started my cnc conversion for Precision Matthews PM-25MV Mill - Page 3


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

  1. #41
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    Default Re: started my cnc conversion for Precision Matthews PM-25MV Mill

    Quote Originally Posted by 109jb View Post
    This is because my ballnut setup uses springs to force the ballnuts apart resulting in absolutely no backlash. The spring force is about 100-150 pounds driving them apart. On most double nut setups the ballnuts have shims between them to provide as little backlash as possible without binding, but because of screw lead errors the shimming cannot eliminate the backlash without binding the screw at some locations, so this method usually still has a little bit of backlash. Not much, but still a bit..
    Yep. I have a tiny bit of binding in places (minimal) after shimming. I've got down to 0.01mm on X and 0.025mm on Y. Near enough. I've gone a bit mad with 1100oz steppers which should cope. If anything the nuts will eat themselves before I have step problems

    All this has made me strip the column again for the 4th time. Decided to rip out that crap DFU I just put in in have a go at getting my 2 single nut mashing design right. Took 0.13mm worth of shimming to get it to loosen off from where I had it. Seems to run smooth by hand now and looks like there is about 1 degree of free area. With any luck I'll be within a backlash of 0.03mm.



  2. #42

    Default 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.)



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    Default 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?



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    Default

    Wish you success, all good things come to you



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    Default 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.



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

    Quote Originally Posted by sundewzer View Post
    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.
    what type of grease are you using?



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

    Just what I had sitting on the shelf. As long as you are greasing at regular interval anything with moly in it will be good enough. At Least that is my opinion.

    https://www.amazon.com/SL3144-Extrem.../dp/B004L41SRK



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

    little update i had to flip the ball nut around on the screw here is a little video



  9. #49
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    Default 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



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    Default 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.



    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

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    Homann Designs - http://www.homanndesigns.com


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

    We can't get anything 'great' in the u.k. imo (it sucks).
    Looking like these are what I'll be going with:
    https://www.cnc4you.co.uk/Stepper-Mo...H401-03-Nema23
    They're 4nm with 3mh inductance so I'll be using them on 60v supply for x,y.

    I'd like closed loop but not as a 'kit' which is out of budget.
    Something like a 4.5nm motor around 2mh ind, 80vAC driver and a 2x 35vAC toroidal wired series for 70v.
    Ah well, maybe later on



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

    I was wondering if there would be any interest of buying if I made a few extra X/Y/Z Ballnut Mounts for the PM25MV this would help me out to buy few more parts for my PM25MV and may help someone else who needs to make them. It may take me a few weeks to get them done, If any one would like too see what they look like here is a video:



  13. #53
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    Default 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/



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