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IndustryArena Forum > CNC Electronics > Spindles / VFD > ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?
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  1. #1
    Join Date
    Mar 2010
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    42

    ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    I purchased a hulk of an knee mill Acer 4vk that had somewhat been cannibalized, missing break lever, gear shift knob ect.
    Thinking I knew what I was doing I put in a VFD, and an 8" pully at the motor and 2.5" pully at the spindle, trying to get more rpms from the 1750 rpm 5HP motor.
    My tool stalled instantly, in a aluminum block, and after researching I'm finding that AC induction motors lose their torque at lower rpms, that why Mills change their speed mechanically. Is this correct?
    The mill is so old I was thinking of installing a servo, used, that may be cheaper then rebuilding the top and back gears, some parts are discontinued.

    Thoughts? Could I have set up the VFD incorrectly?
    Cheers.
    Thanks,
    Chris

  2. #2
    Join Date
    Dec 2013
    Posts
    5717

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    You can get away with a 0.75:1 ratio on the spindle drive with a 3 HP, and with a 5 HP motor maybe even a 0.5:1 ratio, but not a 0.312:1 ratio. But.... You have to use a sensorless vector VFD to drive it. If your VFD is not sensorless vector it won't work for that application. Sensorless vector control will allow near 100% torque down to about 0 RPM

    Check your VFD specs and see if says something about ''SVC'' mode, or something like that
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
    Join Date
    Mar 2010
    Posts
    42

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Thanks, that helps. I was worried about the pulley ratio, seemed too much. I looked around and seems my VFD is capable of vector mode, but double check me:
    Click image for larger version. 

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  4. #4
    Join Date
    Dec 2013
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    5717

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Yes, I think that says sensorless vector. Set the parameters per the manual, then run run the auto tune function. I think you will see a big difference.

    I am able to run my 3HP spindle from about 10 to 6000 RPM with a 0.75:1 pulley ratio. My 1750 RPM nameplate motor is rated at 6000 RPM max, but I have never run it that fast. I run out of torque power tapping 1/2-13 in steel at 200 RPM, and have to use back gear.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
    Join Date
    Mar 2010
    Posts
    42

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    That is great to hear, but what worries me is that I'm pretty sure I did do that when setting up the VFD. The pully ratio doesn't help but I'll check it again. What size pullys are you using?

    Thanks!

  6. #6
    Join Date
    Dec 2013
    Posts
    5717

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    I'm not exactly sure what size pulleys I'm using. They are Gates HTD timing pulleys for a 30mm belt. The motor pulley is about 4 inch, and the spindle pulley is about 3 inch, sized to give me a 0.75:1 ratio. Originally when I did the direct drive conversion, I used a 1:1 ratio with poly-V pulleys, about 1 1/4'' wide, about 4 inch dia. on both shafts. And I think if I had to do it over, I would use poly-V pulleys rather than the HTD pulleys. The HTD drive is a bit noisy.
    Jim Dawson
    Sandy, Oregon, USA

  7. #7
    Join Date
    Jun 2011
    Posts
    692

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    How big of a cutter and what RPM's are you using? Vector drive should be able to keep full torque much lower into the RPM's, but it won't get you back any of the torque you lost by going to such an extreme pulley ratio.

  8. #8
    Join Date
    Mar 2010
    Posts
    42

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Jim, Skrubol,
    Thanks for you replies, I stalled on a 1/2'' rougher in aluminum block, obviously something was wrong.
    I took Jim's idea and ran with it: After finding I nuked my VFD by power cycling too often I've replaced with the same maker, but updated model: teco westinghouse e210-205-h3:
    Entering in the parameters for the motor ect, then checking them about 50 times I still have an error when I try to auto tune:
    Leakage inductance error.

    No Idea what this means, but I only could guess it's a grounding issue, which my last vfd didn't complain about, or I wonder if I need a filter in front of the VFD. When I try to run the motor is jerks violently. I'm trying to use Sensorless Vector Mode on my 5hp, 3.7 kw inductance motor. What's the big deal?

    Any suggestions?
    Thanks Guys,
    Chris

  9. #9
    Join Date
    Dec 2013
    Posts
    5717

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    ''Leakage inductance. ... The winding leakage inductance is due to leakage flux not linking with all turns of each imperfectly-coupled winding.''

    https://en.wikipedia.org/wiki/Leakage_inductance

    I had to look that one up, never heard the term before. That kind of seems like a bad motor winding maybe?

    Could the jerking be caused by acceleration being set too low? Will the motor run correctly in V/F mode?

