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Basic Design Techniques for Rapid Injection Molding Prototyping

Engineers use rapid injection molding to quickly produce parts and prototypes for design analysis. It is highly efficient but simple and reliable for a certain quantity of components and material types. Rapid Injection Molding Prototyping, like other molding processes, has several key considerations for optimization. Following the correct procedures will ensure quality and repeatability while minimizing waste. So what should be considered when designing for rapid injection molding prototyping?

Basic design for rapid injection molding prototyping

Part features for tool design:

  • Wall thickness: This is the most critical design requirement for molded parts. The general rule of thumb for wall thickness is between 0.080 to 0.160 inches (2 to 4 millimeters).

  • Core geometry: Core components give you the same functionality and provide benefits such as increased strength and reduced material.

  • Draft: Reduced sharp transitions optimize the flow of molten resin.

  • Ribs: Designing ribs with wall thickness of about 50% to 60% can prevent sink marks.

  • Ejection: Tilted vertical walls make it easy for your parts to pop out without any drag or punch marks, reducing damage and waste.

Other features for tool design: 

Undercut, side action, gate location, and ejector pins are some of the features that will help you create a good rapid injection molding prototyping design.

Shrinkage and processing tolerances: 

For aluminum molds, typical machining tolerances are around 0.0045 inches (0.11 millimeters) and plastic shrinkage tolerances are around 0.002 to 0.025 inches (0.050 to 0.635 millimeters), depending on the material.

Cost analysis: 

Shortening delivery time increases manufacturing costs. Analysis will help you find the best balance point for your rapid injection molding prototyping project. Comparing material costs, labor hours, tool design, processing methods, and other considerations can balance cost and speed.

Colorants and additives: 

Adding color and other materials outside the resin can help improve the performance of rapid injection molding prototyping prototypes. Additives such as engineering fibers, UV inhibitors, and modifiers can significantly improve physical properties by slightly increasing material costs.

Common applications for rapid injection molding prototyping

Rapid prototyping is a cost-effective shortcut to traditional molding, with the main difference being delivery time and mold materials. These cost-effective rapid injection molding prototyping prototype applications include: rapid prototyping iteration, product development testing, bridging tool implementation, small-batch production of on-demand parts, and variable part needs.

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