Electric noise from torch

[Johnajablonski@aol.com]

I have mounted a plasma torch on my shopbot and it crashes quite often. It will usually make a single cut, but if it is a series of cuts with connect at Z pull-ups, it will freak out. I called Tech support and they said it was electric-noise. I noticed the cables which are provided are not shielded. Does anyone have experience with this phenomina ?

[peter k]

what is the make and model of plasma machine that you are using? if it uses high frequency to start the arc then it is not suited for use on ANY cnc equipment . i have been cutting for 3 years now with no noise problems.

[Johnajablonski@aol.com]

I have a Themo Dynamics Pac-25. It is a light duty, max1/4 inch cut. I like it very much because of it's clean cut and very narrow kerf. It operates at 20amp max. It does not seem to have a problem at a start but on pull-ups on the Z axis, which also is the closest axis to the torch.

[Dave Provoncha]

You guys may want to look at plasma cam's web site to see what they recommend... high frequency is a real problem

[blast@softcom.net]

We're just getting started with our SB . It's hooked to an ESAAB plasma cutter. None of us has formal training on programming. When we ran S_prbsbp.sbp it didn't stop when it went past the end of the part and lost contact. We also tried to run a program to drill holes with the step command, it would run over and over but not move the step unless it was in relative mode.
Is there anyone on the west coast who could do a little tutoring in exchange for a slight fee or barter?

[bill.young]

Hi Carol,

I might be able to help with your problems with the s_prbsbp routine. What kind of probe are you using with it and what's your pattern made of? Does it always get lost in the same place? And when it gets lost, did you notice if the indicator for that input switch in the ShopBot software is on, off, or flickering?

As for your hole-drilling problem, I'm not familiar with plasma cutters ( or the step command ), but I'd bet the s_drill.sbp sample file could be modified to work for you. It does a good job of drilling holes in an array, and should only need to be modified for the torch-control part.

Bill Young

[blast@softcom.net]

Thank you Bill,
We are using the ShopBot probe on a steel part. When it reaches the end of the part the input switch lights up but the probe doesn't stop and it did not record anything. We do have it hooked to input #2 instead of input #1. But we edited the file to use #2. We are drilling the holes with a drill. I didn't see the s_drill.sbp file so I will check that out today.

[bill.young]

Carol,

First let's make sure that you didn't miss one of the input switch references when you went from switch #1 to switch #2. There are a bunch of "ON INPUT(1,0)" commands that have to be changed to "ON INPUT(2,0)". I count seven of them and it's easy to miss one.

There is also a test for a system variable that might have gotten missed. If you look near line 140 in the file you'll find this line..

&testval=%(51)

It records the value of the input switch (if it's on or off) and needs to be changed to...

&testval=%(52)

If this one got missed then the probe could have moved away from the edge and turned the #2 switch ON ( remember the probe turns the switch ON when there's no contact and OFF when it makes contact), but the program would be reading the #1 input which would be OFF because nothing is connected to it.

Since you're using a steel pattern, you might think about using the s_edgsbp routine to do your file. It works by simple electrical contact so you would need to connect your steel pattern to the input switch with a single wire, but it would have 2 advantages.

First, you would use a piece of metal rod in your router instead of the probe so there aren't any moving parts (other than the ShopBot of course!). Second, if you use a rod that's the same size as your bit (or plasma cutter kerf), you won't need to worry about bit offsets... they'll already be done. There's a description of all the edge-finding routines at Bill's Corner on the ShopBot web site.

Let me know if this solves the problem; if not we'll have to dig a little deeper.

Bill

[blast@softcom.net]

Bill,
We put the probe back on input #1 and restored the program to the original. It worked perfect. It probably would have worked okay had we known what to change %(51) to, we tried to change it to on input 2 not aware of %(52). Found the drill program you advised, it's great but we haven't quite got how to dissect it, yet. We moved our plasma to input #2 and the proxy switches to #3. Thank God you put in proxy switches. We hit z insted of y and would have smashed our probe into our metal table, OUCH! We cut our first piece of metal with the plasma and everything worked great! It was freezing out but when the part came out right we were warm all over. Thank you for your advise, especialy on a Saturday. Can't wait to cut some more.