[sparkness]

Hello all, here I go with my build
2.5 x 4 plasma table (32" x 50" actual travel)


Small footprint, rigid, light gantry for speed, accurate
Gantry steel frame not welded together but supported by a welded steel frame
Axis are linear guideways, X hiwin 15mm and Y thk 15mm
Ballscrews 10mm lead for X and Y

Plasma torch: Hypertherm powermax 45
Electronics: geckodrives, stepper motors, mach3

Here are the drawings of the x and y axis, the X is mounting to 2 x 5 x 3/16 rectangle tube,

[sparkness]

Squaring up the steel,had to take .085 to square the ends up, not square at all from the steel supply. Checking for flatness a little high in the middle .010" so I'm removing some metal. the rectangle tubes are 60" long

[sparkness]

Drilled, taped and machined steel tube for linear rails and ball screws. I clamped the straight edge to the linear rail then adjusted the rail up and down till I got it parallel with the top of the steel tube

[sparkness]

The back side of the rectangle tubes is where the welded seam is and needs to be made parallel and flat

[sparkness]

Main frame almost completed, a few mistakes,did not zero the DRO properly. Welded-up mis-drilled holes, Re-milled and drilled, Repaired and back on track



I milled both frame connecting tubes at the same time so that the X axis will be parallel when bolted together. I will make a tool to check and indicate deviation



A little primer and sanding, still not perfectly flat but getting better

[sparkness]

supporting frame welded and primed and ready for paint

[sparkness]

Here is my control and PC in the same enclosure, I made my own break out board, 5 opto-isolated inputs 4 step-direction outs, 2 relay outs, 1 opto-isolated output, 2 built in 5v isolated power supplies, and charge pump safety circuit, THC from http://www.candcnc.com. I still need to add a 4th motor drive (slave for x axis and power supply the PC is an older 32bit 2Ghz AMD single core 500 Meg ram, ext video card, no network, no sound, no cd-rom, clean install of windows XP with 90% of the services disabled, runs mach3 at 100Khz perfectly - but I only need 35Khz for my lead and motor combo which is 10mm lead and gecko 400 lb/in motors (lin Engineering 5718L made in USA) so this will give me theoretically 413 IPM provided the gantry light enough and friction is reasonable, maybe more Ill test to get max rapids with no missed steps.



Breakout board schematic

[sparkness]

supporting frame painted, X-Y frame painted, I used Acrylic Urethane automotive paint, ready for assembly. Bolted all together. The Y direction seems a bit flimsy, it feels like I will need to add a diagonal support



I used extra thick and high strength washers and bolts it only added a little the to total cost









Did a final sanding where the linear rail mounts using a 1/2" block


Mounted Linear Rail, Motor and Ballscrew

[sparkness]

here is the X axis Home /limit switches installed



here is the microswitch cover



and here is the Ball Nut mount ready to attach to the X axis side plate

[Nacs Fab]

Could you give us your source for home switches and their covers? Great build! Thanks!

[ajclay]

Sparkness, you've got a nice build that's for sure... Going a little deeper than most with the details..

I can't help thinking about the ball screws.. I mentioned this on another post, but most didn't give it a second thought..

Ball screws will not tollorate any plamsa dust. A guy just can't wipe them enough to keep off the dust. Mine locked up in a couple of hours of operation.

By hook or crook..... you will have to cover them sooner or later, or install some kind of serious wipers.

Just a "heads up".. That dust is a killer for a lot of things...

aj

[sparkness]

Ball screws are mounted on the outside of the plasma table and I will install an aluminum angle on the frame and the gantry to help keep dust out. Well see what happens. As far as the covers for the micro switches I used potting cases from http://www.polycase.com/ cost was about a $1.00 each

[sparkness]

I opted to use ball screws because of the cost and simplicity, the 3 ballscrews,nuts and supports cost $438 delivered with ends machined, if I used gear rack I would have had to drill and counter bore x number of holes and make a reduction belt drive mechanism for a little less money, but more time,thought and labor.And as we Know the first design gets built then scraped for the third unbelievable great design which still needs a little tweaking!

[sparkness]

I'm building my own table for the enjoyment and knowledge gained. Hopefully it will work well with out too many bugs.

[johndjmix]

VERY VERY clean table!

[ajclay]

I'm building my own table for the enjoyment and knowledge gained. Hopefully it will work well with out too many bugs.

Sparkness......... If you were only in my town... I would of liked to help you with that table. Taking the easy way as you mentioned isn't the best way to learn. It's the journey and time spent that makes you more "worldly" if I can call it that. That's what gets you another step up on the ladder over the other guy....

I would learn from helping on the project. That seems the only way I learn and make head way is to have a project. No one wants to pay their dues to learn.

This world we live in makes us that way for the most part....

Don't rush through it just to see it cut. That's what 99% of the projects on here turn out to be for one reason or another.....

I drilled and taped holes for weeks.... not days on my project.

aj

[sparkness]

I'm not rushing at all, slow and steady.

[pimpbike]

I've seen people use ballscrews before for plasma tables but the pitch on the screws they used were coarse. I'm wondering if you'll encounter issues with those finer pitch screws. When you need to move very fast cutting light gauge metals, you'll need to spin those screws at a higher RPM. Hopefully you won't encounter any whip. Plasma cutting is a dirty process even with a water table so you'll need to keep an eye on the screws for dust build up. Maybe making some bellows covers to protect them might be a good idea.

[sparkness]

Im using 10mm lead so at 1000 rpm I will get 393 ipm and Im right near the critical speed for 16mm diameter screw

[pimpbike]

I might be wrong but I don't think you'll be able to spin those steppers at 1k under load and not lose steps but I guess we'll see. I don't know the specs of your motors but my similar sized motors on a R&P setup with a 3:1 reduction I can't get close to 1000 rpm out of them without it losing steps.