Initial Height Skip (IHS) not functioning properly

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06 Jun 2022 21:10 #244690 by Uthayne
So I believe I've narrowed down the issue with this to this particular line in the plasmac.comp where axis_x_finish is set (see below).

When thc is enabled (but not active during a cut), it should use this block of code to determine the cut_offset and in turn compare that to skip_ihs_distance:
else if((axis_x_finish || axis_y_finish) && first_cut_finished){
                            cut_offset = sqrt(pow(axis_x_finish - axis_x_position, 2) + pow(axis_y_finish - axis_y_position, 2));
                            axis_x_finish = 0;
                            axis_y_finish = 0;
                        }

However, axis_x_finish and axis_y_finish are always set to 0 if auto_volts is enabled based on my testing. The causes the cut_offset calculation to be incorrect.

Here is the line which I believe is incorrect, as it is the only place that axis_x(y)_finish is set.
if(thc_enabled && ((!use_auto_volts || (use_auto_volts && target_volts)) || !torch_enable)){
                    axis_x_finish = axis_x_position;
                    axis_y_finish = axis_y_position;
                }else{
                    axis_x_finish = 0;
                    axis_y_finish = 0;
                }

Watching halmeter while cutting I can see that target_volts is always 0. This causes the ((!use_auto_volts || (use_auto_volts && target_volts)) to always be false when auto volts are enabled, and the OR comparison to !torch_enabled is always going to be false when we are cutting anyway. In turn, this causes axis_x_finish to always be 0 which breaks the IHS skip logic later on. This is verified by ENABLING THC, but DISABLING TORCH which causes the above else if statement to be true and axis_x/y_finish is correctly set. I mentioned that IHS skip functions properly if I do a dry run but not while the torch is on.

What is target_volts supposed to be set at? Should the statement be ((use_auto_volts || (!use_auto_volts && target_volts))?

I haven't dug into this any deeper after realizing that disabling auto volts causes IHS skip to function properly again. This should get me by for now...

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07 Jun 2022 03:23 - 07 Jun 2022 07:17 #244702 by phillc54
target_volts is the voltage that the THC is attempting to maintain. If the velocity doesn't reach the cut feed rate then there will be no target voltage set.I can see what is happening (or not happening), I think a new flag is required to indicate whether THC was active at the end of the cut.

Edit:The attached patch seems to work OK, I will do a bit more testing tomorrow and will push if all goes well. 
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Last edit: 07 Jun 2022 07:17 by phillc54.
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07 Jun 2022 19:36 - 07 Jun 2022 19:37 #244734 by Uthayne
I cut a 48"x48" sheet full of parts with ~300 pierces and the IHS skip was working. The only remaining bug which I saw is that when THC is not active, it should calculate x/y distance back to the last successful probe. It currently uses the start of the last pierce, even if that pierce had it's IHS skipped. This causes a series of pierces which are within IHS skip distance away from each other to "runaway" and not cause a need to re-probe.

Example with the test file attached, a series of small holes where THC will not be active but are within the IHS skip distance of 0.3" apart (holes have a center-to-center gap of 0.25"). The first hole at the bottom of the order is probed but the subsequent holes are not because they are each within 0.30" to one another. The third hole should trigger an IHS event as it is >0.3" away from the first hole which was the last successful probe.
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Last edit: 07 Jun 2022 19:37 by Uthayne.

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08 Jun 2022 00:19 #244742 by phillc54
Oops, it appears that I don't understand my own documentation. 

I will take a look ASAP, it may not be today.

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08 Jun 2022 07:38 #244756 by phillc54
I think this one should be close.
 
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