"Don't Machine Top of Stock" not working

Hello, I received my Nomad just a few days ago. Right now I’m trying to mill out a design in acrylic. I load in an STL, and select “Don’t Machine Top of Stock”, however it still tries to mill out the entire stock piece. For this project I need to use the ball cutter. I noticed the flat cutters worked, but I’m not sure what happens if I trick it. (if I just trick it and use the other bit.) I don’t want to wait for the Nomad to cut the air for over half its duration, and the shape is a bit too complicated to simply zone it out. Any feedback will be appreciated, thanks!

Is it perhaps the roughing path that is doing it? Don’t machine top only applies to x-y finishing i believe.

@Paul, it would help to see a screenshot of your workpiece. Don’t Machine Top of Stock applies to workpieces that have flat top surfaces flush with the top of the stock. If you don’t select Don’t Machine Top of Stock, MeshCAM will skim the top surface unneccessarily. But if you have a curved-top workpiece and don’t want MeshCAM to machine outside its boundary, you use Machine Geometry + and specity a margin of around your cutter diameter. MeshCAM always operates on the cutter centerline, so specifying the cutter diameter allows for a little kerf around your workpiece. Actually I usually use about 3/4 the cutter diameter.

@dr_g, Don’t Machine Top of Stock will apply to all toolpaths, but effectively would not apply to roughing because there is nothing to rough above a flat-topped workpiece that is flush with the stock. :smile:

depending on the particular job, a roughing operation that is set to leave 0.00 stock occasionally will jog at z=0.00 which can cause issues. took me quite a few frustrating hours and several ruined parts to figure that one out. i think it’s a calculation issue with meshcam.

now when i get that i manually edit all z0.000 to z1.000

So, I loaded the STL back in and tried again, it worked flawlessly. I don’t know what was causing the error earlier, and I haven’t been able to replicate it. Sorry for being such a noob, thanks for the fast response :smile:!

Also make sure that your stock isn’t taller than your parts.

For some reason with Meshcam 5 this was a huge problem for me. I would have to purposely make my stock thinner than my parts by a smidge.