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Thread: VFD on a Bridgeort Mill

  1. #1
    Join Date
    Feb 2004
    Location
    St. Louis, MO
    Posts
    37

    Default VFD on a Bridgeort Mill

    I have a full size Bridgeport Milling Machine that has been operating on a Rotary Phase Converter in my home shop for several years. I am thinking about a adding or installing a VFD to obtain control of the spindle speed.

    What do I need, or will this even work or is it wishing thinking on my part. Should I leave well enough alone, why reinvent the wheel, if it isn't broke! I need another project but I am electrically challenged.

    I hear so many great things about VFD's I feel the need for one but since the mill came with a rotary phase converter, which also powers my surface grinder, am out of luck or are Variable frequency drives only for people that don't have a rotary phase converter and have to start somewhere to get the milling machine to turn so that they can make chips.

    I am a an amateur hobby machinist with more money than brains but I would like to have as many bells and whistles as possible.

    Thanks

    Jack

  2. #2
    Join Date
    Apr 2010
    Location
    Canada
    Posts
    2,755

    Default

    What is the HP?
    I converted two XLO's I had until recently to VFD's, these had the vari-speed head, but also had the 1:1 and 6:1 G.B.
    I had a steal of a deal on Mitsubishi VFD's (I bought a full pallet of them).
    I used a 1:1 timing belt in place of the Vari-Speed and of course, retained the G.B.
    I used the auto tuning to get it in the ball park and then tweeked it.
    These mills were also CNC, so I incorporated the At-Zero-Speed and Up-To-Speed outputs to control motion until the VFD was ready etc.
    Max.

  3. #3
    Join Date
    Feb 2004
    Location
    St. Louis, MO
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    Default

    Thanks for the Reply Max

    I have the model with a 1 1/2 HP Vari-speed head.

    What does G.B. stand for?

    Jack

  4. #4
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    Apr 2010
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    Canada
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    Default

    Mine were 2HP but they also did a 1.5HP version.
    GB = Gear Box.
    I also used them with a RPC initially.
    Max.

  5. #5
    Join Date
    Sep 2001
    Location
    Mountain Brook, AL
    Posts
    1,188

    Default

    Best to avoid the myriad cheap Chinese VFD, commonly found on ebay. A site such as https://www.automationdirect.com/adc...y_drives_(vfd)
    supplies reputable VFDs and a google on VFD suppliers will show several other such suppliers.

    VFDs for such as your mill come in 115v and 220v single phase sources, your choice depending on your shop voltages. A second option is V/Hz or 'sensorless vector control'. V/Hz is the historical
    older type which has no compensatory feedback to boost the motor power at low speeds. The sensorless type VFD does have such compensation. Eg: my mill has V/Hz type VFD and at under
    6-8 Hz output from the VFD, I can stall the spindle by hand. A sensorless VFD would compensate for my hand grip by increasing power to the motor. This may be of interest if you do power tapping
    with larger taps. It should be straight forward to unhook your ON/Forward-OFF-ON/Reverse switch to the VFD controls panel and the motor to the VFD output. Any relays or motor controls can
    be made redundant by the VFD. It should be noted that long term operation of a motor at under 30Hz or so might result in overheating of the motor and overspeeding the motor by running the
    VFD above perhaps 90 Hz may be detrimental to the spindle or motor bearings. Many VFD are rated for much higher Hz output than 90 Hz but it may not be prudent to go much above 80-90 Hz.
    Steve

  6. #6
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    Apr 2010
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    Canada
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    You definitely want the sensorless vector type.
    Most of these motor are 4 pole, so I always limit the top RPM to ~120Hz.
    For one, I figure that most motor manufacturers are going to use the same bearings and balancing spec for their 2 pole, as they do their 4 pole versions.
    Max.

  7. #7
    Join Date
    Mar 2015
    Location
    Central Ms
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    1,129

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    You stated that your mill has the variable speed head, and runs off a RPC. Why would you want to go to a VFD and open a new can of worms?
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard

  8. #8
    Join Date
    Oct 2008
    Location
    MO
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    515

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    Dave C has it right.
    You have a running mill without spending a dime!!!!~

    THANX RICH
    People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!!!

  9. #9
    Join Date
    Feb 2004
    Location
    St. Louis, MO
    Posts
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    Default

    Thanks Everyone

    After a great deal of research I have found this VFD

    https://www.precision-elec.com/shop/...r-drip-rating/

    I hope it is the one that will work on my Bridgeport Milling Machine, Yes I had a big ass Rotary Phase Converter but it was a loaner to get me up and running but now the man that gave it to me wants it back. So its time for me to go to plan B and I still want to make things in my shop.
    I am hoping that I can install and program a VFD because I am "Electrically Challenged" and I don't want to let the smoke out of it.

    Jack

  10. #10
    Join Date
    Mar 2015
    Location
    Central Ms
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    As the late Paul Harvey used to say: "And now you have the rest of the story".
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard

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