PP60C Poor performance with CNC cutting--- Duty Cycle issues???

[Tacoma747]

I have a PP60C that is ~5 months old, overall I have been impressed with it, but I am having problems getting good results with it on 1/4" and thicker steel. The PP60C is supposedly rated to cut over 1" thick, all I can say is I don't see how it would be possible.

I can only cut 1/4" steel at about 25ipm at about 40-45 amps to get a decent cut. This is with automatic torch height control functioning. I was cutting some 3/8" steel today and it cut fine at 20ipm if I ran it at 50-55 amps. I am perfectly fine with that, except that after about 5 minutes of cutting it stopped cutting, then started again, then stopped, etc. I can only assume this means it was running too hot and shut down for a second or two.

As many of you CNC guys might know, that causes BIG problems when something doesn't cut right the first time, ATHC won't work properly the 2nd time around, and running it without ATHC on metal that is nowhere close to flat all the way across is tough.

What amperage/speed should I be cutting at? I tried dropping the amperage down to 45 (and 15ipm) but it will barely pierce the 3/8", and even then it cuts out after cutting for a bit.

The hypertherm settings suggest 45amps at 32ipm for 3/8" steel, the PP60C (at least mine) wouldn't come close to doing that, it wouldn't cut cleanly at 45amps at 20ipm.

[zoama]

I'd check all electical connections from both ends of the ground to the terminal connections in your breaker box.
I'd even pull the breaker itself to make sure the bus bar isn't burned ( from poor contact ) I've had that happen before... caused one leg to drop out intermittently.

[Rambozo]

When it stopped cutting, did it turn on the warning light on the front panel?

[SeanMurphy265]

What's your air pressure, and do you have a sufficient air compressor? the reason I am asking is that on some of my first cuts it would not cut properly. I had a leak in my air hose and the cutter was not getting enough air. I'm not sure hypertherm is a good comparison they cost twice as much as the pp60c.

How did you get your THC to properly work with burntables thc?

[Tacoma747]

Is the warning light the little yellow light? I *think* it stays on all the time, but I may be wrong.

Electrical connections are all good, it's all new matter of fact (well, since I bought the table in February)

I got the ATHC working by just pulling the feed for the control box directly off the red and black wires going to the CNC port (and wiring in a 100K resistor)

[Tacoma747]

Oh yea, and the compressor seems to do fine, it never drops below 90psi really, once it hits 90 the compressor kicks on till it gets to 135 I think, the regulator at the plasma is set at 65 I think. If it were a compressor issue I would imagine it might cause problems when cutting thin metal as well. The problem I am having happens more often when running at 60 amps, so I can only come to believe that it is because it is hitting the duty cycle limits.

[performance]

If I remember right the 60C has a duty cycle of 100% around 45 amps at 98 volts or so. So that means unless you are 45 amps or under with the voltage less than 98V, you are going to have to give it a break. Something about CNC cutting people don't realize is that the units are designed to run at the maximum amperage for the consumable you have. So, don't run the unit with a 1.1 or 1.2 mm hole in it and expect it to cut well when it needs a .9 mm hole. The unit will cut up to 1 inch but not in CNC. CNC cutting is about 1/2 of the quality rated cut with any plasma cutter. The unit is rated for a max of 7/16 in CNC.

[Tacoma747]

Doesn't make much sense to advertise it will cut 1", sell it with a CNC torch, suggest it not be used with handheld torches, then say it can only cut 7/16" when used with CNC.

Best I have found, there is only one size available on the nozzles for the A81 torch head.

I backed it down to 45 and it still shut down, I can also only assume the voltage going in is 220V??? There isn't any way to adjust voltage on it is there? Not sure what you mean when you say it should be less than 98 volts.

Lastly, it is kind of hard to give it a break when it won't cut ONE part without messing up, I can't start/stop it mid cycle and have anything turn out well...

[sportbike]

Are you connected to all of the CNC connection pins on the unit itself or did you connect to the wires directly to determine when the ARC was OK and to sense the voltage? Could it be the ARC OK signal is dropping and causing the issue?

[zoama]

Not sure what you mean when you say it should be less than 98 volts.

That's output not input.

[sportbike]

BTW, the specs do say 7/16 for CNC use. The pp50 is listed at 1/4" for CNC.

[performance]

There's also air pressure involved. Torch height etc. If you read the specs, it is pretty clear how it is rated. We break it down in CNC use, and Hand held use. We're no different than anyone else on that. You can purchase a hand held torch for the unit. There are smaller consumables available for the torch. The voltage is the cutting voltage of the arc. If your voltage is running higher than 98 volts then duty cycle will be reduced. You are cutting with a combination of both amps and voltage, so both are a factor in duty cycle, though it's rarely discussed. There are other things that affect duty cycle as well, including air space around the welder, humidity, and localized air temperature.

As you compared units to the Hypertherm earlier...The Hypertherm PM45 only is 100% duty cycle at 32 amps...but it is still rated higher for CNC cutting at max amps with only 50% duty.

[performance]

Ok,
I've cut and pasted some info here for you, and it has the numbers of the 1.0 torch nozzle. You can get them from trafimet, or river-weld, if you like.