Torch Dragging

[biggator850]

Need some help ya'll! I have been cutting about 6 months or so with good success. Have cut several sheets of 16ga mild steel. Last night I switched out to a new sheet for a large part and the torch tip keeps dragging. I watched it as it was cutting and it looks like I am having two problems: sheet flexing when the torch touches down and the sheet rippling as it cuts from the heat.

I thought the THC was supposed to monitor the tip voltage and automatically adjust so the cut height clearance was maintained even if the sheet did flex some. Did I miss something here?

I know the omic sensor is primarily for cutting real thin material and tends to have issues if the sheet and/or tip is dirty. Should I just switch Mach3 to run Ohmicly verse THC?

I ended up donning welding gloves and holding the sheet down with my hands following the torch around the cuts. The piece came out salvageable, but I need to understand and fix the problem. Can anyone offer any help?????

I'm running a TruCut machine with Powermax 85 cutting with a 65A tip running at 55A cutting at 75IPM using .06 Cut Height.

Thanks,
BC

[gary42095]

with a powermax 85 running 65amp consumables, cutting 16g you should be at


65amps
.06 work height
.15 pierce
.1 delay
260 ipm
according to book spec with sheilded consumables

i think you are cutting much too slow for one thing,75ipm you could just about cut 3/8ths plate. i would use fine cut or 45amp regular consumables if you have them
no matter what ,speed it up ALOT that should take care of most of you issues i think it shouldnt warp from heat cutting anything significant and at the right speed you should not have any real heat affected area

[gary42095]

also i know when switching sheets make sure your slats dont have a bunch of crap stuck to them from previous cuts, that will make uneven surface. which i think height control can adjust to, but why leave room for any chance of f'ing up a sheet out of laziness

[acourtjester]

The THC and Ohmic sensor do 2 different things. You are correct the the THC should track the arc volts and move the torch up/down as needed. The ohmic sensor is to detect the metal surface at the start of each cut operation only. They are separate functions once the ohmic sensor helps to set up the pierce height. The pierce happens and then after delay then the torch moves and after a another delay the THC comes into play to control the cut height to the end of the cut.
What is happening is you are cutting to slow and the kerf may be to wide and that is messing up the arc voltage causing the THC to dive. I had a problem when I first set up my DTHC when I got to the end of the cut and crossed over the lead in kerf the torch would drive I had to use path rules to turn off the DTHC just before the end so it did not see the voltage change.

[biggator850]

Thanks Gary!

I just switched the tip out to Fine Cut. Ran it at 120 IPM and dang near perfect. Ran again at 150 and it was rough dross. Running it now at 200 but it looks like the dross is going to be pretty bad. I am running regular Fine Cut, not the low speed. How do you know what speed to run?

I was told, rule of thumb, run at 60% of the speed in the Hypertherm cut charts. Does that hold true all the time?

Have you found that Fine Cut consumables have a better cut quality that regular shielded? What about cut life?

I am somewhat new to this and there is no one I know in my area for help so I am looking to you guys on this forum to help me. Ross at TruCut has been absolutely GREAT when I have had to call him, but it isn't his job to raise me!

Thanks,
BC

BTW,
The torch tip still is not holding the cut height clearance and dragging some, but it is not causing it to jump around as bad with the fine cut tip. Any ideas?

[grindergary]

Thanks Gary!



I was told, rule of thumb, run at 60% of the speed in the Hypertherm cut charts. Does that hold true all the time?

Have you found that Fine Cut consumables have a better cut quality that regular shielded? What about cut life?

I am somewhat new to this and there is no one I know in my area for help so I am looking to you guys on this forum to help me. Ross at TruCut has been absolutely GREAT when I have had to call him, but it isn't his job to raise me!

Thanks,
BC

BTW,
The torch tip still is not holding the cut height clearance and dragging some, but it is not causing it to jump around as bad with the fine cut tip. Any ideas?

First off, When they say 60% of book values, they mean for cutting small holes. Follow the cut charts to the letter for a start. You can always move some either way as you cut. Make sure you have your voltage set correctly and you should be good to go.

If I remember correctly, 45 amp fine cut runs at about 250ipm.

I used fine cuts and they last a long time if you don't crash the torch.

Gary

[Shane Warnick]

I cut 14g @ 213 ipm 45 amp finecut. Go faster. Stsrt @ book spec then if it skips and doesn't cut all the way through slow down 3-5 ipm until it cuts all the way all the time. Run some line tests until you get speed and THC dialed in. Then do a few circles ( 2-3" diameter) then some squares. I second the suggestion you are cutting too slow. Clean / check your work clamp / ground as well before anything else. Check both ends machine connection could be loose. It may be hanging and not even hooked up. Or just dirty or on rust etc. Trust me we have all chased a gremlin just to see that damn clamp on the floor after an hour of head scratching. There are those that have, and then the rest. Who lie and say not me!!!
Shane

[biggator850]

Thank you Guys for your help!!!!!

I sped up the cut speed and it is cutting dang near perfect.

[gary42095]

should always go by book spec, and then adjust if needed. if you dont have the manual, download it from hypertherm website

[tnbndr]

The manual is also on the CD that came with your plasma cutter.