Low cost plasma table - do-able for $500 - $1K?

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Hey Guys

Have lurked here many times over the years. Finally decided to register & post. Sorry for the long post, but the more info I can provide, the better my chances of getting accurate answers.

Anyway, like almost everyone else here, I'd like to build a plasma table.

My needs however are different to a lot of others. I have a plasma cutter which I usually use to cut structural steel. Hand cutting is adequate for this purpose. But I also use it for hobby/prototype work where accuracy & appearance is desired. Not .01mm accuracy, but just neat looking, consistent cuts - which I just can't do by hand.

So I plan to design & build a suitable table - one I can assemble & disassemble when needed. As I am not in the business of cutting steel, I never work with full size sheets, so I see no need for a large table - 1200 x 1200 (4'x4') or thereabouts will be plenty big enough. The design however, will be easily adapted to a larger table.

Having spent many weeks reading posts on this & other forums, I have got some understanding of the CNC process and many ideas, but I still have many questions.......

The main question however is cost. Am I dreaming to think I could make a working one for about $500?? (plus software if necessary)

Keep in mind:

I already have a plasma cutter.
I have enough steel to make the table & gantry.
I have a PC/screen, a metal enclosure, other misc items.

Regarding software, I have a CAD program. I need to find a free CAM software but if I can't, I'll buy SheetCAM. I'm happy to try EMC2 for the control software but will buy Mach2/3 if needed.

My main costs will be the stepper motors, drivers, power supply, & the drive system.

I have mig/tig welders as well as metal bandsaw/chopsaw, pedestal drill, mag drill, bench & hand grinders & many other misc tools. No milling machine or lathe, so will design the build to not require the use of these. I have gained some electronics experience over the years - hopefully enough to wire everything up & get it working.

I am a big fan of the KISS system. The table will mostly be built from SHS (square hollow section) & RHS (rectangular hollow section) tube of different sizes & flat plate that I already have laying around. I don't need large heavy sections. I can/will put braces in as needed to make it solid enough not to move or vibrate but light enough to assemble/disassemble as needed.

I plan on using bearings (skate bearings) running on RHS . The bearings are cheap - 50c ea, easily available & replaceable if need be. I have built a small prototype and it works well. Everything is easily adjustable with no play anywhere. It rolls along effortlessly. The design is simple and adaptable to tube of different dimensions. I envisage the gantry weighing no more than 15 - 20Kg. (less than 40Lbs)

For the drive system, I will use chain. Again, cheap, easily available & replaceable if need be. Tensioned correctly they should have little/no play & be as accurate as I need. Anyone can get enough chain for free if you know where to look & I will only need to buy the sprockets when I work the gearing out.

As the gantry will be light, I'm hoping to get away with smaller motors. I don't need a lot of speed or torque. Most of my cutting is 6mm or thinner mild steel. I also plan on using 2 motors for the main axis - one per side, wired to work together. Reason for this is lower costs & simplicity. Shafts & pillow blocks add $$ and require more work to assemble/disassemble every time.

I do plan on having a z axis. Initially I may try ball transfer units to keep the torch to metal distance correct but I'd like the option to incorporate DTHC. I'll probably drive this directly using threaded rod instead of chain to simplify things.


In regards to motors/drivers, will something like this work?

I chose the 4 axis one because of the 2 motors & drivers I need for the main axis. Is that correct, or do you use the one driver for both motors?

If there is enough interest, I will document the build with pics & cad drawings where necessary.

If you have read this far, I would love some feedback & advice, especially from those who have built their own CNC table.

[rk396]

$500 might be a bit low. I built a table (4x4) about a year ago, for $700-$800. And that was with already having the plasma cutter, steel, and PC (like you). Your design sounds very similar to what i built (Skate bearings).

I just switched to EMC2 and like it very much, so i would recommend that. Sheetcam is very good as well.


Good luck.

[jlnading]

I built my machine, spent more than I would have liked, but it's very strong, can route and plasma cut. I did save money casting and machining all of the Y and Z axes parts. I bought all the electronics and stepper motors, Mach 3 was also included from http://www.candcnc.com/ . Bought belt reduction from CNC Parts Kit , very pleased with both, give them a look, also see my pictures, Jeff.

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Originally Posted by rk396 $500 might be a bit low. I built a table (4x4) about a year ago, for $700-$800. And that was with already having the plasma cutter, steel, and PC (like you). Your design sounds very similar to what i built (Skate bearings). I just switched to EMC2 and like it very much, so i would recommend that. Sheetcam is very good as well. Good luck.

$700-$800 is very good. A few Q's...

Did that cost include SheetCAM?
What size steppers?
What sort of driver boards?


