Hello, I have a small CNC mill which I normally use for cutting wood like hard maple, without much problem. I often use small bits of 0.6 .. 1.0 mm.
This time I tried a 2 mm carbon fiber plate instead. It is fixed on a soft foamy plastic and fully submerged in water. The spindle rotates at its maximum of 12000 RPM. Carbon steel bit diameter is 0.8 mm.
I started with a small feed of 35 mm/min, depth step about 1 mm. It was a simple outline. Seemed to work smoothly, until the bit broke after about 10 cm. I lessened the feed to 20, then 10 mm/min. Did not help, the bits keep breaking after 5 ... 15 cm of feed. These are the same end-mills which I use for hard woods. I put one broken piece under microscope, near a new bit:
The broken piece is to the right, the new bit to the left. They both look sharp and indistinguishable, as far as I can tell.
What could be the source of the problem?
This time I tried a 2 mm carbon fiber plate instead. It is fixed on a soft foamy plastic and fully submerged in water. The spindle rotates at its maximum of 12000 RPM. Carbon steel bit diameter is 0.8 mm.
I started with a small feed of 35 mm/min, depth step about 1 mm. It was a simple outline. Seemed to work smoothly, until the bit broke after about 10 cm. I lessened the feed to 20, then 10 mm/min. Did not help, the bits keep breaking after 5 ... 15 cm of feed. These are the same end-mills which I use for hard woods. I put one broken piece under microscope, near a new bit:
The broken piece is to the right, the new bit to the left. They both look sharp and indistinguishable, as far as I can tell.
What could be the source of the problem?