Wright CNC Height Control Problem

[sterling rod custom]

We have a new wright cnc table. We are having a cutting height issue. Whenever we are cutting the torch slowly drifts down until hitting the material and gets stuck. Any help would be greatly appreciated.

[beefy]

Is the gcode commanding it to do that move. That's the first thing I eliminate whenever a problem like that exists.

And are you sure it's not the material itself is sitting on an upward slope, making it appear the torch is moving down.

Have you tried the same cut with THC disabled. Does it still happen.

If you are using THC control, is the actually cut volts much higher than the set volts. The THC would move the torch down to try and reduce the actual volts to match the set volts.

[adbuch]

Is the gcode commanding it to do that move. That's the first thing I eliminate whenever a problem like that exists.

And are you sure it's not the material itself is sitting on an upward slope, making it appear the torch is moving down.

Have you tried the same cut with THC disabled. Does it still happen.

If you are using THC control, is the actually cut volts much higher than the set volts. The THC would move the torch down to try and reduce the actual volts to match the set volts.

I agree with Keith. I would disable the THC and see what happens.
David

[OffRoadDevilDog]

Some Wright CNC owners in the owners group experienced this and found wires inside the control box going to the THC control to be loose.

[DuncanMotorsports714]

I have a Wright CNC first generation table with Mach 3 and a Proma THC. I can never get the THC to work with Mach 3. When I run cuts the THC voltage changes, basically showing the torch is farther away from the material. But on Mach 3 the z axis doesn’t change. I’ve ran the test function on the proma and it moves the torch up and down. But after that it still doesn’t work. I’ve tried it with the THC button on and off on Mach 3. Any help would be greatly appreciated.

[adbuch]

Here is some information from Jim Colt of Hypertherm that may be of some help to you.
David

"Re: THC Voltage Issue - Proma THC Hypertherm PM 65

by jimcolt » Mon Jan 07, 2019 1:17 pm

The arc voltage listed in the Hypertherm cut charts is correct, assuming:
- You are cutting at the book speed. Lower than book speed will make the torch run closer to the material and you will need to run a higher voltage in order for the torch to maintain the necessary .06" cut height for best cut quality.
-worn consumables will make the torch run closer to the material, again as consumables wear you must raise the voltage to maintain cut height.
- Something out of calibration in the wiring between the Hypertherm voltage divider and the THC will affect the accuracy of your height control and voltage readings.
- an incorrectly set or out of tolerance voltage divider will affect the accuracy and voltage readings.
- low plasma cut pressure will cause the torch to run closer to the material.....again, raise it by raising voltage.

Arc voltage (Actual) can be read with a DC digital meter by connecting inside the power supply to the work (+) and electrode (-) connections on the main power board. Set the torch at a fixed height (usually .06") exactly at the book specs over a piece of steel, set speed as the book specs says, new consumables in the torch....and do a cut with the THC off. The meter will read within a couple volts of the book arc voltage (this voltage is determined by the laws of physics, the resistance of the arc, the length of the arc and the air flow....assuming that all of these are set at book specs. After doing this test you can get another meter and measure the voltage divider output....if the divider is set at 50:1, then it should read 1/50th of the meter that is reading the work to electrode voltage. No rocket science....and most that tell me there voltage is wrong usually have something (speed, physical height, air flow/purity, amperage or used consumables in the torch).....there are a lot of things that affect the relationship between voltage and height.

The only important thing is that the THC maintains the physical cut height throughout the cut in order to compensate for warpage and the material....correct physical height is important, the voltage setting is not at all important. Don't worry about your voltage reading...adjust the voltage to maintain the book physical cut height (again, usually .06" with a Hypertherm for best cuts). Generally if the THC wiring / electronics is off by 10 volts...then on all thicknesses just change the setting by 10 volts and it will maintain the correct height.

There are THC's that use a process called voltage sampling....this process calibrates the height control at the beginning of each cut. You set a cut height, you never have to set or even look at the arc voltage...and the physical cut height is maintained. This technology has been on high end industrial machines for over 20 years...and is on a number of light industrial / entry level tables. Takes the mystery out of accurate height control! Jim Colt

[DuncanMotorsports714]

I use the settings in the Hypertherm book. When I am running cuts the z axis does not adjust to maintain the correct voltage. If I run a test through the THC it works and I see it adjust in Mach 3. But once the actual cuts are are being done the Z axis does not adjust to maintain the correct voltage. It just stays at .06”. It does this with brand new consumables as well

[adbuch]

You don't need to worry about the correct voltage reading, as long as the torch physical cut height stays at 0.060" (or close to that distance).

As Jim said:
"the only important thing is that the THC maintains the physical cut height throughout the cut in order to compensate for warpage and the material....correct physical height is important, the voltage setting is not at all important. Don't worry about your voltage reading...adjust the voltage to maintain the book physical cut height (again, usually .06" with a Hypertherm for best cuts)."

