Arc stopped mid cut and now won't reignite

[pat8703]

Hello

I was making a cut with my Pro table on some 1/4 aluminum with a razor cut 45. I am using the machine torch with THC.

The cut was going well for several feet until it randomly cut out and the program self-terminated. I had already cut about 15 linear feet without issue. I restarted the cut at the beginning of the line section that failed, and I got air and pilot but didn’t fire. I then advanced the program to the next line section. I got air, pilot, and the machine fired, pierced, and cut but the arc cut out after about 3/4”. I then retried that second line section re-start. Air, Pilot, no arc.

So I moved power cycled both the control box and plasma cutter, moved to a clear section of metal outside the cut area, and in the fire control software, I manually engaged a cut. Air, pilot, no arc. Then swapped to the manual torch, disconnected the control box from the razor cut, and the plasma cutter functioned fine. Next I changed the consumables on the cutting torch. Air, pilot, no arc. I took the cover off of the control box to see if something had burned up or shorted out. The board looked good. TX/RX lights were flashing on the main board and THC daughter board. I power cycled the machine again, and got only air - no pilot. I tried this again a few times. Air, but no pillot, no arc.

Where do I begin diagnosing the issue? I believe I’ve ruled out the razor cut machine since it works on manual mode. How can I manually trigger the machine to fire using the CNC input connector? Where do I go from here?

[TinWhisperer]

@pat8703

Where do I begin diagnosing the issue?

Welcome to The forum @pat8703

I would start by making sure that you’re actually supplying enough dynamic airflow to the unit.

I would also make sure that your torch is mounted correctly and the bottom mount is not crushing the area of the torch where the moving bits are inside.

@pat8703

How can I manually trigger the machine to fire using the CNC input connector?

Shorting out the trigger wires will fire the torch.

@pat8703

Where do I go from here?

Quarter inch aluminum that has a habit of getting little chunks of aluminum flakes stuck to the nozzle and then if you run it too long after that it’ll distort the round nozzle opening.

@pat8703

I had already cut about 15 linear feet without issue

In one continuous cut or was this multiple cuts?

[mechanic416]

That could be caused by the internal regulator going bad. Also if your getting pilot arc your getting fire, your just not getting arc transfer to the work piece. This could also be caused by a bad work clamp not connected to the work piece.

[pat8703]

Thank you for the responses.

Regarding dynamic airflow, the machine cuts fine with the manual hand held torch on the same material. Airflow with both machine torch and manual torch is similar, and internal air pressure regulator is rock-solid at 70 when on purge mode

[quote=“TinWhisperer, post:2, topic:45999”]

I would also make sure that your torch is mounted correctly and the bottom mount is not crushing the area of the torch where the moving bits are inside

[/quote]

I’ve only used this machine with the machine torch over the last 4 years and have cut hundreds of parts on it. I will check the mount but there was no noticable failure of the mounting bracket or issue with the torch mounting.

[quote=“TinWhisperer, post:2, topic:45999”]

Quarter inch aluminum that has a habit of getting little chunks of aluminum flakes stuck to the nozzle and then if you run it too long after that it’ll distort the round nozzle opening.

[/quote]

While I understand that and have experienced consumable wear problems before, changing the consumables should have rectified that issue. I have even disassembled the torch head several times to ensure it was assembled correctly.

@TinWhisperer

In one continuous cut or was this multiple cuts?

The part I’m working on has two cuts, one approximately 4.5 ft and the second approximately 6ft. The second part completed the 4.5ft cut and got halfway around the 6ft cut before failure.

@mechanic416

That could be caused by the internal regulator going bad. Also if your getting pilot arc your getting fire, your just not getting arc transfer to the work piece. This could also be caused by a bad work clamp not connected to the work piece.

Regulator on the plasma cutter or on the control board? Certainly not the air pressure regulator as that functions fine.

The ground clamp was always on the work piece, so that’s not an issue. Again, the cut works fine when I tested using the manual torch with cnc controller and machine torch disconnected.

And I was getting a pilot from the cnc until i removed the cover? I had assumed dust causing an internal short but inside was clean.

@TinWhisperer

Shorting out the trigger wires will fire the torch.

Knowing this will let me troubleshoot the machine torch and cnc input signal from the controller and the receiver circuit in the plasma.

[mechanic416]

If everything we suggested is fine then most likely the machine torch is bad. It could be anything from a bad wire to the electrode plunger sticking or jammed up.

[ds690]

It’s definitely not the signal from the control box. The only thing the torch fire relay does is close a circuit. It essentially takes two wires and connects them together. If you get air from the torch when it is commanded to fire, the box is doing its job.

All of your symptoms point to the issue being the machine torch.

[pat8703]

Thanks all. When I get a chance I will check the control board trigger output and try to manually fire the plasma cutter head with the machine torch by shorting the leads. What’s off to me is that the manual fire mode in arc control stopped triggering the air flow