[grahamcowan]

I got the quote back from a local sheet metal fabrication shop and they want $550 for some 26ga sheet metal, sheared to length and broken into a box. They didn't even have a piece wide enough so I was going to have to seam weld two box halves together anyways.

Crap.

Back to the drawing board. Or at least the scrap yard...

[grahamcowan]

...you must cater to her every whim.

Well not exactly, but the wife (CFO) certainly enjoyed seeing these.

[grahamcowan]

I was sorting through all the pictures I took of my table build process and found a few you all might like to see.

The first picture should give you a better idea of how massive the 80/20 #2040 X-axis gantry is. In fact, 80/20 actually designed their extrusions to have the internal cavities pressurized, if your application requires it.

The second picture shows how much work I had to do to get the Z axis just right. I had to lay out those tiny #6-32 screws to such a tight tolerance that I was afraid I would have to weld the hole closed and start over if I screwed up. Those miniature linear rails are made from hardened steel -- not aluminum like the other rails. I know; I tried to drill one out to have some wiggle room on the alignment. Didn't happen.

The third picture shows an up-close view of the torch holder. If I had to do it again, I'd probably redesign this. There are three tiny allen set screws that hold the torch in place, but when you tighten them up, you are just screwing them down into the torch cup itself, and it isn't very solid -- fiberglass, at best. A better design would be a clamping system with a hinge in the back and one screw in front.

The fourth picture gives you a better idea of my Y-axis drive system. Yeah, I know, give me the lecture and flak about using driveshafts. They wobble at high speeds. I know. I'm pretty much limited to about 120in/min before either the wobble is so bad that the torch wiggles or my stepper motors stall. Eh, I don't care.

The fifth picture is a closeup of the drive system on the X-axis carriage. I love stainless, but man it stays hot long after you've finished welding it. I think I burned my fingers 3 or 4 times on this one bracket before I was done with it.

Before you ask, yes there is slop in the drive nuts when the shafts change direction. I think the nuts travel maybe, at most, about 1/64" or less. On a 1/2"-8 shaft and 200 steps per revolution on the motor, I'm not worried in the least. Maybe if I was cutting very precise parts I would be, but if I demanded that kind of precision I would be using a laser.

Speaking of lasers... my friend has a 150W CO2 laser that's not being used. Maybe that will be an upgrade for my table. =)

Let me know if I can help with any questions or build problems. I'll do my best.

[grahamcowan]

This will probably be my last post unless anyone has questions.

Here's the cost breakdown of the table:

Not counting the plasma cutter, I spent $3,722.27 on parts. That includes everything bolted, welded, drilled, etc.

If you include the plasma cutter, the total is $5,700.79.

I didn't count the cost of the computer because I had one lying around begging to be put to good use. The software isn't counted, well, because 100% of it is free. Ubuntu, EMC, GCam, QCad, XFig, etc. It was all free. Gotta love open source!

There were some incidentals thrown into the budget as well. I bought 10lbs each size 1/16", 3/32" and 1/8" ER70s6 mild steel TIG wire and a magnetic TIG torch holder from WeldingDepot.com.

There were 33 orders for parts with 11 of them being from McMaster-Carr.

The most expensive order was the 4 linear rails.

The cheapest was 4 stepper motor driver current set resistors.

As I said before, 650+ holes drilled, 240+ holes tapped with everything from 1/2"-13 to #4-40, and countless welds.

When I disassemble the entire table when we move I will finish welding the 2" steel tubing together.

Other than that, it cuts great and the software is nice and intuitive for someone like me that doesn't like idiot-proof solutions.

Anyone in this forum that has built their own CNC table, pat yourself on the back. It's a helluva lot of work, but the end result is worth more than anyone could imagine.

Have a good one!

[ej4]

Fantastic build info. I've been browsing for a couple months here for ideas, and I have to say this is one of the simplest, cleanest designs I've seen yet. Very straightforward.

A couple simple questions, if I may -

...so I welded them in pairs. I took B-Line unistrut 4-hole splice places and 4-hole T's and welded them together, then welded them to the ends of the cross braces. After tacking them up and making sure both pairs of braces were the same length, I cut them apart.

Can you explain this a little further? I think I understand what you wrote, but I'm not seeing how this guarantees four equal braces.

Also, what are the specs on your linear rails? It's probably a common part, but I'm not finding the rail+truck sets on mcmaster or ebay; I must be looking in the wrong place...

Thanks-
Ed

[grahamcowan]

From my previous post: ...so I welded them in pairs. I took B-Line unistrut 4-hole splice places and 4-hole T's and welded them together, then welded them to the ends of the cross braces. After tacking them up and making sure both pairs of braces were the same length, I cut them apart.

Can you explain this a little further? I think I understand what you wrote, but I'm not seeing how this guarantees four equal braces.

