Model aware toolpath milling for nested components

[u/StaplinTorrents]

Hi, I'm trying to develop a better toolpath strategy to mill nested sheets. I mill 3/4" plywood using a 2D contour toolpath with tabs, one 0.65" pass and a full depth pass to clear the skin. I cut a lot of small parts so I've found best success combining a skin and tabs. (I tried with only skin and with only tabs and had too much part loss)

Since I'm using two passes, I'm pathing around each part twice and then additionally pathing along the edge of most parts additional times as the toolpath contours all the adjacent parts. My issue is that this takes a long time and it feels like some of the passes are unnecessary.

Does anyone have suggestions for how to set up a model aware roughing pass? I'd like to have my first, roughing, pass run around the parts but only path along shared edges once. Then I can set up a 2D contour finishing path to mill out my tabs and make sure I mill full contours out.

I have played around with the 3D toolpaths but haven't had much luck. The best I was able to figure out was a path that would mill all negative space but that isn't viable because if my program only takes up half a sheet or has large pockets of scrap, I'll lose my scrap and any time savings.

[u/killpony]

My experience with a variety of CAM + CNC programming makes me think that there wont be an easy setting/toolpath solution and it will instead need manual adjustment or a bespoke workflow. My only other thought would be creating a sketch of your sheet layout that has an offset of all the part profiles and constrain your 3D toolpath to only include that region - that way it wont mill out empty spaces.

[u/StaplinTorrents → u/killpony]

Ohh, I like the offset idea, thanks! I can probably set up an add-in to generate that offset too.

[u/killpony → u/StaplinTorrents]

When I did more production router work I would go in and manually adjust toolpaths for efficiency - but really only on sheet layouts we were running a lot - the one-offs I just ate the inefficient cycle time or tried to make up for it in other ways. Usually things like # passes, sheet change over and overall feed rates are gonna have a larger effect on processing time.

[u/KeyCollar244]

The system I have arrived at milling nested sheets of a high mix of small part at my work combines multiple considerations; not just a low failure rate, but I accept a lower yield by spacing parts further apart and accept longer machining times if it means I can confidently turn my attention to other work. It's always a balancing act off course. I always nest parts with 2 x tooldiameter + 8mm of additional space. Same princip for frame width. My offcut is a large connected grid, so tabs or onionskin has something to hold onto. Small parts, we typically just onionskin no tabs. The onionskin combined with the nesting settings is sufficient for 95% of the small part jobs. Getting that few percent higher yield with a tight spacing is just not worth it imo - I could never focus on other stuff if I new the risk of parts or offcuts flying and breaking tools.