Plasma cutter, automation project

[jimgerken]

Not exactly a tractor project, but I am hoping this will allow me to build better attachments. In fact, I put the snowblower on hold a few weeks ago, in anticipation of cranking out some cool parts for it with this NC plasma table. The attachment shows a closeup of the 9"x9" truck which will haul the torch handle across the metal (X axis). The truck rides on a gantry which moves fore and aft (for Y axis). The computer will also turn on and off the plasma cutter, so multiple sets of non-connected lines can be cut at once. For instance, think of a complicated shaped sideplate for the snowblower, with a 15" diameter shape blending to a flat, then angling upward and forward, turning down to a small radius, then backwards to the start of the 15 inch diameter again, then it needs a bearing thru-hole and three slotted bolt holes for the hangar right in the middle. All this from 3/16" flat in about a minute to 0.025" accuracy. Plus, both right and left identical. And the uses list keeps growing.

 

[Anonymous Poster]

Yep a very handy gadget. I used to work for a company that made comforter quilting machines. they had a 12'X12' flat bed with a precision jackscrew driven split sewing head on dual liniear bearings. A massive beast. we had to align them to within about .020 of perfect. I saw the potential for a cutting rig like you have. would just to have had to mount a plasma cutter instead of a sewing head. just feed the cad drawing into the pc and like magic it cuts the part. Expensive though those machines cost about 75K.

 

[Anonymous Poster]

try this site. http://www.plasmacam.com/

 

[jimgerken]

Yes, I saw that. A quick call revealed the price tag at $8900, without PC, without plasma cutter. Mine will complete for less than $400 plus labor, plus old PC, plus my plasma cutter. I will have about five weekends of time into it, I believe at this point. My software will be the big difference. Plasmacam's sounds quite advanced, with text and a lot of automation in the image preparation. Mine will be based on DANCAD3D and DANCAM/DANPLOT. I cannot say yet how fancy it will get with scanned images, etc. At least, the DANCAM will send a set of 2D lines created by DANCAD3D to the cutter and produce a part of the proper size. A few details: my system minimum step equals 0.006", max speed looks to be around 6 inches per second, which should suffice for the thinnest materials, working cutting area is designed at 4 feet square but could be expanded if desired,

 

[brantley]

Definitely post more pics as you make progress. I do not have a workshop built yet, but when that happens one of my dream projects is to build a CNC table for my plasma cutter.
I do have a few questions. What size steppers are you using? Are you building your own driver for the stepper or using something already built? What brand of plasma cutter do you have?

 

[jimgerken]

The steppers are 75 oz/inch NEMA 23 units. The driver is a Brewington tech Chopper 7026, 3 amps per motor per phase, and I am using a 32 volt input. The chopper driver keeps the current limited to a user-selected max while pumping the voltage way up for speed and torque. The motors are 6 volt inputs, 1.2 amps per phase. Plasma is the ThermoDynamics Cutmaster 38 with Itorch. I wish I had a machine torch for the NC table.

 

[Gfranklin]

I like it. I guess it's in gettin the rails dead parallel and then permitting some type of bearing bolt position adjustment? Is a machine torch a CNC mounted oxy/accetelyne torch? I saw one of these gas torches do the stainless steel mounts for my scoot's highway pegs. For days I envisioned all the things I could make with that. This is doing it again. Keep us posted and pictured.

Greg

 

[jimgerken]

Greg, a machine torch is a plasma torch built straight and without a trigger, intended to be used by a robotic arm. There is no trigger since there is no operator. The machine torches are compact and easy to adapt, compared to the big ergonomic operator torch I have.
Here is a recent photo, I'm about two weeks from cutting metal with it now.

 

[Anonymous Poster]

Interesting project!

Can't understand how I missed this thread previously...keep those updates and photos coming!

Bill in Pgh, PA

 

[jimgerken]

Here's a shot of the power transformer, driver card, one of the two cooling fans. I call this collection the "Power Chassis", and its all mounted on that black tray made of a couple pcs of angle iron and a strip of 1/8 by 6 flat iron. An aluminum enclosure goes over it all, with another fan in it.

