2D Adaptive and small diameter end mills (broken tools)

[Anonymous]

I have a deep (20mm) narrow (6mm) slot I'm attempting to cut using a 3mm straight end mill (21mm flute) and a 2D adaptive operation. I've set feed/speeds/WOC per HSMAdvisor recommendations (notably 0.4mm for Optimal Load, 1/3 of what F360 recommends), but I keep breaking tools (costing me ~$15.00/each and lots of runout optimization time).

Can anyone see any glaring mistakes I'm making in my setup? I've attached the model for reference.

HSMAdvisor settings:

Material: 6061-T6 Series Aluminum 95 HB
Tool: 3.000mm 4FL Carbide None Solid End Mill
Speed: 94.2 SMM/ 10000.0RPM
Feed: 0.0133 mm/tooth 0.0533 mm/rev 533.40 mm/min
Chip Thickness: 0.0133 mm
Reference Chip load: 0.0267 mm
Engagement: DOC=20.00 mm  WOC=0.40 mm
Effective Dia: 3.000 mm
Cross Section: 0.89 x Dia.
Power: 0.06kW
MRR: 4.27 cm³
Torque: 0.06 N-M
Max Torque: 0.14 N-M
Cutting Force: 37.1 N
Deflection: 0.19 mm
Max Deflection: 0.27 mm
Comment: 
Operation Comment: 
Additional Operation Info: 

[Steinwerks]

The first thing I'd do is tighten up that tolerance. .1mm (or nearly .004") is too loose for small tooling, and generally speaking too loose for adaptive toolpaths where utilization can be maximized and pushed to the limits of the tool safely.

Essentially this will allow the toolpath to diverge outside of such a small tool's limit and take too large of a cut. I would reduce the tolerance value by an order of magnitude to .01mm for starters.

Edit: also, what is your machine and what are you using for chip evacuation?

[randyT9V9C]

What is your stick out? I played with this in my calculator and I could get it to work in theory using a cut width of 0.01mm but if I pushed it more or increased my stickout over 21mm then deflection was likely too high. Your 6.6xDiameter. Can you slot it out using a 6mm endmill? 

[zero_divide · Accepted solution]

Hi,

Your problem is this:

Engagement: DOC=22.00 mm  WOC=0.40 mm
Deflection: 0.16 mm

Your deflection is too large.

What happens is the ednmill is leaving 0.16 mm on the wall due to deflection. Which is huge by the way

So next time it cuts the same wall, it has not 0.40mm to cut, but 0.55mm

This leads to even more deflection and so forth until the endmill breaks.

HSMAdvisor just does not expect deflection to play any role in increasing the actual width of cut.
And for bigger cutters it is true.....

At 0.16mm deflection it is close to breaking anyway.
I would suggest setting your WOC to 5% maximum (leaving everything else the same). This should give you 0.06mm deflection which is still a lot, but should be manageable.

My personal way would be to use a necked 2 flute tool with short stubby flute and mill the thing in several DOC passes

[Anonymous]

Neil,

Great! I'll set the tolerance as you've suggested.

I'm using flood coolant. I had a bit more success today by slowing the feed rate. Will continue to experiment.

Thanks for replying so quickly!

[Anonymous]

randy,

My tool stick out is 22mm. I have some 2 flute and 3 flute 5mm end mills on the way.

I was looking at some reduced diameter shank end mills as well (Maritool). These would lend themselves well to a multi-pass stepdown methodology.

Thanks!

[Anonymous]

Thanks Eldar. I'll pay more attention to the deflection value.

The multi-pass step down strategy you proposed could work...was just hoping I could use the full LOC. Regardless, I'll give it a try.