VFD Speed modulator to counteract chatter in a lathe
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  1. #1
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    Talking VFD Speed modulator to counteract chatter in a lathe

    I have an import lathe that is not that rigid. Therefore I often have issues with chatter.
    I have come across several time on a solution that might medicate some of this chatter proble.
    Since chatter is actually a resonence condition and it takes some time to develop. I mean, the chatter does not start right away, it may take a second or two to develop into the disturbing form.

    If the spindle speed is varied constantly, this does not allow enought time for the chatter to develop. I have done this manually, since I have a VFD, and it looks like it could do something for the problem.

    For this reason I have designed a device that involves a microcontroller (Atmel Atmega32) and some PWM filtering. I am at the moment of making a housing for that thing and the go into practical testing with the lathe.

    This VFD Speec Modulator is compatible with the Huanyang VFD's and controls it directly. It uses the 10 Volt output from the VFD so no extra power supply is required.


    forumshot.jpg


    I have made a video series of this thing in YouTube at Finno Ugric Machining

  2. #2
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    This post is skating on the edge of spam...

    The proper way to prevent oscillation, is to find the component and geometric circumstance that's causing chatter, and fix it.

    While the chatter IS resonance, modulating cutter speed assures you'll get inconsistent cut quality and poor precision.

  3. #3
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    You are quite right - changing the speed will have an impact on surface quality and therefore one should give other countermeasures priority. In my case, with the Chinese lathe, this is sometimes mission impossible. Probably I need a new lathe - or more precisely - an old lathe which is rigid enough.

    That all being said, the cutting speed is one term of the equation and it is the easiest to manipulate if there is a VFD already installed.


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