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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > started my cnc conversion for Precision Matthews PM-25MV Mill
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  1. #1
    Join Date
    Jan 2012
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    163

    started my cnc conversion for Precision Matthews PM-25MV Mill

    Hi,

    I started my cnc conversion, I machine all the mounts now I need to order my ball screws next, here is one of many video's i posted look at this one or all Thanks, please let me know or recommend/ helpful tips I should know for this is my first cnc mill conversion and any help i would appreciate it!
    Thanks


    https://www.youtube.com/watch?v=xCGt8fY1hwM

  2. #2
    Join Date
    Dec 2005
    Posts
    436

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    I suggest to not machine parts untill you have the purchased components in your hands and verify dimensions first.
    Especiallly if you buy cheap chinese components, dimensions might be out of tolerance.

  3. #3
    Join Date
    Jan 2012
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    163

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    you have a good point, this is a proven plans and why i did it this way, if i ever do this again i will purchased the components first

  4. #4
    Join Date
    Feb 2019
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    18

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Those like really nice!
    Are you using FK10/FK12 bearing cartridges by the looks of it?
    I'm going down the same route, though I bought all of my electronics/motors/software so far, ballscrews came in today, and my FK bearings plus couplers are a month or so out yet on the slow boat from china, so I haven't started machining anything for the conversion yet.

  5. #5
    Join Date
    Jan 2018
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    1516

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by BrianPM View Post
    Those like really nice!
    Are you using FK10/FK12 bearing cartridges by the looks of it?
    I'm going down the same route, though I bought all of my electronics/motors/software so far, ballscrews came in today, and my FK bearings plus couplers are a month or so out yet on the slow boat from china, so I haven't started machining anything for the conversion yet.
    I'm 3/4 the way through converting one myself using my X2 to make the parts.
    I made my own bearing blocks to accommodate 32x12x10mm 7201-2RS Angular contact bearings for my 1605 screws.
    Seeing how well they work I wouldn't go back to anything else.
    I've packed my double nuts with some aluminium foil to make them tighter (they do now have a little drag). I've only got my Y axis properly set up atm but with the packed nuts and AC bearing combination my backlash has shown >0.001" (0.02mm).

    Once this is finished I'll use it to change my X2 from thrust to AC bearings.

    I went with 1100oz Nema 34 motors so added extra fixing points to the base and table for the bearing mounts. A fair amount of weight comes with those 34 size motors!

  6. #6
    Join Date
    Jan 2012
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    163

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    hey brain,
    yes i when with FK/FF10 and 12 they have Angular contact bearings/ who did you buy your ballscrews from?

  7. #7
    Join Date
    Feb 2019
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    18
    Quote Originally Posted by rmachinist View Post
    hey brain,
    yes i when with FK/FF10 and 12 they have Angular contact bearings/ who did you buy your ballscrews from?

    https://www.ebay.com/itm/PM-25MV-cnc-conversion-kit-precision-matthews-balls-crews-machined-as-drawings-/253926681285
    They took about a week to get in from China, which was faster than I expected.
    I’m still waiting for couplers and bearings.

  8. #8
    Join Date
    May 2008
    Posts
    1185

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Yes, working on them
    youtube videos of the G0704 under the name arizonavideo99

  9. #9
    Wish you success, all good things come to you

  10. #10

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    If you get your X axis adjusted correctly the weight of the servo/stepper and hardware is absolutely inconsequential. For example, I tighten my ways until the X stalls, but I do that with two 4" vises and a 6" 3 jaw chuck at the end of the table at maximum overhang. I then take off the 6" chuck and generally the table runs freely. The two vises and the chuck are like 70lbs worth of weight. Even if I machine with two vises they are never at the end of the table, alway near middle, maybe slightly offset right to account for my tool height touch off on the left. Suffice it to say, this test shows how insensitive your table should be to weight changes.

  11. #11
    Join Date
    Feb 2019
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    18

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    I didn't check my ballscrew lengths, only tested the ends to make sure they fit the bearings and preload nuts correctly. I'm just starting to machine the conversion parts now.
    If Z or Y are too long, I figure I could cut/grind them down.
    X- I can make my motor standoff a little taller.

    I'm taking a shortcut with the motor standoffs to save a lot of time since I'm doing all the cutting manually.
    I ordered these for the x and y mounts, they are a little tall, so I should just need to cut them down to the proper height. https://www.amazon.com/RATTMMOTOR-St...gateway&sr=8-6

    I ordered a Nema34 mount as well, but its design is different (hollow) and I thought I would have to do significant modifications to get it to work, so I sent it back. Turning the standoffs on a lathe would be a lot easier in this case.