David

[DuncanMotorsports714]

I get that. But let’s say my settings for my Hypertherm say 70 volts for the material I am cutting. When my machine starts cutting the voltage will climb. To what ever which means the torch is farther away from my material than the .06”, but Mach 3 will say .06”. So the z axis isn’t moving to adjust to maintain the gap from the torch head to the material. I can tell the torch isn’t maintaining the correct height, from the Wright the cuts come out. I will usually get a beveled cut which tells me the torch is to far away.



Would grounding the table have anything to do with what I am dealing with? I heard people grounding there table. But I’ve never been told to ground it. Obviously the plasma cutter is grounded to the material. But does the table itself need to be grounded?

[adbuch]

If you pause while it is cutting and measure the actual cut height, what distance do you actually measure? If you disable your THC and cut the same part at a fixed 0.060" cut height, how does the edge bevel and cut quality compare to the same part with THC enabled?
David

[DuncanMotorsports714]

I’ll have to run a test on that. I’m guessing the best way to measuring it would be to go off the z axis and where it set to zero and what the difference is where I am getting the beveled cut.

I apologize if I sound frustrated this has been going on for a long time. And Wright CNC has had issues trying to figure out what is going on and they have sent me several Mach 3 profiles to use. I gave up on worrying about the THC for a while. But I want to refine my cuts as I am getting busier with my orders now.

[adbuch]

I would suggest doing a series of test cuts, maybe a 6 inch straight line - with your THC enabled. Start with the Hypertherm book setting for arc voltage for the particular thickness of your material, make the first test cut - but pause it before the end of the cut and measure (and record) the torch to work piece distance. Change your arc voltage by 10 volts, cut another 6 inch straight line, pause and measure/record the torch to work piece distance. Repeat this in 10 volt (or 5 volt) increments (both greater and less than the specified book voltage setting) and measure/record the torch to work piece distance. So if the book setting is 70 volts, do this straight line test for 80, 90, 100, 110, 120 as well as 60, 50, 40, 30, 20 and record the actual cut heights you measure. If the cut height is actually changing as you change the voltage setting, then you know that your THC is working, but not calibrated.

You could use a piece of 16 ga. steel (or 0.060" thick aluminum) as a thickness gauge to slide under the torch (between the torch shield and material surface) to measure the cut height. Then use some combination of "feeler gauges" (thickness gauges) in combination with the 0.060" piece for measuring distances greater than the 0.060", and some others for measuring the torch height when it is less than 0.060".

If your torch height never changes, then there may be a problem with your actual THC/electronics. If your torch height does change, find the voltage that gets you the closest to the target 0.060" cut height and use that voltage.

Once you initialize your machine (home your machine) at startup, then Mach3 will keep track of the Z distance as the Z stepper motor moves to change/adjust the Z height. The output from the THC should cause the Z height to change (if necessary) in an effort to maintain the target voltage and corresponding cut height.

David

[DuncanMotorsports714]

Ok thank, I will give this a shot tomorrow. Thank you for your help

[adbuch]

You're welcome! Let us know what you find out.
David

[DuncanMotorsports714]

So i ran my machine on 16GA material using the Hypertherm settings. Mach 3 Z axis said .06 during the cut, actual height was .01. Ran it multiple times, and the z axis on mach 3 never changed from .06 even with the different voltage settings. My table is not perfectly level so when i start my cuts i have to zero the z-axis on mach 3 to get the best cuts. Yea after doing what you suggested. I dont get any movement on the z-axis even when i adjust the voltage on the THC.


Also, i check the test setting on the Proma THC. And when i run a test, it does move my torch up and down during that. but that is it. I have a customer that wants to cut corrugated. And I have done some test cuts and the torch can not follow the path of the corrugated, it will bind or just drag the torch up the metal.

[adbuch]

It sounds to me like your THC unit may be functioning properly, but the interface between the THC and Mach3 as not allowing the THC to communicate with Mach3. This would involve either the script they provided, or some of the Mach3 settings related to the script.
David

[DuncanMotorsports714]

Any advice on where I should start to resolve this issue. Could the issue be in the post processor in sheet cam?

[adbuch]

I do not believe this problem is related to the post processor. It is more likely either a problem with the Mach3 script provided by Wright, or some setting (or settings) in Mach3. Did this ever work properly (or at all) since you purchased your table? Is there a separate users forum for the Wright cnc tables, and if so have others encountered this same problem? If you could find someone withe the same table from Wright, perhaps contact them to find out which specific script they installed for the THC, and perhaps get some screenshots of their Mach3 settings pages to compare to your settings.
David

[DuncanMotorsports714]

Good idea. I bought the table first with out the THC not knowing exactly what the THC did . Until I did more research about it later. So I purchased the THC through them and followed there setup. I’ve contacted Wright about this and they sent me a special profile for Mach 3 to use. It did work when they were on the phone with me. (And that’s always how it works with tech support) and now it doesn’t. Nothing has ever changed in the settings that I did. Sounds like I need to do more research and contact other users to see if this is a consistent problem

[adbuch]

OK. Let me know what you find out.
David

[Pcustomsteel19]

My Wright Cnc table had the same issue. Not sure if the solution is the same but the wires were wired backwards on my torch height controller. switched the wires around and had no issue since.

[adbuch]

Thanks for that information. Hopefully the OP will read this - it may help.
David