TruCut XT THC issues?

[JillS]

I have a Trucut XT running Mach4. The hard drive crashed in '22 so I had that replaced and reloaded my sheet cam and Mach4 along with the table tools with Hypertherm settings. My issue is - I load my 12" straight line cut .tap file from sheet cam to Mach4 and start the run. The torch goes down, touches the metal, comes up to pierce height, pierces, then goes down right next to the metal for about 2 1/2" and then does about an inch of steady climbing up to about 1/4" off the metal and halfway cuts through the metal until the end of the 12" cut. This is 14g steel set at Hypertherm cut settings. My THC is on and reads the HT set volts and the tip volts within 2 points of each other.I have an air gauge at back of HT and it reads a steady 115psi. I have my table grounded with a 10' ground rod about 8' from table, my ground to table is clean, and I clamp my ground to the metal I am cutting. An odd thing about the Mach 4 is my Process tab always, no matter what sheet cam code is imported on the file, reads process#49 (1/4" steel 105A, 144 THC set volts). Not sure if this is a reference tab or it actually plays a part in the code because I always manually input under the and federate what the HT chart class for. I had another Trucut owner send me his sheet cam version of a simple circle .tap file to see if my Mach 4 Process tab changed and it didn't. Any ideas would be greatly appreciated.

[acourtjester]

I have not used Mach 4, but this should be similar to most controller software. You did not say what THC you have. First in your cut plan (G-code) the torch should be controlled by the g-code and after the pierce drop (pierce delay) to the cut height of 0.060". It should not move from that height until the THC takes over control (torch movements) for a delay time (THC delay) for maybe 0.5 to 1.0 seconds. This is for the arc voltage to stabilize and THC start looking at the set voltage level reference. There also is a voltage tolerance in the THC so the set voltage tracks the arc volts close with torch movements.

pierce height.JPG (14.69 KiB) Viewed 2497 times

[JillS]

Thank you for your explanation on how the THC works. My understanding is that the Trucut XT has an integrated THC programmed by the owner. I'm assuming this is in his sheet cam and Mach 4 tools? After my hard drive crashed, I had to rebuy the license to Mach 4 and re-set up the system - wondering if I missed something that allows Mach4 to gain everything it needed from the sheetcam program?

[acourtjester]

I have seen problems when mixing software packages, Some use different G-code commands from other programs. They then do not function as expected. I am seeing a problem with Linuxcnc running a router routine in their Axis screen set. I generate a G-code that has a tool maned in it as part of the G-code. It will not work, I can generate that same routine with EstlCam which puts an shortened tool name in the G-code and it works fine.
I know it is not anything like your problem, it is just an example of mixing software. Have you posted your problem on the Mach 4 forum, or SheetCam's forum, you may find some else who had a similar problem and can instruct you on a fix. There may be a macro in one of the packages you are missing. I know SheetCam has code snippets for optional operations, example slowing down when coming to a corner when cutting.

[JillS]

I emailed Mach 4 support but haven't posted on the Mach 4 or sheetcam forum here. I'll try those as well. I'm kinda leaning towards the software issue since my torch tip volts and THC set volts seem to be be running close on the screen.

[weldguy]

Have you tried just reducing your set point voltage in an attempt to reduce the cut height?

If 144 volts achieves a 1/4" height I would try 134 volts and see where that gets you. Continue to test until you achieve the correct cut height.

I am not a Mach4 user so I could be way off but it is possible that there is a setting like a voltage offset or something that is different from your last computer setup.

Don't get too hung up on the voltage number right now, just find a voltage value that achieves the correct cut height and go with and maybe as you work with your new setup you may find the difference from your previous setup.

[JillS]

I tried but it started out dragging so badly even adjusting by 5 volts - I think I have a a problem with the software versions but working on that right now. Thanks for the idea.

[weldguy]

So your saying that 144 volts sets your cut height at 1/4" and reducing it 5 volts to 139 volts causes it to drag on the material?

[JillS]

Sorry been away - the Process tab on the Mach 4 screen always displays this one tool(process) So I think its merely reference because I've always manually set the parameters of the pierce, cut height, etc. off the HT chart. Someone told me theirs changed depending on the thickness of metal they programmed in SheetCam. That'll be my next find is the version of SheetCam that I'm supposed to be running with the older version of Mach4.

[acourtjester]

SheetCam generates the G-code using the tools selected (pierce height, cut height, travel speed for each metal perimeters). Mach 3 or 4 ( or most controller software) follows to perform the operation as the G-code dictates. Your original problem to me looks like a THC problem, THC commands can override G-code control as the cut operation progresses. By this I mean THC controls the Z axis once it gains control after the start of cutting. You could have an intermittent problem with wiring or signal interference in the THC electronics. Here are 2 examples of G-code control, one show normal plasma start only one Z movement. The other shows many Z movements under G-code control, these are 2 different operations only for example for you to see. Learn to look at the G-code to see how things work, in a normal plasma G-code you will only see one Z movement at the start between the M3 and M5. The THC will control the Z movement while cutting but will not be seen in the G-code.

Z movement one.JPG (62.25 KiB) Viewed 2317 times

Z movement many.JPG (78.05 KiB) Viewed 2317 times