I'd love to see some pics if possible.

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Originally Posted by jlnading I built my machine, spent more than I would have liked, but it's very strong, can route and plasma cut. I did save money casting and machining all of the Y and Z axes parts. I bought all the electronics and stepper motors, Mach 3 was also included from http://www.candcnc.com/ . Bought belt reduction from CNC Parts Kit , very pleased with both, give them a look, also see my pictures, Jeff.

Jeff, thanx for the pics. Table looks great. What size is it? What was your approx cost? (if you don't mind me asking) What size steppers & drivers?

[jlnading]

Originally Posted by start here Jeff, thanx for the pics. Table looks great. What size is it? What was your approx cost? (if you don't mind me asking) What size steppers & drivers?

The table is 5' x 5' to cut a 4' x 4' piece of plate steel, the cost was right at $5000.00 for the table, already had the plasma cutter, built the frame and the grid, 2007 was when I bought the electronics and steppers, the complete kit was $3000.00, price of the kit has come down considerably from http://www.candcnc.com/, the belt reduction, all three I bought from CNC Parts Kit when I could have built them, the gantry as you see in the picture [I bought] is 80/20 extruded aluminum, I made the side slides for it, I had all the bearings, so the belt reduction and the 80/20 extrusion was right at $1000.00. The steppers are 720 oz three of them the z stepper is 480 oz, the electronics use four gecko 203v drivers, very good system. All other parts I either made or bought for another $1000.00, so I think I could have saved $2000 to $3000 if I had of had the time, and know what I know now, it was a complete learning experience for me, well have fun ,thanks Jeff.

[Down&Dirty]

It is definitly possible. My last table was 2'x3'. I kept it small so it wouldn't take up a lot of shop space. I think it was about $400 with all the drives and steel. The one I am building now is a 4x5 and is going to cost a little more. For the X axis I am using CRS in the 3/8"x2" variety. This allows me to make things adjustable. The Y is 2x2 box, and the Z I am springing for linear rails. I was going to use chain but found that timing belts will cost me less and won't require the work of a chain.

I am not sure I would try and build something 4x4 that I would be taking apart. You could easily build a 2x2 that was portable and sat on the metal to be cut. Then nothing has to be taken apart to be put out of the way. You would be limited to a 2x2 part, but with the right positioning you could just move the machine and keep cutting.

[jcc3inc]

Sir,

If you will email me with your address, I will send you a CD with 15 + pictures of the 32" x 36" test bed machine I made for trying out my CNC controller. I use the machine for routing so it could also be used for plasma cutting. Max speed is 250 IPM; it was designed to be made with easily available parts as you will see. I'd post the pix here but there is a limit of (3), I believe.

Email jccinc-at-owc-dot-net

Regards
Jack C.

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Down&Dirty - That is great to hear. The more research I do, the more I realise it's possible. I'm not sure what CRS is. Cold Rolled Steel? Circular Rolled Section? It would be great if you could provide a pic or 2 & some info on stepper size and driver board make.

I have been thinking about it and realise that by spending a little more I can end up with something bigger/stronger/better? but I'm not sure I need to....

I found a seller selling toothed belt for $10/meter and gears for about the same price. It's not a large chunk of money but chain & cogs should be considerably less.
Here is a table YouTube - cnc plasma $650 for driberif85 and cnczone good luck built using chain that appears to be a very simple design, yet cutting well. In all the research I have done so far, correctly tensioned chain will have no backlash and be accurate to better than .01mm. So I'm thinking why use belts?

When I said a table I can take apart, I think just being able to remove the gantry from the main table shouldn't be too hard to do. Then maybe remove the legs (or fold them up) and stand the table on it's side. But if it proves to be too hard, then I won't bother with it and just build a permanent one.

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jcc3inc - thank you for the kind offer, I'd love to see them. But rather than spending time & money sending the CD all the way to Australia, why not register an account with Photobucket? Upload the pics there, then link to them from your post. That way you will help any other people reading this thread who may be interested in seeing your machine.

[rk396]

Originally Posted by start here $700-$800 is very good. A few Q's... Did that cost include SheetCAM? What size steppers? What sort of driver boards? I'd love to see some pics if possible.

I did not figure the cost of sheet cam in the build cost. I was just starting out, so the demo version was good enough to get me going. I've recently purchased a copy of it.

The steppers i used where Nema23 ~380 oz-in. With a 36V power supply, and a G540 Drive. (All from Kelling). This has been a great combo, and I've now retrofitted some older CNC equipment with this same combo.

I used belts to drive all the axis, which was a cheap way to go. Mcmaster Carr was the source for this.

I'll see if i can scrounge up some pics to post.