Thc not becoming active during cuts

working on setting up a gen 1 conversion kit, and duting cutting my thc is reading voltage, but it is not activating. the 4 lights next to the voltage meter do not come on. it is grounding out on my sheets as it is not turning on. i have a video i will post in a moment. i am using the gen 1 kit, as well as a hypertherm 45xp.


It’s not active because your torch speed is less than 85% of the program speed.

Firecontrol turns off the THC wherever the torch speed drops below 85% of the program speed. Your program speed is 105 and the Torch speed never gets close to that during the cut.

If you use path rules(Sheetcam) or feed optimization(Fusion) to slow down for holes or other features, it will shut off the THC for those features.


that makes sense! im coming from UGS so im not used to having that feature, just letting sheetcam do it. if i have path rules in sheetcam, i should set it to 1% correct?

As far as slow down within SheetCAM rules, I’ve found 50% to be effective.

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i think i keep mine set at 52% in sheetcam

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so this comment has led me to a new issue. i have my feeds set at 105ipm. even with no path rules set, the machine is not going over 24.7 ipm while running. thoughts?

Post the code and/or some screenshots of your Sheetcam settings. Maybe something obvious will stand out

You can keep your path rules the same. You want the THC to turn off for holes and any other slow downs. That prevents the Torch from diving when the voltage changes during the slow down.

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so i think i figured out the problem. i have retrofitted the firecontrol box onto my delusional designs table. the software is designed to read steps/mm as which is what you get from the lead screws. my table runs on a gear track and has a travel resolution of 29.618 steps/mm. i have updated this in the firmware and although firecontrol is recognizing that, it is not adjusting how the thc and torch speed is calculated. the table is running at the 105ipm, however due to the firecontrol software’s programming. i am going to have to figure out a workaround to get it to function correctly. it would be amazing if langmuir would add a way in firecontrol to “add your own table” or change the settings to allow for retrofits. this could be a big money maker for langmuir.

There is a thread here somewhere where a user described how to change the settings in Firecontrol. It apparently uses GRBL commands and the steps can be calibrated.

I found the thread. Firecontrol updates - #17 by djlois

As a workaround for the THC, you could change the percentage of the program speed that the THC cuts off. That can be changed in the THC settings menu in Firecontrol.

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i sent the poster my number. im hoping he calls me because i want to see how he is compensating for something. i fixed my thc issue. i was inverting the z and y axis in grbl as apposed to rewiring them. that was causing the z axis to move up when the thc would say to move down. fixed the wires and that is taken care of. the last thing i need to get taken care of it the calculation that fire control does for the torch speed. when jogging with it set to 300ipm, the torch speed says 76ish. and while cutting it is moving slow. at 105ipm the torch speed reads between 25 and 40ipm when cutting at 50 ipm the torch is moving around 10-12ipm. but not all the time. sometimes it moves much faster lol

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It looks like Firecontrol is seeing your torch speed as about 25% of the program speed. As a temporary fix to get the THC active, you could change the THC cutoff to around 20% or less in the Firecontrol THC settings.

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So good news, not sure why i didnt think of this sooner, but i used the dip switches to change the microstepper. Im now running at 118ish mm/step. That is physically as close as my setup will be able to get. I have some upgraded steppers leftover that go even further but the next setting would be double 118 at the next setting. When i get a chance tonight im going to go through the firecontrol files and see if there is anhthing that can be changed on the backend to modify the 125mm/step down to the 118.

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