Erratic Z-axis

[MAS]

I have a problem with my plasma cutting machine that I can't figure out what's causing it.
When I run a cutting program with my plasma torch on and cutting the Axis DRO reads erratic, up & down readings and the Z motor does not respond to this.
When I run the same program with the plasma off the Axis is rock steady as it should be.  X & Y work perfectly with the plasma on or off.
What could possibly cause this?
My setup is:  CandCNC MP3000 & 4 axes driver box with Applied Motion 3540M drives. (Flashcut 3.5amp microstep box)
hypertherm 1650 Plaz cutter.

[Tweakie.CNC]

Sounds like it is electrical noise to me.
Are you using shielded cables, properly grounded ??

Tweakie.

[MAS]

My Z-Axis wiring is the same as X & Y  which work fine.
The computer & electronics are not ground at the AC line, only
the hypertherm is grounded.  I tried grounding the carriage to the table
to the hypertherm and to the building, that did nothing.

[BR549]

YOU need to move over to the Mp3000 CCC yahoo site TOM is the expert on CCC plasma CNC.

Being that the DRO shows the movement as well I would rule out noise. Sounds like something is not configed right on the MP3000 setup and is cause erratic behaviour.

You do realize that the Z is suppose to do that with the thc on and cutting right? OR is it that teh Z motor is not responding and not moving to correct?

(;-) TP

[MAS]

BR, I did some testing tonite and it's not the settings in the MP3000.
I ran a test cut and all this setup ever does and did since I've had it is dive into the plate.
I hooked up my hyperthern remote switch that came with my machine and unplugged the
db9 cable to the voltage divider board and ran the cut program again and lo and behold no diving and no erratic Z DRO readings!
 I actually cut a part!  Plugged the db9 cable back into the MP3000 ran the program again and torch dived into plate.  Trashed the tip probably.
 Something is wrong with that card or mach 3 software.  Tom's brochures on his equipment state his stuff is interference resistant.
By the way I did post at CandCNC and so far no one responded yet except Tom.
I will call him in the morning and tell him what I found out.

[BR549]

IF the torch is diving into the plate either your cut parameters are wrong or the up/down polarity is backbackwards and it is moving DOWN when it should be moving UP .

Just a thought, (;-) TP

[MAS]

BR, that would be really nice if those were the problem.

[BR549]

Will the  self test on the DTHC run OK?

(;-) TP

[MAS]

Yes Sir that checks out.  Tom @ CandCNC thinks I have some kind of ground loop between the plasma and the MP3000 unit.
I was thinking maybe my plasma unit has a faulty filter capacitor somewhere and is generating more noise than it should.
I have a Hypertherm 1650 machine, one of the earlier ones.  It's a great machine though.