Plasma cutter, automation project

jimgerken · Dec 31, 2002

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 · Jan 5, 2003

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

How much do plans cost?

How much is the software?

Jim

jimgerken · Jan 7, 2003

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 · Jan 7, 2003

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 · Jan 7, 2003

<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 · Jan 8, 2003

Shielding:

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

An oscilloscope will help you find the noise.

Jim

JimMc · Jan 8, 2003

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 · Jan 9, 2003

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 · Jan 10, 2003

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 · Jan 12, 2003

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.