Shortest Cutpath option

Hey Les,

I have noticed a few things about the path optimizations. It seems to me when the shortest path option is selected, it does not seem to actually travel in the shortest path. At least for open contours. In the attached file “MillEngraving.zip”, the first “l” in “hello” is cut from the bottom to the top and then it rapids back to the bottom of the letter to start the second “l”. The shortest path would just be to rapid over to the top of the second “l”, wouldn’t it? Does this have something to do with the cut direction perhaps? I wouldn’t think open contours could have a direction associated with them though.

Originally i noticed this when etching bend lines on a part that is laser cut. It does the same thing, etch starts at the bottom and goes up, then rapids back to the bottom and travels up again. Why not just rapid over instead of rapid down and over? Then it travels all the way back to the left edge of the part to start the cut, but i just assumed that was because they are two different operations. Why travel 75" back to the left when the next cut could just be 1" away?

Take a look at the two job files when you get a chance and see if it is just how the program interprets it or if it is something that could be improved.

Thanks Les!
LaserEtchExample.zip (28 KB)
MillEngraving.zip (5.91 KB)

SheetCam won’t move start points. Having SheetCam unexpectedly moving your start points could cause problems in a lot of cases.

I dont quite understand there Les… sheetcam does move start points… Sheetcam actually initially places the start point anyways and any time i reorder parts or manually locate a start point, sheetcam does indeed move the other start points. So i do not follow what you mean at all.

Sorry, I was referring to open contours. On open contours the position of the start point controls the cut direction and the offset side.

Operations aren’t currently aware of each other. The ‘Start position’ option in the cut path tab gives the operation a hint as to where the cutter is likely to be. When auto optimising the first start point will be nearest the point selected in ‘Start position’.

Oh ok, i see now. But i still dont quite understand. If sheetcam doesnt know which offset you intend for the open contour, then how does it know which end to put the start point on, so why would it matter if it automatically places them at the shortest path when shortest path option is selected? You would still likely have to manually adjust the start point anyways if you want a particular offset, no?

I assumed the operations being different was the problem with the long rapid between the etch and the cut moves. It seems there have been several issues that come up in the forum with the operations not being aware of each other. I suppose there is no good way to do this? No way to somehow remember the last tool location? I would think this would be beneficial for both jet and router/mill cutting operations, wouldn’t it?

With open contours SheetCam has no way of knowing which end is the correct one when you create the operation so it puts the start point on the start of the line as it was drawn.

As you are likley to have to manually move the start point on open contours there isn’t much point in trying to optimise the cut distance by moving them for you.

No way to somehow remember the last tool location? I would think this would be beneficial for both jet and router/mill cutting operations, wouldn’t it?

It can be done. I didn’t do this originally due to the extra CPU load. If you make a small change to one operation you are forcing every succeeding operation to be re calculated. If you have a lot of operations this could add a significant amount of time to the path calculations. That was around 10 years ago. Nowadays processors are much faster so it’s not as much of an issue. I might revisit this once I have the code back up and running. Currently it’s in pieces as I’m upgrading to wxWidgets3 and Visual Studio 2019. This is the first big toolkit update sice I started TNG and a lot has changed over the years.

As you are likley to have to manually move the start point on open contours there isn’t much point in trying to optimise the cut distance by moving them for you.

What i am getting at here is, i have never had to offset an open contour and cannot think of a reasonable situation where you regularly would have to do so. I am sure there are a plenty people that do that use sheetcam though. Since they likely have to manually change the start point anyways, why not have sheetcam automatically place the start points with the shortest path and the least amount of rapid to reduce machine wear and total job time as much as possible for those who are not offsetting the open contour (which i honestly feel is the majority of users).
The two others we have here that are now using sheetcam do not look at the start points closely and just click a button and hit go, so they are getting a lot more movements for no reason and are experiencing problems with the leadins overlapping other parts. (hence my topic a few weeks ago about the start point clearance setting and placement relative to other parts)

It can be done. I didn’t do this originally due to the extra CPU load.

Yes, quite a bit has changed in both hardware and software since then. I am sure it is quite an undertaking to upgrade to those latest versions. I’ll leave you alone now and let you work lol :smiley: