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 faced with metal-to-plastic concerns. Examine plastic materials, behavior and selection, engineering design, manufacturing considerations and assembly methods.

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

All sessions are Face-to-Face unless otherwise noted.

Date: Mon.-Tue., Oct 8-9

Time: 8am-4:30pm

Location: UWM School of Continuing Education

Instructor: Robert Malloy

Fee: $1,090

CEUs: 1.4, PDHs: 14

Enrollment Limit: 40

Program Number: 4830-10957

Registration Deadline: Mon., Oct. 8

Register Now

Date: Mon.-Tue., Mar 11-12, 2019

Time: 8am-4:30pm

Location: UWM School of Continuing Education

Instructor: Robert Malloy


$1,090 by Fri., Jan. 11, 2019.
$1,190 after Fri., Jan. 11, 2019.

CEUs: 1.4, PDHs: 14

Enrollment Limit: 40

Program Number: 4830-11482

Registration Deadline: Mon., Mar. 11, 2019

Register Now

Date: Thu.-Fri., Mar 14-15, 2019

Time: 8am-4:30pm

Location: University of Wisconsin-Stout, Memorial Student Center, 302 10th Avenue E, Menomonie, WI

Instructor: Robert Malloy


$990 by Mon., Jan. 14, 2019.
$1,090 after Mon., Jan. 14, 2019.

CEUs: 1.4, PDHs: 14

Enrollment Limit: 40

Program Number: 4830-11568

Registration Deadline: Thu., Mar. 14, 2019

Register Now