Designing Plastic Parts for the Injection Molding Process

Get a fundamental overview of plastic part design for the process of injection molding – ideal for engineers and designers who are accustomed to working with metals but are faced with metal-to-plastic concerns. Examine plastic materials, behavior and selection, engineering design, manufacturing considerations and assembly methods.

Participants in this course receive an electronic copy of “Plastic Part Design for Injection Molding,” 2/e by Robert Malloy included with registration.

This course can be applied to the Plastics Technology Certificate.


Robert Malloy

Robert Malloy

Robert Malloy is an Emeritus Professor at the University of Massachusetts-Lowell in the Plastics Engineering Department and has been a faculty member at UMass-Lowell since 1987. Prior to joining the faculty at Lowell, he was a faculty member at the ... read more

Who Should Attend

Engineers and designers who are accustomed to working with metals and are faced with metal to plastic concerns.

Benefits and Learning Outcomes

  • Learn how to select an appropriate plastic material formulation
  • Discover how to work within the manufacturing limitations associated with the injection molding process
  • Understand how to approach plastic product development and establish end-use requirements

Course Outline/Topics

Plastics Materials

  • History of Plastics
  • Plastics vs. Polymers
  • Molecular Weight and Distribution
  • Chemical Structure
  • Morphology and Crystallinity
  • Additives for Plastics
  • Property Data Sheets
  • Melt Flow Rate and Viscosity

    The Injection Molding Process

  • Molding Cycle
  • Molding Machine
  • The Injection Unit
  • Reciprocating Screw
  • Clamp System
  • Ejection System
  • Clamp Tonnage

  Type of Injection Molds

  • Two Plate Molds
  • Three Plate Molds
  • Hot Runner Molds
  • Standard Mold Bases

Mold Cavity Filling

  • Non-Isothermal Filling and Orientation
  • Gating Scheme
  • Types of Gates
  • Runner Systems
  • Mold Filling Simulations
  • Flow Leaders
  • Weld and Knit-lines

 Cooling, Shrinkage and Warpage

  • Cooling time estimations
  • Cooling Circuits
  • Molded Part tolerance
  • Mold Shrinkage Variables
  • Warpage Sinks and Voids
  • Material Supplier Shrinkage Data

  Part Ejection / De-molding

  • Part Ejection Process
  • Design for Ejection
  • Establishing the Parting Line
  • Ejection Forces
  • Effective Surface Finish
  • Ejecting Features
  • Collapsible end Expandable Cores

Other Injection Molding Processes

  • Insert Molding
  • Multi-shot Molding
  • Co-Injection Molding
  • Gas Assist Molding
  • Structural Foam Molding
  • Liquid Silicone Molding
  • Metal Injection Molding

Mechanical Property Behavior

  • Short Term Stress-Strain Behavior
  • Long Term Stress-Strain Behavior Molecular

  Design for Enhanced Recyclability

  • Primary vs. Secondary Recycling
  • DFER Guidelines
  • Sourcing Recycled Plastics

  Prototyping Plastic Parts

  • Machined Prototypes
  • Rapid Prototypes
  • Cast Prototypes
  • Molded Prototypes

Assembly Molded Plastic Parts

  • Design for Assembly
  • Mechanical Fasteners
  • Snap Fit Assembly
  • Press Fit Assembly
  • Thermal and Solvent Welding
  • Adhesive Bonding

BASF Snap Fit Assembly Guide


Some knowledge of plastic materials, injection molding and engineering principles is useful, although the basics are introduced.


"The instructor was the best one I’ve ever had for a seminar or training class. I’m definitely going to come back to UW-Milwaukee for future classes."  —  Mary J. Glander, Task Force Tips

Hear from past participant - Natalie Gamez

Date: Tue-Wed, May 21-22, 2024

Delivery Method: In-person With Livestream

Time: 8am-4:30pm CT

Location: UWM School of Continuing Education or view on Zoom

Instructor: Robert Malloy


$1,255 by May 7, 2024
$1,395 after May 7, 2024

CEUs: 1.4, PDHs: 14

Enrollment Limit: 25

Program Number: 4830-15883

Registration Deadline: May 14, 2024

Register Now

Date: Tue-Wed, Nov 12-13, 2024

Delivery Method: In-person With Livestream

Time: 8am-4pm CT

Location: UWM School of Continuing Education or view on Zoom

Instructor: Robert Malloy


$1,255 by Oct 29, 2024
$1,395 after Oct 29, 2024

CEUs: 1.4

Enrollment Limit: 25

Program Number: 4830-16341

Registration Deadline: Nov 5, 2024

Register Now


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