I am using a Tormach to machine an Ice Ball Press similar to this one (How to make an ice ball maker). This involves milling out a 3" hemisphere into 2 blocks of Aluminum. I've actually been successful milling out one of the hemisphere's already using a 1" ball nose using InventorCAM with the HSM milling operation. This has worked pretty well and done a nice job. I am using Inventor and InventorCAM for this.
My question is this: I have modeled the other hemisphere to include a small embossed letter in the bottom of the sphere (~0.5" letter width/height, 0.1" deep). To do this requires the use of a much smaller end mill to get the precision edges around the letter. I've attempted to model the CAM passes in the following way, but not having much success:
- 1st pass - HSM operation, 1" ball nose with 0" tolerance so the 1" ball nose carves out the majority of sphere as much as it can
- 2nd pass - HSM operation, 1/8" end mill with 0" tolerance (have also tried increasing to 0.004", etc.)
I was expecting that by setting up like above, that the 1" ball nose would carve out most of the sphere and the 1/8" end-mill would just cleanup the bottom of the sphere and emboss the letter. But what is happening is that it does the full pass with the 1" and then comes back and tries to cut the entire sphere with the 1/8" end-mill as well. With the 1/8" speeds, that will take absolutely forever. I'm not understanding why the program thinks it needs to cut the upper portions of the sphere since the 1" ball nose has already cut them with 0" tolerance. So there should be nothing remaining that it needs to cut.
Ideas?
Dave