Torch raises during cuts. FRUSTRATING

[ajk2004]

Hey guys,
I've had a c and cnc system for about 3-4 years. I am running mach3 and sheetcam. I have a weird problem that has been happening ever since I got the machine up and running. I know the problem will happen so I have to babysit the machine knowing not if it will happen but when. Randomly during cuts (usually during long cuts) the torch will start to raise off of the metal. The down light is on, meaning the system is trying to lower the torch, but it keeps raising. I quickly kill the cut. Otherwise it will screw up the piece. I have to then go to the previous M05, restart the cut, turn torch off until I get to the spot where I stopped it and manually turn the torch back on. Does anyone know how to fix this or what is going on? Thanks
Andy

[whiskeymike]

Sorry, I don't have an idea for you. That seems really odd. I run Mach3 and sheetcam and don't experience it. Do the volts jump/drop at that point? Is the cut on top of/adjacent to another cut line? When it happens, does the arc break and the torch go out, or does it come back down, but boogers up the piece?

The fact that you rewind and replay and it doesn't repeat is really odd. I was wondering if you had rules on speed (like lower speed if corner is steeper than x). How often does it happen? Out of 10 or a 100 pieces, how many times? Have you turned off rules? If it's frequent, what happens if you turn off torch height control? What kind of table/gantry do you have?

[djreiswig]

Is your work clamp connected directly to the material?

[WyoGreen]

I'm guessing that this is a Mach3 system. So Mach3 is telling the torch to lower, but this is a CandCNC system, so the torch raising and lowering is under control of the DTHC system. So what is the voltage display showing while the torch is raising? If you are cutting a thicker piece of material that doesn't warp, you could try turning off the DTHC and see what happens then.

That's all I have for now, Steve

[robertspark]

what version of mach3 are you running?

can you post your mach3 profile?

[SeanP]

Try lowering thc rate in mach, I think it's in relation to your z motor settings, default is 30, I'm down to 12 on mine, seems to be a good balance between thick a d thin on mine.

[tcaudle]

Hey guys,
I've had a c and cnc system for about 3-4 years. I am running mach3 and sheetcam. I have a weird problem that has been happening ever since I got the machine up and running. I know the problem will happen so I have to babysit the machine knowing not if it will happen but when. Randomly during cuts (usually during long cuts) the torch will start to raise off of the metal. The down light is on, meaning the system is trying to lower the torch, but it keeps raising. I quickly kill the cut. Otherwise it will screw up the piece. I have to then go to the previous M05, restart the cut, turn torch off until I get to the spot where I stopped it and manually turn the torch back on. Does anyone know how to fix this or what is going on? Thanks
Andy

If the down indicator is ON in MACH then its MACH that moving it the wrong way or the motor tuning is such its stalling th emotor and making it move the wrong way. All the THC can do is "suggest" to MACH to jog the motor a certain direction . YOu need to confirm that when you jog the Z the readout increases and taht if you fast jog back and forth it never misses going the right direction . The DTHC has a seperaate feedrate speed and direction setting . Once it takes over the Z it uses ITS setting to control the speed/diraction etc. On DTHC IV machines the THC rate means nothing