THC gradually lowering into material during cuts

Greetings, I have a Crossfire Pro with the THC running a Razorweld cut 45.

I recently had an issue develop where the machine is running into the material as it makes longer cuts, typically the final outline of a project.

I went through the troubleshooting but didn’t see anything the described what I’m seeing, I did check the connections as well as the THC connection screws to ensure it’s not riding the drive screw.

After running my last two failed cuts I watched the fire control a little more closely and it continually gets a trigger in the Z axis reading saying Height Control, I’m not sure why it keeps triggering and moving it closer to the material until it contacts but never lifts off.

I ran through and verified nothing is out of level all my slats are nearly flat with very little variation. The material isn’t warped in the areas I’ve attempted cuts I’ve ran the machine X and Y with the torch low to see if the gap closes and haven’t see any indication of it coming closer to the material in any directions.

It’s normal for the Z axis readout to say “under THC control” when the THC is on.

Watch the THC control panel to see if the THC is commanding a “down” movement, when the issue happens. Also watch for a voltage change that could be causing the THC to lower the torch. A voltage spike will cause the THC to lower the torch, in an attempt to lower the voltage.

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Weird. Usually the THC will lift up until you flame out and trash your consumables.

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It still trashed my consumables

What are your live voltage numbers? Smart or nominal?

What cutter and how is it wired?

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I’m pretty new to this so I’m not sure where to get that info from.

The cutter is the Razorweld Cut 45 with the standard torch using the THC box included in the kit.

So are you using the raw voltage inputs or the divided inputs on the THC box?

The live voltage numbers are displayed on the firecontrol screen. If you aren’t typing in a voltage number, then you’re using smart voltage.

When the z axis gets wet and dirty, you can see some voltage at rest. Check for voltage readings showing in firecontrol while the table is just idle.

Run the THC test as well.

I’m betting you have some resting voltage. You typically only see THC problems like this on long cuts because then it has the time to over adjust. It’s probably lowering on short cuts too but not long enough to cause the torch to hit the material.

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I’ve seen this condition so many times, every time it doesn’t recover.

Have you measured your actual height of the torch when you are expecting it to be at, say, 0.06 inches?
Run this gcode thru FireControl. It will use the IHS to cycle touching the metal and then lifting up to the 0.06 inch mark. It does have the 0.02 springback/backlash in there so it is possible your measurement could 0.08.
cut height test.tap (224 Bytes)

I was having my torch hitting the metal a lot and then discovered that the cut height, that I assumed was 0.06 was closer to 0.02.

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I haven’t done any manual measurement, I was on a deadline for a project so this morning I ran it without the THC and everything worked as intended so I’ll continue troubleshooting the issue when I am able to get back to my shop.

Good morning @AdamW, if you could let me know the live voltage during the issue, this will help us diagnose whether the VIM box is stepping the voltage down correctly. Usually when the THC moves the torch down to the metal, the voltage is raising too high, or the THC chip/Motion Control board is malfunctioning. Please let me know and I’d be happy to help!

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Ok so I ran the THC test and it’s showing the following

0.0v resting voltage

119.8v live voltage

I ran a test program and recorded the THC section.

The smart setting nominal is 103.3v

I managed to capture the movement the downward movements triggered at Live voltage 106.3 and 109.5

There were some up movements as well at 98.8, 98.2, 96.8, 95.9

My recording didn’t capture the movement values unfortunately.

My program settings in fusion are as follows:

Kerf .055”
Head Clearance .03937”
Feed 95 in/min
Pierce clearance .055”

Not sure those are good or bad they’ve been working well for me until I developed this issue.

Material is 16g mild steel sheet.