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TitleCh10
TagsCross Link Fiberglass Extrusion Composite Material Polymers
File Size2.6 MB
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Page 27

Manufacturing Processes for Engineering Materials, 5th ed.
Kalpakjian • Schmid
© 2008, Pearson Education

Mold Features

FIGURE 10.28 Illustration of mold features for injection molding. (a) Two-plate mold, with
important features identified; (b) injection molding of four parts, showing details and the volume
of material involved. Source: Courtesy of Tooling Molds West, Inc.

(b)

Main
runner

Gate

Cavity Guide
pin

Guide pinSprue

Cavity

Branch
runner

(a)

Gate

Sprue

Part

Main
runner

Cold slug well
Branch
runner

Page 54

Manufacturing Processes for Engineering Materials, 5th ed.
Kalpakjian • Schmid
© 2008, Pearson Education

Design of Polymer Parts

(b) (c) (d)

Extruded product

Die shape

Original
design

Distortion Modified
design

(a)

Thick

Pull-in (sink mark)

Thin

FIGURE 10.57 Examples of design modifications to eliminate or
minimize distortion of plastic parts. (a) Suggested design changes
to minimize distortion. Source: After F. Strasser. (b) Die design
(exaggerated) for extrusion of square sections. Without this
design modification, product cross-sections would not have the
desired shape because of the recovery of the material, known as
die swell. (c) Design change in a rib to minimize pull-in caused
by shrinkage during cooling. (d) Stiffening of the bottom of thin
plastic containers by doming, similar to the process used to
make the bottoms of aluminum beverage cans and similar
containers.

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