What Are The Common Plastic Molding Processes?

There are 23 common plastic molding processes, including injection molding, extrusion molding, rotary molding, blow molding, vacuum forming, compression molding, rolling molding, foam molding, winding molding, lamination molding, film covering molding, pouring molding, drip molding, cold pressing modeling, compression molding, resin transfer molding, extrusion, thermoforming, hand lay up molding, laser rapid prototyping, melt deposition molding, CNC machining, 3D printing.

Injection Molding & CNC Machining & Laser rapid prototyping: Working Principles

1.  Injection Molding‌

‌● Working Principle‌:

‌Material Preparation‌: Plastic pellets or powders are preheated and fed into the hopper of the injection molding machine‌.

‌Melting & Injection‌: The material is heated to a molten state (160–220°C) and forced into a closed mold cavity via a screw or plunger mechanism under high pressure‌.

‌Cooling & Solidification‌: The molten plastic cools and solidifies within the mold (cooling time depends on material and part thickness)‌.

‌Ejection‌: The solidified part is ejected from the mold, completing the cycle‌.

‌● Key Features‌:

Suitable for mass production of complex-shaped parts with high dimensional accuracy‌.

Requires precise control of parameters: injection pressure, temperature, and cooling time‌.

2.  CNC Machining‌

‌● Working Principle‌:

‌Digital Design‌: A 3D model is converted into machine-readable instructions (G-code) using CAD/CAM software.

‌Material Removal‌: A computer-controlled machine tool (e.g., milling machine, lathe) uses rotating cutting tools to remove material from a solid block (plastic, metal, etc.).

‌Precision Cutting‌: The tool follows programmed paths to achieve the desired geometry, with tolerances as tight as ±0.01 mm.

‌● Key Features‌:

Ideal for prototyping and low-volume production of high-precision parts.

Compatible with thermoplastics (e.g., ABS, nylon) and composite materials.

3. Laser rapid prototyping

Laser rapid prototyping (LRP) is an additive manufacturing technology based on the discrete pile up principle, which converts three-dimensional digital models into solid parts through layer by layer processing. 

The core process and technical characteristics are as follows:

1.  The principle of layered stacking manufacturing uses CAD software to slice the 3D model in layers along the Z-axis direction, generating a series of 2D cross-sectional data, with each layer typically ranging in thickness from micrometers to millimeters.  ‌

2.  Laser layer by layer processing: Powder materials (such as SLS technology): Laser beams selectively sinter powder materials, causing them to melt and bond and solidify, forming the current layer structure.

3.  Layer by layer stacking molding: After each layer is processed, the worktable is lowered by one layer height, and after laying powder or resin, the next layer of processing is continued until the entire part is completed.  ‌