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  • feeds and speeds for milling variable pitch scroll

    Discussion in 'Machining' started by sosji1950, Sep 10, 2011.

    1. sosji1950

      sosji1950 New Member

      Mar 2010
      Likes Received:
      Hello all

      I have to manufacture some variable pitch in-feed scrolls to convey bottles into a star wheel.

      I have a 3 axis CNC mill with an indexer which is able to synchronise with the CNC. We have cut leads both fixed and variable previously but it took some time to set up and confirm.

      Can anyone assist with formulas to calculate / determine

      (A) A fixed lead( say 100 mm lead on 100 dia shaft)
      (B) A variable leads say ( 1st lead 100mm, 2nd 110mm,3rd 120mm,4th 130mm,5th 140mm per Revolution)

      By changing the rotation rate of the programmable indexer in RPM and the CNC feed rate in mm per minute

      Once the leads have been determined, to have a formula that can calculate determine the actual helical cutting feed rate, while maintaining the correct lead / leads.

      I need to do this in order to rough out and then finish and or to allow for cutting different materials.

      If anyone can assist I would be grateful


      Sosji :)
    3. Ramana Rao

      Ramana Rao Well-Known Member

      Jan 2012
      Likes Received:
      Sosji, It is a long time since your post, and the issue may have been resolved by now. However the problem is interesting and from a design and machining point of view. with the specification regarding size, diameter and the maximum and minimum gaps of the screw, a dual lead might work instead of a variable lead. A dual lead screw has the two flanks with different leads, with the result, the gap width varies progressively from end to end

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