7i76E + THCad 10V

Right at the moment I have no clue why my system appeared in bipolar mode, and I see luck of information from the manual to put right parameters to config.

According to manual
"Measured input voltage can be calculated from the THCADs output frequency
using the following formula:
V= VFS * (FOUT - FZERO) / (FFS - FZERO)
Where FOUT is the output frequency of the THCAD, VFS is the unipolar full scale
range 10V or 300V or custom value determined by external resistors.
FFS is the full scale
output frequency on the calibration sticker, and FZERO is the 0V input output frequency
on the calibration sticker."

So I have the calibration data on my card, and FZERO for unipolar mode is 120000, FFS =926100 and VFS=10
How can I convert these parameters to bipolar mode?

Oleg

Not sure why you would you want to
Plasma systems will always be unipolar so W1 should be down and the unipolar settings are correct
(if you run in /32 mode, divide the FZERO and FFS by 32)

And how to convert these constants if board running bipolar mode? There are no info for this mode in the documentation...

You can take FZERO and add 1/2 of FFS for bipolar mode FZERO

But if this is being used for a plasma height control you dont use bipolar mode at all

Thanks, for the update - I'm going to play with it today. Am I right that VFS parameter in bipolar mode is 10V too?

The VFS scaling remains the same but the range becomes -5 to +5 V because of the offset

How are you using the THCAD?

If its for a a plasma torch height control, bipolar mode is wrong and you should set the jumper to unipolar mode

Now I'm using in usual manner in unipolar mode on standard scale factors, works like a charm. One thing which slight annoying me it's jamping frequency due to lack of sync between 7i76e board and the THCAD, but this is not big issue.

Guys, I'm using thc.comp along with the THCAD board. Recently my system started missing right position on Z coordinate. Initially it was rare issue, but now it's totally nightmare. Is it known issue? Need to fix it fast.

I have several times analysed my touchoff (attached) and didn't find anything what could result something related to z coordinate disorder. Here is g code snippet from my ngc file:

G0
X723.3253 Y874.3354
G0 Z20.000
o<touchoff> call [3.800] [0.4] [1] [3810] (Touchoff and start cutting) --> the parameters meaning: [pierce height] [pierce delay] [cut heigh] [speed torch will move from pierce height ot cut height]

G3 X724.2329 Y876.8905 I-2.2776 J2.2478 F2286.0
X723.2955 Y878.8608 I-3.1852 J-0.3073 F2640.0
X721.6077 Y877.4663 I-0.2679 J-1.3945
G1 Y870.9663 F2640
G3 X724.4477 Y870.9663 I1.4200 J0.0000 F2640.0
G1 Y877.4663 F2640
G3 X723.2955 Y878.8608 I-1.4200 J0.0000 F2640.0
M5 (Torch Off)
<---- error happens at this moment
G0 Z30.000 <--- as result real position of cutter is either too high or too low

as result when it does the next probing it either trigger before it reach Z20 or it can't reach matherial in touchoff because Z is limited with 0

I'm preatty sure it caused by the logic of work of thc.comp, maybe interfere with a way I'm using it or maybe caused by latency spikes.
I'm preatty stuck and preparing to rewrite thc.comp in a way to breack the exclusive control over z axis in this component by release z axis feedback to the system. Feel it will be not so easy to do, so if you think I can manage this more simple way lete me know..

If I recall correctly any offset the thc applies while the torch is cutting is removed when the torch is turned off and the z axis is commanded to move up. So when the torch is first turned off and some height correction had been applied to Z during the cut the Z position will be off by that correction. It will not be corrected until the Z axis moves a sufficient amount up to remove it.

Couple things to try...
Increase the raise height of Z after the cut to allow more movement to remove the offset.If your machine has more Z travel
If the raise height cannot be increased perhaps add an extra movement to take up the correction.

The slats on my machine are a bit far apart and when working on light metal which might be warped I find it might be better to be able to probe below Z0.
In my case I prefer to make these moves at a slower rate so I use G1 instead of G0.

Rick G