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Stepper size for a Rotary Table?

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  • Stepper size for a Rotary Table?

    I'm building a 4th axis. I'm converting an 8" rotary table directly coupled to a stepper motor.

    Is a 500 oz-in one large enough or should I go larger?
    I have a 900 oz-in, but it seems rather large/heavy and it's a NEMA 34 size. A NEMA 23 size would work out dimensionally better, but 500 oz-in is about max for that size.
    Dean

  • #2
    Take a look at the 8" table sold by www.tormach.com .

    I think in their specs they say what size motor they are using, if not you can probably figure it out from the size and current requirements.

    Paul T.
    www.power-t.com

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    • #3
      Motor size

      Tormach web site shows nema 23 for 6 inch and nema 34 for 8 inch.

      Larry
      Larry on Lake Superior

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      • #4
        I have fitted an 8" Vertex RT with a direct drive 650 oz-in motor, as per the Tormach table. It will drive the table at full speed (5 rpm) with the table locks on without a hicup, so my guess is that 500 oz-in would be OK.



        Phil

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        • #5
          Phil, I'd like to add an 8" fourth axis to my machine but I'm tight on dough so I'll have to do it the home brew way you did.

          Did you select the Vertex table for any particular reason?

          Was there anything unexpected in fabbing up the bracket and coupling and getting it to work?

          Thanks,

          Paul T.
          www.power-t.com

          Comment


          • #6
            A few years ago I sold a 10" rotary table for scrap metal. It was rotated 60 degrees at a time by putting air to the cylinder. Every time the air was inergized it rotated 60 degrees and locked in place. Someone gave it to me I saved it 16 years never used it so I trashed it 5 years ago because I could never find a project for it. Wish I had been on this forum 5 years ago I bet someone here would like to have it.

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            • #7
              Originally posted by gary350
              A few years ago I sold a 10" rotary table for scrap metal. It was rotated 60 degrees at a time by putting air to the cylinder. Every time the air was inergized it rotated 60 degrees and locked in place. Someone gave it to me I saved it 16 years never used it so I trashed it 5 years ago because I could never find a project for it. Wish I had been on this forum 5 years ago I bet someone here would like to have it.
              Was that the Erickson Flash indexer or something like that? If memory is correct the scrap pile was an appropriate spot because it could not be converted over to a motor.

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              • #8
                Thanks guys,
                I have looked at the commercially converted tables and they are using anywhere from Tormach's 650 oz-in to Industrial Hobbies 1250 oz-in.
                If I were to use a belt/pulley drive I could gear any way I needed, but the Vertex type table doesn't have enough space to add what I consider a needed roller bearing without major parts re-design to accommodate the side loading.

                Philbur,
                Thanks for the picture. It appears my design is similar to yours. I am very impressed with my Taiwanese made table. The only fault I have is it needs another thrust bearing on the fore end of the drive shaft, the aft end has one in place already.It's very well made.
                I'll take some pictures to document any problems.
                This should be very simple
                Dean

                Comment


                • #9
                  An 8" vertex needs a minimum of 420 oz in up to 650 oz in, anything over this is overkill as you need to take the 90:1 gear reduction into account.

                  What is more important is the supply voltage going to the stepper,
                  If you can use the high power drives and run at 70 - 72 volts then you will get far greater performance than running at 30 odd volts.

                  The 8" vertex can be converted to double ball thrusts but there is no room for bearings on the worm shaft.
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                  Comment


                  • #10
                    I use the Vertex because that's what I already had.

                    Have a look here:

                    http://www.franksworkshop.com.au/Wor...otaryTable.htm

                    Phil

                    Originally posted by PaulT
                    Phil, I'd like to add an 8" fourth axis to my machine but I'm tight on dough so I'll have to do it the home brew way you did.

                    Did you select the Vertex table for any particular reason?

                    Was there anything unexpected in fabbing up the bracket and coupling and getting it to work?

                    Thanks,

                    Paul T.
                    www.power-t.com
                    Last edited by philbur; 12-06-2010, 08:17 PM.

                    Comment


                    • #11
                      I machined some off the outside end of the eccentric and added a second thrust bearing. Seemed to work well enough.

                      Phil

                      Originally posted by deanq
                      The only fault I have is it needs another thrust bearing on the fore end of the drive shaft, the aft end has one in place already.It's very well made.
                      I'll take some pictures to document any problems.
                      This should be very simple
                      Dean

                      Comment

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