Standard production runs for injection molding normally run from hundreds of thousands into even millions of parts, so the time and cost of mold creation are minimal compared to the value they provide. Short runs tend to be 10,000 parts or fewer, even into the hundreds. Costs for these smaller runs are usually reduced by using less expensive materials for molds, such as aluminum or a lower grade of steel. These molds produce the same quality products but are usable for a shorter number of products.

At Bennett Plastics, we offer decades of expertise in full-service custom plastic injection molding which is suitable for customers large and small. Contact us today to learn more about our complete range of in-house capabilities.

Polyethylene terephthalate (PET) has excellent chemical resistance and barrier properties, good strength, rigidity, fatigue endurance, and abrasion resistance.

Runners and Gates of PET Injection Mold All conventional types of gates can be used. Gates should be 50–100% of the part thickness.

Typical Applications of Polyethylene terephthalate (PET) Automotive – mirror backs – grille supports – head lamp reflectors – alternator housings Electrical applications – motor housings – electrical connectors – relays – switches – microwave oven interiors Industrial applications – furniture chair arms – pump housings – hand tools – PET bottles and containers

Plastic injection molding is one of the most popular manufacturing techniques in use worldwide, in large part because a high volume of identical parts can be rapidly created from a single mold without a loss in quality. Its main drawback is tied to the expense and time necessary to design and produce the steel mold used in production. While these costs are inconsequential over a long production run, they can be high for small runs, so adapted techniques for short production runs can make small volumes just as worthwhile.

PET is highly sensitive to moisture at high temperatures and exhibits excessive warpage when reinforced with glass fibers. The promotion of crystallinity is achieved through adding nucleating agents and crystal growth accelerators. Crystalline moldings exhibit high modulus, gloss, and heat distortion temperatures. Warpage is minimized by the addition of particulate fillers such as mica. When low mold temperatures are used, transparent moldings can be obtained with unfilled PETs.

Chemical and Physical Properties PET is an aromatic polyester produced from the polymerization of either terephthalic acid (TPA) or dimethyl ester terephthalic acid (DMT) and ethylene glycol (EG). The glass transition is approximately 165°C [330°F] and the material crystallizes over a temperature range from 120°C–220°C [248°F–428°F].