bitraf / bitraf-cnc

CNC-related research and projects at Bitraf
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Dynamic spindle RPM when cornering (future feature discussion) #9

Open Jaknil opened 6 years ago

Jaknil commented 6 years ago

I suggest we break out the discussion of dynamic spindle control to this issue. @JensDyvik

Summary of the idea: We want to use the laser mode in GRBL to dynamically slow down the spindle as the feed speed is decelerated due to cornering and the like. If done right this will give us a more constant chip load and reduce unnecessary heat buildup massively when using high rpm spindles.

Things we will need to look into:

I guess low melt-point plastics will be an acid-test to see if we have got it right.

Looking forward to trying it!

JensDyvik commented 6 years ago

I dont think we need to worry to much about spindle speed up delay.

  1. With constant spindle speed we already have quite good performance
  2. The biggest problem is not corners but cutting jobs with a lower speed over a longer time. For instance small diameter helical entry into metal when using adaptive clearing. Or many small features in a row for instance when milling small teeth. So that makes spindle responsiveness even less of an isssue.

I think the GRBL firmware allows PWM duty cycle to be mapped to a minimum value. If this is correct i suggest we start testing at with a range from 25% to 100%. I dont think we have any need for zero spindle spindle in corners.

I think starting with testing with Bark Beetle is a good idea. If these tests are successful we can dive into modding the GRBL firmware so that dynamic laser mode works with M3 instead of M4 commands and that the spindle will spin during G0 moves. This will allow generic post processors to work with dynamic spindle speed.