Path rules question with video to explain.

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Deezl Smoke
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Path rules question with video to explain.

Post by Deezl Smoke »

2019 ArcLight dynamics, PM105, Linux, Sheetcam, CandCNC.

Please let me say up front that I do understand that my using of path rules in this way does/is somewhat of a bandaid for other issues, but I have been having good luck experimenting with path rules to combat those other issues, and perhaps someday soon I will discover what those issues are and resolve them. But for now, I'm curious if you can give me a few pointers on this.
Here's a youtube link to a video short I made of what I hope to accomplish.
https://www.youtube.com/watch?v=Hre5AprGpxE

The only path rule that should be active in this cut, is for circles smaller than 2", set feed rate to 65%, and THC to off. On the "small circles" rule, it does not give me the options of "include lead out", or lead in etc.
If you watch the feed rate in the video, you'll see the lead in go full speed and turn thc on for a brief second, then it goes to the reduced speed until lead out. At lead out, it goes full speed again.
Now one of the issues that I hope to resolve someday, but for now have had success with is, I have to use the "over cut" option, and typically by about .25" to .35". Otherwise the inside cut on these heavier plates does not complete the cut. I think some of that is because the lead in is at full speed. I'll see if I can find one of the cut outs to show the plasma stream at lead in.
Before I go making a bunch more path rules that might conflict with one another, (which I have done in the past) what path rule would you suggest?
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sheetcamCS2
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Re: Path rules question with video to explain.

Post by sheetcamCS2 »

I believe you have the path rule correct in this case for the most part. I'm attaching a photo of a similar case, smaller circle to allow the drawing to scale down to 2mm grid. The 100% feedrate at end of cut is in the 'over cut' distance, 3mm in my case.
As for THC returning to ON state at end, is that because you have a code snippet to do so and end of cut ?

The reason I overcut is to minimize the alternative lead out divot. I turn off the torch with a path rule at 3mm before end, so I'm already into the leadin kerf, but the command is applied with continuous motion (also to minimize divot), and the overcut is merely to give the relays and plasma source the runway to actually kill the torch while still in XY motion. In the scenario, the 'cut' path is complete, so when feedrate returns to 100%, it's not a problem relative to cutting of metal. The toolpath in the photo is not making use of the 3mm before end torch off path rule, the rule is off.
Screenshot 2025-03-15 095841.png
Deezl Smoke
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Re: Path rules question with video to explain.

Post by Deezl Smoke »

That's very interesting. I checked, and my "use code snippet" says none.
I'll have to give no leadout idea a try with the over cut. That might just be the ticket.
I'll have to work on the thc ON momentarily with the torch at full speed. Should I use "on lead in" with the small circles?
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sheetcamCS2
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Re: Path rules question with video to explain.

Post by sheetcamCS2 »

That's very interesting. I checked, and my "use code snippet" says none.
I misread your original post, you did not mention the THC turning on at the end of the cut, my bad. Code Snippet NONE at end of cut is what you want, you already have that right.
I'll have to work on the thc ON momentarily with the torch at full speed.
two ways I know to solve this:
1) make your THC delay long enough that it exceeds the time to cut the leadin. By that time, your path rule has already turned it off.
2) group all holes in one layer (when you CAD or sheetcam menu Mode-Contour, right click for context menu), before the Operation to cut the hole layer, run a Code Snippet that turns off the THC, run another Code Snippet to turn on the THC before you cut with other Operations.
Should I use "on lead in" with the small circles?
I have not experimented with that recently, but I believe it had a weird side effect, I quit using it but don't recall why.
update: I just tried using 'on lead in' path rule with a 'on small circle' and I got expected result, THC off before lead in and 65% feedrate of leadin. However I also got the THC off for 'on small circle' rule after the leadin. So if you don't like that redundancy, although it won't hurt other than to slow command processing time by a few ms which could perhaps stall XY motion, then make a rule set just for circles and apply it to an Operation for grouped circles.
btw- I'm testing this on sheetcam v7.1.40 (7.1.35 should be fine on linux, I can't recall if .40 is available for linux)
Deezl Smoke
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Re: Path rules question with video to explain.

Post by Deezl Smoke »

Cool information. Thank you for that. I do not mind the ms process time. For my jobs it wont matter. I'll set that up again and try. I had some path rule conflicts a while back which is why I cleaned them up, maybe went too far and removed too many.
I think my thc delay is at 2 seconds. On heavier plate, maybe need to increase that to 3.
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