Plastic Injection Molding

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Plastic Injection Molding

Injection molding is used for manufacturing a wide variety of parts. Once a component is designed, a mold is made and precision machined to form the features of the desired part. The injection molding takes place when a thermoplastic or thermoset plastic material is fed into a heated barrel, mixed, and forced into the metal mold cavity where it cools and hardens before being removed.

Using this process, Spectron Manufacturing produces products of more complex and intricate shapes that would be too difficult or costly to machine. The injection molded plastics process also allows many parts to be created at the same time with the same mold. Other advantages include high production rates, low labor costs and an excellent part to part tolerance. With plastic injection there is very little need to do anything to finish the part after it is molded.

Plastic Injection Tooling

Mold and die are used interchangeably to describe the tooling applied to produce plastic parts. They are typically constructed from pre-hardened steel, hardened steel, aluminum, and/or beryllium-copper alloy. Of these materials, hardened steel molds are the most expensive to make, but offer the user a long lifespan, which offsets the cost per part by spreading it over a larger quantity. For low volumes or large components, pre- hardened steel molds provide a less wear-resistant and less expensive option.

Plastic Injection Molding
Carbon Steel Tooling

  • Life expectancy = 5k cycles
  • Tooling = 2 weeks
  • Samples = 1 week
  • Production (Qty 10k) = 3-4 weeks
P-20 Steel Tooling

  • Life expectancy = 200k cycles
  • Tooling = 3 weeks
  • Samples = 1 week
  • Production (Qty 10k) = 3-4 weeks
H-13 Steel Tooling

  • Life expectancy = 400k cycles
  • Tooling = 4 weeks
  • Samples = 1 week
  • Production (Qty 10k) = 3-4 weeks
Plastic Injection Molding Materials

Many types of thermoplastic materials are available, and selection depends on the specific application. The following are some of the most common materials being used:

  • Polyethylene (PE)
  • Polypropylene (PP)
  • Polystyrene (PS)
  • Polycarbonate (PC)
  • Thermoplastic Elastomer (TPE)
  • Acrylonitrile Butadiene Styrene (ABS)
Plastic Injection Design Criteria
  • Ideal wall thickness of 2mm – 4mm (.080 inch to .160 inch)
  • Thin wall injection molding can produce walls as thin as .05mm (.020 inches)
  • Uniform wall thickness is preferred, otherwise the change in thickness should be as gradual as possible.
  • Recommended rib thickness should not exceed 60% of nominal wall thickness.
  • Draft angles for ribs should be a minimum of 0.25 to 0.5 degree of draft per side.
  • At corners, we suggest an inside radius of 0.5 times the material thickness and an outside radius of 1.5 times the material thickness.

Plastic Injection Molding

Plastic Injection Molding

What our customers say

“Without Spectron our project would not have been as successful as it was. They demonstrated the teamwork, knowledge, and ‘can-do’ attitude needed to pull off a difficult order”

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