Messages

271

General Mach Discussion / Re: corners getting radiused at higher speed on plasma table

« on: February 01, 2012, 09:01:52 PM »

rrc1962 - a peace offering 

No biggie.  I'm kind of in the "build the machine to suit the need" camp rather than the "build the machine and then figure out how to make it work" camp.  We pretty much agree.  The best solution is acceleration...which is a bit confusing.  With 960oz/in motors and a 50 pound gantry, his machine should be able to run some very high acceleration numbers.  Up until this post, I hadn't noticed where he posted his accel numbers.

272

General Mach Discussion / Re: corners getting radiused at higher speed on plasma table

« on: January 29, 2012, 01:43:11 PM »

Short of rebuilding the machine so you can achieve triple digit acceleration, the CV setting are the next best thing.

Which is more or less what I said.

[/quote]

Actually, you equated using the CV setting as "hitting the proverbial CV nut with a sledge hammer."

My point was that if you don't have to power to accelerate and decelerate the load at an acceptable rate, you either use the CV settings (which is a workaround to the real issue) or you rebuild your drive system to achieve the speed and acceleration you need.

273

General Mach Discussion / Re: corners getting radiused at higher speed on plasma table

« on: January 29, 2012, 01:18:07 PM »

When you have a gantry weighing a few hundred pounds traveling at 300IMP, it takes a lot to slow it down.

300 ipm you think that's fast?

It is when you have a gantry weighing a few hundred pounds and you built the machine using NEMA 23 motors, which is VERY common.

274

General Mach Discussion / Re: corners getting radiused at higher speed on plasma table

« on: January 29, 2012, 12:16:36 PM »

Although we try not to use any of the CV crutches, when running at 250IPM+, they work better than exact stop.  Running a plasma in exact stop at those speeds just causes the machine to shake.  The "proper" fix would be to (1) increase acceleration until the problem goes away or (2) slow the job way down. 

Option 1 isn't possible in most cases as it would take accelerations that the machine is not capable of.  Most plasma machines (even the high end industrial machines) are not build for speed and acceleration.  When you have a gantry weighing a few hundred pounds traveling at 300IMP, it takes a lot to slow it down.  Short of rebuilding the machine so you can achieve triple digit acceleration, the CV setting are the next best thing.

275

General Mach Discussion / Re: corners getting radiused at higher speed on plasma table

« on: January 29, 2012, 10:53:53 AM »

You can either turn on "stop CV on angles" and enter 89 degrees....or turn on "CV distance" and set it to something like .01".  I agree in that if you're not getting rounding on outside contours, your CAM is probably rolling the tool around the corner.  What CAM are you using?  Post some code of a square with an outside offset.  

276

General Mach Discussion / Re: Mach3 Web Site

« on: January 22, 2012, 06:39:23 PM »

Downloads lock up Firefox.  That's been happening since as long as I can remember and on numerous PC's.  Downloads through IE work fine.

277

General Mach Discussion / Re: Configuring Mach3 For Plasma

« on: January 21, 2012, 10:02:17 PM »

When you can buy a new 60A plasma for $450, you know you're not getting much.  I wouldn't spend a whole lot of time...or especially money...trying to make it work.  You'd be better off with a older used TD or Hypertherm.

278

General Mach Discussion / Re: Configuring Mach3 For Plasma

« on: January 21, 2012, 07:36:32 PM »

Ok I have the machine working now, having configured it like tripleblack suggested. Thank you very much for that. Next bridge to cross is that as soon as the plasma fires it causes a e-stop. Even when I don't command the G540 to fire the plasma it sets it off when I turn on the torch manually. My plasma cutter does have HF start and I have tried shielding my cables as best possible. Any suggestions?

That's most likely because the Chinese plasma you're using (1) has HF arc start and (2) emits tons a HF noise.  As soon as the torch fires, the surge of HF noise on the system causes the eStop.  Increasing debounce may or may not help.  We tried setting up one of those machines and went all the way to 10000 on debounce with no luck.  Turned out that even just running the plasma 50 feet away by hand and not even attached to the CNC table would still trigger an eStop on the table.

I've heard of some people using these machines with some degree of success.  The first thing you want to do is make sure your grounding in by the book.  Shielded cables grounded properly and everything, even the PC,  grounded through a ground rod driven as deep into the ground as you can get it.

If you turn off ALL inputs (IE: limits, home and estop) it may work.  It didn't in our case as even on a properly grounded system, there was enough HF noise to interfere with the motor signals.

279

General Mach Discussion / Re: GANTRY RACKING

« on: January 17, 2012, 11:55:52 PM »

You could connect the two screws mechanically and run a single motor.  Any time you run two motors slaved, you stand the chance of the two going out of sync.

280

General Mach Discussion / Re: Anybody within driving distance of East, TN area want to have a Mach meet up?

« on: January 15, 2012, 10:21:53 PM »

I'm in Nashville, but I can barely get away for lunch, never mind a trip all the way to Knoxville.