Hypertherm MAX20 & C8 Relay not working

[CPierce18]

I have a question that deals with either the C8 A/C Relay, or a Hypertherm MAX20 built in the late 80's. I have my cnc plasma cutting table all wired up, torch switch wired up to the c8 relay. I checked that the relay is closing when the code says to fire the torch. All is good. I then hooked up the wires for the plasma torch to the C8 relay and ran it thu the code again and this is where I'm having a hard time figuring out what's going on.

When the code closes the relay to fire the torch, the plasma cutter will flow air and then for a split second it will fire the plasma, then cut out, but the air continues and i can hear rapit clicking in the plasma unit like the relay in the plasma unit wouldnt stay on. I've had this happen to me before when I would use it as a manual plasma cutter and all i had to do was change consumables and it would be fine. So I did just that, changed consumables but it will still flow air and fire the plasma for a split second, then cut out and the air would flow and I would head that same clicking coming from the plasma unit.

Now the next this I did was check that the plasma cutter would run fine without going through the C8 relay. All I did was take a short piece of wire and and touch the 2 torch wire terminals to bypass the relay and complete the circuit. I did that, the air flowed, the torch fired, all was fine.

So I'm stuck. I'm leaning toward the C8 relay as being the problem, but I know it's working because it the circuit closes and the plasma flows air, but the torch wont stay lit.

And I'm also leaning towards the plasma unit becuase I hear that rapid clicking like the relay in the plasma unit wont close.


Could my relay be to small for the load of closing the plasma switch? I didnt blow out the fuse on the C8 board. Im no electrical engineer but could there be enough voltage getting through the relay to open the soloniod to flow air, but not enough voltage geting through the C8 relay to close the plasma unit relay to fire the torch? (maybe the plasma unit realy is dirty & dusty?) When I measured the voltage running thourgh the torch switch, it read 24vac. Can the relay not handle 24vac.

Can someone help me out?


Chris

[Alan Bradford]

Hi,
Not knowing what you are driving the relay with, I would guess you have a power or noise issue.
The Max-20 running at 20 amps will pull every available electron form a 120 VAC 20 Amp circuit.
If your cnc/control circuit is running from the same 120 VAC circuit it may be resetting from a momentary drop in supply voltage.

The MAX-20 did not have a machine interface as it is only a 20% duty cycle system.
It was never designed for machine cutting.
You can only cut for 2 min then wait 8 min for it to cool down.
The 120 outlet can also overheat if this is exceeded.
I think that at 10 amps it is 50% and 6 amps is 100%.
Not terribly productive.
I have a MAX-20 and it overheats and shuts down when you exceede the duty cycle.
I am on the road and do not have access to a manual so I dont remember what C8 does, but if you short out the trigger wires the machine will fire.

Good Luck,

[CPierce18]

Here’s my NEW problem! Everything is wired up correctly was running fine (minus the plasma relay). I purchased a larger relay & wired it up. I flipped the 5V switch to power my breakout board, and I flipped the 5V switch to power my relay board. I tested out the relay to see if it worked. I clicked the torch on button in mach 3 and using a multimeter check that the circuit opened up. The lights on the board came on… All went well!! To this point I still have not hooked up any wires from my plasma cutter to the circuit boards. I want to take baby steps to be positive everything is working.

I turned all the power off and arranged the wires to make it all look perdy. I then flipped the 5V switch to power my relay, but forgot (Brain-Fart) to flip the 5V switch to power my breakout board. Here is where my heart stopped. Remember I have no plasma cutter wires hooked up to my relay yet. I then plugged in the 36V power supply to power my drivers & motors. When I plugged it in, the light on my breakout board came on for a second, then went off. Then it dawned on me what I forgot to turn on the power for the breakout board! I flipped the switch to power the breakout board, then tried to jog my motors around, and nothing worked. I tried to activate the relay, and that didn’t work either! I inspected the breakout board and saw no burnt capacitors or anything. The ONLY axis that DID work was the Z+. The Z- did not work! My guess is that I SOMEHOW shorted out the breakout board. My table WAS working fine, I didn’t unscrew any wires, or change anything… I just added 1 relay. Could the short have happened because I plugged in my motors before I plugged in my breakout board? My next questions is… is it possible to short out my drivers but by plugging them in?


HELP!!! I’m going on my 3rd breakout board!!!

[Alan Bradford]

Hi,
I would rewire everything so it comes on and off with one switch. That way you dont forget toturn on something important.

I have no idea what type of breakout board, what type of CNC software/hardware you are using or how you are wiring things.
With out a schematic it would be hard to tell you what is wrong.
It is like driving blindfolded and having someone on a cell phone giving you directions to drive.

We need more information to help.