Red screen height ctrl losing arc

[Dan Kitchen]

I have a new to me used red screen height unit. Was acting funky so I sent it to Onexia for repair. They seemed to have issues but replaced a board inside and claimed its good. I am still having an issue which is new. It will start a cut like normal and while it is cutting it will lose the arc, raise up to home position, immediately come back down and touch off, pierce, and continue cutting all the while the machine is in motion thinking it has been cutting the path the whole time. My table is grounded, the plasma ground is on the material being cut, the torch whip is separated from the rest of my wires in my cable carriers, the fuse is good, and this is happening in both auto and manual modes it does not act like the voltage is low or high. I tried to upload a video but it won't work. I paid them $400 to repair this and it is still not working. Looking for some advice besides that is old go buy a new height system. Thanks.

-Dan

 

[Dnmeistr-LECS]

It could be the relay, by-pass the relay to test it. Jump across the start input contacts when the gantry moves into position, this will cause the torch to drop and begin cutting, when the part is finished cutting you can open the contacts. By testing it in this method you are determining if the relay is at fault or is it the height control box.

 

[Dan Kitchen]

Good idea I will try this later and report back thanks.

 

[Dan Kitchen]

Update: a fellow red screen user mailed me his spare box to test and I have the same results. Torch raises and loses arc randomly while cutting.

I even lowered my torch to pierce height, lowered my delay, and took the input and output wires off the back of the box and tied them together to run as if I had no height box. Still same results. I guess I will try welding a stud to my frame and make a star ground so I can ground everything.

There is a rectangular male terminal end with a ground symbol on the main board inside the height unit... I assume I can run a ground wire off of that? See pic.

Maybe I can ground the gantry and smart motor too? My torch whip is zip tied to one side of my cable carrier and the wires the other but maybe I can gain an inch by moving it to the outside of the carrier would that help?

Thanks

 

[Dnmeistr-LECS]

Yes you can use that post as a ground terminal. Do the following tests:
Test 1 - Dry run with the the switch set to no cut, does the torch stay in the down position the entire run (Note have to switch to Manual mode as well)
Test 2 - Switch set to Cut and Manual, jump the Start Input wires when gantry moves into position, torch will drop and begin cutting when finished cutting remove jumper across Start Input contacts; does the torch stay down the entire run.
Test 3 - Switch set to Cut, Auto with proper Set Voltage, jump Start Input contacts, does the torch stay down the entire run. If torch raises up in steps it is not reading voltage from plasma cutter.
Test 4 - Switch set to Cut and Manual, Start Input wires connected to Plasma Relay box, does the torch stay down the entire run.
Test 5 - Switch set to Cut and Auto with proper Set voltage, using plasma relay does torch stay down the entire run.

 

[Dan Kitchen]

Wanted to post an update. Added a start ground to my table frame. Ran the ground rod to it, plasma lead to it, ran ground wires to my gantry as well as lifter station, and another ground lead for the work clamp. Have had no issues since! Thanks.