Rods "Spaceship" Scratch built Plasma Cutter build

30 Jul 2018 10:28 #115115 by rodw

robertspark wrote: Am I reading the resistance correctly.... 11k ohm?

Checked my notes. Should be 2.2 k ohm as per advised by PCW.
03 Jan 2019 09:39 #123398 by rodw
I've been ignoring my plasma build for a long time becasue I sold my Everlast to another forum member with the intention of buying a Hypertherm XP45 but other priorities have got in the road. But now my table is sitting in a shed with a 3 phase power point beside it and I really need to get it going now the new year is with us.

So a question for the plasma guys on the forum. I have found an older Brand new in box 120 amp Thermal Dynamics A120 machine with CNC interface and a SL100sv machine torch at a very good price from a dealer. Its not much more than what I was intending to spend and about half the price of a Hypertherm 125 amp machine.

This machine is coloured blue and the current model is green. The torch is the same. Did anything change other than the paint?

Would it be worth buying or is it going to be a headache?
03 Jan 2019 17:08 #123414 by islander261

Does the machine have the "full CNC interface board" with voltage divider or just the the ArcOK and Arc Start signals available on the CPC connector?

I think the newer machines have different controls and are closer to HT in features. The one thing I don't like is the cutting current setting knob. You are entirely dependent on TD's calibration being correct, no actual arc current feedback. I have pencil marks on my panel to aid in reproducible setting.

One thing with any TD machine is that the cut tables are really lacking compared to an HT. This is actually the reason I made my "Franken Torch" by grafting the Duramax parts onto the front of my SL100sv torch. Not really a problem for you with all the THC testing you did, the process for finding the correct cutting parameters is the same and the book does provide a starting point. I think I get better consumable life with the HT parts.

One strange to me feature is that if the SL100sv torch shield touches the material while cutting the machine will throw an error and stop cutting. This caused me no end of grief with my old commercial controller. So much so that I hacked the unit to prevent this from happening. This most likely isn't necessary with my new LCNC control with the good THC.

My TD power supply hasn't missed a beat in ten years of use. I am careful to feed it clean dry air and clean out the dust once a year. The ambient temperature here is much cooler than Oz. The front panel looks the same as mine accept for the A120 logo which is A60 on mine.

Make sure you get a really good deal from the dealer, plenty of consumables thrown in etc. This is an old stock machine and not the latest and greatest.

03 Jan 2019 22:50 #123437 by rodw
John, thanks for your input. I'm not sure if I want another experiment. I did note that there is no voltage divider as standard. That might not be a bad thing as the THCAD10 could be mounted on the machine and fed raw arc voltage.

The newer TD machines (eg. a40i/a60i) have a switch on the divider board to select between tip contact as being for ohmic sensing or an error signal and have ohmic sensing built in. I wonder if that error you had was by design?

I did have a good trawl through the plasma spider forum last night and some liked the machine but it was obvious you needed to set it up properly for each cut with correct pressure and tip.

So it sounds like I need to get them down under the price of a Hypertherm 65 to make it worthwhile considering.
03 Jan 2019 23:20 #123439 by islander261
I actually have my homemade voltage divider inside my A60 with the divided voltage on the correct pins of the CPC connector. My THCad is mounted in a small box that sits on top of my my A60 and also serves as the terminals for the Ok to Move and Arc Start signals. This way I am not trying to send an analog signal across the noisy shop floor.

I was told by TD customer support after a lot of questions that the shorted shield feature was a request from one of TD's OEM customers. It is only active when the SL100sv torch is used, when the hand torch or aftermarket machine torch is used it is not active. It works by sensing the presents of the second air solenoid valve in the torch.

Yes, you should get a significant discount to take that unit off the dealers inventory.

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