Arc gap too high

[bigbearzfan]

Hoping for some help here folks
I have a Thermal Dynamics Cutmaster52 on a Precision Plasma gantry with a home built table. I am running Mach3, SheetCam and a MP3000 DTHCII Digital Torch Height Control from CandCNC. The issue I am having is that the tip height doesnt seem to stay were I feel it needs to be. The cut height in the book is .19" I cut alot of 14ga hr. The settings call for 70psi, .19 cut height, 190ipm at 40amp with a 40amp tip. Long straight cuts are ok, but if I do art work I have seen the gap as large as .45" The other issue is it wont alway maintain the cut. sometimes it just gouges it, not cut it. I grind it clean where I ground, the ground clamp has been taken apart cleaned and new connectors installed.

[WyoGreen]

Have you tried cutting the part with the DTHC turned off and observing what the voltage display in Mach3 is doing. I suspect the DTHC is trying to raise the cut voltage to match your set voltage. You probably need some cut rules in Sheetcam to slow down the the feedrate when cutting circles, etc.

Steve

[bigbearzfan]

I have done cuts with the dthc off and as long as the metal is flat, it cuts fine. The gap stays where it should. the voltage is dead on.

[jimcolt]

Just to clarify: Your height control uses actual arc voltage feedback from your plasma cutter. When the torch is further from the material (arc length is longer) then the arc voltage is higher, when the arc length is shorter, then the arc voltage is lower.

When you say the gap gets as high as .45"...then your arc voltage will be very high, perhaps over 160 volts. So your voltage is not "dead on"!

I suggest doing a little troubleshooting with your height control. When you have it active, it will auto adjust the torch to work distance based on your inputted preset arc voltage. If the gap gets higher, the height control will move the torch closer to the material so that the actual arc voltage is the same as the preset voltage.
If you fix your height control, the height will be correct, and your cut quality will dramatically improve.

Jim Colt Hypertherm

I have done cuts with the dthc off and as long as the metal is flat, it cuts fine. The gap stays where it should. the voltage is dead on.

[mike 1948]

I have seen posts lately where people are having cut issues with HRS.
I use a CM52 with hand torch on 12-14 ga. CRS and cannot cut at 190 without issues. I normally run around 130 and try to cut at .15 approx.
I "thought" that when the torch slowed in the corners the THC would lower to get to the correct volts. Could your up/down pins be reversed?

Mike

[WyoGreen]

After reading your post a few more times, how are you determining the .45 gap? Are you physically measuring it, or are you reading it off the Mach3 screen? If you are reading it off Mach3, then you may have a problem with losing steps on the Z axis. If you are physically measuring it then we have to figure out why your Dthc is raising it so high. From your post, it sounds like the problem you are having occurs when you are cutting curves, arcs, holes, stuff like that, where you are changing direction and speed a lot. As I mentioned before, you may be able to cure a lot of your problems by using Sheetcams cut rules. A search on Plasma Spider will turn up lots of tutorials on cut rules. It could also come back to noise and table grounding issues.

Steve

[bigbearzfan]

Thanks for the input so far.
Jim, The gap I am referring to is the read out in mach. The Z will get as high as .45 but the Volt read out stays within a volt or two of the preset.
Today I played with acceleration in the motor tuning and it made a drastic difference. I have had the machine for about 2 years and it seems like it use to cut better than what it has been lately.

Mike, The pins are not reversed. I have played with the speed sometimes it helps sometimes not