  12. #12
    Join Date
    Feb 2019
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    18

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by BrianPM View Post
    I didn't check my ballscrew lengths, only tested the ends to make sure they fit the bearings and preload nuts correctly. I'm just starting to machine the conversion parts now.
    If Z or Y are too long, I figure I could cut/grind them down.
    X- I can make my motor standoff a little taller.

    I'm taking a shortcut with the motor standoffs to save a lot of time since I'm doing all the cutting manually.
    I ordered these for the x and y mounts, they are a little tall, so I should just need to cut them down to the proper height. https://www.amazon.com/RATTMMOTOR-St...gateway&sr=8-6

    I ordered a Nema34 mount as well, but its design is different (hollow) and I thought I would have to do significant modifications to get it to work, so I sent it back. Turning the standoffs on a lathe would be a lot easier in this case.
    I just finished machinging my x-axis mounts this weekend, and took some measurements of the ball screw- the ball screw length looks to be dead on.
    (Things are slow going, I've only had time to make chips late at night or earlty in the morning on weekends lately.)

  13. #13
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    Jan 2012
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    163

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by BrianPM View Post
    I just finished machinging my x-axis mounts this weekend, and took some measurements of the ball screw- the ball screw length looks to be dead on.
    (Things are slow going, I've only had time to make chips late at night or earlty in the morning on weekends lately.)
    you have any pictures like to see what yours looks like compared to mine? i still need to buy a few more things I'm saving up for closed loop steppers, what type of fittings are you going using for greasing your ball screws?

  14. #14
    Join Date
    May 2019
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    27

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    One the MV30 I was able to get away with changing to 90 degree zerk fitting. Only thing I had to do was remove some material for clearance for the Y.

    https://photos.app.goo.gl/uXqxxMGMHiksJ15F7

    https://photos.app.goo.gl/DFL5kHAgvXVw12px6

    I have a cheap small grease gun from walmart that just barely fits. This allowed me to grease everything with only removing the dust covers.although I will need an extension tube for the X. Hoping to just add 4" flexible grease hose.

  15. #15
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    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    what size of OZ stepper motors should i go on the pm25mv?

  16. #16
    Join Date
    Mar 2017
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    35

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    I was using 400 oz in steppers on X and Y, and a 1200 on the Z (though that was way overkill for the Z).

  17. #17
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    Jan 2012
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    163

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    when shopping for steppers motors do you know of a good source buy them from reasonable priced ? what size of power supply you think i may need

  18. #18
    Join Date
    Aug 2005
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    1091

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by rmachinist View Post
    when shopping for steppers motors do you know of a good source buy them from reasonable priced ? what size of power supply you think i may need
    570oz.in on the X & Y axes are suitable. The Z is a bit more problematic. I use a 570 on the Z with a 2.5:1 belt reduction. Also I’m driving these from a G540 that is only supplying 3.5A per phase, whereas the motors are rated at 5A. The motors are only supplying about 400 oz.in per phase.
    As you can see from the video below the performance is fine.

    https://youtu.be/AjfhQUBjBjI

    I’m in the process of converting it to a power drawbar which will add weight to the head. It will be interesting to see how it goes then.

    Quite a lot of people use a 970oz.in or 1200 for the Z axis.

    Assuming you are in the USA automation direct.com has suitable motors and power supplies.

    To size the power supply, add the rated current of the 3 motors and then multiply by 2/3. For three 570 motors rated at 5A your power supply should be rated at 3*5*2/3=10A

    Also, use a 48Vdc supply.

    Cheers
    Peter


    Sent from my iPhone using Tapatalk Pro
    -------------------------------------------------
    Homann Designs - http://www.homanndesigns.com/store

  19. #19
    Join Date
    Nov 2006
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    20

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by rmachinist View Post
    when shopping for steppers motors do you know of a good source buy them from reasonable priced ? what size of power supply you think i may need
    https://www.omc-stepperonline.com/

  20. #20
    Join Date
    May 2019
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    27

    Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by rmachinist View Post
    what size of OZ stepper motors should i go on the pm25mv?
    What I did for an estimate on for the 30MV was take my hardest material to cut, SS 304 for me, and guessed at my the toughest cut. I used https://fswizard.com/www/ to get some rough numbers and if you click the blue bar on top you get cutting force. I am not sure if it is radial and axial combined but I assumed worst case it was all radial, came out to about 180#.

    Put that in a lead screw calculator. https://www.amesweb.info/Screws/Lead...meThreads.aspx and got about 800 oz in.

    I knew I wanted Teknic Clearpath SDSK motors so my choice was easy and went with 1100 oz in on all 3 axis knowing that my X and Y are overpowered for 80% of my jobs. I am sure the 640 oz in would have been find but it was $20 more for the bigger motor and I am a sucker for a cheap upgrade.

    I am sure this isn't the best method and I would love to hear what others have done to size their motors.

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