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Author Topic: Convert Mill machine to Plasma and back.  (Read 4936 times)

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Convert Mill machine to Plasma and back.
« on: October 07, 2012, 07:17:07 AM »
I've spent hours and hours looking for some kind of information on this, but to no avail. So now I'm going to ask.

I have a Milling machine that I built about 6 years ago and have been using with great success since. I do my drawings in Autocad, Cam in BobCad and cut with Mach 3.

I have a Miller Spectrum 125C Plasma cutter that I would like adapt to my table so that I can occasionally do some metal cutting (I'm building an airplane).

I've picked up bits and pieces from the forum about Plasma but basically I know nothing about setting it up.

The question is...Where can I find the Newbie info about how to set up the plasma for CNC..... Book? Forum? Person? Religion? Cult? Someones Wife?  Heck I'll take anything at this point.

Thanks for any help.

Re: Convert Mill machine to Plasma and back.
« Reply #1 on: October 07, 2012, 10:19:59 AM »
What do you have for a plasma?  Is your CNC a mill or a router?  

If it's a mill, you may not be able to hit the speeds you'll need for plasma.  If you do set it up for plasma, you'll only do it once.  Plasma dust, which are tiny metal particles, will get everywhere and you'll spend the next day cleaning the mill.

If it's a router, it's a little easier convert and clean and your feed speeds should be faster.  Even with a router, it's not something you'll want to do all the time.  Having done that before, I wouldn't even run a router table in the same vicinity as a plasma table.  Unless you have a good downdraft or water table, which you probably won't just doing a conversion to a mill, the plasma dust will be almost unmanageable.

Converting the plasma to CNC depends on the plasma.  Any of the reputable manufacturers sell a divider/CNC interface board.  Depending on the plasma, that can be anywhere from $100 to $300....or if you look at a service manual for the plasma you can figure out how to do it without buying their board.  We used to build our own interface for Thermal Dynamics and Hypertherm, but started using their factory boards about a year ago.

Sorry....Just noticed you said your plasma was a Miller Spectrum.  We don't mess with miller.  You'll find that even the techs at miller are largely clueless on setting up their machines for CNC.  They did tell me once that ARC OK, Start/Stop and arc voltage were all available by tapping into the main board.  You would have to make your own divider board.  Miller does have a CNC interface "Box" that either plugs into the plasma or comes with their machine units, but when I asked for availability and pricing on it, they didn't know what I was talking about.
« Last Edit: October 07, 2012, 10:27:35 AM by rrc1962 »
Re: Convert Mill machine to Plasma and back.
« Reply #2 on: October 07, 2012, 02:28:28 PM »

Thanks for the reply. My CNC is a router and I can hit the speeds for the Miller Plasma. I had figured to modify my table so that I can insert a water bed that would be removable without much fuss. I don't know what a divider board is. I was planning on piggy-backing the torch head to my router mount and then to find a way to trigger the plasma on and off through the software. This probably shows my lack of knowledge in this arena, but that's why I'm asking.

Thanks again for the reply
Re: Convert Mill machine to Plasma and back.
« Reply #3 on: October 07, 2012, 06:30:09 PM »
Typically you have three signals to deal with that are related to the plasma.  (1) Divided arc voltage goes to the THC.  Miller does not have a divider board available, so you'd have to make one.  If you don't want to use a THC, you wouldn't even need it.   (2) ArcOK or OK to Move is a relay inside the plasma that closes after arc transfer has occurred.  When Mach3 THC is on, that signal tells Mach that you have a good arc and motion can begin.  You can run without this, but if the plasma does not strike a good arc for some reason, Mach will just start moving anyway and you're part will be ruined.  You can compensate for not using ArcOK to a degree by using a G04 dwell.  (3) Start/Stop is a circuit in the plasma that when closed, starts the torch.  Hook it up to a relay fired by Mach3 to start the torch.

Offline BR549

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Re: Convert Mill machine to Plasma and back.
« Reply #4 on: October 07, 2012, 07:08:21 PM »
You can get the divider boards from Cand CNC if you want THC. They also make a low cost version of the THC.

IF you did not want thc it is a matter of finding the ARC START relay terminals.  You CAN run without the ARC (ok) signal. The worse that happens is you have to stop and restart the machine IF the arc does not strike OR goes out I have run many days without it when it goes out and am waiting for a replacement board. (;-)

For the Z you can run as a normal axis OR build a floating Z to find the top of the material. AGAIN you CAN run without it you just have to adjust the torch to the top of the material and manually zero the axis. OR as a local fellow does he only has 2 axis XY and an adjustable z that he sets to the cutting height.  Not perfect but it does work for him.

It really depends on how much control you want to have over the process. (;-)  

NOW be warned that Plasma IS the nastiest process of all the CNC's. That plasma dust is very fine and gets into everything. Once ity gets there it is a matter of time before it wears something out OR shorts out a PCB. (;-)  AND darn near impossible to get it all back out of the machine.  The rail bearings soon become consumables.

BUT it IS a fun process(;-)

(;-) TP
« Last Edit: October 07, 2012, 07:12:24 PM by BR549 »
Re: Convert Mill machine to Plasma and back.
« Reply #5 on: October 09, 2012, 06:04:35 AM »
Guys, Thanks for the help, it's the kind of information I need. I'm looking into it and will probably give it a shot. I'll let you know how it ends up.