adjust the tension as I want it.

So that's Y done, just X and X-slave to do when time permits

[awemawson]

Having replaced the other sets of bearings and belts it's now time to return the plasma table to the welding shop.

Now it came in quite cheerfully on the fork lift, but someone's added bits and bobs all over the place making it neigh on impossible to get the forks anywhere useful. The welding shop is down one concrete ramp across a yard of coarse road planings and up another concrete ramp, so not feasible just to roll it on it's castors. However there is an 18 inch step between the two ramps - if I could pick up the table on strops with the JCB 803 and gently lower it on the lower side of the step I'd be virtually there 

Now rigging this beast is not straightforward - the only realistic places for strops are the four corner pillars, and because of the electrical enclosure the balance would be wrong - however it has the advantage that the strops would miss the gantry which is a bit delicate 

So, four strops duly fastened, then joined to a fifth linking strop and the JCB advanced into position. Sure enough it's hanging down as expected on the cabinet corner but the gantry is clear. I gingerly drove forwards having raised the boom a bit, and lowered the table onto the top of the welding shop ramp.

At this point the castor on the lower corner decided to collapse  It not only was taking the full table weight but probably a bit of inertia load as I came down. Rubber hammer was applied to get it roughly in line and I managed to roll the table safely into the shop.

Then a quick call to roadside assistance produced my 10 ton railway jack and I was able to replace the castor temporarily with one of the non rotating non locking ones that I'd taken off - I'll have to try and source a proper one when the dust settles.

Rebuilding the PC, the PC monitor table and Hypertherm cutter along with the swinging gallows bracket, all of which I'd removed for the journey, put it back in a state that I could test for any damage. I'm pleased to say it all still seems to work.

I just need to cut a 12" diameter hole in the workshop wall, and I can then test it in earnest actually cutting 

This of course has released my 'project space' for more fun and games