Wright CNC THC

[Tankersley7w]

Hello everyone,

I’ve read through all the posts I could possibly find on THC yet I can still not figure out my problem.

I have a Wright CNC light industrial 4x8 table with a Everlast 62i plasma cutter. I use Sheetcam to generate the g code and I use the program (MyPlasm CNC) that Wright CNC provided to move the machine around. I can get everything to work except the THC (Torch Height Control). The Torch height controller is made by proma electronics. I have tried changing the voltage and turning the THC on and off witchin the program. Nothing works. The torch stays at the same cutting height. I also checked the wiring to see if it is wired backwards but everything seems to be in the correct place.

Would anybody have any thoughts on why my THC isn’t working. Below is a link to the THC I have. On page 3 it says “b. Plasma interface ( integrated THC controller and OHMIC )”. I am unsure if this is the only module I need to have a working THC or not. Any suggestions?

Thanks!

[acourtjester]

I am not a MyPalsm user but if it has a diagnostic page where you can see the different signals. See if there is a torch up and down and Arc Ok indicators. The Proma has a test section where it will cycle the 3 signals outputs. Look at the indicators to see if they are showing, next if the torch actually moves with the up/down signals ( use a large voltage spread for enough time to see movement). If it does not you need to find out why, something is not set correctly.

[Tankersley7w]

Thanks. I’ll give it a shot. I haven’t seen a diagnostics page anywhere but I’ll look for one.

[Tankersley7w]

So there is no diagnostics page anywhere.

[Tankersley7w]

Also sometimes the torch won’t move upon pressing start. It will strike an arc, but won’t move after that. I have also noticed that when my torch is moving and the metal is warped, the torch head will come into contact with the metal and the ohmic sensing tip and will continue to cut. I thought that it was supposed to stop if it came into contact with anything. The ohmic sensing tip works off the touch off but not when moving around the cuts. Any thoughts on any of these issues?

[adbuch]

I have also noticed that when my torch is moving and the metal is warped, the torch head will come into contact with the metal and the ohmic sensing tip and will continue to cut. I thought that it was supposed to stop if it came into contact with anything. The ohmic sensing tip works off the touch off but not when moving around the cuts. Any thoughts on any of these issues?

I think the control program will determine what the torch does when it comes into contact with material. For the initial sequence where it lowers to touch material (zeros the Z height), raises to the pierce height, pierces and then lowers to cut height and starts cutting the control program controls this sequence. If after the torch starts cutting following the cut path, it happens to come into contact with the material - the resultant consequence would depend on the control program. It could be programmed to stop (or pause) under this scenario, or it could simply ignore this contact and continue to cut. It all depends on the control program. On my Plasmacam table, if the torch shield/nozzle comes into contact with the material being cut - the machine will stop and an error message will appear on the screen. This will also sometimes occur if a piece of slag gets stuck between the shield and nozzle creating a false "contact" signal.
David

[Tankersley7w]

Okay that makes sense for the ohmic tip sensing. I still can’t figure out the THC though. I think my program (MyPlasm) isn’t reading the voltage correctly from my plasma cutter (Everlast 62i). I tried changing the jumper on the voltage divider card Within the plasma cutter to a 50:1 ratio since they come standard with a 16:1 ratio. I thought that might help but nothing changes. When I run the machine. The voltage read in the program is saying 6, no matter what I set the THC voltage to. The I’ve set the voltage all the way from 150, 125, 100, 78 ( recommended per thermal dynamics cut charts for the material I’m using), all the way down to 0. 0 is supposed to be auto THC. Whatever that means. Nothing works. All the cuts seem to be about a half inch cut distance. Then it varies where the material warps.

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[Rodw]

Ahh Everlast!. That take me back. You need to read this thread I posted.

viewtopic.php?f=111&t=23700

I'd also suggest you check the divided arc voltage with a multimeter while you are cutting with the THC connected and also without to check the THC electronics is not influencing the divider ratio. I used a 96v power supply plugged into the divider to do this test without cutting... a 48V power supply would probably do.

[Tankersley7w]

Ahh yes good post. I have read that about 3-4 times now. It looks like I need to put that jumper on the voltage divider card. At least that I what I made of it. I don’t have a power supply to test unfortunately.

[Tankersley7w]

So I jumped the pins together just as in this photo below. I hooked everything back up and it blew air but didn’t strike an arc. It just kept clicking. Sounded like a stove top trying to light. This THC is trash.

