Newer plasma user needs help with MP3000 DTHC

[Turboedgs]

Need a little help:

I am running the MP3000 DTHC on my plasma table. It is self constructed table.

The problem that I have been trying to solve for the last month is a random move up in the Z axis right at the same time the torch fires. This move up should not happen as I have a THC delay setting long enough to delay for the pierce, the plunge to cut height and a second or so of the cut move.

The move is not due to any g-code, nor is it due to any noise getting into my system. The reason I know this is because when I run a set of g-code with the THC turned off the program will execute perfectly. Noise can be eliminated from the equation due to the plasma unit being off and the up move still happens when the torch on/off is triggered in Mach.

The THC seems to be working fine other than this issue.

The scenario is this: The torch moves to pierce position, touches off the material, pulls up to pierce position, fires and simultaneously moves up, executes the pierce delay if there is one, moves to cut height if it can and starts to cut, then the THC delay comes out of delay and Mach starts to see the THC signals the Z moves accordingly to those signals.

When the torch moves up at pierce it usually ends up around .170 - .250?. If I have the tip saver feature set at a low percentage, say 2%, the torch will never get down to the cut height. If I turn off the tip saver I get a crash into the material.

Besides the move up at pierce everything else in the THC functioning seems to be operating as designed, however this move up throws everything else off and there is usually a fault error or the cut is no good due to the extra height during the cut.

I took a few quick videos that better illustrate the problem I am trying to fix. Sorry for the narrow screen and lower resolution, I only had my phone with me today when I was working on this issue.

http://www.youtube.com/user/eMotionCNC? ... gnKx9WFzl4

http://www.youtube.com/user/eMotionCNC? ... kOL6rNBFsA

http://www.youtube.com/user/eMotionCNC? ... GajnfKXGSw

If anyone has and idea of what might be causing this I would appreciate the help.

I posted this same thread on cnczone sorry if it is redundant. I have also been loging this issue w/ the candcnc guys but they cant seem to pinpoint the cause.

Thanks
Brian

[jimcolt]

I'm sure Tom from CandCNC will be of help. It looks to me like your arc voltage control is active as soon as the plasma torch fires.....the torch arc voltage will be low when first transferring to the plate, and the height control may be trying to increase voltage by raising the torch. In reality...the arc voltage feedback control loop should not become active until the torch is moving and up to speed in the x and y directions. I am not familiar with the settings in Mach3....but perhaps it is an avc delay setting that needs to be longer? The arc voltage control should become active after the "arc good" signal (meaning the arc has transferred to the plate) and after a time delay to allow the motion to get up near programmed speed.

Jim Colt Hypertherm

[Dennis]

Waiting to see how this plays out, very intresting topic... Nice videos as well.

[Turboedgs]

That is what I thought first as well?it?s not going into delay; well it actually is going into delay after the up move and pierce.

What will happen is the torch fires with the simultaneous up move then it sees the arc ok and any preset delay takes effect after the random move up.

I have performed this operation literally hundreds of times during which I have been able to at least understand what is actually taking place regarding the symptoms. And it took that many times because it is so fast to understand the dance that is taking place. At first glance you think, Mach setting, Code, Noise, or delay...but it is none of these. I have changed everysetting in mach and the THC plug-in, I have reloaded up revs and down revs of the software, I have demonstrated that the move happens with no code in Mach and demonstrated the problem with the plasma unit on and off eliminating noise from the check list.

The torch fires and at that moment the sensor card sees a low (0, 7, 20 volts) voltage and sends an up signal at the same time as the ARC OK signal. Once the system sees the ark ok signal it will execute the delay as you see a down led light up in the video with the plasma unit on and the torch does not move down.

At first I was convinced that the delay wasn?t executing but once I put some longer delays into the system I could see it actually was delaying but the delay cycle isn?t happening soon enough to prevent the first move up.

In the two videos demonstrating this random up move problem you will notice that when I have the plasma unit off the up happens in spurts, the up led and the arc ok led light up together then turn off and then they wash rinse and repeat. This scenario leads to my Z moving into the max THC limit that I have defined as 1? in Mach. When I perform the same test with the plasma unit on it will only go up on the first dual flash as the arc is present and it sends a volt reading to the system, in turn initializing the delay, etc.

To me, and I can be wrong, it feels like a hardware problem with the sensor card. It is almost as if the feedback loop is too fast or not calibrated correctly. Unfortunately, there is no documentation regarding how to calibrate the sensor. But what do I know....

In regards to Tom and the crew at CandCNC working it out?.I certainly hope I can get some sort of resolution?he is aware of the issue and hopefully has his little elves working on it. He is a busy guy though and I need this resolved quickly (been working on it for a month) so I had to expose the problem to more than one source in search for a solution.

Thanks guys!
Brian

[minnfatz]

Post your question on the CNCzone forum. Tom is on there all the time and I have had every issue I had resolved within 24 hours.

[jeeplogic83]

Turboedgs,
I have the same set up I hope this helps
my 12ga profile is set up like this
tip size- 40 amp
Feed Rate- 85
Tip volt preset- 84 (not within hypertherm specs but works)
Span Gap-4
THC Delay-1
Upper fault -200
Lower Fault - 50
Tip saver -2
Arc OK Current - 15
Cut Current -0
Current Tol- 22%
In the General TCH Settings the only thing I have checked is --Auto THC ON
If you use sheet cam you have to edit your post processor
I use the PLASMA MP 3000-DTHC post
I went in and modified the post so the Z switch offset is .01
I tried to upload a Screen set but it would not let me. I do not use the screen set that came with my system from Tom there were some basic faults with it that screw everything up. shoot me a email and I will send you the screen set I use. Since I replaced the screen set and use these settings I have had no random raising of the torch head.
Also sign up for the Mach 3 forum through the artsoft web site there are guys on there that reinvent how Mach works on a daily basis and know there stuff that is where I got the new screen set.

Hope this helps- email me though it only works with the new screen set.

[rock4xfab]

Turboedgs,
I have the same set up I hope this helps
my 12ga profile is set up like this
tip size- 40 amp
Feed Rate- 85
Tip volt preset- 84 (not within hypertherm specs but works)
Span Gap-4
THC Delay-1
Upper fault -200
Lower Fault - 50
Tip saver -2

Arc OK Current - 15
Cut Current -0
Current Tol- 22%

In the General TCH Settings the only thing I have checked is --Auto THC ON
If you use sheet cam you have to edit your post processor
I use the PLASMA MP 3000-DTHC post
I went in and modified the post so the Z switch offset is .01
I tried to upload a Screen set but it would not let me. I do not use the screen set that came with my system from Tom there were some basic faults with it that screw everything up. shoot me a email and I will send you the screen set I use. Since I replaced the screen set and use these settings I have had no random raising of the torch head.
Also sign up for the Mach 3 forum through the artsoft web site there are guys on there that reinvent how Mach works on a daily basis and know there stuff that is where I got the new screen set.

Hope this helps- email me though it only works with the new screen set.

The number in red, if those are filled in In toms screen sets you will have issues. Those are only for the new DTHC.