Weld line suppression
First Claim
1. A process of operating an injection molding machine to manufacture, in a mold cavity, a substantially weld line free plastic part comprising the steps of:
- injecting a measured quantity of foamable plastic material from the machine into the cavity;
reducing the volume of the cavity along with the volume of the material therein sufficiently to produce an essentially foam-free part; and
allowing the material to solidify.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for suppression of weld line weakening by virtually eliminating weld lines is disclosed. The process involves the near explosive injection of a metered amount of foamed thermoplastic molding material into an enclosing compartment formed by partly closing a compression type mold followed immediately by compression molding of the well mixed foamed material. The process finds particular utility in the manufacture of very long fiber reinforced parts. Variations on mold design and clamping cycles yield a variety of parts having foamed regions surrounded by more dense un-foamed regions. The method is particularly well adapted to the manufacture of large, very long fiber reinforced, foam-centered, hard surfaced, light weight, rigid parts.
17 Citations
14 Claims
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1. A process of operating an injection molding machine to manufacture, in a mold cavity, a substantially weld line free plastic part comprising the steps of:
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injecting a measured quantity of foamable plastic material from the machine into the cavity;
reducing the volume of the cavity along with the volume of the material therein sufficiently to produce an essentially foam-free part; and
allowing the material to solidify. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A process of operating a molding machine to manufacture, in a mold cavity, a substantially weld line free plastic part comprising the steps of:
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pre-closing the mold cavity after molding a prior part to form an enclosing compartment;
explosively filling the enclosing compartment with a molding material; and
rapidly compacting the material within the enclosing compartment.
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- 9. The process of claim 9 wherein the step of rapidly compacting immediately follows completion of the explosively filling step.
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11. A process of operating an injection molding machine to manufacture, in a mold cavity, a substantially weld line free plastic part comprising the steps of:
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injecting a measured quantity of foamable plastic material from the machine into the cavity;
reducing the volume of the cavity along with the volume of the material therein a controlled amount so as to produce a foam-centered, hard-surfaced part; and
allowing the material to solidify. - View Dependent Claims (12, 13, 14)
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Specification