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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > About to start PM-728 CNC conversion I need advice.
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  1. #1
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    Sep 2015
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    About to start PM-728 CNC conversion I need advice.

    Just got the mill in. It looks great installing it went perfect. I'm now collecting items for the conversion. I originally decided
    on Clearpath NEMA 34 servo's. But now I'm thinking this may be an over kill. I seen a few examples of people using NEMA 23's
    I think a NEMA 34 on the Z axis because it does more heavy lifting, but X and Y should be ok for NEMA 23. If I need 34's I'll do it,
    I just don't want to over do it.

    Anybody have any thoughts or experience?

    RonL

  2. #2
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    Re: About to start PM-728 CNC conversion I need advice.

    Nema 23 for the X-Y is fine. With CP you don't really save any money with the 23. The small Nema 34 are OK too and they will stick out less.

    Nema 23

    https://www.teknic.com/model-info/CP..._voltage=75VDC

    If you want to go to Nema 34 for the X and Y.

    https://www.teknic.com/model-info/CP..._voltage=75VDC

    For the Z.

    https://www.teknic.com/model-info/CP..._voltage=75VDC
    youtube videos of the G0704 under the name arizonavideo99

  3. #3
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    Re: About to start PM-728 CNC conversion I need advice.

    Thanks Dave

  4. #4
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    Re: About to start PM-728 CNC conversion I need advice.

    RonL:

    I've been considering for some time getting a PM-728VT for CNC conversion. Finally ordered one earlier this week. When I placed my order I saw PM now "has" a CNC conversion kit for this mill, $900. I asked but he who I talked to had zero information as yet. I'll likely email PM and ask for details, like what motor mounts that kit has.

    I'll likely tuck the steppers back towards the machine, X & Y, to save space. I need to touch the mill but without seeing it I'm thinking NEMA 23s on the X & Y and a NEMA 34 on Z. If I can tuck the X & Y motors backwards they'll have a timing belt drive with likely a 2:1 reduction.

    I hope you'll start a thread about your conversion. I look forward to hearing more.

    Thanks.

    Hugh

  5. #5
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    May 2004
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    5

    Re: About to start PM-728 CNC conversion I need advice.

    I'm working on a build (have posted some over on HM forum New PM-728V-T Mill | The Hobby-Machinist
    After spending the big bucks on the mill I also went big with the Clearpath servos. Went with 23 and 34 incase I end up going with the PM kit.
    this was from an email from Matt last Sunday

    " It should be around that time yes, as long as all still goes as planned.
    The ball screws are double nut, 7001 end support bearings, cast iron brackets, etc.
    I believe the screws are Rolled C5 screws, ill have that info for sure in the next 10 days or so. Trying to use ground, but they are so expensive, and there is really no advantage we can find, not yet anyway. "

    I went with the bigger 2005 screws but the 1605 should be plenty (and if C5 that would be great)


    Using a Centroid Acorn setup. encoder on the spindle and plan on speed control.
    I follow Sam (CNC4XR7) and Franco on youtube so mostly a combination of what they have done.

  6. #6
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    Mar 2017
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    Re: About to start PM-728 CNC conversion I need advice.

    I am really interested in finding out what they use for a controller for the brushless motor. Do you think you could take a close up photo of it and post it?

    I have the Precision Mathews 1228 lathe and I bet they are using the same controller that it has. When you are doing your conversion you will probably want to control the spindle and that means feeding the BLDC controller the right signals. When I converted my lathe, this was the most difficult problem.

    Also, where is the RPM sensor and how does it work? Optical? or Magnetic?

  7. #7
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    May 2004
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    Re: About to start PM-728 CNC conversion I need advice.

    I have not popped the cover but if you check the vids on youtube that Franco has done. Smoked his board and shows it.
    https://www.youtube.com/watch?v=f2CtnotqFzQ&t=560s
    Not sure what type of sensor it has but I will be using an encoder that interfaces with the acorn board. if you check my post you can see the RPM on both the PM and from the encoder/acorn.

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