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Author Topic: Proma THC - Moves Z up but not down.  (Read 14448 times)

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Proma THC - Moves Z up but not down.
« on: November 02, 2012, 09:52:56 PM »
Just got around to wiring in my Proma Compact THC and it works in test mode, moving the Z axis up and down.  But when it's running g-code it will move up when the THC signals up, but it will never moves back down when the THC is signaling down.  The diagnostic page indicates that it sees the down pin high, but no movement.   I'm running licensed Mach3 with a Sound Logic PC-2-route M-2 breakout board.  And I have switched the up and down pins and still it move up, but not down.  I'd sure appreciate any help.  It' great having it just do half the job, it will be sweet when it does the whole job.  :)

Re: Proma THC - Moves Z up but not down.
« Reply #1 on: November 02, 2012, 10:24:56 PM »

Offline BR549

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Re: Proma THC - Moves Z up but not down.
« Reply #2 on: November 02, 2012, 11:04:19 PM »
There are several things that come to mind BUT not knowing exactly what you have setup screen wise it is hard to guess.

Plasma with THC has extra things that go bump in the night that REG mill screens do not have.

Min THC move
Max THC move

I would gues that you have checked to see that MACH3 is SEEING the down input during a cut  when it should be going DOWN in Z ?? Dianostic screen and verify that eh THCdown LED is going active. IF it IS then it shoudl be a setting in MACH3 that is blocking the movement for DOWN.

What have you got the min/max z THC values set to ?? IF the min is too hiogh then it will NOT go lower than the setting ??

How about the antidive. That is a setting that STOPS the down move during certain conditions that MACH3 may see during a cut such as crossing a open slot OR the material drops out from under the torch quickly like a heat expansion JUMP as the metal heats up and expands to the point that it JUMPS.

ALSO you may want to check that in the pin setup that you do NOT have simulate checked as this CAN mess up the THC logic IF it gets both signal types internally.

YOu may also want to uncheck the" USE thc even when not in THC mode". 

Just a thought, (;-) TP

« Last Edit: November 02, 2012, 11:08:44 PM by BR549 »
Re: Proma THC - Moves Z up but not down.
« Reply #3 on: November 03, 2012, 10:57:20 AM »
Thank you very much.  Your assumptions are correct. Here is a video of a test:  http://youtu.be/cXc5-VPiej4   I didn't ever see the Max/Min THC move settings because I'm using the Mill profile as I have done for years.  I'll switch to the Plasma profile and try it again.
Re: Proma THC - Moves Z up but not down.
« Reply #4 on: November 06, 2012, 11:40:33 PM »
Got it working!  Thanks for the assistance.  Here's the video:  http://youtu.be/kf8S3rL3wYw

I'm wondering now if there is a better way to do this, as there is no apparent way to get it to go below 0 on the Z.   I guess I could tell the CAM program that my material is a half inch thick and then set Z:0 below the material on my table?  What's the normal work around?


Offline stirling

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Re: Proma THC - Moves Z up but not down.
« Reply #5 on: November 07, 2012, 06:04:03 AM »
Hi Doug

That (stock) screenset is old and buggy. Amongst other things, the THC min DRO is incorrectly formatted and hence doesn't allow -ve numbers. Download a copy of a screen designer and change the format string from %1.3f to %+1.3f and then it'll allow negetive numbers. You may also want to physically lengthen the DRO a tad so you can actually see the -ve sign.

(Course there are other THC's available that have a shiny new bespoke screen AND FULL SUPPORT  ;)).


Re: Proma THC - Moves Z up but not down.
« Reply #6 on: November 09, 2012, 01:59:19 PM »
Thanks again Ian.   I got the screen designer, made that change and it is much better.  Really appreciate the assistance.    Next up is a floating head.   And recommendations?  --Doug
Re: Proma THC - Moves Z up but not down.
« Reply #7 on: July 12, 2013, 08:36:29 AM »
I have a similar problem. I have tried all the remedies suggested, but still can't get Z to go down on jog. All axes work fine on fast jog (with shift key). X and Y work fine in standard jog. Z works upwards on standard jog, but when you try to jog down you get no movement and all axes lock out, requiring a manual reset to get anything going. I have reversed polarity of Z direction pulse (to eliminate possible mechanicals) and the problem reverses, with requested upward movement causing lockout. I suspect this may be linked to THC, but I have disabled THC inputs and it is still the same. Under program control Z axis moves on G0 commands, but on THC (PROMA) it shows a request to go down, but no actual movement.

Any ideas please.