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

  1. #13
    *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
    I think one of the heaviest cuts in 6061 aluminum I've take was a 1/2 inch flat endmill 20 in/min, .1" doc, .2" load. I tend not to push for aggressive cuts. This cut was not problem. Even after the gear-up to get a higher spindle speed I still have 1.4HP at the spindle.
    rcheli,

    That really is very impressive results. I may have to rethink my negative bias towards timing belts causing too much noise and vibration. I see you can get both the servo motor you referred to and a driver for $660. The cost is comparable to going with a good quality VFD and Leeson 3-phase motor with the added benefit of having the encoder built in. However, if I go this route I would have to commit to using a timing belt since I don't want to have any doubt that my belt will slip when rigid tapping.



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

    I think if you do a really good job making the timing pulleys concentric and all it really helps get rid of most of the vibration. My machine has some backlash (even with ballscrews for some reason) and the controller's software I use currently has backlash comp disabled so mine ended up not completely concentric. My stock spindle setup was an HTD timing pulley being driven from the quill and it was actually pretty quiet even at max RPM (you know, the measly 2100 RPM). The hardest cut I took with this setup in aluminum was .375" doc and .075" woc @ 20IPM. 2100 RPM and it worked, but it put an audibly heavy load on the spindle. I think the fact that it was geared for max torque is really the only thing that kept it from chattering because the surface finish was pretty nice.



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

    Quote Originally Posted by CNCJoseph View Post
    rcheli,

    That really is very impressive results. I may have to rethink my negative bias towards timing belts causing too much noise and vibration. I see you can get both the servo motor you referred to and a driver for $660. The cost is comparable to going with a good quality VFD and Leeson 3-phase motor with the added benefit of having the encoder built in. However, if I go this route I would have to commit to using a timing belt since I don't want to have any doubt that my belt will slip when rigid tapping.
    Micro rib belts are probably quieter but I wanted rigid tapping. I think my spindle bearings and the spline interface that allows the quill to work is where most of my noise comes from. Another fellow on here geared his at 2:1 for 6000 RPM. If you want to do ridged tapping and are geared at anything but 1:1 you will need an index signal that gives one pulse per rev of the spindle. I used a slot type photo sensor and a disc with a slot mounted on t he spindle. The A/B quadrature signals come from the drive.

    The other items I bought in addition with the servo and drive are:
    The cable to connect it to the PC for testing and setting parameters. $32 (I think)
    A 500 watt regenerative braking resistor $78.97 shipped Direct from DMM Technology
    2 - SCHAFFNER FN2010-3-06 EMI POWER LINE FILTER, 3A, 740UA $17 From Amazon
    1 - 631-FN2030-30-08 FN2030-30-08 30A EMI FILTER $42 From Mouser

    The tech support from DMM Technology Corp was outstanding.

    Good Luck
    John



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

    Quote Originally Posted by CNCJoseph View Post
    dazp1976, that is a very unique idea and one I never considered. I just went out to the shop, pulled the spindle pulley and measured things up. The spindle pulley has a 45 mm ID on the 1:1 ratio (max speed). The bottom of the V-grove channels on the spindle pulley has an OD of 58 mm. That means the wall thickness of the spindle pulley is 6.5 mm. However, there is a key that protrudes 3 mm into the ID wall of the spindle pulley meaning you can only machine the spindle pulley OD down 7 mm before you hit the key. Just to be safe you would probably machine the OD down 5 mm. That would give you a 60 to 55 pulley setup which would increase your max RPM from 2500 to 2727. I'll try and insert an image of the spindle pulley below:

    IHow to Increase RPM on PM-25MV (or similar G0704)-cncelements-spindle-pulley-jpg
    That'a a pretty big ID.
    That's that idea dead then. I've got a similar machine being delivered this week (supposedly).
    https://www.amadeal.co.uk/acatalog/A...4.html#SID=373
    It's rated as 2800rpm and was hoping I'd have an easy option of bumping up to around 4k for the 6mm cutters.
    Oh well.
    Going to take me months to cnc it first anyway.



  5. #17
    *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
    Micro rib belts are probably quieter but I wanted rigid tapping. I think my spindle bearings and the spline interface that allows the quill to work is where most of my noise comes from. Another fellow on here geared his at 2:1 for 6000 RPM. If you want to do ridged tapping and are geared at anything but 1:1 you will need an index signal that gives one pulse per rev of the spindle. I used a slot type photo sensor and a disc with a slot mounted on t he spindle. The A/B quadrature signals come from the drive.