 

[jimgerken]

Here's a shot of the completed Power Chassis, with enclosure on, and almost mounted to the cutting table frame. It needs to be close because of all the motor and switch wiring . The end you see has an orange-colored Fram automotive air filter shaped into a curve to make it fit, as a cooling air inlet filter to try to keep the electronics cleaner in this somewhat harsh environment.

 

[JRP]

We want to see more! How about a bill of material?

How much do plans cost?

How much is the software?

Jim

 

[jimgerken]

No plans, so far.
Bill of materials would take a while to put together, maybe once its done and I get more time.
Software is a Beta test copy of Dancad/Dancam, free to download, tough to use so far.
I now have a four foot square plotter, almost working well. What it won't do right now is tolerate the plamsa cutter firing up without loosing position wildly. I need some shielding or filtration somewhere, and I have a few software problems to overcome yet. Will spent more time this weekend to get to the bottom of it.

 

[motelman]

When I went to school for robotics, we had set up a plasma cutter with an older robot. The first time we fired the plasma cutters torch, we had a run-away, kind of exciting and scary if your standing by it. You will need to have all I/O relay isolated between the PC and the cutter, and very good ground. That should solve the run-away problems. BTW we toasted a couple boards from the robot from the feedback when someone removed the ground wire.

 

[hazmat]

<font color=blue>I need some shielding or filtration somewhere</font color=blue>

Start with shielding all signal carrying wires. Hopefully you can avoid the filtering.

Believe it or not, aluminum foil wrapped around the wires will do wonders. A little more elegant is some copper tape wrapped around the cable. You can also get knit copper shields to run your cables thru.

If you need a source for the shielding, let me know.

 

[JRP]

Shielding:

You can also use flex conduit. It will also protect the wires.

An oscilloscope will help you find the noise.

Jim

 

[JimMc]

The noise will be very easy to find. Just look any where near the hi freq lead to the head and resonating from the workpiece. /w3tcompact/icons/smile.gif Seriously, use sheilded cable for all control circuits and ground them all. The braided style should suffice for your project. In all our CNC systems, the cabling is considered a consumable and is replaced at either 1 or 2 year intervals. Depending on your run time you should get a lot longer life. But beware, all that flexing does not bode for a long lifespan, especially on cheap cabling. Once you start to have open circuits or inconsistencies, dump the control wiring and replace it. It'll save you a lot of headaches.

Looks like a fun project, enjoy it!!

 

[jimgerken]

Thanks to everyone for the input/ideas/encouragement. I have not had any time to explore the plasma interference problem yet, but I did download a fresh copy of Dancad/Danplot Sunday and succeeded in getting it roughly installed and configed last nite. The new copy seems to be working better, all functions work now (cut speed defined by line color config chart was not working...). Three times while doing motor speed tests last nite I had a new error concerning a limit switch being open, which it was not. So perhaps I have a limit circuit problem which the continuity tests did not identify. Will explore more tonite...

 

[JRP]

I have lots of Tektronix oscilloscopes for $70 if you need one to look for the noise. It would also help with stepper tuning.

jrpoux@wcnet.net

 

[jimgerken]

Wow that's a great price on a Tek scope. thanks but I already have an old one if it comes to that. So far, my experiments have shown that I can disconnect all inputs to the driver board (limits and homes), and disconnect Y and Z axis motor leads, running only the X axis motor, and it still is upset by the plasma. So I am going to get some shielded cable this week. Otherwise, the new software sure works well. I figured out pretty much everything I need, including how to make a repeating pattern in case you want multiples of something. To do this it is as simple as putting in how many and which axis to propgate them in. Right now all the machine does is draw on paper, but that is enough to learn the software, and probably a good idea not to be burning out metal 'til I know the process real well anyway. Thanks again guys, will hopefully have more news in a week.