Zone: Injection Molding
injection_molding.jpg Overview

Injection molding is a fast, high-volume, closed molding process that uses, most commonly, reinforced thermoplastics, such as nylon with chopped glass fiber. In the past 20 years, however, automated injection molding of BMC has taken over some markets previously held by thermoplastic and metal casting manufacturers. They include electrical and automotive components, appliance housings and motor housings, to name a few. The use of BMC must be justified by production volume because the cost of both molds and presses is relatively high. When injection molding BMC, a ram- or screw-type plunger forces a metered shot through a heated barrel and injects it (at 5,000 psi to 12,000 psi) into a heated mold, where the liquefied BMC flows easily along runner channels and into forming cavities. Heat build-up is controlled to minimize curing time. After cure and ejection, parts need only minimal finishing. Injection speeds are typically one to five seconds, and nearly 2,000 small parts can be produced per hour in a multiple-cavity mold. Long-fiber reinforced thermoplastics (LFRT) are materials with long (6.35 mm/0.25 inch or greater) fiber reinforcement and make up one of the fastest growing fabrication categories. Leading this expansion is one of the oldest forms, glass mat thermoplastic (GMT) and two of the segment’s newest: precompounded (pelletized) LFRTs (long-fiber reinforced thermoplastics), also known as LFTs, and inline compounded (ILC) or direct LFTs (D-LFTs).


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Most Recent Content: Injection Molding
Reinforced Thermoplastics: LFRT/GMT Roundup

Recent advancements in these reinforced thermoplastic technologies are expanding their performance, enabling new applications.
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Overmolding expands PEEK’s range in composites CompositesWorld

A new polymer and a hybrid process enable production of complex, high-load-capable, fiber-reinforced brackets and clips in minutes.

Thermosets vs. thermoplastics: Is the battle over? CompositesWorld

Dale Brosius, the chief commercialization officer for the Institute for Advanced Composites Manufacturing Innovation (IACMI) and a regular CW columnist, sees a shift in the industry from infighting between proponents of thermoset and thermoplastic composites to a healthier competitive atmosphere that serves to make composites overall more competitive with legacy materials.

Understanding the influence of fiber orientation on structural analysis of fiber-filled parts CompositesWorld

The effect of fiber orientation on material properties is a key way the injection molding process impacts mechanical performance. Doug Kenik and Angie Schrader of the Design, Lifecycle & Simulation product group at Autodesk (Waltham, MA, US) illustrates two ways fiber orientation influences the structural behavior of fiber-filled parts and discuss the need for a bi-directional approach to design and analysis.

Carbon fiber as a replacement for glass fiber in D-LFT auto parts CompositesWorld

Research progresses toward attainment of 80-90% of continuous carbon fiber tensile modulus in lighter parts molded from direct long fiber thermoplastic compounds.

The ends will be justified by the means CompositesWorld

CW Editor-in-chief Jeff Sloan recalls the one question he's consistently fielded throughout his quarter century in magazine editing and publishing: “Don’t you worry about running out of things to write about?” Here's his answer.

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