Machine taking off too soon

[TerraWombat]

I've been away from my machine for a bit and just got back onto it tonight to cut out some project ideas I've been working on recently. I think this is something easy, but I've just been away too long and have forgotten a lot of the settings. Anyway, the problem is that my machine isn't giving the torch enough time to fire up and create a good arc. It will take off before the arc is complete and will leave me with a part that has some uncut spots on it.

Take a look at this video to see for yourself.

[nomedia="http://www.youtube.com/watch?v=PJ7tvH8fEcE"]YouTube - Jeep Comanche Hitch Sideplate Plasma Cut[/nomedia]


Any thoughts?

[jimcolt]

You need to look in your plasma system manual under machine cutting parameters and look up the recommended pierce delay time for the materials, thickness and power level you are cutting at. The pierce delay time then must be set in your machine setup parameters. This time allows for the plasma to fully penetrate the plate and stabilize before movement occurs.

Jim Colt Hypertherm

[TerraWombat]

Thanks Jim. I use sheetcam to create my G-code and I've saved a variety of different profiles for different thickness metals. this particular piece was 12Ga. mild steel. The closet to that thickness in my plasma metal is 0.135" which is what I used. I don't recall the pierce time off the top of my head, but I had it set to exactly what the manual states (I want to say around 0.6 to 0.9 seconds).

[jimcolt]

i don't know what your plasma system is (make, model) or the power level you are running at....so I cannot offer much on the line of advice! From the video it appears there is no pierce delay at all.

Jim

[TerraWombat]

Thermal Dynamics Cutmaster 52. I agree, it's almost like there is no delay at all. I'm going to brush up on my G-Code and verify that SheetCam is adding a delay.

[TerraWombat]

A portion of my G-Code:

N0310 M03
N0320 G04 P0.4

Looks like I'm only giving the torch 0.4 seconds of dwell time before it takes off. I'll look into increasing this time as it seems my machine is a little slow at producing an arc, especially on the initial fire. It seems to get better as it relights at various spots on the part down the line.

[plain ol Bill]

I don't use any delay time at all on 12 ga. using 40 amps, pierce at .150 and cut at.08.

[TerraWombat]

I'd agree that I shouldn't need much, if any, delay for 12Ga., but it's not the thickness of the metal that is holding me up. When Mach3 gives my plasma the call to run and you hear the relay click, it takes a while for the arc to actually come on. By the time I get a good arc, my machine has already moved about a quarter of an inch. The first pierce is always the worst and then it gradually gets better over time.

[panozeng]

If you're running Mach you might also want to verify in the settings window that your machine is set for time units of seconds. The other option is milliseconds, which makes .4 basically nothing. I had this issue when I first got my machine running - couldn't find the setting at first in Mach to get the units all jiving...

[TerraWombat]

Thank you for the suggestion - I will look into that.

[TerraWombat]

My 'G04 Dwell in ms' box is unchecked.

[Mike 1948]

I'd agree that I shouldn't need much, if any, delay for 12Ga., but it's not the thickness of the metal that is holding me up. When Mach3 gives my plasma the call to run and you hear the relay click, it takes a while for the arc to actually come on. By the time I get a good arc, my machine has already moved about a quarter of an inch. The first pierce is always the worst and then it gradually gets better over time.

I also have a CM52, Are you using a doughnut current transformer for your "OK to move signal" or the Thermaldyne CNC wire harness? I had issues with the current transformer that was installed in mine, it all went away when I bought the $40.00 wire hareness and hooked it up.
Maybe the start cartridge in the torch head is goobered up. Or the small filter inside the case is possibly getting plugged and not giving enough air flow to blow the start cartridge back quickly enough.

Just Some Thoughts
Mike