Help with end of cut problem

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RAD
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Help with end of cut problem

Post by RAD »

When i run a job at the end of the cut the z axis does not retract up to the rapid clearance it just remains at cut height and goes to x/y zero. This only happens on long runs. Any ideas?

I have installed a powermax 45 XP with CPC but with hand torch modified for remote firing. I have wired my own cpc interface cable with a connector I bought from ebay, i have wired everything in the cpc except pin 13 which is for ground ( i am not sure where to ground it to)

I am using the minithc torch heigh control which has worked well with my old powermax 800 which did not have a CPC port but was wired to use raw arc voltage etc.

I now have the minthc wired to the CPC of the new 45 XP and i am having this problem at the end of the cut.

What may be the possible causes for this? When i do a dry run it works well but when i turn on the plasma and enable the thc this is where it goes crazy at the end of the cut. I am using mach3 ans sheetcam. Thanks in advance
D.I.Y 4x4 CNC Plasma Table with water tray
60 Gal. A/C + D.I.Y Aftercooler + Water/Oil seperator + Desicant air dryer
45XP (CPC with hand torch)
MiniTHC
UCCNC + Sheetcam + Inkscape / AutoCAD
jimcolt
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Re: Help with end of cut problem

Post by jimcolt »

What CNC machine, what height control, what software? Jim Colt Hypertherm
RAD
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Re: Help with end of cut problem

Post by RAD »

jimcolt wrote:What CNC machine, what height control, what software? Jim Colt Hypertherm
My machine is a DIY using stepper motors, the height control is the MiniTHC http://minithc.com/ (miniTHC universal kit) I am using sheetcam and mach3.

I have attached a video in a zipped folder (sorry about the quality of the vid had to compress it so i can upload here)

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D.I.Y 4x4 CNC Plasma Table with water tray
60 Gal. A/C + D.I.Y Aftercooler + Water/Oil seperator + Desicant air dryer
45XP (CPC with hand torch)
MiniTHC
UCCNC + Sheetcam + Inkscape / AutoCAD
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acourtjester
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Re: Help with end of cut problem

Post by acourtjester »

I watched the video and it sounded like the Z motor stalled and that is why it did not raise up.
You may try reducing the Z velocity and acceleration a little (mach motor tune).
DIY 4X4 Plasma/Router Table
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13" metal lathe
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RAD
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Re: Help with end of cut problem

Post by RAD »

acourtjester wrote:I watched the video and it sounded like the Z motor stalled and that is why it did not raise up.
You may try reducing the Z velocity and acceleration a little (mach motor tune).
that sound is actually the plasma cutter, is that normal? also you can see how the flame dies down, its not an instant flame out

The system runs fine when I do a dry run with the plasma off, the problem only happens when I do a long cut, short cuts are fine.

The last system was working well with the older powermax 800 but I had to open the unit to access the raw arc voltages, get the arc ok signal via a sensor (from the miniTHC kit) and modify the hand torch but with this new 45 xp everthing is connected to the CPC port, this is the only thing I did different.

Could the problem be from mach3?
D.I.Y 4x4 CNC Plasma Table with water tray
60 Gal. A/C + D.I.Y Aftercooler + Water/Oil seperator + Desicant air dryer
45XP (CPC with hand torch)
MiniTHC
UCCNC + Sheetcam + Inkscape / AutoCAD
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acourtjester
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Re: Help with end of cut problem

Post by acourtjester »

I am only going on the grunt sound which happens just as the Z would be moving up, which it does not.
To Change the Z acceleration and velocity number lower is a quick check and easily return to the original numbers.
These are in the Mach 3 Motor tune section under the config tab.
While on the main screen in Mach you can move the Z up and down by pressing the page up then page down keys. Do this as fast as you can you may hear that grunt noise.
There will be other in a short time giving their ideas, that is what is so helpful about this site :)
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT
RAD
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Re: Help with end of cut problem

Post by RAD »

thanks i will check my z axis velocity
D.I.Y 4x4 CNC Plasma Table with water tray
60 Gal. A/C + D.I.Y Aftercooler + Water/Oil seperator + Desicant air dryer
45XP (CPC with hand torch)
MiniTHC
UCCNC + Sheetcam + Inkscape / AutoCAD
tcaudle
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Re: Help with end of cut problem

Post by tcaudle »

Also if you are using the MACH3 THC logic there is a setting for THC Rate (or there should be) that sets the velocity under THC. The lift at the end of a cut is a distance and if you are losing steps DURING a cut it will think its higher than it really is and just sit there (or worse go down instead of up). Stop it at the end and see what the Z DRO says. If its not where the torch actually is it last lost position.
RAD
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Re: Help with end of cut problem

Post by RAD »

Thanks guys i decided to install a copper ground rod to the table and this seems to have helped so far, did two jobs and everything went well.
D.I.Y 4x4 CNC Plasma Table with water tray
60 Gal. A/C + D.I.Y Aftercooler + Water/Oil seperator + Desicant air dryer
45XP (CPC with hand torch)
MiniTHC
UCCNC + Sheetcam + Inkscape / AutoCAD
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