[Islam]

I've purchased a new PM 65 with machine torch for about 6 monthes to replace the Chinese plasma unit on my DIY table using THC301d and controlled by mach3 and so impressed about its quality, and going to purchase a new PM 85 recently for my new plasma table under construction.

But sometimes I face an intermittent problem at the end of the cut when the arc doesnt respond to the (Torch off) control signal and remains on which results in product deformation.

I noticed that this is often happens in long cuts, and only for torch off.
I do not know if the cause is either the air quality or the (nozzle - electrode) life time or something else.

But I noticed that the problem almost disappears when using a new electrode and nozzle, or by cleaning the old nozzle and raise the rust from the electrode tip.

Any advise will be appreciated.
Thanks a lot.

[jimcolt]

When the start signal....which is a set of closed contacts from the cnc machine or THC electronics....is released (contacts open) the plasma DC power switches off, which stops the plasma arc. I suggest monitoring these output contacts between your machine and the plasma......sounds like they are not working properly. Also....if you are using a hand torch on your machine make sure the selector switch on the front panel of the plasma power supply is in the "cut" mode.....not in the "trigger lock" mode. Trigger lock (depending on how you wired the start signal) could cause this to occur. Using a machine torch with the proper interface through the optional CPC connector for machine cutting could eliminate this issue.


Jim Colt

I've purchased a new PM 65 with machine torch for about 6 monthes to replace the Chinese plasma unit on my DIY table using THC301d and controlled by mach3 and so impressed about its quality, and going to purchase a new PM 85 recently for my new plasma table under construction.

But sometimes I face an intermittent problem at the end of the cut when the arc doesnt respond to the (Torch off) control signal and remains on which results in product deformation.

I noticed that this is often happens in long cuts, and only for torch off.
I do not know if the cause is either the air quality or the (nozzle - electrode) life time or something else.

But I noticed that the problem almost disappears when using a new electrode and nozzle, or by cleaning the old nozzle and raise the rust from the electrode tip.

Any advise will be appreciated.
Thanks a lot.

[Islam]

When the start signal....which is a set of closed contacts from the cnc machine or THC electronics....is released (contacts open) the plasma DC power switches off, which stops the plasma arc. I suggest monitoring these output contacts between your machine and the plasma......sounds like they are not working properly. Also....if you are using a hand torch on your machine make sure the selector switch on the front panel of the plasma power supply is in the "cut" mode.....not in the "trigger lock" mode. Trigger lock (depending on how you wired the start signal) could cause this to occur. Using a machine torch with the proper interface through the optional CPC connector for machine cutting could eliminate this issue.


Jim Colt

Finally, after Jim advice I did fix the problem.
Focusing on the control issue without disturbing by any other issues like air quality or nozzle life time helped to define the problem.

First monitoring found that THC electronics and its output contacts were working properly, the plasma unit is in the cut mode and all of the connectors between PC, THC and plasma unit are well connected.

It was noise issue, The 15 m optional machine interface cable part no. 123896 was totally wrapped around itself beside the plasma unit.
By unwrapping and shielding it by aluminum foil connected to the ground, the plasma unit worked properly without this intermittent problem.

Thanks Jim for the problem analysis and your advice