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Thread: How to Increase RPM on PM-25MV (or similar G0704)

  1. #37
    *Registered User* CNCJoseph's Avatar
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by rcheli View Post
    rcheli,

    Thanks for the part number. I decided to go with the Leeson 1.5 hp motor for this project but will file this part number away for future projects.



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    *Registered User* CNCJoseph's Avatar
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by steelcogs View Post
    There's a good chance I'll get 220 outlets anyway since that's a good excuse to buy a welder too...
    I was thinking the exact same thing!

    Quote Originally Posted by arizonavideo View Post
    OK I have a simple answer for the RPM problem if you want to stick with the stock motor which should be fine for most people.

    Make a new front pulley. In order to get to lets say 5K or 6K it has to be smaller. The large bore prevents you from going vary small. Just make the new pulley taller. This allows for the hi speed pulley to have a OD of about 1.3" and you now have room to make it a three speed setup over the stock two speed.

    For the motor it needs to be raised up about 1.2" If you don't make a new pulley a spacer might work. If you make a new motor stand then you can make room for as large of a pulley as you might want so any RPM could be had.

    If you guys watched the 9000 RPM video I made I said I dont think you should run the thing that fast.

    You might get lucky on the balance of your spindle but with a bolt on pulley it will never be totally balanced. On the belt drives that I used to make for the IH mills I would mount the pulley to the flange and then mount the spindle in the bearing holder and then finish turning the groves on the pulley. I could hold .002" of runout that way and it still at 8000 RPM or so you still have vibration.
    Great suggestion! You would also need to modify your power drawbar setup if you intend to go that route as well, but it could be a good way to increase RPM and keep the stock motor.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by CNCJoseph View Post
    rcheli,

    Thanks for the part number. I decided to go with the Leeson 1.5 hp motor for this project but will file this part number away for future projects.
    Do you mind specifying the parts you ultimately decided on? I haven't decided exactly on mine yet, so if it looks good, I'm not against following the same path.



  4. #40
    *Registered User* CNCJoseph's Avatar
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by hackish View Post
    Do you mind specifying the parts you ultimately decided on? I haven't decided exactly on mine yet, so if it looks good, I'm not against following the same path.
    Sure Hackish,

    The motor I selected is this one:

    1.5HP LEESON 3600RPM D80C model C80T34FZ18

    It is rated at 20:1 constant torque ratio. The posted max RPM is 3600 RPM, but the manufacture says I can probably take it to 75 Hz.

    I'm still trying to decide on the VFD. My original post in this thread has links to VFDs I am looking at for this motor. There are cheaper VFDs like the HUANYANG VFDs you see online but many of them don't have the option to add a breaking resistor. Some of the reviews on these units also make me nervous.

    I am also looking online for a good deal on a used 1.5 kw Emerson Commander SK VFD. More pricey, but a very good quality unit. I'll finalize the other components once I have the VFD figured out.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    What does 75hz give you? About 4500 RPM? I wonder what the proper CnC manufacturers are using to get 10k RPM?



  6. #42
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    All the 3600 RPM motors have a smaller in diameter rotors compared to a 1750. The max rotational speed should be a lot higher for the smaller rotor. The real frequency limit is the inductance of the motor. It will produce less torque over 75 Hz. Still I see no reason not to run to 100hz. I have run mine like that often. The fan makes a fair amount of noise. The better motors like the Leason generally are balanced well and run smooth at most RPM.

    youtube videos of the G0704 under the name arizonavideo99


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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by hackish View Post
    What does 75hz give you? About 4500 RPM? I wonder what the proper CnC manufacturers are using to get 10k RPM?
    About 22kw servo's (30hp, 122nm give or take) looking at a Haas.
    Plenty of power there for belt driven overdrive spindle via timing pulleys/belt.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    I always thought the big machines used direct drive spindles. I wasn't thinking of a big 30hp vmc, as I think a small one can be had at about 3hp.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by hackish View Post
    I always thought the big machines used direct drive spindles. I wasn't thinking of a big 30hp vmc, as I think a small one can be had at about 3hp.
    Had a look at the Syil X7. Advertised as 2.2kw, looks a bit misleading that one.
    Yes it has a 2.2kw driver but motor itself shows as 1.1kw AC induction.
    https://manualzz.com/doc/7089976/use...-top-cnc-mills
    1450rpm so again belt overdriven to achieve 200-6000rpm.

    I think the Tormach is belted overdriven as well.

    Never seen a servo or induction motor rated to 10krpm so they need a belt drive setup to bump them up.
    Only seen those smooth spindles like you see on the routers rated to higher rpm which I reckon wouldn't be any good on a mill. Prob due to insufficient torque.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Quote Originally Posted by dazp1976 View Post

    I think the Tormach is belted overdriven as well.
    I could be wrong, but from the research I've done, the PNC1100 uses a 1.5 hp motor that is over driven up to 85 Hz (5,100 RPM). It is belt driven.

    Leeson is telling me I can over drive my motor up to 75 Hz (4500 RPM). If the spindle doesn't give me too much vibration, I plan on pushing it to 85 Hz.



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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Update

    Leeson has gone above and beyond. Since the motor I ordered won't be in stock for another 6 weeks, they went ahead and shipped me a similar motor but with a different face from their warehouse in Indianapolis. They also shipped me the face I need to essentially convert it into the same motor I ordered. It arrived today.


    How to Increase RPM on PM-25MV (or similar G0704)-leeson-c-face-b14-jpg

    I also pulled the trigger on a new Emerson 2hp VFD (SKBD200150) on ebay.

    Time to start working on my CAD/CAM files and installing 220V in my shop.

    Last edited by CNCJoseph; 11-16-2018 at 08:00 AM.


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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    this is how I did speed up my machine - up to 10 000 rpm
    https://www.cnczone.com/forums/bench...704-ideas.html

    just one comment, at begining the top two bearings even at 6000 rpm were wery hot.(not the spindle bearings) I took them out to change them, but they looked OK, mounted them back and from then, they work up to 10 000 without heating.



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