Slowing down the spindle around corners?
14 Dec 2016 06:26 #84074
by jerzmacow
Slowing down the spindle around corners? was created by jerzmacow
Does Linuxcnc have the ability to slow down the spindle according to feed rate changes the trajectory control makes? Is this even possible with the way Linuxcnc is written?
My spindle has speed control, and it chatters when going around corners. This is with wood, so the feedrate is very high (400ipm).
If this were possible, it'd improve tool life I think. It'd also be very very cool
My spindle has speed control, and it chatters when going around corners. This is with wood, so the feedrate is very high (400ipm).
If this were possible, it'd improve tool life I think. It'd also be very very cool
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14 Dec 2016 09:55 #84080
by andypugh
Replied by andypugh on topic Slowing down the spindle around corners?
As is generally the case with LinuxCNC, most things are possible with a little effort.
I assume that you are wanting to keep a constant feed-per-tooth value?
I see that there are two useful-looking HAL pins:
motion.requested-vel
motion.current-vel
I don't have a machine to try it on at this moment (I am at work
but you could watch those two pins with Halmeter to see if they show what they sound like they should show.
If they do, then you could take their ratio (needs two HAL components, there is no HAL divide, you need to invert one with linuxcnc.org/docs/2.7/html/man/man9/invert.9.htmll and then use linuxcnc.org/docs/2.7/html/man/man9/scale.9.html) and feed that into a second scale component that modifies the spindle speed request before it is sent to the spindle drive.
In practice I think I would use a "lincurve" to determine the spindle override factor, the simplistic approach here would tend to stop the spindle at times when you didn't want it to. Also, you probably need to consider the effects of feed-override.
I assume that you are wanting to keep a constant feed-per-tooth value?
I see that there are two useful-looking HAL pins:
motion.requested-vel
motion.current-vel
I don't have a machine to try it on at this moment (I am at work
![:-) :-)](/media/kunena/emoticons/smile.png)
If they do, then you could take their ratio (needs two HAL components, there is no HAL divide, you need to invert one with linuxcnc.org/docs/2.7/html/man/man9/invert.9.htmll and then use linuxcnc.org/docs/2.7/html/man/man9/scale.9.html) and feed that into a second scale component that modifies the spindle speed request before it is sent to the spindle drive.
In practice I think I would use a "lincurve" to determine the spindle override factor, the simplistic approach here would tend to stop the spindle at times when you didn't want it to. Also, you probably need to consider the effects of feed-override.
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14 Dec 2016 13:58 #84089
by Todd Zuercher
Replied by Todd Zuercher on topic Slowing down the spindle around corners?
I run a lot of woodworking machines, and I've never had a problem with "chatter" at a corner caused by excessive spindle speed. Usually for us if there is a chatter mark on the wood as you describe, it is because of the part (or scrap material) moving due to inadequate clamping (vacuum table).
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