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  1. #1
    Hi gang, would love your input on this, got a drill press with 1HP motor, unfortunately at the time of purchase I didn't get to test it thoroughly so I'm stuck with it, it is fine for the most part but changing the belt pulley ratio is a big hassle in this model basically. (and indian company with no website as far as I know) , is it possible to keep the belt at a position and just put a VFD and use that to change the speed/torgue?

    motor information:
    CG Commercial motors
    230v 1ph 5.5A 750W 1.0HP 1425RPM

  2. #2
    Quote Originally Posted by Noplace View Post
    Hi gang, would love your input on this, got a drill press with 1HP motor, unfortunately at the time of purchase I didn't get to test it thoroughly so I'm stuck with it, it is fine for the most part but changing the belt pulley ratio is a big hassle in this model basically. (and indian company with no website as far as I know) , is it possible to keep the belt at a position and just put a VFD and use that to change the speed/torgue?

    motor information:
    CG Commercial motors
    230v 1ph 5.5A 750W 1.0HP 1425RPM
    Yes, but you need for that to work well - 4 pole 3 phase motor rated at ~1400rpm. Then you would be able to control it in the range of 600-3000. As you see is not enough. So you need DC motor, say from a thread mill, or even better would be a servo motor. Expensive? Then change belts...
    project 1 , 2, Dust Shoe ...

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  4. #3
    Yes, you can easily do it.
    Use a 2 pole 0.75kw compact frame motor and an Inverter-Drive of decent makes and your top speed limit will give you plenty of range, I have a 2 pole 0.75kw compact frame motor which runs at 7000 rpm on my benchtop mill, I used it to replace a DC motor/controller which wouldn't give me a usable 1000rpm to 7000rpm.
    Motor 150 new, Inverter Drive 100 NOS from eBay.
    Regards,
    Nick

  5. #4
    DC brushless from China?
    https://emvioeng.com
    Machine tools and 3D printing supplies. Expanding constantly.

  6. #5
    Quote Originally Posted by magicniner View Post
    I have a 2 pole 0.75kw compact frame motor which runs at 7000 rpm on my benchtop mill, I used it to replace a DC motor/controller which wouldn't give me a usable 1000rpm to 7000rpm.
    Nick, how did you do that? It sound a bit sci fi. At how many Hz you run it and hows that that it still works?
    project 1 , 2, Dust Shoe ...

  7. #6
    I mentioned to a colleague that changing belts on my drill press was a bit of a pain and he said some people had used Sturmey Archer bike hub gears instead of the pulleys and can then change to lots of speeds. They are pretty strong to take the pedalling loads. Then you just have a lever on the side of the machine to select the gear.
    Or some of the fancy drill presses have a pair of cones to give a range of continuously variable speeds without even stopping the machine. Again sliding a lever selects the speed. Probably an expensive option though?
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  9. #7
    Quote Originally Posted by Boyan Silyavski View Post
    Nick, how did you do that? It sound a bit sci fi. At how many Hz you run it and hows that that it still works?
    Boyan,
    It's a Siemens 420 (soon to be replaced with a 440) Inverter Drive with an Electro Adda 0.75kW 2 pole motor I'm not sure of the Hz it runs as I've programmed the VFD display to show RPM, I'll check the Hz at 7000rpm later today as I have an aluminium profiling job later today.
    My experience so far is that these things tend to just work if you use decent quality gear, the availability of good, clear, English documentation makes programming the Siemens VFDs a 10 minute job.
    I read a thread somewhere where Sir John Stevenson gave details of converting larger 3 phase motors to milling spindles with integral collet chuck and running them without issues at ridiculous speeds, 7000 rpm does what I need but I suspect I have left a substantial safety margin and that it could easily run faster,
    Regards,
    Nick
    Last edited by magicniner; 30-03-2016 at 03:26 PM.

  10. #8
    There's a lot of good info here but possibly not so useful to someone without the technical background to follow the discussion!

    In short, I think that the answer to the original question is, yes, fixed pulleys with variable-speed motor is a practical proposition, but you need a VFD plus replacement 3-phase motor to do it. You can't make a simple single-phase motor into a variable speed motor just by feeding it from a VFD - unfortunately.

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  12. #9
    Quote Originally Posted by magicniner View Post
    Boyan,
    It's a Siemens 420 (soon to be replaced with a 440) Inverter Drive with an Electro Adda 0.75kW 2 pole motor I'm not sure of the Hz it runs as I've programmed the VFD display to show RPM, I'll check the Hz at 7000rpm later today as I have an aluminium profiling job later today.
    My experience so far is that these things tend to just work if you use decent quality gear, the availability of good, clear, English documentation makes programming the Siemens VFDs a 10 minute job.
    I read a thread somewhere where Sir John Stevenson gave details of converting larger 3 phase motors to milling spindles with integral collet chuck and running them without issues at ridiculous speeds, 7000 rpm does what I need but I suspect I have left a substantial safety margin and that it could easily run faster,
    Regards,
    Nick
    A bit off topic. Now i need your help here. I have the micromaster 420 on my belt grinder coupled with 3kw motor, and have it programmed 0-100 hz so i reach 0-3000rpm , its 4 pole 3 phase motor. The problem is where do i make to be able to change the frequency from the operating panel? i did it once, but forgot how. Read the manual 100 times, but still can not change frequency from panel up and down button, which drives me crazy.
    project 1 , 2, Dust Shoe ...

  13. #10
    Quote Originally Posted by Neale View Post
    There's a lot of good info here but possibly not so useful to someone without the technical background to follow the discussion!

    In short, I think that the answer to the original question is, yes, fixed pulleys with variable-speed motor is a practical proposition, but you need a VFD plus replacement 3-phase motor to do it. You can't make a simple single-phase motor into a variable speed motor just by feeding it from a VFD - unfortunately.
    lots of great information surfaced in the thread, appreciate if you can just let me know what would be the problem in using a 1ph VFD?
    got my eye on this one http://www.ebay.com/itm/0-75kw-Frequ...16402#shpCntId and seems it would work, am I missing something?

    Click image for larger version. 

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