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Make Parts Fast Classroom now in session: Injection molding

Injection molding is one of three technologies to manufacture parts. (The others are machining and additive manufacturing.) Injection molding offers a predictable and scalable process for rapidly prototyping and producing products. The process begins when an injection-molding provider creates a mold that will hold the material used to create the part. The mold has a cavity that is shaped to cast the production part. Making this mold can take a number of weeks, but once it is made, it can be used to churn out hundreds of thousands to millions of parts. One caveat here is that the cost of making the mold can be high — especially if the part to be molded is very complex.

Once the mold is made, it’s mounted on an injection-molding machine. Then material (either plastic resin or metal) is injected into the mold under ram or screw-type plunger pressure. The material fills every nook and cranny of the mold cavity and solidifies into the shape dictated by the mold.

In this Make Parts Fast Classroom, we cover these and other injection-molding processes in more detail — as well as the wide range of materials that can be used to make injection-molded parts. We also cover best design practices to get injection-molded parts with tight tolerances and top durability. Enjoy.

Leslie Langnau 

Managing Editor, Design World

Injection Molding Classroom Sponsored by


What is additive molding?

A look at overmolding options

What is metal injection molding?

Additive molding is a manufacturing technology that can make products that are stronger or lighter and with the desirable qualities found from a molding manufacturing process. 

Overmolding is an injection molding process typically used for high-volume production.  It is a way to add an additional layer of resin to a part that has already been injection molded.

Metal Injection Molding (MIM) is a mature technology used to produce high quantities of small and complex components.

The PTI DFM Tool 


How to design robust injection molds

10 best practices for injection molding

Injection Molding Cooling Time

The goal is to provide mold makers, design engineers and molders with the common language and core knowledge required to design injection molds that exceed time, cost and quality requirements.

Injection molding is a highly repeatable, highly scalable process. But there are a few best practices that ensure tolerance, form, fit, and function.

As engineers (part, mold, or process), we need to understand which factors influence cooling and how that ultimately determines the cycle time. 

PTI Engineered Plastics - Virtual Tour

Featured Resources

Avoid Common Engineering Mistakes

Design for

Manufacturing Success

Technology Tuesday: Jonathan Cottrell of PTI talks design for manufacturing and injection molding

Reducing the Cost of Validation


Which is better, 3D printing or injection molding?

3D printing and injection molding, should you use one versus another? Review best design practices and tips when working with both 3D printing and injection.

Is 3D printing cheaper than injection molding?

3D printing is not as fast at making products as injection molding. Thus, when the need is for thousands of the same product, injection molding can be the more cost- effective choice.


Women in injection molding

Jamie Cone is Engineer II at BD Technologies & Innovation in Research Triangle Park, NC. She graduated from North Carolina State University with a Bachelor of Science degree in Biomedical Engineering with a concentration in biomaterials.

Tim Witherow of PTI Engineered Plastics recognized

PTI is very proud to announce that our own Tim Witherow, Senior Manager of Manufacturing, Assembly and Automation, has been named a Rising Star of the plastic industry by Plastics News. 

PTI Engineered Plastics is a leading American injection molder and manufacturer of plastic components and assemblies. Servicing the medical, automotive, defense/aerospace, and commercial/consumer products industries, PTI specializes in low to mid volume plastic injection molding, for simple to complex projects, prototype to full production.

From our 160,000 square foot advanced manufacturing facility in Macomb, Michigan, we offer 4,000 square feet of ISO Class 8 Cleanroom and 5,000 square feet of controlled environment, with both areas offering assembly and packaging services. PTI has an array of value-added services which include ultrasonic welding, EMI shielding, pad printing, laser marking, and more. We’re fully versed in IQ/OQ/PQ validation protocol, and Production Part Approval Process (PPAP).

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