Using speed variation to counteract chatter in a lathe

I am very interested to see how this works.
Robert
 
Jeez, I should do a better job thinking about what Ive read rather than think what I ve read ! I apologize. Caught me off gaurd thinking outside the box. I m no electric guru that s for sure and way too mechanically minded. Many sleepless nights worrying about setting up the new lathe with a vfd for this old screw machine guy. Still have the occasional flashback when I hear the gadget click! but heres a thought or maybe a question?
Manipulating speed up and down even when degenerative is power applied constant having a constant load. Or does power just get backed off like a combustion engine?
Every bit does help but I have enough wizardry to catch up on for now! I ll go back to my dials and my Vernier Caliper now.
 
Actually, in this video, Haas presents exactly the same thing. They call it SSV (Spindle Speed Variation). They seem to be using sine wave for speed modulation. IMHO it would be better to use triangle wave as that one stays equal time at any given speed whereas sine wave stays longer time at the extremes.
If this little guy can do the same thing as an add-on for a chinese VFD, I sincerely hope that the Chinese make a cheap copy from it !
 
Ave on YouTube (potty mouth) made a VFD spindle speed changer - sadly I can't find the video at the moment. He built some dort of feedback mechanism though. When there was a resonance at all, the speed would be changed - and only then. If the resonance recurred, it would change again. So it wan;t continuous change but in response to a sensor - which minght cause it change conimuously after all, of course.
It seemed a really clever solution to me.
 
I have also seen Ave's video - and I am also not able to find it. Reason ????? I do not know if the thing that he owns a Haas machine has anything to do with it :)
 
The PCB design is ready. Next, send the Gerber files to some chinese PCB manufacturer and then just wait...

The video is HERE.
 
Norppu said:
IMHO it would be better to use triangle wave as that one stays equal time at any given speed whereas sine wave stays longer time at the extremes.
Click to expand...

The issue with triangular wave variation is the instantaneous direction reversal at the top and bottom of the waveform. Of course on a real machine it won't be instantaneous, but the actual response could depend on the particular machine. For consistency it would be best to use a modulation envelope that all your machines can respond to in a consistent fashion. Or maybe it doesn't matter that much. The mathematician lurking inside my head made me type this :grin:
 
Producing a beautiful sine wave in a 8-bit MCU is way harder than producing a triangle wave. I always prefer the easy way out and if the triangle can do it - then it can do it. The practical guy between my ears made me type this :)
 
Sine wave to represent acceleration, triangle to represent translation, right?

I think you are getting into interesting territory. Would be cool to put a mic on the tool and vary speed based on filtering frequencies out of the range where harmonics exist.
 
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