Insert injection molding is the process of forming plastic around a non-plastic insert, which can be as simple as a metal rod or as complicated as a battery. When plastic is molded onto the insert, the two components augment each other, resulting in a more reliable final product that offers advantages from both materials. Usually, engineering plastics are used for insert injection molding because of their superior characteristics, such as their resistance to damage, their tensile strength, and their low weight.

At PDI Molding, we provide in-depth, comprehensive insert injection molding services and work with various plastic grades, including both consumer and engineering grade plastics. We also operate 21 different molding machines, including robotic sprue pickers, automated conveyors, coordinate-measuring machines (CMMs), and a vertical press that uses a rotary table and engineering-grade plastics. Our advanced setup and over 40 years of experience allow us to handle even the most complicated assignments with reliability and precision.


Vertical Presses with Rotary Tables

Compared to horizontal molding machines, vertical presses are usually more versatile and efficient. At PDI Molding, we pair our vertical press with a rotary table, which allows us to make the mold and insert the part at the same time. A rotary table holds two B halves of a mold so the operator is able to add inserts to one B half while the second B half is molding product and mating with the A half. Vertical presses that use rotary tables are precise and methodical, making them ideal for processing complex inserts.


Engineering-Grade Plastics

Commodity plastics can be used in many different applications. However, they are relatively weak, unsuitable for high temperatures, and susceptible to chemicals.

Engineering-grade plastics, on the other hand, have better mechanical and thermal properties than commodity plastics. They are durable, fire-retardant, and chemical-resistant, making them perfect for specialty applications such as those found in the medical and safety industries.

Examples of engineering grade plastics available with insert injection molding include:


Insert Injection Molding vs. Injection Molding

Insert injection molding and injection molding are similar processes, but inserts add durability and strength. For example, two plastic components that mate together to form a hinge can be made with standard injection molding. If the components are going to be used in a weight-bearing application, however, metal inserts are needed to create more stability. Components made with insert injection molding are stronger than standard plastic parts but still lighter and less prone to corrosion than metal.

Overall, inserts are used in applications where characteristics of both the plastic and the insert material are needed.


Insert Injection Molding vs. Overmolding

What Is the Difference Between Insert Injection Molding and Overmolding?

Overmolding is a compounding process that molds an additional layer of plastic over a previously molded component. Additional inserts are not incorporated into the component for the purpose of augmenting it like they are during insert injection molding, which is also only a one-step process.

At PDI Molding, we offer injection molding, insert injection molding, and overmolding to address our customer needs. At this time, we don’t provide two-shot injection molding.

Having Trouble Deciding Which Injection Molding Process Is Right for Your Application?

Injection molding processes are somewhat similar, but certain methods are best suited to specific applications. Injection molding usually works better for creating simple, lightweight components that are cost-effective; insert injection molding is best reserved for products that demand durability and are more expensive to produce; overmolding is ideal for components with multiple layers.

For help deciding which injection molding process you should use, contact PDI Molding. If you already have an idea about what you need, request a quote online today and we’ll respond as quickly as possible.

Insert Injection Molding Capabilities:

General Capabilities
  • Injection Molding
  • Custom Fabrication
  • Prototyping
  • Testing
  • Inspection
  • Mold Making
  • 24/7 Lights Out
  • Operation
  • Global Clientele
  • Material Requirement
  • Planning
  • Inventory Control
  • 3 Shifts
  • Insert Molding
  • Assembly
  • Engineering Changes
  • In-House Mold
  • Maintenance
Work Space Capacity

55,000 square feet

Product Capabilities
  • Small to Medium Parts
  • Low Volume
  • High Volume/Low Mix Capabilities
  • Insert Molding
Mold Process Type

Custom Insert Injection Molding


Engineering and Commodity Thermoplastics grades including but not limited to;

  • ABS
  • Acetal
  • Acrylic
  • Copolymer
  • Polypropylene
  • Nylon
  • Polyaryletheretherketone (PEEK)
  • Polycarbonate
  • Polyester
  • Polypropylene
  • Polystyrene
  • Polyurethane
  • Thermoplastic
  • PEI
  • All thermoplastic materials except PVC, Silicone, & PTFE
Temperature Range

Melt temperatures up to 800°F

Machine Maximum Velocity

Up to 12 in/sec

Clamp Tonnage

Min: 35 tons

Max: 385 tons

Shot Size The maximum weight of plastic that can be displaced or injected by a single injection stroke. Generally expressed as grams of polystyrene.

Up to 676 grams of PS

Learn more about Shot Size in our glossary

Number of Cavities The number of cavities in the mold used to produce multiple products in one molding cycle.

1 to 32 cavities

Learn more about Cavities in our glossary

Part Thickness

.020 and up

Tolerance (+/-)


Secondary Services
  • Part Assembly
  • Hot Stamping
  • Machining
  • Heat Staking
  • Sonic Welding
  • Flushing/Cleaning
  • Hardness Testing
  • Leak Testing
  • Moisture Testing
  • Force/Break Testing
  • Destruct Testing
  • Continuity Testing
  • Part Decorating
Surface Finish

Mold customer texturing and engraving

Additional Services
  • APQP – Advance Product Quality Plan
  • Process Validation
  • Insert Molding
  • Dew Point Controlled Facility
  • CNC Machining
  • Electric Discharge Machining (EDM)
  • Mold Acquiring Capabilities
  • Mold Evaluation
  • Mold Maintenance
  • Mold Making
  • Domestic Tooling
  • Overseas Tooling
  • Tool Design
  • Product Development Assistance
  • Mold Flow
  • Tooling
  • Inspection
  • CMM Inspection
  • Optical Measuring Machine
  • MRP
Production Volume
  • Prototype
  • Low Volume
  • Small Run
  • High Volume
  • Large Run
  • Long Run
Lead Time

Quoted on job by job basis
Rush Services Available

Just- In Time/ Ship To stock

Industry Focus
  • Aerospace
  • Automotive
  • Construction
  • Communication
  • Consumer Goods
  • Defense
  • Electrical
  • Electronic
  • Fire Safety
  • Firearms
  • Maritime
  • Medical
  • Military
  • Printing
  • Optical
  • Telecommunications
Industry Standards
  • ISO 9001:2015
  • TS (quality standard developed by the automotive industry)
  • RoHS Compliant
  • WEEE Compliance
  • Material Composition Declaration IPC 1752
  • ITAR
  • SVHC
  • Proposition 65
  • Lights Out Manufacturing
  • 3 Shifts
  • 24/7
File Formats

Preferred format is SolidWorks, but we can also accept;

  • AutoCAD (DWG,DWZ)
  • DXF – Drawing Interchange Format, or Drawing Exchange Format
  • IGES – Initial Graphics Exchange Specification, ANSI file format.
  • Inventor (IDW, IPT)
  • IronCAD (ICD,ICS)
  • JPG or JEPG – Joint Photographic Experts Group
  • PDF – Portable Document Format
  • Pro-E or Pro/Engineer (DRW,PRT,XPR)
  • SolidEdge (DFT)
  • STEP – Standard for the Exchange of Product Model Data