Mini lathe motor whining noise


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Thread: Mini lathe motor whining noise

  1. #1
    Member rdsn's Avatar
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    Default Mini lathe motor whining noise

    I have a 16" x 8" mini lathe. It's one of those generic, gray, chinese mini-lathes, no brand name associated.

    Amonst other deffects, which I can work out, there's an irritating whining noise (high pitch noise).

    I have removed the motor and checked that the noise comes from the motor.

    I have also disconnected the motor from the lathe and connected another motor I use for other stuff and that I know to be quiet.

    Regardless of the voltage provided both scream if connected to the lathe's electronics.

    I read that the problem is the frequency used by the PWM module.

    What can be done to get rid of this noise? I see a couple of adjustment screws in the electronics board but I don't know what they do.
    (I haven't changed anything yet)

    I can provide a video and a couple of pictures later. Thanks

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    Community Moderator Al_The_Man's Avatar
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    Default Re: Mini lathe motor whining noise

    What is the nature of the motor? DC ? AC? BLDC?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Member rdsn's Avatar
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    Default Re: Mini lathe motor whining noise

    It's a 750W motor with brushes which has a 220V sticker on it. I believe it is a DC motor, It only has 2 wires running from it.

    Here's a link for a video (in reality the noise is much higher than in the video): https://bit.ly/2ZmsjjB

    Here are a couple of pictures, I know they're not great but they are what I have for the moment.:
    Adjustable components (don't know what they do): https://bit.ly/329sITs
    PWM module (?): https://bit.ly/326tb99



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    Community Moderator Al_The_Man's Avatar
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    Default Re: Mini lathe motor whining noise

    Did it suddenly start this or was always there, It appears it may me a simple PWM drive, if so often the main reason is too low a PWM frequency.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Member rdsn's Avatar
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    Default Re: Mini lathe motor whining noise

    It was always there from new.



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    Default Re: Mini lathe motor whining noise

    PWM module (?): https://bit.ly/326tb99
    This picture is of the back from the digital RPM readout. This is connected to the 5 Volt powersupply (2 pin connector) and a proximity switch (3 pin connector). I have the same on my small lathe.

    The 2 potmeters are probably for setting the minium and maxium rpm. I have a similar (not identical) board on my mini lathe.



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    Member rdsn's Avatar
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    Default Re: Mini lathe motor whining noise

    Yes, you're right. Yesderday when I got home from work I tried to connect those wires to another PWM module and that checked out, it is only for the readout (of course, the "in" and "out" are disconnected).
    Also, disconnecting that module, all works well but without RPM reading.

    The potentiometer wires go straight to the circuit board so the PWM module is integrated there as well. The question remains, is there something that can be done to replace/filter/change the frequency driving the motor?



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    Default Re: Mini lathe motor whining noise

    is there something that can be done to replace/filter/change
    Maybe... it depends on the type of circuit that's driving the motor. See if you can identify the power output device on the board that is closest (electrically speaking) to the motor... or failing that, post a bunch more detailed photos so we can try to figure it out...



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    Default Re: Mini lathe motor whining noise

    @RDSN
    That is hard to say. My board controller version doesn't make that noize. To modify the board you need schematics and even then, it not guaranteed to work.

    You could however replace the controller. If you google, you will find a lot of them.

    One of my lathes has a Siemens DC motor controller. I can't take a picture of it because the back is standing against a wall and I can't move (+ 260 kg) that thing without taking it appart.



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    Default Re: Mini lathe motor whining noise

    I will both try to identify the power output device and take detailed pictures to post here.

    Preferably I would like to avoid modifying the board and just add something in series with the motor (if possible) or just bypass the original PWM module and add a different one. But first show you guys some pictures of the board in order to identify it. Thanks



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    Community Moderator Al_The_Man's Avatar
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    Default Re: Mini lathe motor whining noise

    You can try a choke in series with the motor, but with PWM you should not normally have to do that, this is one advantage to PWM.
    It must be running a very (abnormally) low PWM frequency in order that you can hear it, the ones I have used are completely silent, including the Treadmill versions.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Member rdsn's Avatar
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    Default Re: Mini lathe motor whining noise

    I have added some close up pictures here: https://bit.ly/2zyEtXj

    Also, I'm attaching a schematic of the lathes wiring (sorry about the drawing, I'm not an electronics guy).

    Attached Thumbnails Attached Thumbnails Mini lathe motor whining noise-20190829_213917-jpg  


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