Slaving a thc300b into a blue point plasma230

[jeremyrockjock]

I have no diagram of the wiring of my plasma230 and I am trying to figure out what is what. I can trace wires but when the instructions say raw tip volts wire, work lead or table ground cable terminal I want to make certain I am using the right connection. One question I probably need to know ahead of time is that will this plasma machine work for this whole setup. I have done some cutting with it without the thc and the biggest concern I have is the torch shut off function. If the torch fires and reads no ground it will shut off. I have tweeked the fire delay in mach 3 to help with it but is the thc going to make it worse? I hate when the torch fires and penatrates the metal, pauses long enough to shut off before the steppers start to move. I just want to know if I should be using a different, more suitable plasma machine. Am I wasting my time with the plasma230?

[Torchhead]

Most plasma cutters will turn off if the arc current drops too low. Making a pierce and sitting there (pierce delay too long) will result in it shutting off. The torch just senses the current flow (not a ground detection) and if you don't have a good workclamp connection to the material (i.e workclamp clipped TO the material). I don't know anything about the plasma230. It looks to be a HF start unit so it should work for automated cutting.

Where are you setting the pierce delay? What are you using to generate the G-code? There is a value in MACH called THC Delay. It causes MACH to ignore any signals (strange or not) from the THC after a pierce. It's defaulted to 1 sec. Increasing that may help.


Tip Volts = Arc Volts = Gap Volts
ARC OK = Arc Xfr = OK to Move

Things to remember:
1. Workclamp is NOT ground (until you clip it to something that is already grounded.
2. Your table needs to be grounded locally with a ground rod(s)
3. Cutting with a plasma unit that has no available cut chart requires you do a series of test cuts and take notes. The first number to determine is the "cut gap" (how far above the metal you hover as you cut)
4. You can't use drag tips for automated cutting
5. There are a lot of parameters to master to get good cuts.
6. There is no "Easy Button"

You can make that plasma work it's just going to be a lot more work to get all the settings worked out.


TOM caudle
www.CandCNC.com

[jeremyrockjock]

Thanks Tom, I am able to get around the shutoff feature but making longer lead in cuuts and 0 sec pierce delay. I was playing with it last night and it worked pretty good. I also found out about the drag tips. It kept getting crap built up on it. I looked into getting different tips but I don't think they have the non drag type for this machine. I think I am going to look into getting a different machine.

[Torchhead]

Make your own non-drag tip. Just grind off the end of the outside shield until the nozzle end can sit down on the material. Drag tips hold the nozzle off the material a set amount and makes operation with a THC pretty much worthless. The tip has to drag on the material to get anything close to a decent cut and that gets ugly on complex cuts with kerfs closer than the drag tip radius.

TOM caudle
www.CandCNC.com

[jeremyrockjock]

I could turn the tips in my lathe.
The wiring diagram form the machine doesn't help me much as far as finding the arc ok connections and the raw tip volts. Can you give me some pointers on what wiring or curcuits to look for or follow? I have converted the diagrams. The only one I have figured out is where the amp sensor goes.

[Torchhead]

UNPLUG THE PLASMA FROM THE AC LINE BEFORE YOU DO THIS: Find the wire that goes to the electrode in the torch. It will probably be more than one heavy wire but they will be the same color and all attach back to the same spot to carry the higher amps.

Pull out the electrode itself and using an ohmmeter or continuity tester confirm that from where the electrode connects to your internal wires is close to ZERO ohms. Mark the wire as "-". Follow the Workclamp back into where it attaches inside the unit. Mark that as "+". You now have your Raw tip Volts + and -.

That unit, like most air plasma units, does not have an place to pick up an ARC OK signal. Only Hypertherm realized that a lot of people running the midsized machines were using them for automated cutting, and made the dry contacts (relay output) for ARC OK (Arc XFR). TD offered a add-in "automation card" for 300.00 that did what the Hypertherm did for free. So far Miller, Lincoln, ESAB and others still hold to the concept that you shouldn't be using their non-industrial machines for automated cutting so you have to develop the ARC OK externally.

All of the THC Sensor Cards from us have circuitry on it to use a simple AC current transformer (CT) and measure the AC input current which is proportional to DC output current. There are DC current sensors (Miller has one as a option) that has a reed relay and you loop the workclamp wire through it and it trips when current flows to the cut. Crude but it works. I think it's overpriced for what it is but I don't have Millers overhead! In either case you need to have some form of current sensor that will give a simple ON/OFF signal (open/close contacts) to the control software.

Why do you need ARC OK? Well, it holds motion until you have established an arc (are really cutting metal). Otherwise you program in a set pierce delay then the XY takes off even if it's not cutting. That is reason enough, but it also stops motion if you lose arc along the cut. Coupled with IHS and proper pierce gaps and cycles, it adds full automation to the process.

We sell a cheap CT (current transformer) to use with our THC Sensor card that slips over one of the AC wires into the machine and gives a ARC OK output to MACH.

The only other signal you need to interface is the TORCH SWITCH. That is a simple process of finding where the two switch wires coming from the Torch handle are connected (once again your ohmmeter is your friend) and tying the TORCH Switch terminals in parallel (either switch will fire the torch). The Scotchlok terminals to tie wires in without cutting or stripping work wonders here. Simple test is after the wires are tied in and to the terminals on the Sensor card you should be able to fire the torch by shorting the wires.

AT ANY POINT if live testing you don't feel comfortable get a person that has some electrical wiring experience with medium-high (up to 200 volts) experience AND LET THEM DO ANYTHING THAT INVOLVES ANYTHING WITH PLASMA CASE OPEN AND IT TURNED ON.

With virtually ANY plasma unit but the Hypertherm 1000 to 1650 and the new TD 52, 82 and 102 series (and their A series with a connector on the rear) you will have to dig around and do some investigative work to find the three magic connection points. Sometimes the actual physical connection locations even vary from one model to another. Side note: The new Hypertherm 45 still has the ARC XFR and "START" (Torch switch) connections on an easy accessable connector on the rear but no long have two nice quick connect terminals (J15 & J16 in the 1000) for Raw Arc volts (Raw Tip Volts). They DO have a white paper on where to connect inside for the RAW arc volts and even a "kit" to make it easier with step by step instructions. TD still has their head in the sand and gives you no clue to access the un-divided (RAW) arc volts inside their unit. It's not hard to figure out but they seem baffled why anyone would want that!

TOM caudle
www.CandCNC.com
Totally Modular CNC Electronics

[jeremyrockjock]

Awesome Tom, Thanks for the info. Here is where I am at.

Tip volts leads connected to work cable lead and to the torch lead
Torch trigger leads connected to the trigger wires
Current sensor connected to the work cable wire.
Arc ok leads not connected
Turned on power and pushed the trigger. The arc ok lights come on both on the curcuit board and the display and the read out shows approx 200. Do I still need the arc ok leads connected?

[Torchhead]

The THC300 is not our product (It's based on a design I did about 5 years ago, but several circuits have changed) so i can't take it much further. You need to have ARC OK working ff when there is no arc to the metal (not just when you fire the torch in the air) and ON when there is, to get true automated plasma cutting. Get with your vendor and get the last bit working.

TOM caudle
www.CandCNC.com

[jeremyrockjock]

Thanks again Tom.

[jeremyrockjock]

What type of signal is the sensor board's arc ok looking for? Continuity or voltage?