    Just a side note, I almost never turn power off to my VFD. The only way to turn it off is with the breaker in the shop distribution panel.

    EDIT: look at page 4-206, 4-207 in the manual https://www.vfds.com/manuals/teco/f5...ies-manual.pdf
    Jim Dawson
    Sandy, Oregon, USA

  10. #10
    Join Date
    Jan 2005
    Posts
    15362

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Quote Originally Posted by toolbag33 View Post
    Jim, Skrubol,
    Thanks for you replies, I stalled on a 1/2'' rougher in aluminum block, obviously something was wrong.
    I took Jim's idea and ran with it: After finding I nuked my VFD by power cycling too often I've replaced with the same maker, but updated model: teco westinghouse e210-205-h3:
    Entering in the parameters for the motor ect, then checking them about 50 times I still have an error when I try to auto tune:
    Leakage inductance error.

    No Idea what this means, but I only could guess it's a grounding issue, which my last vfd didn't complain about, or I wonder if I need a filter in front of the VFD. When I try to run the motor is jerks violently. I'm trying to use Sensorless Vector Mode on my 5hp, 3.7 kw inductance motor. What's the big deal?

    Any suggestions?
    Thanks Guys,
    Chris
    Check the motor windings for a short, you may have taken the motor out with the VFD at the same time when you stalled it

    Make sure you never turn the VFD Drive main power off when the motor is running, this will take out the drive and sometimes the motor, the max Hz you can use with your motor is 100Hz 120Hz if you are careful so if you where running higher than this then you most likely took the motor out and the VFD at the same time when you stalled it
    Mactec54

  11. #11
    Join Date
    Mar 2010
    Posts
    42

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Quote Originally Posted by mactec54 View Post
    Check the motor windings for a short, you may have taken the motor out with the VFD at the same time when you stalled it

    Make sure you never turn the VFD Drive main power off when the motor is running, this will take out the drive and sometimes the motor, the max Hz you can use with your motor is 100Hz 120Hz if you are careful so if you where running higher than this then you most likely took the motor out and the VFD at the same time when you stalled it
    Thanks Mac,
    I've talked to a few more people today and I've a feeling that might be what happened. I have not been back to the shop but I'll test the motor straight to the 3 phase first thing. Ouch. These lessons are expensive. How, and why did that happen? The wrong settings, or amps fried one of my windings? I know there is a shop close by that works on electric motors, maybe it's worth fixing it?

    Thanks Guys,
    Chris

  12. #12
    Join Date
    Jan 2005
    Posts
    15362

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Quote Originally Posted by toolbag33 View Post
    Thanks Mac,
    I've talked to a few more people today and I've a feeling that might be what happened. I have not been back to the shop but I'll test the motor straight to the 3 phase first thing. Ouch. These lessons are expensive. How, and why did that happen? The wrong settings, or amps fried one of my windings? I know there is a shop close by that works on electric motors, maybe it's worth fixing it?

    Thanks Guys,
    Chris
    What took the motor out if it is damaged can be more than one thing, over current over torque stall prevention Parameters not set to suit the motor, I would say when it stalled the current went to 200% there are Parameters to set to protect the motor when you stall a motor like this most likely yours are at the default of 200% this will kill the windings on a regular AC motor


    Fixing if it has a problem can be a doable solution, but may be better to get an Inverter duty motor a Baldor washdown motors are good for 6,000 RPM if you buy the right one, are you using 3Ph power supply or using 240v single phase

    They cost more money, but sometimes you can get a good buy on Ebay or other sites
    Mactec54

  13. #13
    Join Date
    Mar 2010
    Posts
    42

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Mac,
    So motor is good, and v/f mode seems to work okay. I looked into inverter motors and they might be a future investment. Wondering why svl mode didn't work.

    Thanks for the tips!

    Sent from my SM-G920V using Tapatalk

  14. #14
    Join Date
    Jan 2005
    Posts
    15362

    Re: ACER WITH NO SPINDLE GEARS: VFD OR 3KW SERVO?

    Quote Originally Posted by toolbag33 View Post
    Mac,
    So motor is good, and v/f mode seems to work okay. I looked into inverter motors and they might be a future investment. Wondering why svl mode didn't work.

    Thanks for the tips!

    Sent from my SM-G920V using Tapatalk
    Good to here, the motors on the Acer mills where quite good, some models had a VFD Drive as standard

    There is not a lot of difference when running in Sensorless vector mode any way, in V/F mode the torque is linear so not a lot of difference you would see with a standard AC motor

    There are most likely some Parameters that where not set correct for Sensorless Vector control
    Mactec54

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