cnc plasma cutting issues. Please help!

When I first got my table up and running it did a great job but, now (1 month later) its not cutting right. Sometimes its fine like smaller less complex jobs even if i nest a sheet with many parts but, when i do a more complex job like a sign with graphics then it messes up. I put in the code using sheetcam and it starts out fine but then the cuts start not cutting in the right place. it could be as simple as the inside of a circle or the letter o the hole comes out but not always in the center or the cut placement may be off from were it is supposed to be. Ive heard of ghosting being a problem with plasma cutting tables but, I'm not sure if that's the problem or not. I did change my x axes from a lead screw to a rack and pinion but, its tight and i tested it for repeatability and it seems fine also it was doing this even when it had the lead screw. I plan on doing the Y axes next. I have a hypertherm powermax 45 xp. The bob board is a 5 axes chineese board. Anyway looking for any help you can give. Its been a bit of a journey to say the least but would really like to get this problem worked out so i can make a business out of this.

Sounds to me either your stepper motors moves a bit right before the torch strikes a pierce resulting in the starting point on the leadin being out of position ,this could be because of a emi issue or you have flex in your x axis - flex meaning your x axis isn’t moving firmly and has a play or stutter when it moves.


Sent from my iPhone using Tapatalk

I had something similar happen several years ago after I had to change the mother board on my computer. It would have an intermittent stutter in either the X or Y direction which would lead to out of position cuts. After a couple very frustrating months of dealing with this I finally ended up installing a completely different mother board and the problem immediately went away. The best I could tell is that it was being caused by the frequency of the plasma cutter. If I turned the plasma cutter off and ran through the program the problem would go away.

Yes if your gantry is strong and there’s no play between the motors and the pinion then there’s a good chance it’s the frequency (emi) that’s causing this ,are u using shielded cables for your motors and limit switches?... I’m currently having severe frequency issues this my plasma machine, the mistake I made was to buy a hf start after I finish build my gantry ... I knw the blowback plasma machine is suitable for Cnc plasma “well so iv been told” but it’s pricey so I’m considering to try a pilot arc machine and c if it’s gna work in for me


Sent from my iPhone using Tapatalk

ok makes sense thanks for your input

i got the hypertherm powermax 45 xp for that reason it is a blowback plasma but i may have to look closer at the wires

Do u maybe know if a pilot arc machine will be better then my current hf machine regarding emi?


Sent from my iPhone using Tapatalk

Hi, is your problem solved yet?


Sent from my iPhone using Tapatalk

If it were EMI most likely it would happen on ALL kinds of cuts.. Detailed cuts can have more challenges if you are getting torch dives and bad touch off. The cheaper chinese motor drivers are notorious for having motion problems and overheating if you run them anywhere near the published specs.
Having rack and pinion on the Z will cause other problems. Most THC's need fairly fine motion (more steps per inch) or they tend to oscillate because they overrun a lot quicker. Rack an pinion tends to work better on the long axis where speed is more important than accuracy. Even them its best to consider belt reduction or gear head to make the resolution higher and get more torque for acceleration.