Injection molding of gears

A 980 kN injection-molding machine is used to make 110-mm-diameter spur gears with a thickness of 10 mm. The gears have a fine-tooth profile. How many gears can be injection molded in one set of molds? Does the thickness of the gears influence the answer?

Question

Injection molding of gears

A 980 kN injection-molding machine is used to make 110-mm-diameter spur gears with a thickness of 10 mm. The gears have a fine-tooth profile. How many gears can be injection molded in one set of molds? Does the thickness of the gears influence the answer?

Accepted Answer

Because of the fine-tooth detail involved, the pressures required in the
mold cavity will probably be on the order of 100 MPa. The cross-sectional (projected) area of the gear is [latex]\pi (110)^2/4=9503 \ mm^2[/latex].Assuming that the parting plane of the two halves of the mold is in the midplane of the gear, the force required is

[latex]\frac{9503}{10^6} imes 100 imes 10^6=950.3[/latex]kN.The capacity of the machine is 980 kN. Therefore, the mold can accommodate one cavity, producing one gear per cycle. Because it does not influence the cross-sectional area of the gear, the thickness of the gear does not directly influence the pressures involved, and hence the answer is the same for different gear thicknesses.

Question 10.7: Injection molding of gears A 980 kN injection-molding machin...

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