So did the test again, this time:
- I removed the collet nut, to remove any give it might have
- I positioned the DTI tip inside the collet holder
- I pulled on the collet holder from the outside with the luggage scale
The result was much worse than before:
| Movement | Weight | Force | Stiffness |
|---|---|---|---|
| 10 µm | 0.45 kg | 4.5 N | 0.45 N/µm |
| 50 µm | 2.1 kg | 21 N | 0.42 N/µm |
| 100 µm | 5.4 kg | 54 N | 0.54 N/µm |
HSMAdvisor reports that the cut I was having issues with should have produced only 0.2 kg of cutting force, so ~5µm of give. However given the long stickout, perhaps there’s a lever effect going on, magnifying the size of the effect?
Around 7µm on the inside of the collet holder and I’m using collets rated to 5µm. Ordered some 2µm collets to try too.
I can try the tool shank but I’m iffy about that because the shank usally has a lower rating than the tool itself.
I tried both ways to be sure but yep.
Yes, I’m aware. I saw these feed rates and checked with the feeds and speeds calculators and the resulting power and torque requirements seemed well within the Nomad’s specified capabilities. The only thing left seemed to be rigidity, hence this thread.
I tried a more Carbide3D-friendly option and ran the 274Z at 8mm DOC, 0.06mm WOC, 10kRPM and 850mm/min feed rate. This actually worked just fine despite producing the same 0.2kg cutting force as the other endmill I had issues with.
However with both endmills I’ve seen little stringy bits of stuff coming out of and getting briefly stuck in the endmills so the problem seems almost certainly chip evacuation rather than machine rigidity.