1F9098BF-5D27-44D2-895B-744445CCD9F4.jpeg

[Rodw]

Did it fire the pilot arc?
I think I may know what the problem is. If there is insufficient resistance in the THC circuit, Oxide will build up on the Arc OK contacts in the Everlast and you will get intermittent operation. The solution is to use a pull down resistor to ensure the everlast gets > 100 mA but you need to know the voltage going through the arcOK relay from the THC to work out the resistor required. Then you need to calculate the power requirement in Watts.to spec the resistor. Wattage. For 24V we used 2 x 270 ohm 5W resistors in parallel which gave 90 ohms @ 15 watts.

[Tankersley7w]

No, there wasn’t a pilot arc either. Just air. Where would these resistors go after I calculated for the correct ones?

[Rodw]

Well thats a trouble when you have a closed unit. The resistor should go from the THC input to GND. So where is that?

What happens if you trigger the torch by shorting the relevant terminals on the Everlast?

[East German]

Hello
Why don't you take the 1: 1 signal from the material clamp and torch! The MyPlasmCNC THC can also process the signal. Then the correct voltage should be displayed in the display window. It has to be connected differently to the THC module.

Peter

[Tankersley7w]

I will do that. Do you know how to hook up the plasma cutter to the THC module for the 1:1 ratio?
I have been looking at the below diagram and pins 5 and 7 are for the raw arc voltage. I am just confused as to how I am supposed to hook that up properly to get the THC module to read it properly. Ive read posts on it like this one: https://forum.langmuirsystems.com/t/eve ... ltage/7685

But I still can’t make sense of it all.

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[East German]

Yes 5 and 7 or directly to the material clamp and torch.

[Rodw]

Pin 5 & 7 will give you raw arc voltage for those THC's which support it. Note there are 100k resistors in each side of the circuit. This is to reduce it to non lethal voltage. On my sensing hardware, this resistance has to be taken into account.

[Tankersley7w]

Currently pins 4,6 on the voltage divider card are hooked up to pins 4,6 on the CNC plug which go to the red marked wires in the picture below. I plan on taking pins 4,6 on the cnc plug and and soldering them to pins 5,7 on the voltage divider card. That way the two red marked wires in the picture will be going towards the 1:1 raw voltage on the voltage divider card. Now would I need to swap the black wire (the one in the photo with the red mark) to the far right position where it says electrode/torch or do I keep that wire where it is at?

5F97A2E8-F47B-4BF6-9B2A-4810A00507D9.jpeg

Pretty much I would just be moving both wires from the 50:1 to the 1:1.

[East German]

Here is a Hypertherm 1100 with 1:1 Signal on the Board.

Works fine!

Peter

[john78]

Currently pins 4,6 on the voltage divider card are hooked up to pins 4,6 on the CNC plug which go to the red marked wires in the picture below. I plan on taking pins 4,6 on the cnc plug and and soldering them to pins 5,7 on the voltage divider card. That way the two red marked wires in the picture will be going towards the 1:1 raw voltage on the voltage divider card. Now would I need to swap the black wire (the one in the photo with the red mark) to the far right position where it says electrode/torch or do I keep that wire where it is at?5F97A2E8-F47B-4BF6-9B2A-4810A00507D9.jpeg
Pretty much I would just be moving both wires from the 50:1 to the 1:1.

Move the wires from 4,6 to 5,7 on the CNC board that is in the plasma. Then move the black wire to the electrode/torch and leave the red wire where it is on the proma interface. That will give you raw arc voltage to the plasma interface board. As for the 100k ohm resistors. They are not there to drop the voltage they are current limiting resistors. You will still have raw arc voltage at the plasma interface card. Be careful.....can be up to 300VDC and is lethal.

[Tankersley7w]

Awesome. I will give this a try and let you all know what happens. Thank you!

[Tankersley7w]

Ok so I’m hooked up to the 1:1 voltage and the myplasm interface on the computer screen reads 60-65 volts when cutting 20 gauge steel. THC is still not working. I feel like I am doing something wrong. I’ve tried different g code files just in case that was the problem. I tried setting different voltage again for the THC. THC still won’t move the torch.

[john78]

Do you have the ability to check the cut voltage with a volt meter? I would measure the voltage at the proma plasma interface to see if the raw arc voltage was correct. Remember this voltage can be up to 300vdc.

[Tankersley7w]

Do you have the ability to check the cut voltage with a volt meter? I would measure the voltage at the proma plasma interface to see if the raw arc voltage was correct. Remember this voltage can be up to 300vdc.

I am getting the same reading at the proma plasma interface as what the computer is reading on screen.

[john78]

Sounds like there is something wrong with the CNC interface board or its wired wrong.

Found this. https://plasmaspider.com/viewtopic.php?f=111&t=23700 Might be related.

Can you check the raw voltage going into the CNC interface board?

Did a quick search and found all kinds of people with issues with that cnc interface board. From what I have read best to hookup raw arc voltage directly to the torch and work lead connection and bypass the cnc interface for the voltage.