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Thread: VFD (variable frequency drive) for drill press.

  1. #1
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    Default VFD (variable frequency drive) for drill press.

    Picked up this 3 phase 220 volt 1.5 HP electric motor off Craigslist for $25.00. The seller had no way to demonstrate functionality so that's all I was willing to pay given the risk it was junk.

    I ordered the VFD drive with plans to install the setup on drill press *if* the motor functioned okay.

    The gamble paid off. This is one neat upgrade!

    Here's a photo of the unit set up as a garage floor bench test.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. Default

    Quote Originally Posted by fyidiy View Post
    Picked up this 3 phase 220 volt 1.5 HP electric motor off Craigslist for $25.00. The seller had no way to demonstrate functionality so that's all I was willing to pay given the risk it was junk.

    I ordered the VFD drive with plans to install the setup on drill press *if* the motor functioned okay.

    The gamble paid off. This is one neat upgrade!

    Here's a photo of the unit set up as a garage floor bench test.

    What is the model and rating of the VFD?
    Does the motor to develop sufficient torque at low RPM's?

    Thanks,
    rivets

  3. #3
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    Here's all the motor's information.

    Sufficient torque? Considering this isn't going to be a 1:1 drive ratio it should have enough speed to generate more torque than the belt system is capable of transmitting.

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  4. #4
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    A basic VFD will not have a lot of torque at slow speeds. To overcome that many VFDs have a tach input so the drive can boost the motor when it is stalling. There are also issues with proper cooling at low speeds. The best thing is to setup the belt system so the motor runs at nameplate speed or above for most operations. Inverter duty motors can be overdriven way over speed. Standard motors can still go a lot, but the insulation might have issues with very high frequencies. It's always better to run the motor over speed than under. Many VFDs can go as high as 400Hz so the motor will run 6.6 times the nameplate speed. While that motor probably can't handle that, it can at least do double or triple speed. Then setup your belts to get the max spindle speed you want and use the VFD to go down from there. If you plan on tapping or drilling super large holes in hard materials, you still may need to swap a belt from time to time.
    Long arc, short arc, heliarc and in-the-dark!

  5. #5
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    The motor with the old bearings made rattled and vibrated. Apparently, the previous owner of the motor thought it did too. The interior was stuffed with too much grease.

    I cleaned up the mess, pulled the old bearings, and replaced with new. If you need bearings try CBR Bearings. I've been dealing with them for years for wheel bearings on dirt bikes and street bikes -- small company with big individualized service. I have no interest in them other than as a satisfied customer.

    With the old bearings I set the max hertz to 150. With the new bearings it's silky smooth all the way to the VFD's max hertz drive of 240.

    #1 Armature and old bearings removed. New bearings in boxes on right.
    #2 Old bearings above and new bearings below. Steel tube to be used for pressing on the larger bearing.
    #3 Large bearing being seated in the hydraulic press.
    #4 More detail of the armature. The black socket in the lower left was used to seat the smaller bearing.
    #5 Armature with new bearings installed waiting for motor reassembly.

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  6. #6
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    Scrap yard sourced 5"x5" tube of 10 gauge used to create a new larger mounting bracket for the 3 phase motor. It's on my list to acquire but have yet to add one of Swag Off-Road's DIY bending break kits for the 20 ton HF press. So, to create the necessary shape of this bracket I just used the tube's corner stock.

    The nice thing about operating the plasma cutter in the winter... No moisture problems with the compressed air.

    In addition to the seam welds there are three plug welds on each side to keep it all together.

    Once the final holes are drilled the bracket will receive a cleaning and painting.


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  7. #7
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    Today the box for the VFD was fabricated.

    Photo #1. Nice clean edges of the 5"x5" 10 gauge tube after cutting.
    Photo #2. Assembled box, top, and mounting flange all welded together.
    Photo #3. Right side of the box so more of the mounting tang is visible. Three plug welds as well as a couple of lap joint bonds.
    Photo #4. Box mounted to drill press. The black motor mount was fabricated earlier in this thread.
    Photo #5. Test fit of VFD electronics. Mounting holes for the VFD as well as power cabling holes still need to be drilled.

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  8. #8
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    Quite a sturdy box. Be sure you meet the ventilation requirements of your VFD. They often specify to be mounted a minimum distance from vent obstructions. Is it passive or fan cooled?
    Long arc, short arc, heliarc and in-the-dark!

  9. #9
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    Cooling should be okay; the heat sink on this unit is *huge*.

    FYI, when researching VFD and other drill press modifications I found these guys:

    https://www.roguefab.com/category.php?category=DPRKS

  10. #10
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    The VFD is capable of accepting 110 or 220 volts single phase to create the 220 volt 3 phase output. Currently there's no 220 permanent service in the garage. For various welding projects I just run a temporary extension cord from the electric oven circuit.

    So, the wiring for the drill press needs to be beefy enough to deliver the necessary amps.

    A photo of the wiring work-in-progress.

    Click image for larger version. 

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  11. #11
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    Careful running that motor that fast. It won't like it for long.
    240Hz = 7200 RPM.

  12. #12
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    Quote Originally Posted by Paul Moir View Post
    Careful running that motor that fast. It won't like it for long.
    240Hz = 7200 RPM.
    With the right bearings it should be no problem to run at that speed. BTW your math is a bit off as 240Hz on this motor will be 6960 rpm.
    Long arc, short arc, heliarc and in-the-dark!

  13. #13
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    There's no need to run it that fast for anything other than a no-load demonstration.

    The protective box/hood paint job finally dried and I managed to get it all mounted up and wired into the drill press.

    Turning it down to 10Hz in order to test cut a 1.5" hole saw hole in 1/4" plate steel worked perfectly. Being a 1.5HP motor there's no stalling it at such a slow setting. However, the belt system can be made to slip with enough downward force on the quill.

    All in all, I'm happy with the resulting functionality of the project.


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  14. #14
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    Quote Originally Posted by Rambozo View Post
    With the right bearings it should be no problem to run at that speed. BTW your math is a bit off as 240Hz on this motor will be 6960 rpm.
    Not worried about the bearings - - is the rotor balanced to handle those speeds?

    Will centrifugal force cause anything to become dislodged, warped, or fly off?

  15. #15

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    Quote Originally Posted by LincTex View Post
    Not worried about the bearings - - is the rotor balanced to handle those speeds?

    Will centrifugal force cause anything to become dislodged, warped, or fly off?
    The post you're responding to is over 2 1/2 years old. It's no problem but it's good to check the dates before replying. I'm sure the man has no use for the higher speeds. The purpose would be to adjust speed for different size drill bits without having to move the belt between different size pulleys. 50-3000rpm would be plenty of range.
    Last edited by zoama; 09-03-2017 at 03:57 PM.
    2013 250EX : SSC Pedal : I-MIG 250P 20' Profax gun : Power Plasma 60 p80 torch : 3M Speedglas 9100XX : Evolution Rage 3 DB cold saw

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