Injection molding

Injection molding is considered one of the most common plastic part manufacturing processes. It can be used for producing parts from both thermoplastic and thermoset polymers. The process usually begins with taking the polymers in the form of pellets or granules and heating them to the molten state. The melt is then injected/forced into a chamber formed by a split-die mold. The melt remains in the mold and is either chilled down to solidify (thermoplastics) or heated up to cure (thermosets). The mold is then opened and the part is ejected.

(XLK Manufactuter Base Injuection Machine)

A Typical Injection Molding Process

In spite of the relatively expensive tooling cost, injection molding remains the most popular manufacturing process for plastic materials in mass production, thanks to its low operational cost, high throughput, and the flexibility to make parts with complex shapes.

Polymers commonly used for injection molding include

• Polystyrene (PS)

• Acrylonitrile Butadiene Styrene (ABS)

• Polyamide (PA)

• Polypropylene (PP)

• Polyethylene (PE)

• Polyvinylchloride (PVC)

Other short fiber reinforced plastics

Injection Molding Design Guidelines

Use uniform wall thicknesses throughout the part. This will minimize sinking, warping, residual stresses, and improve mold fill and cycle times.

Use generous radius at all corners. The inside corner radius should be a minimum of one material thickness.

Use the least thickness compliant with the process, material, or product design requirements. Using the least wall thickness for the process ensures rapid cooling, short cycle times, and minimum shot weight. All these result in the least possible part cost.

Design parts to facilitate easy withdrawal from the mold by providing draft (taper) in the direction of mold opening or closing.

Use ribs or gussets to improve part stiffness in bending. This avoids the use of thick section to achieve the same, thereby saving on part weight, material costs, and cycle time costs.