Plastic Part Design for Injection Molding

Today, designers are challenged with multiple requirements while designing plastic parts. Major emphasis is on economics, functionality, manufacturability, and aesthetic appeal. Some compromise during the design process is inevitable; in some cases, trade-offs like these lead to pre-mature failures. The most common mistakes made by designers when working in plastics are related to wall thickness, sharp corners, creep, draft, environmental compatibility, and placement of ribs.

This course will cover the fundamentals of part design for the injection molding process. Topics such as materials selection, mold design, optimum molding, effects of stress-strain and creep on part design as well as assembly techniques with working examples will be thoroughly discussed in class. The objective of this course is to provide the student an overview of basic part design considerations for products molded with thermoplastic resins. It will help educate the student a proper way of material selection, develop a functional design and work within the limitations of the injection molding process.

 Course Highlights:

• Fundamentals of Plastics
• Plastics Overview, Material Selection, Injection Molding  and Mold Design
• Properties of Engineering Thermoplastics
• Short-term, Long-term (creep/relaxation)
• General Principles of Plastic Design
• Wall thickness, radii, bosses, parting line, draft, fillet, undercuts, holes, inserts
• Design for Stiffness
• Ribs, Gussets
• Dimensional Analysis of Part Design. Tolerance Analysis.
• Mold shrinkage, Effects of molding and tooling and environment on part performance
• Assembly Techniques
• Snap-fit, Press-fit, Threaded inserts, Sonic Welding
• Failure Analysis
• Techniques used to analyze part failure
• Emerging Technologies
• Over-molding, Mold Flow (flow simulation), 3D Printing
• Prototyping

 Course Benefits:

• Working knowledge in plastic part design that can be applied to improve product quality as well as productivity.
• Understanding of plastic behavior over time (creep, relaxation) and environmental effects on plastics (humidity, temperature, chemicals, etc.)
• Establish end-use product specifications.

Course Typically Offered: In class during Winter and Fall quarters 

Prerequisites: Engineering background is helpful but not required.

Next steps: Upon completion of this class, consider enrolling in other courses in the Mechanical Analysis and Design Certificate.

More information: Contact unexengr@ucsd.edu to learn more about Mechanical Analysis and Design course offerings.