There you go - got it in one.

Ok thats good, thanks.

(or upgrade to a PM45 and use a THC that can be configured to send ArcOK by magic instead of using a pin)

Can we just not order some of these magic pins? 

Ok, with the massive help of this forum, progress is being made, I have now switched to G28.1 Z setting and rewired my THC for Arc-Ok using the now free probe input pin on my BOB.

However, this is the code I am testing...

G28.1 Z3.00 F250 (probe surface)
G92 Z0 (reset DRO)
G00 Z4.00 (move up by limit switch offset)
G92 Z0 (set zero)
G00 Z5.00 (move to some arbitrary point to measure the torch gap with a 5mm spacer)

Seems nice and simple, if i type it in by hand in the manual screen on Mach, it all works perfectly. leaves the Z DRO at 5.0000mm

But if i run it from a .tap file containing just that code (plus M30 at the end) it works but leaves the Z DRO reading a meaningless 11.4799mm every time???

Can this be fixed???

I have tried putting a delay after the DRO reset lines but no change.


I also have one missing link somewhere - If i untick "allow THC even when not in thc mode" which i guess should be unticked now, I get no action on Z axis even though the diagnostics is showing my THC commands coming in nicely??

Pressing the screen THC button does nothing.

Any ideas?

Post an example of your tap file.

If you find it raising in z as the program runs through the cut file it may indicate your Z THC speed is set TOO fast and you are losing steps.The longer it runs the more steps are lost and the HIGHER the Z dro will climb.  If at teh end of the file you try to return to say Z5.000 it will crash the torch into the table.

Remember the THC z control is a slap and go situation. There is ZERO ACCEL/Deaccel parameters it just switches the motor on wide open and shuts off clean.  Normally you will run a THC speed of about 20% of rapid speed as a start.

IF you retick that control will it work properly again (;-)  If so just retick it.

Just a thought, (;-) TP

No, you are misunderstanding me.

The action on the stepper motor is fine.

What is going on is that If I untick the allow-THC box as it should be when using arc signals etc, the system will not respond even though the diagnostics screen is showing my signals coming in nicely.

With the box ticked, It works but can not be stopped so if I want to run small holes, I have to disconnect the THC physically!

That box should be unticked when under plasma control and you have a THC. The setting is for when you are not running a thc and want to adjust it manually using an up/down switch.  DO you have a set of keyboard buttons that you are emulating the signals Thc up/down or a set of physical buttons

(;-) TP

OK you asked 2 different questions, which one do you want to work on first ??



That box should be unticked when under plasma control and you have a THC. The setting is for when you are not running a thc and want to adjust it manually using an up/down hand switch. By chance DO you have a set of keyboard buttons that you are emulating the signals Thc up/down or a set of physical buttons   They may very well OVERIDE your THC in Mach3.
 
(;-) TP

Let's fix this one first, it's the most important...



No there are no buttons, that I know of, the screen is the standard plasma set plus one button that Hood or Stirling added for me some time ago that allows my cheapo pendant to set the work origin point.

The diagnostics screen shows all ok - all three inputs show up as required but there is no connection to z axis regardless of the setting of the THC on/off toggle.

OK so you are saying the when you run a cut file the ArkOK led is active , and the Thcup, Thcdown leds are active as needed BUT the Z does not move?

IS the THC turned on in mach3 ?

When not cutting are the 3 leds mentioned above turned off ?

(;-) TP

Hang on a minute, you may have something...

Does mach only allow the signals through when the button is on AND code is running I.e.making a cut??

I had put the THC into test mode which sends out a continuous arc ok signal plus alternating up / down signals.

I presumed this would then activate the z axis when the THC on button is pressed regardless of a cut being made.

If so then this sort of stuff really should be in the manual.