Backlash, Deflection and Vibration


It’s all consistent which is good. I’m sure I recognise that spreadsheet he used :wink:

Also interesting to see how close to the mark Millalyzer is on the cutting performance predictions.

Be interesting to see if the same speeds are possible on an XL or XXL with it’s larger deflections. I note he was using a Z+ for that which is a good vote for that as a non-wobbly Z axis.


Not really. The VESC tool reports and logs input power, not output (cutting) power like Millalyzer and other calculators predict. Millalyzer’s estimates are also highly dependent on endmill geometry (rake angle, edge radius, helix angle, etc.)
Nice to see how little power is required to mill aluminum though!


Bah humbug, what am I going to use the other 2kW in my spindle for then? Heating? :cold_face:


Not so sure about high-feed endmills. Normally, those have a small lead angle (kappa or KAPR) of about 10° - in a way that makes them a V-bit with a very blunt 160 degree tip angle. As they are designed to cut with the face only (not the circumference), that limits the maximum axial engagement to very small values (for 10° lead, that is 8.8% diameter, or ap < 0.5 mm for a 6 mm tool). The lead angles gives you axial chip thinning, so you’d want to increase feed violently (theoretically by 5.8 times at 10°) to reach appropriate chip thickness values. At such high feeds, the steppers have lost most of their torque, so it might not be terribly practical, but certainly worth a test.


The Shapeoko Pro approach seems like a really reasonable solution to this problem. I wonder if anyone has measured how it performs. :question:

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Well, I kinda did as it happens…kinda. I wanted to do the industry standard “stand on the X rail” test I’ve seen someone do on another machine, but me on my Pro. But I wanted more science! So I stood my 185 lbs on the center of the X rail, which is the worst case scenario, and not the best case of standing near the sides like the other machine. I also added a dial indicator, because the difference between play and science is measuring. My Pro is on a kinda torsion box bench, so pretty sturdy.

My 185 lbs ass getting on the bed caused around 0.005" of defection between the bed and X rail.

This grown child getting on the X rail caused 0.015" defection between the X rail and bed.


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