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Cutting during traverse

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IHscouts
Posts: 8
Joined: Sun Aug 04, 2013 7:54 pm
Location: St. Clair MO

Cutting during traverse

Postby IHscouts » Thu Mar 22, 2018 5:32 pm

I'm back asking for help again..... :(

The TM2 table that I bought is second hand and has started to give me issues. It has started to keep the torch on during traverses. It doesn't do it all the time, last night after everyone quit for the day I was messing with it and it cut 16 parts perfectly. But today, it started acting up again. The part that I'm cutting has one hole in it. Once the hole is complete it will not shut the torch off and do a rapid traverse to the exterior of the part. Which leaves a nasty gouge line in the part. Sometimes it will shut the torch off once the exterior has been cut, sometimes it will not and travel to the next part.

Could this be a signal interference due to poor grounding? Could it be the contacts in the AVHC not opening up when they should? Could it be that it needs a forklift taken to it??LOL

The problem didn't start until I was about half way through a 4X8 sheet and was thinking it could be a bad cable causing it. (A broken connection or something in the cable.) But last night it ran fine and today it started again.

The plasma cutter is a Hypertherm 65 with a machine torch.

One of the things I don't like about the G-code it generates is that you can not see the M commands for the torch. Which I could always see on my old home brew table running Mach3 with sheetcam as the post.

islander261
Posts: 139
Joined: Sun Jan 12, 2014 2:30 pm

Re: Cutting during traverse

Postby islander261 » Thu Mar 22, 2018 9:09 pm

IHscouts

A little more detail as what is happening will help. Does the torch raise to make the G00 move? Does it stay at cutting height? Does the torch height control appear to be correct only the torch never stops firing? Will the torch stop firing if you press the cut enable button on the AVHC(make LED go off).
Will the torch go off if you hit the space bar on the keyboard (feed hold)?

Have you checked your machine software setup against the manual? The end of cut delay(in M51 setup line) can be important to wait for the AVHC.

If this is a cable/connector problem then it is an intermittent short between two wires or pins. Opens will not cause this to happen. Unless you just changed your electrical connections or moved some of the equipment recently it is unlikely this is an EMI or grounding issue. I don't have the Hypertherm recommended fancy single point ground or ground rod and have never had an EMI issue with my TM2 setup. My plasma power supply is on the adjacent side of the table from my control mess. My torch cable is bundled in the cable track with all the AVHC and stepper wires.

Using the AUX commands does the torch fire and shut off when commanded (Cut must be enabled on AVHC)? If you don't want to actually fire the torch when doing this test unplug the CPC connector from the plasma and watch across pins 3 & 4 with an ohm meter or continuity tester, you are looking for relay contacts to close and open on command. You may need help or 4 hands to do this alone.

This should keep you busy for awhile. PM me if you want some phone help, I'm on the west coast and get up late.

John

IHscouts
Posts: 8
Joined: Sun Aug 04, 2013 7:54 pm
Location: St. Clair MO

Re: Cutting during traverse

Postby IHscouts » Thu Mar 22, 2018 9:59 pm

John

No. The torch does not raise. It will pause for a very very short time and stays at cut height then continue to the next cut.

The height controller appears to be working fine as it cuts the part. It registers any voltage change and the torch moves accordingly. But when it's giving these issues the torch will not stop firing. It will travel the traverse with the torch fired at cut height scaring the plate.

Haven't tried the cut enable button on the AVHC yet. Will try that in the morning. I have tried to do a feed hold from the CPU but it doesn't seem to register like it should.

Hitting the feed hold is somewhat of a crap shoot. Sometimes it works, sometimes it doesn't and the torch will sit on one stop and stay firing.

I did just move this table into my shop. It was fully operational when I picked it up and it was only offline for about 24 hours. I have not checked the software against the manual yet. Before this issue started, I had cut around 60 plus parts out of the same sheet with no issues. The sheet hasn't left the table or moved. My setup sounds similar to yours, the plasma is parallel to the table, about 4 feet from the table and about 3 feet above it. My torch cable is also bundled in the carrier with the AVHC cable.

I did some dry runs with it earlier and was getting continuity across 3 & 4 at the AVHC when the torch was firing. Would lose the continuity when I should in the program. When I crossed 3 & 4 together, I was able to fire the torch with no problems.

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WyoGreen
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Location: Cheyenne, Wyoming

Re: Cutting during traverse

Postby WyoGreen » Fri Mar 23, 2018 11:01 am

My torch cable is also bundled in the carrier with the AVHC cable.


It's normally not a good idea to run the torch cable in the carrier with other motor/control cables. It can introduce noise from the plasma firing into your control cables.

Steve
Precision Plasma gantry
CommandCNC Linux controller w/Feather Touch & PN200 hand controller
HT-45 plasma cutter
Plate Marker
CNC Router table

islander261
Posts: 139
Joined: Sun Jan 12, 2014 2:30 pm

Re: Cutting during traverse

Postby islander261 » Fri Mar 23, 2018 11:56 am

IHscout

Well the new information helps to narrow the problem down. The AVHC thinks it is still being commanded to cut. Carefully check the wiring between the "relay box", the relay box can take several forms depending on when you system was shipped, and the AVHC. Also check the that the relay box is always responding to commands correctly. My best guess is that you have a bad connection that is shorting to another connection or a faulty relay box. The problem can be in either the output wiring or the input wiring to the relay box if it is not the relay box. I replaced the relay box on my system with a cheap 4 channel relay board I bought online some place because I wanted switching under program control for more than one channel. I will open up the old relay box I have this morning and check out what can go wrong. I seem to remember that I was appalled at how it was so cheaply constructed when I replaced it.

The feed hold will not stop any commands already in signal generator buffer, it usually stops at the end or beginning of the next line.

I was not recommending to anyone to place your plasma cable with all the rest of your cables. I was just stating how my system is wired and that it has never caused me any problems. Now it you have an older or Chinese HF start plasma power supply I will say this is asking for trouble.

John

islander261
Posts: 139
Joined: Sun Jan 12, 2014 2:30 pm

Re: Cutting during traverse

Postby islander261 » Fri Mar 23, 2018 2:17 pm

IHscout

I was thinking about your problem while grinding this morning. The fact that you just moved the table is very significant from a power/grounding point of view. So do a dummy cutting test.

Place a piece of material on your table, it can be plywood if its flat enough, you aren't going to actually cut any thing. Connect the work lead from your plasma to the table slats if you use a non metallic test piece. Load a program that had the G00 failure into your controller. Make sure to disable the cutting on your AVHC (LED off). Turn on your plasma power supply. Run the program. It should do everything except fire the torch, note that the torch will run at the initial cut height so you need a flat surface. Repeat several times with other pieces of shop equipment in use at the same time. If it runs ok then you do have a potential power grounding issue. If it fails the test ( doesn't do the G00 moves right) then repeat with the plasma power supply turned off. Do you have EMI issues when using other pieces of equipment, particularly TIG welders?

Check that all the table electronics are connected to a good outlet with a good safety ground connection. Plug all the electronics into the same known good outlet strip and plug that into known good outlet that has a good safety ground connection. If you are in an industrial building that uses the metallic conduit for the safety ground try and find a circuit to use that has a wired ground connection. Think about hiring an electrician to check that all the neutral bonding and safety grounds are up to current code.

John


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