1/2" issue Mach 3

[kbenz]

I was cutting 1/2" today. sheetcam, mach3, pm65. I was cutting holes .562". slowed it down to half speed for better hole quality. had to increase volts by 15 to keep torch from diving in to the metal. My anti dive is turned on in mach, but i'm not sure if its set right. it is set at 60? also my ohmic sensor light stays lit the whole time its burning 1/2" ??

[I Lean]

Turn off the THC when cutting holes like that, then your voltage won't matter and the height will stay constant.

[kbenz]

Turn off the THC when cutting holes like that, then your voltage won't matter and the height will stay constant.

shouldn't the anti dive not take care of that though?

[I Lean]

I don't think so--as I understand it the anti dive is just for when you're crossing a kerf, or the lead-in, something fast and short-duration. I might be wrong though, since I've never noticed mine actually working that way.

[beefy]

Anti-dive in Mach comes in at the percentage feedrate setting that's entered in there.

So if it was set at 60% and your normal feedrate was 100 ipm then any speeds below 60 ipm would cause Mach to turn off the THC.

The thing where going over a void causes the THC to lock the Z axis is different. That has nothing to do with speed but is sensing a spike in voltage and locking the down movement of the Z to prevent a torch crash. On my Candcnc sytem it is called Tip Saver and there's a percentage setting which is only a few percent so if the voltage rises to that (2% would actually mean 2% above target voltage) the Z is locked. When the torch has crossed the "void" and is back over solid metal the voltage should come back to normal and the tip saver turns off.

How are you setting your reduced feedrate for the holes. If you are entering a new feedrate in your gcode then that becomes you new feedrate setting and is thus 100%. I'm guessing the 60% setting in anti-dive is when the feedrate is reduced by Mach itself as it handles sharp corners, changes in direction, etc. Remember a change in direction actually required deceleration and acceleration and a temporary decreasing in speed. I believe it is under conditions like these when the anti-dive will turn off THC. I do NOT know if using the feedrate overide buttons on the Mach screen will cause activation of the anti-dive if the feedrate is reduced below 60%.

Many people put the holes on a separate layer in Sheetcam, and create a second operation for them with a different feedrate plus code snippets to turn THC on and off, often using M101 & M102 commands.

Keith.

[kbenz]

ok, that makes some sense. I put the holes on a diff layer, at a reduced speed. so it's actually 100%. Thanks for explaining that

wonder why I only have this issue with thicker steel?