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Fourth time's a charm

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  • Fourth time's a charm

    Just finished putting the fourth motor in my Logan lathe, and hopefully, it's the last one for a while.

    Do I keep blowing them up? Nope- it's a case of More Power! (Tim Taylor grunting noise.)

    The lathe originally came (to me, anyway) with a 3/4HP single phase. I used it that way for several years before I decided I needed a little extra grunt. I swapped that motor for a 1-1/2 HP single phase, and while that helped a bit, it was a "compressor start" motor so it tended to rather violently start up each time.

    Then after finding out how useful a 3-phase/VFD combo on my Sheldon is, I started thinking about converting the Logan as well. I eventually ran across a brand-new 2HP WEG motor and installed it, along with an Automation Direct VFD:



    Now, in one of those brain-lock moments, I'd fixed on the idea of replacing the 1725 rpm motor with another 1725, despite also thinking I needed to boost the spindle RPM... Then I had the epiphany.

    I'd already had a 2HP TEFC motor sitting around, but the brain-lock kept dismissing it since it was a 3450.

    So this weekends' project was to re-swap motors again, hopefully for the last time in a while.



    Ignore the orange cable- it's just a temporary pigtail until I can get dedicated 220V to that side of the shop.

    I'd gone with a slightly larger pulley on the other 3~ motor, to give a bit more spindle speed. I went back to the original pulley for this motor, so I should now have right at 1,200 rpm. That's still 'slow' compared to a similarly sized Hardinge, for example, but it's still a good boost.

    And, here's a better shot of the new control box:



    It's a solid-plastic utility box from the local Home Despot. It was completely blank, not even any "scribed" areas intended to be punched out, which made it easy to mill and drill to whatever configuration I wanted.

    The bracket is a steel weldment and uses factory (or at least existing) mounting holes. It's quite rigid and placed to that it's within easy reach, but still lets the top belt cover open fully.

    The controls are, of course; start, stop, speed and reverse. I like it so much I just might make a second box for the ACTech VFD on my Sheldon, which doesn't yet have a reverse switch.

    Doc.
    Doc's Machine. (Probably not what you expect.)

  • #2
    Good looking control box. Needs flex but.. I guess where you live you have to order..Heck, my shop needs flex here and there.

    A ten turn speed pot will direct interchange with that one. You can get a indicator dial if you like, but they cost more than the speed pot. I put a normal dial on two of mine.
    Excuse me, I farted.

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    • #3
      There's nowhere on the VFD for anything like strain relief, and being enclosed in the cabinet base pretty well protects the cabling. Flex conduit or other measures would be superfluous.

      Now, when the final supply wiring is installed, that'll be in conduit outside of the machine, and connected to the cabinet with flex. And the control box cable is already armored- you can see a bit of flex conduit right below it in the first photo.

      Doc.
      Doc's Machine. (Probably not what you expect.)

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      • #4
        Originally posted by Dawai
        Good looking control box. Needs flex but.. I guess where you live you have to order..Heck, my shop needs flex here and there.

        A ten turn speed pot will direct interchange with that one. You can get a indicator dial if you like, but they cost more than the speed pot. I put a normal dial on two of mine.

        I am a fan of your youtube vids... I would assume you are allergic to flex

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        • #5
          What's that thing with the big handle just to the right of the headstock?

          Roger
          Any products mentioned in my posts have been endorsed by their manufacturer.

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          • #6
            Originally posted by Doc Nickel
            Now, in one of those brain-lock moments, I'd fixed on the idea of replacing the 1725 rpm motor with another 1725, despite also thinking I needed to boost the spindle RPM...
            I'm confused. How fast do you need the motor to turn ? And since you already had a VFD, couldn't you use the VFD to spin the 1725 rpm motor up to 3500 rpm ?

            Since converting my lathes to VFD, the lathe gearbox has seen very little use, as the VFD frequency control gets the job done 99% of the time.

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            • #7
              Originally posted by winchman
              What's that thing with the big handle just to the right of the headstock?

              Roger
              Funny, I stumbled across the Doc's YouTube assets just last night. The thing to the right can be understood by watching this video:

              http://www.youtube.com/watch?v=rqclIfMKVS8

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              • #8
                Bingo. The "thing with the handle" is a fixed cross-slide. It holds two tools, one on either side of the spindle axis, and it's used in turret production. At the time I did the first part of the motor mod- in the first photo- I still had my turret setup installed.

                If you watch the video that Keelan found, you'll see in at least one spot where the spindle actually slows down during a cut. That was shot back when I still had the 1-1/2 HP single-phase. You wouldn't think that an extra 1/2 HP would make that big a difference, but this current 3~ setup seems to have a lot more grunt.

                I'm confused. How fast do you need the motor to turn ? And since you already had a VFD, couldn't you use the VFD to spin the 1725 rpm motor up to 3500 rpm ?
                -Suffice to say I need more spindle speed than the lathe had, as delivered (delivered to me, anyway.) If I had my druthers, I'd like to see 3K rpm, since I mainly work in relatively small-diameter aluminum.

                I'm not at all certain the headstock or jackshaft bearings can withstand sustained speeds that high, but from asking around, 1200 rpm- double the supplied speed- appeared doable and unlikely to strain anything. Yes, I'm being possibly unreasonably cautious, but I already spend a bunch of money on these machines. Don't need to buy more trouble just yet.

                After getting my head 'round straight, bumping up the motor speed was a simple upgrade, especially since I was swapping the motor anyway. I'll run it at 1200 for a while, and see how well it works. I'll keep an eye on my bearing temps, both by feel and by laser thermometer, and if everything stays copacetic even after a few hours of turret work, I may well start thinking about bumping up the top speed even more.

                I have a 2-1/2" pulley on the motor now- that's the one that came on the original 3/4" hp. Swapping that for a 3" would push the top speed to about 1440 rpm.

                As for using the VFD to overspeed, that's an option for occasional use, but you wouldn't want to use it on a regular, daily basis- in large part due to heat buildup in the motor. A $12 pulley swap beats buying another $100 or $200 motor after the insulation fails in a year or two.

                Doc.
                Doc's Machine. (Probably not what you expect.)

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                • #9
                  Three phase motors have a lot more torque (both starting and running).

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