THC Timing?

[Red Earth]

When we make multiple cuts, the torch takes from two seconds to several minutes to fire, after the initial cut, varying on each cut greatly. ON occasion it will throw a slight arc and the computer gets a false "torch ok" signal as well.

The torch is a Hypertherm 600.

Any ideas?

Phil

[cut more]

Red Earth,
I have a hypertherm 1000 on a practical cnc table. I have seen something similar. After your torch turns off there is probably an air purge to cool the nozzle in the torch. I had to set up a delay in my software to allow the torch time before re-starting. I can't explain the up to 2 minutes time though. You could call Hypertherm to see if that is normal for that type of torch, they are great guys and have been helpful for me.
Cutmore

[Alex S.A]

Guys,
You can try adjust the start plasma time to about 8 or more seconds. It works properly to Powermax 1000. If the machine starts plasma before the purge ends, the machine will keep stoped and some error message can appear in the CNC screen.

[Torchhead]

The longest I have EVER had to wait for a start is about 3 sec if the purge air has turned off during a long move to another pierce. All other pierces happen instantly. PowerMAX 1000 G3. I cut all day with one.

TOM CAUDLE
www.CandCNC.com

[Graybeard]

I'm using a Powermax 600 machine torch on my unit and I don't experience slow starts, so it is not normal for these units. Once in awhile, I do have a situation where it won't start at all, generally when I am careless about starting an edge cut to trim a sheet. I cut 3/8 sheet all day today - slow - and never experienced a start delay other than the one second recommended. I do set a five second purge at the end of my cut when cutting anything 1/4 inch or thicker.

[Red Earth]

First of all, I am the other half of "Red Earth" but we are trying to work together to solve a few issues. I gotta say, you guys on this board are great! Holy cow, if I had come on here sooner, I might have saved a lot of grey hair and ulcers.

At any rate, we are starting in this plasma CNC stuff from scratch. I have multiple collegiate degrees and let me tell you, 11 years of college was nothing compared to learning this! We are now several months into this project and are now to the point were we know enough to be really dangerous. We are getting things accomplished, but there are several issues that still plague us and this one is one of them that we have had from the beginning. Of course, the company that sold us the table has been way less than helpful.

So forgive the less than intelligent questions.

As was previously said, the plasma cutter is a hypertherm 600, machine torch. It will sit and "cycle" air before firing over and over for a rather long time. Sometimes it will even briefly arc, but not start up. Before I blame it completely on the plasma unit, could it be the way I have the thing wired into the THC? It has done this since it came out of the box. We don't get any kind of error messages on the screen.

We run sheet cam, could it be the pierce delay or pause at end of cut setting? (I am assuming this is what you are recommending to check Cut More?)

We have had so many problems with the set up of this CNC that it could be something really obvious and stupid so please don't be afraid to point out the possible obvious and stupid solutions that you might assume we should know because there is a good chance we don't!

Thanks so much for your suggestions and help guys, we will need a lot of it as well as your patience. I feel at this point like I need a 12-step CNC-anon program!

Gayla

[cut more]

After reading this,
"It will sit and "cycle" air before firing over and over for a rather long time. Sometimes it will even briefly arc, but not start up."
I was wondering how high is the torch above the material when the torch is doing this? I have seen something like this if the torch is too high or maybe if the ground was not connected to either the material or the table.
Cutmore

[Red Earth]

Cut More,

The table itself is well grounded. It also does this even with the ground clamp from the plasma cutter connected to the material.

I use a pierce height (usually) around .065, but I have played around with the pierce height to see if it would make any difference and it doesn't seem to.

Gayla

[cut more]

Red earth,
Can you post the code that is being run by the machine when this is happening? This may shed some light on what is happening. One other thought, How old is the torch nozzle? As they get older sometimes they do not work quite right even though the arc looks decent to the eye.
What type of THC do you have?

Cutmore

[Red Earth]

Cut More,
First of all, thanks for your interest in helping me out, it is appreciated.

It will take me some time to post code. However, it does it just about on every thing we cut. My procedure is to draw in Corel (12), then it goes into BobArt, then to BobCad, then to Sheet Cam, and finally into Mach3. I have some issues with how all this is accomplished as well but that is a problem I will tackle after I hopefully get this issue here resolved. But at any rate, that's how I generate G code.

Now realize, I haven't made the room in my brain to learn the "whats and whys" of G code yet, but I can tell you off the top of my head that it pauses on the "03" command, which I believe is correct? I am not at the shop, so I will double-check that today.

The problem occurs with brand new nozzles. Fine cut or regular makes no difference.

The THC is the MP1000.

Gayla

[Torchhead]

1. Does it do it when you manually fire the torch? Is it a hand torch or a Machine torch? You can manually fire the torch by just shorting across the Torch Switch wires. Do you have the right consummables if it's a hand torch? The tips that come with a hand torch are not made for automated cutting. They have a "drag" tip shield that holds the tip too far off the material. What tip and current setting are you using?

2. If it fails to cut manually then get the Hypertherm fixed.

3. If it works correctly with a manual fire then it's not the Hypertherm.
One thing in the equation eliminated.

4. Setup a piece of material and keep the THC disabled in MACH. Use SheetCAM to process a series of straight line cuts about 18 to 20 inches long. Make sure you use the correct Post for SheetCAM. If you have the floating head (touch off ) make sure the correct switchoffset value is programmed into the SHeetCAM post processor. Open the post in a wordprocessor (Notepad) and find the line were the variable is set. It will look like switchoffset=## where ## is a decimal number. It's different for every table. This is typically a problem if it's trying to fire too far above the material after touching off.

5. With the THC turned off in MACH let it cut a line. Does it still do the on/off pulsing? Watch the front panel of the THC box. Does the ARC LED (green) come on and stay on during the cut? Did you install the Current Sense Transformer? On the 600 we found that you have to makup a 10Ga piece of wire with the clamps on each end to match the board terminals and wrap it 4 or 5 times through the "donut" to get enough voltage to keep the ARC good LED (and the signal to MACH) activated on thinner material. What does the Tip Volts reading indicate while cutting? Is the fault light on?

If the ARC indicator does not stay on in MACH (if running in THC mode) it will stop movement . The torch will attempt to refire but if it's sitting over a cut section it may fail to get an arc good.

If the Arc light and Torch ON in both MACH and on the THC stay on during the cuts manually then we have another problem. If the signal is still pulsing on/off:

Then you have a ground loop or short in the system. 1st take the Table I/O card off the standoffs inside the cabinet. It's the card that all of the Home switches tie to with the LED's. Let it hang in the air and not touch anything. Try the cut test again. If the torch stays on then you are almost there. Remount the card with insulated washers (nylon, fiber, plastic) between the top of the standoffs and the bottom of the PC board.

7. If you still have the problem then we will need to continue to dig.

8. For direct support of the THC join our support site at CandCNCSupport (Yahoo group)

Tom Caudle
www.CandCNC.com

[Red Earth]

Does not do it when I manually fire the torch, or at least, I have never found it to. Almost never does it on the first cut of a piece, but starts in on the second or successive cuts. It is a machine torch and the consumables are correct for the torch. (Also have a hand torch for this unit and have never noticed a problem while using it without CNC, although have used it only once).

We run at 40 amps and most stuff is cut around 80-90 V.

OK Torchhead, will head to the shop and try and sort some of this stuff out. Will hopefully check back in with the info soon.

Thanks!

Gayla