What I did was for each pair of braces (one pair is the upper and lower brace of one end of the table) I took a 4-hole B-Line unistrut T and a 4-hole B-Line unistrut straight splice plate and welded them end-to-end. So I ended up with a bolt plate that had 3 holes across the top and 5 holes down the middle. I clamped it to my weld table and stood the braces up one at a time and tacked them to the new bolt plate.

Easily put, all I did was cut one hole from the 4-hole straight splice plate and weld it to the end of the 4-hole T. That way the new bolt plates that are on the end of the braces each have a bolt hole on opposite sides of the tubing.

After I tacked the braces to the new plates, I made sure that they were all exactly the same length from the outer edges of the plates to the same on the other end (when I say exactly, I mean as exact as a tape measure can muster) and then I finish welded them. Then I cut the plates apart to have 4 braces - 2 with a single bolt on opposite sides and 2 with a single bolt on three sides. The fourth picture in this post (http://www.cnczone.com/forums/showpo...86&postcount=3) shows the final product. Maybe I got lucky in the assembly, who knows, but after I bolted them together on the table, they put the Y-axis rails within 1/32". Not bad for eyeballing.

Also, what are the specs on your linear rails? It's probably a common part, but I'm not finding the rail+truck sets on mcmaster or ebay; I must be looking in the wrong place...

My linear rails are metric. The blocks are about 2" x 2", and the rails are pretty much 55" long. I don't even think they have a part number or brand. Definitely not NHK. I searched and searched all over the place online and ended up on eBay -- these were the cheapest rails I could find (I just now searched eBay again and couldn't find them) so I pretty much designed my whole table around them. I tried emailing past auction winners to see if they got a good deal but I got no replies back, so I just went for it. They were $150 each, which included 2 blocks each. I had to scrounge to find 32 M6 screws to use in them, too.

McMaster is way too expensive to get rails from. They offer brand new, high-dollar rails that are excellent if you can afford them, but really aren't worth it. Keep searching eBay. It took me almost a month to find and decide on mine.

[ej4]

Thanks - I get it now.

-ed

[grahamcowan]

Quick update on my table.

Since I was having issues with my workflow (i.e. getting something from my head to the computer and then to the table) I decided that a Wacom USB graphics tablet would help out.

And indeed it did. I now will be using Inkscape (free!) with my 6x8 Wacom tablet, which is 100% supported by Ubuntu 6.06. It works right out of the box and I can pretty much draw or trace anything I want to. I kept the old assortment of converters, CAM programs, and gcode utilities just in case, but otherwise I'll be using the tablet.

Thought I'd share.

P.S. I did have to recompile GTK with --with-xinput=xfree to have GIMP and Inkscape be able to use the pressure sensitivity on the tablet.

[FPV_GTp]

Very nice build

cheers

[Industrial Dog]

Very nice build! I have completed a table with the same idea of making it a muti-use. It's not anywhere as neat as yours. I've got it running the router right now.

I'm working on the plasma portion of my build and I didn't see any noise filtering on your system. Did you install a choke on your torch trigger?

[grahamcowan]

Very nice build! I have completed a table with the same idea of making it a muti-use. It's not anywhere as neat as yours. I've got it running the router right now.

I'm working on the plasma portion of my build and I didn't see any noise filtering on your system. Did you install a choke on your torch trigger?

What kind of noise filtering are you referring to?

My torch gets turned on only by shorting the trigger contacts together via relay on my PMDX mainboard.

[Industrial Dog]

I'm referring to ferrite clamp on or dough nut type beads that act as a resistor to RFI entering your system from the plasma start arc through your trigger switch wiring.

I was looking at using the same system of a relay to trigger my torch.

[grahamcowan]

I'm referring to ferrite clamp on or dough nut type beads that act as a resistor to RFI entering your system from the plasma start arc through your trigger switch wiring.

I was looking at using the same system of a relay to trigger my torch.

Never really thought of it. On the other hand, I've not had a problem yet. If I do, I am sure I will research the RFI problem and look for solutions.

[rumblfmp]

Cool,

although I am not to sure how a plasma torch can be cool :-)
Love the way you documented this project with the photos and all, gives me some nice ideas for my next project.

Thanks,

Rob

[grahamcowan]

Thought I'd give an update.

I've built a ventilation system underneath my plasma table to draw off the smoke. Works pretty well. I have it vented to a louver in a window nearby. I am using a 12" blower from Northern Tool and it works VERY well.

Also, as a trial, I swapped out one of the drive rods. I had originally installed 1/2"-8 Acme threaded rods for the drive system. Eight revolutions = 1 inch. I bought a 1/2"-8 rod, but this new one has 8 starts. One revolution = 1 inch.

I can now achieve cutting speeds of 720ipm.

[RichInSpirit]

Hi grahamcowan !

Brilliant thread and most inspirational ! It's putting bad ideas in my head !

[Mick40]

Have you had any problems using screws?