Recycled materials from previous operations are reprocessed with new granules before injection. To maintain quality, recycled content is typically limited to 30%.

Thermoplastic molding includes subtypes like rapid injection molding for prototypes and production injection molding for full-scale manufacturing. This method produces precise components ranging from phone cases to car door panels.

As the leading technique for plastic part fabrication, thermoplastic injection molding ensures high-quality products. Originally used for simple items like combs, it now serves industries including automotive, healthcare, and aerospace.

The process involves heating thermoplastic pellets until malleable, then injecting them into molds under pressure. After cooling, the finished part is ejected, and the mold reused. This method is ideal for mass production of identical components.

Finished parts typically require little post-processing. However, steel mold costs make this method less suitable for small production runs, where alternatives like silicone molding may be preferable.

Contrasting Thermoplastic Injection Molding and Thermoset Molding

Thermosets and thermoplastics differ significantly in production processes and molding techniques. Key differences include:

Chapter 2: The Thermoplastic Molding Process

Thermoplastic injection molding is essential for producing precise, affordable components across industries. The process occurs in specialized machines with three main components: injection unit, clamping unit, and mold.

Clamping Unit

The clamping stage secures mold halves before injection, preventing leaks. Proper clamping ensures dimensional accuracy and part quality.

The clamping unit also ejects finished parts and maintains alignment for consistent production. Key components include:

• Platen for mold support
• Stationary platen with nozzle
• Tie bars for guidance
• Clamping systems: toggle, hydraulic, or hydro-mechanical

• Hydraulic clamps offer precise pressure control

  
  

• Hydro-mechanical clamps combine speed with high pressure

Injection Unit

The injection unit melts and injects plastic pellets into molds with precise control.

Key components include:

• Hopper for pellet storage
• Heated barrel with screw
• Nozzle for mold connection

Dwelling and Cooling

After injection, pressure compensates for shrinkage while cooling solidifies the part. Efficient cooling reduces cycle times.

Ejection Process

Ejector pins remove cooled parts from molds. Release agents prevent sticking.

Trimming Process

Excess material is removed for final part preparation.

The Mold Tool

Molds represent significant investments with complex designs.

Mold Channels

Channels ensure proper material flow:

• Locating ring for alignment
• Sprue for main passage

  
  

• Runner for distribution
• Gate for cavity entry