Setting Pierce Height and Plunge Rate Help

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Setting Pierce Height and Plunge Rate Help

Post by Brute29 » Mon Mar 26, 2018 12:12 pm

I am fairly new to the CNC plamsa cutting game and was hoping I could get a little help. I have a couple ideas as to what to change but I wanted to run them by the group in hopes it would speed up the trial and error!

I got a used table and purchased a new Powermax 45XP for the table. I'm running Sheetcam and Mach3.

My problem is when the torch arc is struck it sits in one position for long enough after the arc you can see the metal start "pool". When cutting text this pool melts some of the letters together to where you lose the text. After the arc is struck, it takes probably 2-3 seconds for the torch to lower itself from pierce height to cut height. I do have the "tabs" in the text to keep the centers from falling out.

My thought is that I have the plunge rate set too low and possibly the pierce height too high. I believe the plunge rate is set around 4ipm. I entered the pierce height from the 45xp cut charts, but I should double check that also. I'm not at my table now so I'm going from memory. My other thought is that I may not be zero-ing the table properly. I was told (by the former owner) to move the torch to where you want to cut, lower the torch until it touches the metal sheet, then raise the torch ever so slightly and zero. If this does not sound correct please let me know as this is what I as told and I'm still in the learning process.

It also seems that my kerf width is wider than it should be. After losing some of the letters I did a test pierce and moved the machine manually with the torch on to cut a straight line. The kerf width was noticeably smaller than what I have been seeing in the letters I was cutting. I didn't measure the width but it looked very close to the kerf width the book states it should be.

Am I on the right track or am I overlooking other areas that could be affecting this? And if there is another topic that speaks to the is please let me know, I did some searching but didn't see anything.

Thanks in advance for the help.

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Re: Setting Pierce Height and Plunge Rate Help

Post by sphurley » Mon Mar 26, 2018 1:35 pm

You have pierce delay also in SheetCam. And 4ipm is way slow for Z speed.
A little more info on your system will help
Platform CNC Plasma table
CandCNC Ethercut IV DTHC
Hypertherm 85/CPC/RS485
Miller 350P
Miller Dynasty 280DX

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Re: Setting Pierce Height and Plunge Rate Help

Post by motoguy » Tue Mar 27, 2018 10:44 am

My default plunge rates are 150ipm, fwiw.
Bulltear 6x12 w/ Proton Z axis & watertable
CommandCNC/Linux w/ Ohmic & HyT options
Hypertherm Powermax 85 w/ machine torch
Solidworks, Coreldraw X7, Inkscape, Sheetcam

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