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Variable Speed Options

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  • #16
    Thanks Stepside, I've never seen a saw of that type.



    • #17
      Has anyone seen plans for making VFD for 3/4 HP single phase motor?



      • #18
        A possible alternative to an AC VFD drive would be to change to a DC drive motor.
        Variable speed electronic controllers are available from several supliers. (Try KB Electronics or Extron) Typical speed ratio is 1/30 or 1/50. Supply volts 115 or 230.
        A step down is still required to keep the minimum motor revs. at a figure where sufficient power is developed.(also cooling is a consideration.
        Motors can be obtained from sources such as Surplus Center. (no connection.) They did have drive boards so check that out also.
        I have recently installed a DC drive on my drill press using an ex-treadmill PM DC motor and a KB electronics drive board.
        I spent a lot of effort on the HSM motor drive with unsatisfactory results.


        • #19
          My Grandfather built my bandsaw around 1920 for his barn building business. I don't like to work with wood so I slowed it down using the jack shaft pulley method. Although the saw works great I do have slipping problems with the belt reduction.
          I will probably go to an enclosed gear box reduction. Hey, I just want to cut some metal close to length. Notice I said enclosed gear box ....... not an open ring and pinion gear like Marvel that uses metal fillings for lubrication.


          • #20
            Hi, everyone.
            Keep in mind that i'm no expert, but I've been building an automatic popup saw for our moulding operation. The saw has a pusher that advances the wood to the saw line. A photo sensor senses the marks to cut defects out. The pusher is driven by a motor controlled by a vfd. This is a "smart" vfd and is driven by a plc. The point is that these "smart" vfd's can be programmed to run a motor at as many as 17 different speeds. A plc is not necessary, by the way. You could use four simple toggle swithes and depending
            on the combination that these switches are set is how the vfd knows how to set the frequency to change the speed. Every motor salesman that I talked to advised me not to get an inverter duty motor. They said a regular 3 phase motor will run off a vfd a long time before burning up. They did say that if you run the motor at very low speeds for long lengths of time that you do need to worry about the air flow from the fan. But you can get small fans that could solve this problem. At any rate I can see a lot of applications for these "smart" vfd's. And they can be found on the surplus market. Knowing what I know now, and even though I have 12 really nice DC motors sitting hear, if I have an application for speed control, I would probably go the vfd rout.