    The other items I bought in addition with the servo and drive are:
    The cable to connect it to the PC for testing and setting parameters. $32 (I think)
    A 500 watt regenerative braking resistor $78.97 shipped Direct from DMM Technology
    2 - SCHAFFNER FN2010-3-06 EMI POWER LINE FILTER, 3A, 740UA $17 From Amazon
    1 - 631-FN2030-30-08 FN2030-30-08 30A EMI FILTER $42 From Mouser

    The tech support from DMM Technology Corp was outstanding.

    Good Luck
    John
    rcheli,

    Thanks for the additional details. I actually never knew you needed a separate index signal on the spindle when using a servo motor to drive your spindle for rigid tapping. This makes the servo motor option less appealing to me since you still need to mount a separate encoder (although a much simpler type for indexing). In my mind I would rather just mount a separate OMRON or similar encoder with a 3-phase VFD controlled motor.

    Out of curiosity, could your friend with the similar 2:1 / 6000 RPM setup just use a disk with two slots in it instead of one for indexing purposes or will that throw an error code since I doubt you could perfectly align each slot with one full rotation of the servo motor?



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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)

    Update

    I spent a couple of hours today verifying that the Leeson 1.5HP 3-phase motor will fit on my PM-25MV without needing a spacer between the head and column as seen on some of the G0704 projects. It's going to be tight, but if I go this route I believe it will fit with 2 or 3 mm to spare between the Leeson motor's fan housing and the column. However, a big future challenge will be finding a way to fit both an encoder (for rigid tapping) and a power drawbar on the head of the machine. I researched this a bit but didn't get too far. For now I'll just focus on the spindle motor upgrade. If I try and figure out all three projects at the same time I'll just get bogged down.

    Last edited by CNCJoseph; 10-31-2018 at 01:39 PM.


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    Member arizonavideo's Avatar
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    You still might call Matt. If he can get you a motor its just the right size and will leave you room for the other stuff.

    youtube videos of the G0704 under the name arizonavideo99


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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 arizonavideo View Post
    You still might call Matt. If he can get you a motor its just the right size and will leave you room for the other stuff.
    Arizonavideo,

    Unfortunately the PM-30 motor and controller will only get me to 3000 RPM. I am hoping to get to 7000 RPM.



  9. #21
    *Registered User* CNCJoseph's Avatar
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    Update

    I decided to take the plunge and go for the 1.5HP Leeson motor. Unfortunately, when I called the supplier, they said the motor was out of stock. I called multiple suppliers (whose websites claimed it was in stock) and they all said that they won't have any for two months. As far as CNC conversion projects go, 2 months isn't that long, but I was disappointed as I really felt like I was starting to get some good momentum with this project.

    So, in the meantime, I realized that their might be a simpler method for increasing RPM without even having to do any machining. Why not just replace the DC drive for the PM-25MV with something that could drive the stock motor at a higher RPM? After doing some research I bought a KBCC-125R DC Motor Driver. I found a good deal for a used one on ebay. The KBCC-125R model includes a breaking resistor and reverse capability. If I understand the driver correctly, I should be able to get up to 5000 RPM. Not sure what will happen if I double the speed of the stock motor. I guess we'll find out if I can get the DC drive to work correctly.



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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 additional details. I actually never knew you needed a separate index signal on the spindle when using a servo motor to drive your spindle for rigid tapping. This makes the servo motor option less appealing to me since you still need to mount a separate encoder (although a much simpler type for indexing). In my mind I would rather just mount a separate OMRON or similar encoder with a 3-phase VFD controlled motor.

    Out of curiosity, could your friend with the similar 2:1 / 6000 RPM setup just use a disk with two slots in it instead of one for indexing purposes or will that throw an error code since I doubt you could perfectly align each slot with one full rotation of the servo motor?
    When I said 2:1 I meant 1:2 motor:spindle. But you understood what I meant. I suppose it would work if the pulses were exactly 180 degrees apart on the encoder on the motor.

    This is how I made my index sensor. The reason there are two sensors is one feeds the CNC control and the other feed a tach on my DRO that I had from before CNC.
    I also made that slot a lot bigger by the time I finished it.

    How to Increase RPM on PM-25MV (or similar G0704)-index-jpg



  11. #23
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    Default Re: How to Increase RPM on PM-25MV (or similar G0704)

    The PM-25 motor is a three phase motor. The KB wont drive it.

    A standard 3600 RPM 56C or TC145 motor is really common. Every wash down motor is that.

    youtube videos of the G0704 under the name arizonavideo99


  12. #24
    *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 arizonavideo View Post
    The PM-25 motor is a three phase motor. The KB wont drive it.

    A standard 3600 RPM 56C or TC145 motor is really common. Every wash down motor is that.
    Arizona Video,

    Thanks for the info on the PM-25 motor. Both the PM-25MV product page and the user manual states the motor is brushless but I guess I missed that important piece of info and assumed it was a similar set up to the G0704. A BLDC is a completely different animal.



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

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