Pierce Delay on second cut

General
1

I have a DIY table Hypertherm 30xp. I have having a problem with the pierce delay for my second cut. I have set my pierce delay from .3 all the way up to two with very little change in the time the pierce starts. On the second cut, the torch does not come on until the torch has moved almost 1/2 inch.

2

Does your plasma cutter have an arc okay signal connected to your controller? This should prevent movement until after the arc has transferred and the delay has expired.

3

I have a proma compact THC. It has ark up, ark dn and ark ok. It goes into my BOB. That is the only ark OK that I have. I don’t even know if I have the settings to turn on THC set. I’m not sure about anything concerning the THC since I haven’t started to address if it is even working as I’m trying to get the torch to work correctly. I also think it is strange that the first cut is exactly right but this occurs on the second cut.

4

What BOB are you using? The arc okay for your THC probably just signals it to take over controlling the Z after the arc voltage has stabilized. Your BOB might have an input for the same signal to let it know to begin motion.

5

I had the same problem it was not the delay. I had to change the post processor to trigger twice at arc off . This stops the air flow allowing the torch to relight . If your torch is like mine test by hand at end of cut let off then hit the trigger again air should stop . Hope this helps

6

I agree. @djreiswig and @Mike7 both make good points, for different reasons.
@Mike7 - in your case, you may have the 2T/4T trigger switch set to 4T, which requires a double trigger pull to start and stop the torch. Both my PrimeWeld and HT plasma cutters have that setting. I run on 2T, thus only needing the usual 1 start/stop command and trigger pull.

Arc OK signal from the plasma cutter is certainly the best and most accurate method to delay motion at arc start. My controller does not have that input, so I have to rely on time delay only, that is pierce delay time. Since I have 2 brands to compare, I can report that HT PMX65 is clearly more sensitive to having a longer pierce delay time when air is flowing from the previous cut than when air is not flowing through the torch at the start of a job or on a restart. So I use a pierce delay time in my tool definition for continuous cutting (air flowing at arc start) and I subtract 0.1sec from that value on first pierce (no air flowing). I suspect the longer delay time is needed (air flowing) due to the air solenoid needing to close to reset the nozzle electrode, then open again to flow air, retracting electrode to cause the pilot arc.

7

That is absolutely my problem. When I tested it by hand, it did exactly like you said. the second trigger stops the air flow so that the third trigger immediately fires the torch. Now my question is, how do I change the 2T/4T setting? Is it on the Hypertherm control board inside the box? or is it even accessible? I have emailed SheetCam asking how I can edit the post processor to have a double torch off. Thank you so much for showing me this. I have been struggling with it for some time now and was just about ready to just blow up my DIY table. LOL.

8

see page 4-9 of the PMX65-85 User Manual-

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9

I have tested the torch and you are absolutely correct. When I stop the arc by hand by releasing the trigger the air continues to flow but if I just bump the trigger, the air flow stops. I have tried to edit my pp but it doesn’t seem to work. How do you have your pp set?

10

Look at my previous post. Lou walked me through it ( thanks Lou ) if you can’t find it I will copy it down for you tonight.

11

Thanks Mike7. I did not see the pp program. I would very much appreciate it if you could send it to me.

12

@Mike7 , @NBForrest , I sent the following to ‘Bowden’ via email last week, could be what @Mike7 is referring to…

edit the pp, look for function OnPenUp(). The exact code depends on your pp and controller, but most use M05 to turn off the torch. In that case, as an example, add a second M05, like the following…

====================
function OnPenUp()
   post.Text (" M05\n")
   post.Text (" M05\n")
   if (endDelay > 0) then
      post.Text (" G04 P")
      post.Number (endDelay,"0.###")
      post.Eol()
   end
end
===================
13
1 Like
14

Since you are using an Arduino board, IF it is Uno model and IF you have XYZ limit switches, then pin D11 is likely firing the torch. D11 is a PWM signal which is controlled by ‘M3’ AND ‘S’ (spindle speed or laser power) gcode word, so you should also make the following change…

in OnPenDown() function…
change:
post.Text (“G0”)
post.NonModalNumber (“Z”, pierceHeight * scale, format)
post.Text (“\nM3\n”)
to:
post.Text (“G0”)
post.NonModalNumber (“Z”, pierceHeight * scale, format)
post.Text (“\nM3 S1000\n”)

15

I edited the pp as you advised. It didn’t stop the air flow. Do you have another idea that would stop the air flow. Attached is a video that shows that when I trigger the torch after the first cut had finished, it stops the air flow to allow the second cut to cut as programed. This forum won’t allow a .MOV but you get the idea.

16

@NBForrest , sorry but I advised you wrong. @Mike7 corrected me with his post to this reference: Torch control g-code: need deactivated torch to activate and deactivate automatically - #5 by sheetcamCS2
You may even need to add a G04 P0.5 delay after each M3 and M5, to give the signal time to bounce and the relay time to react to it.

17

Sorry I didn’t help much . My setup is probably different. I have an optical relay connected it does the switching.

18

Lou im glad you said that . Will you right an example of adding this to my code . It works as is but it is so fast you can’t even hear the relay cycle that can’t be good on the relay long term

19

Here is the double trigger torch OFF with a 0.5sec delay between relay signals…
post.Text (“M5\n G04P0.5\n M3S1000\n G04P0.5\n M5\n”)

But the more I think about this, the more I don’t like the double trigger concept in automated CNC use like this because it defeats the post-cut-air-flow time intended to cool the torch nozzle. I believe those few seconds of air flow matter in continuous cutting cycles such as CNC jobs, where the torch is in motion between cutting cycles/shapes. You could increase the delay time in the stmt string above but that causes a lot of water table churn after the cut since the torch is sitting at Z1.5mm rather than retracting and moving to next cut.

I believe the better approach is to figure out how to put your plasma source into a single trigger torch ON/OFF state, that allows the plasma source to manage the post-cut-air-flow time as usual.

20

Is there a way to perform that function just after the ohmic sensor probe? Right now I am triggering it at that point. As soon as the torch touches the metal I pop the trigger to shut off the air flow and that is working pretty well.