Rising cut height during cuts

Before I get started here is my setup

RW 45 (in 2T mode)
PTM60 machine torch from George
60gal dewalt compressor
Copper pipe air dry system with additional air drier/filter
75psi at the plasma cutter
Fusion 360
Consumables from George
.0600 CR sheet
.5 PD
.15 PH
28 amps
70 IPM

I have been doing a lot of troubleshooting with my crossfire pro for the past 3 months. It’s been Hell. Thanks to this forum I’ve been able to fix some of my issues. My biggest issue right now is with the THC.
While cutting a 16g sheet the cut height would rise randomly in a few locations and I would have to rerun those loops to fix the problem. So I started looking into the THC. Passed both of the THC tests so connection seems to be fine.
I decided to start doing some test cuts with making changes with the cut height and noticed I was getting very irregular sporadic differences in measurements.
These were measured after pausing the cut in the same spot for each test.

.06 Found to be .13
.07 found to be .18
.08 found to be .16
.06 found to be .06 (2nd time)
.05 found to be .10
.04 found to be .10
.03 found to be .10
.02 found to be .00
.03 found to be .08 (2nd time)

As you can tell nothing correlates. I have noticed that the IHS does allow the nozzle to tap the sheet to sense location before cutting. I checked all connections several times. Repositioned the torch mount and removed some slack and still haven’t found a solution to this.

Where is the work clamp from the plasma cutter attached? Random results ‘could’ be caused by poor work clamp connection. It should be clamped firmly to the material.

It could also be caused by grounding issues with your control computer or Langmuir Control box.

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Clamp is firmly on the material. I keep my laptop unplugged while cutting

Just taking a shot here but have you tried bumping the amperage up a little bit? Since THC uses voltage to adjust the height I wonder if changing amperage might be a way of getting a steadier voltage. Are you using raw or dived voltage? I’m assuming you’re using the langmuir/razorweld pigtail for divided voltage.

does it raise during a single cut (loop) to the point of extinguishing arc?

or sometimes that single cut (loop) is cutting higher then your target of.06 but finishes without extinguishing the arc?

Are you using smart or nominal voltage in firecontrol? what was the voltage during your test cuts?

Check the travel on the z axis: at 10 ipm use the page up and down key to touch off the torch while observing the travel of the z axis for any binding, slop , chatter. also watch the iIHS indicator in firecontrol.

also check this ring connecting it maybe loose.

these figures were after a few seconds of cutting, could you see firecontrol actively drive up or down the torch to this position? or after it torched off and moved to its cutting position was it at this height and remained there?

Take a very good look at this set of contacts here as well.

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The amperage used was 25-30. Cuts were looking good around 27 or 28 with 16g. I could try turning it up to see if that makes a difference. I am using the wiring for divided

What consumable set are you running? Make sure that the amperage you set on the machine matches the amperage rating of your nozzle.

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So I have experienced both of those scenarios with the cutting but definitely more so on the latter. Most of the time the arc will continue while raising during that loop and then will move to the next loop and cut fine. Very sporadic. It will usually cut correctly once I rerun that loop. Just doesn’t look as great. I also noticed the kerf if some areas of the cut were much larger while observing. Ruined a 30” sign. I checked that screw and it’s on there pretty tight. I have jogged the torch up and down and did see the IHS green light turn on once it tapped the material. Live reading was around 97.0 nominal reading was 110.8

30a tip running at 27 amps gives me the best cuts when working correctly :man_shrugging:

Are you running smart voltage or using a nominal voltage? If using nominal voltage, how are you determining what to set it to?

I haven’t been using smart voltage because it says for 14g or thicker. I haven’t entered anything or changed any of those settings since I bought the machine

Try it using smart voltage.

What do you currently have written in the nominal voltage line?

Or entering a nominal voltage in this range and give it a try.

I did some small test cuts tonight and i’m pretty sure turning the smart voltage on was the solution. Huge improvement Thanks! I wonder why langmuir says to not use it for 16g

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That is great.
What voltage did you have written in the nominal voltage box before switching it over to smart voltage?

I run nominal voltage numbers for every cut I do but I also have a hypertherm who puts nominal voltage numbers in their cut charts. The only way for you to get nominal voltages would be run some test cuts without the THC ( I’m not sure if the live voltage stays active without the THC turned on z axis might have to be just unplugged so it still gathering that data) at the correct height and observe what the live voltage averages and then use that for your real cut.
If you had a random nominal voltage number written in there the THC will just try to chase it up or down to get there.

My hyperthermal run nominal voltages from about 78 to 131 depending on the thickness of material and the torch height.

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It was set at 110.8 Going to cut out a sign today while on smart voltage and ill see if it made a difference. I will post a picture

Not sure if these pictures will upload but here you can see that it did it again. I was able to rerun that loop and get it to cut. Just looked awful. I can clean it up. I noticed on my y axis’ rails some of my bearings are loose and some are too tight. Could that be causing this?

What condition is that nozzle in it looks like it’s gotten hot.

How’s your air supply? I might check your desiccant cell and see what the condition is like.
Wet air can definitely kill a set of consumables quick.

That was a fresh nozzle and electrode.

You don’t want all the bearings tight to rails at all. Some will be loose, and some will have a little resistance at different locations to rails. Go back and reread through the Langmuir setup instructions as to how to set preloads on bearings.

I’ll check the desiccant when I get home. Is there a way to test for moisture in the air?