[Hyudryu]

Hi everyone, I'm having some issues with my endmill corners chipping. I suspect it's during boring operations, just because it sounds nasty when the bit ramps into the workpiece. Everything else, like 2d Contour, adaptive all spit out steady chip streams and sound healthy.

I have a hobby Langmuir MR1 cnc, and I was creating some holes in 6061 Aluminum with a new 3 flute ZRN endmill (6mm). And after that 1 piece I machined, the corners of the flutes were all chipped. This happened on other end mills as well, so I'm not sure if it's because of my end mill selection (3 flute, instead of say a 1 flute), or if it's my speeds and feeds.

The end mill is a metric 6mm (just under 1/4") 3 flute, the hole I was boring was .350" (~8.9mm). On Fusion360, I did a 2 degree bore, at 8000 RPM, 15 IPM feedrate, which is around 0.000625" chipload, with flood coolant. Even at such a light chipload, it still sounds pretty nasty. Like the bits was grinding on rocks.

I'm suspecting maybe the 2D bore operation is not meant for drilling holes, and is only meant for getting to the final ID starting from a slightly smaller ID? I figured it would be fine, since if I ran a 2D adaptive, it would also do a circular ramp into the workpiece. Could anyone let me know what I'm doing wrong here? I am still learning as I go Thank you!

[ToolHIT]

I would try around a 4mm Diameter End Mill. With a 6mm Diameter End Mill ramping into a 8mm-9mm Bore there is a lot of surface contact of the 3mm radius of the 6mm End Mill hitting all at once and not a lot of room for chips to evacuate. If you went to at least half the diameter of the bore then the tool pressure will decrease, the chips will evacuate better and the helical interpolation tool path would work great.

Or you can pre-drill with a 4mm or 6mm Drill and then come in with that 6mm End Mill to interpolate to size. This would lower the tool pressure and make sure the chips evacuate.

Hopefully this helps!

Mike

[OldSchoolProgrammer]

You're on the right track; drill undersize first then finish with an endmill. If you still have a chipping problem use an endmill with a corner radius of about 0.015", but predrilling should solve the problem.

[metalmayhem]

pre-drill as mentioned , and/or use a 2flt which will help with chip evacuation