I received a number of messages asking me to identify the models of machines in the stability lobe diagram in my last post.
I didn't as that should not be the take-away. This is not a machine tool comparison test. What it does show is how different the same tool will perform in different machines. A different tool configuration would change the results.
I made some changes to the diagram to show the endmill manufacturer's recommended speed (the green shading) and depth of cut (the blue dot) from their catalog chart, which was 1500 SFM and 1X Depth of cut at a full slot. Material was 7075 aluminum. Clearly the tool would have chattered in EVERY one of the machines, so with trial and error you would need to keep trying lower and lower depths of cut until it was stable. I also expanded the speed range to 15,000 RPM so you can see the impact on the lobes of each measurement.
The take-way should be that finding the very best speeds and depths of cut, WITHOUT measuring the tool point dynamics, is very hard if not impossible. You are leaving money on the table.
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