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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > PM-25 Belt Drive Mod - 4700 RPM with stock motor
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  1. #1

    PM-25 Belt Drive Mod - 4700 RPM with stock motor

    I searched all over for how to get more RPMs from the PM-25. Lots of options, but I took the simple approach (Maybe simple should be in air quotes?) and made a larger pulley for the motor, a new motor mount that provided space for the larger pulley, and got an appropriate size belt for it.

    The existing motor mount doesn't have room for a larger pulley, but a new motor mount can be built to handle any size pulley you desire. I was shooting for about 120mm pulley but by the time I turned it down on my lathe and mill-turned it on the PM-25 itself, I ended up a little smaller. Oh well. So 4700 RPM instead of 5000. NO big deal.

    Most of my stuff involves smaller end mills with 6mm being about the largest I regularly use. The difference between 2500 and 4700 for my 4 to 6mm end mills is like difference between night and day. It's making me crave a 10,000rpm SYIL or Tormach, but it'll be a little while before I justify that.\

    I did my modeling in Fusion 360, and while it's not perfect it works for me. If anyone is interested, I can provide some pictures, the F3D (Fusion) files, and a link to the size belt I used.

  2. #2

    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    FWIW, here's a quick upload to YouTube. I was testing it with 6061T6 aluminum. SpeedTiger 6mm end mill, 9mm depth of cut and 500mm/min feed rate. It eats aluminum now. I was stuck with about 260-275mm/min feed rate with 2500rpm limit.

    https://youtu.be/ObcXY_5E65E

  3. #3

    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    And here is another youtube video that shows me validating the design with plastic printed parts. The lower half of the mount has been machined from aluminum but I printed the rest just to test it. Amazing that the plastic lasted a couple of minutes of nearly 5000 rpm, but it did! As of today all the blue plastic parts seen in this video have been replaced with aluminum parts I've made on the mill and the lathe and it appears to be working great.

    https://youtu.be/MPe-DVhPyEQ

    Once I had the aluminum pulley done I mounted it and use it with the plastic printed motor mount so that I could machine those parts faster with the higher RPM, so I converted it in stages. I'll also upload a quick timelapse of the pulley being turned on the mill using a lathe cutting tool held in a vise and mill-turn programming from Fusion 360.

  4. #4

    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    Timelapse of the pulley machining. First, I turned this blank manually in the lathe. Bored the center to 12mm, then turned down an 8mm length to an OD of 19mm. The 19mm part of the blank was then held in an R8 collet on the mill. Concentricity appears to be spot-on.

    https://youtu.be/T5tVSp30F-w

  5. #5
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    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    Nice job. it does sound the motor is giving max power. I dont know how it will do like that.
    youtube videos of the G0704 under the name arizonavideo99

  6. #6

    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    Yeah, I was intentionally driving it hard to see how it handled it. Motor got warm but not hot.

    Most of the time I'll be doing closer to 3mm depth of cut instead of 9, and on anything below about 6mm depth of cut with the 6mm end mill the motor doesn't bog down anything like that. That said, it did the same thing at 2500rpm. The motor controller on this mill is not that well designed as near as I can tell.

    This is converted with your CNC conversion kit, by the way. I'm loving it so far. It seems like this type of conversion (larger drive pulley) on a PM30 would be fantastic. 5-6000 rpm with double the power would be fantastic.

  7. #7
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    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    Glad its working out.

    Did you do the spindle bearing?
    youtube videos of the G0704 under the name arizonavideo99

  8. #8

    Re: PM-25 Belt Drive Mod - 4700 RPM with stock motor

    No sir, just designed my system to allow a much larger pulley (and longer belt) and everything else in the spindle is stock.

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