Is it possible to use a $10.00 plasma cutter?

[ssutton]

I just recently completed a 4' X 4' table that will be used primarily as router, but I want to use it as a plasma table as well occasionally. I have an Esab HandyPlasma550 that I acquired that was dead. (it was given to me free) I repaired the main control board and the unit works perfectly now, I have a total of < $10.00 invested in this machine, the full wave bridge rectifier and MOV circuitry was bad. Because I have a $10.00 plasma cutter I am HIGHLY motivated to use it on my table if it is at all possible.

Here are my questions;

1. I think that the 550 uses a high freq. start method, does anyone successfully use this type of start method with there table? The manual says to start the within .020 of the material.


2. What about electrical noise, can this issue be overcome with good grounding and separation techniques?

Again, this will be for occasional use, not production work. I am just wanting to know if this can be done.

Thanks,
Scott

[jimcolt]

There are hundreds of thousands of high frequency start plasma systems operating on cnc cutting machines worldwide. All industrial plasma systems from about 120 amps and above are high frequency start. Industrial cnc machines and their associated controls and electronics have extensive filtering, grounding, and input/output optical isolation that makes them work reliably with a high frequency start plasma. Industrial high frequency start plasma systems use high frequency to start a pilot arc, which allows transfer to the plate from a reasonable distance...3/16" to as much as 3/4" on large systems. This arc transfer distance allows the blowback molten metal to miss the front end of the torch...preventing damage to the nozzle.

The plasma system that you have is a high frequency start WITHOUT pilot arc.....meaning the nozzle must get very close to the plate to transfer the arc. This works acceptably in hand cutting applications as you can tip the torch to cause the molten metal to miss from hitting the exposed nozzle. In mechanized cutting....you will have trouble getting this type of torch to repeatedly pierce anything thicker than about 1/8" without damaging the nozzle...which will affect cut quality. Further...if the material has some dirt or rust on the top surface...often you will have to scratch the nozzle on the material to get it to start the arc.....again, not the best process for mechanized cutting.

Back to the high frequency noise...you did not say what you built for a machine. If it uses a standard PC for control, uses stepper motors and unshielded cables, unfiltered electronics....you likely will have issues with electrical noise interference. You can solve the issues buy adding filters, optical isolation, shielded cables, ground rod......but you likely will burn up a few system components in the process. It may be cheaper to buy a modern plasma with a non high frequency (blowback) start.

I'm not trying to discourage you....you may very well be able to make it work...a few have! There just is no exact science to solving high frequency caused electrical noise interference issues on homebuilt machines. You may want to consult with the supplier of the components used in your build..they may have some advice.

Jim Colt Hypertherm

[flyinwilly]

It's not that bad to use a HF, contact start plasma if you're building from scratch. I use a CUT40 (similar to the ESAB) but it required the use of shielded cable on ALL limit and home switches. I also installed a earth ground for the table. In addition, I had to move the PC about 25' away from the table because it just used to go bonkers while the torch was running.

My torch is a contact start torch, it must be in contact with the material to light.. This required software modifications to the Sheetcam processor ( Les can send you the code) and tweaking to the pierce and cut settings to back the torch away as quick as possible after the plasma start. You'll also need a floating head for the torch so you can find the zero point on the Z axis.

I've had no problems cutting up to 1/8" although the tips wear quickly on the thicker material but they are cheap so it's not a big problem.

You can see what I went through on my build thread - A Different Machine - Downdraft/water table.

With all that being said, I am in the process of buying a Hypertherm but not because of the HF, contact start. I just need to cut thicker material but if you are only going to cut under 11 GA, the ESAB should work OK.

Good Luck,


Willy

[jimcolt]

Pretty much what I said in my response!

Jim Colt