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VFD on a Bridgeort Mill

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  • #16
    I would slow the spindle down for power tapping. If I have to go to the mechanical speed reduction, I don't see the need for changing out the single phase motor,
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard


    • #17
      I know I'm a bit late to the party, but I just wanted to float an alternative approach that works well for me. When I purchase my first BP, VFDs were outrageously priced and my experience with them (ABB drives) was that they could fail any time for mysterious reasons. So I found a 3/4 HP DC motor 90v with a 56C frame and installed that where the previous owner had installed a single phase motor.

      The power supply is 110 VAC and was @$60 at the time. I was able to adjust the variable speeds so that full open was plate speed and could reduce by 5:1 That made speed calcs easy. DC motor is 100% torque down to low RPMs, so worked fine for my needs. This has been powering my M-Head BP for more that 25 years without issue with less noise than the VFD powering my lathe.

      Today, VFDs are much more affordable, with better support and reliability than back when. So I would probably look at that option if the need arose to replace my DC drive, but I wouldn't rule out the DC drive either. Hope this helps with some food for thought.

      Best Regards,
      Last edited by rjs44032; 11-29-2019, 04:23 PM.


      • #18
        Originally posted by rjs44032 View Post
        I. So I found a 3/4 HP DC motor 90v with a 56C frame and installed that where the previous owner had installed a single phase motor.

        Agree, some of the ex-Treadmill motor and drives make a nice combo.
        The DC motors I favour are Johnson, oddly a Chinese Co.also the PWM controller have a lot nicer control than the SCR bridge versions.
        From Golds Gym models.
        Often a reversing relay has to be added though.


        • #19
          Originally posted by MaxHeadRoom View Post
          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.

          I have an XLO as well running on a VFD but I don't use the VFD for speed control its just set at max. I have heard that VFD don't put out the torque at low RPM as they do at high. So I use the vari belt and gearbox. Never tried using the VFD for speed control. What is your experience with torque at low RPM on the VFD? I have seen some videos on YT using VFD on drill presses that seem to confirm torque problems at low RPM. Like to hear your take on that.