28.Unscrewing Mold

28.Unscrewing Mold

1.the gear and rack mechanism,driven by hydraulic cylinder or motor is most often used in the unscrewing mold.

2.the basic structure design–Gear & Rack system:

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3.the basic structure design–Gear & Rack system driven by hydraulic motor:

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4 general guidelines

  • the standardized gear and rack used:
  • (i) AISI – BOSTON
  • (ii) DIN – HASCO
  • material for gear and rack: P20 STL 28~32HRC.
  • try to shorten the length of rack and it should be less than 15”.
  • the gear ration is between 2.5~3;
  • a clearanceof 0.005”is added to the center distance for a smooth operation;
  • the cylinder located on the top side of mold;
  • the specification of molded screw:size,grade,RH(LH) and lead;
  • all the gear and rack data listed on the 2D drawing;
  • the thermal expansion should be considered between gear ring and axis(Min. 0.02mm);
  • no rotation of molded part occurred when unscrewing.
  • the preferred gear/rack data:

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5. the clearance between the gear center

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Or overcut the pitch diameter.

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6. Design Example I

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7. Design Example II

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8. Design Example III

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