Insert Molding

Presented by: Joshua Bush Michael Goetz Michel McCluskey

Introduction

Inserts Provide: Anchorage / Reinforcement Bearing Surfaces / Shafts Internal / External Threaded Sections Thermal or Electrical Conductivity Positioning Nameplates / Lettering Hinging

Background and Theory

An insert is an integral part of a plastic molding consisting of metal or other material which may be molded into position or may be pressed into the part after it is molded

Basic Operation

Types of InsertsTwo general types:

Molded-In insertsPost Molded inserts

Basic Operation (cont.)

Molded-In Inserts Typically for internal threads / studs Metal Inserts Usually Undercut or knurled so they stay in

the part

Basic Operation (cont.)

Post Molded Inserts Uses Molded-in Hole Press Fit / Ultrasonically Fit / Self- Tapping Used for Internal Threads usually

Basic Operation (cont.)

Other Types of Inserts Blind-Hole Inserts Through-Hole Threaded Inserts Protruding Thread Inserts Shoulder-Type Inserts

Basic Operation (cont.)

Other Types of Inserts (cont.) Pressed-in Inserts Expansion Inserts Self-Tapping Screws Flat-type

Equipment Injection molding machine Hand/Pneumatic press (for post molded

inserts)Specialized Molds

Pockets to place the insert Magnetic Insert Holders

Robots / other mechanical ways of putting inserts into molds.

Advantages

Provide metal threading in a plastic partProvide for bearing surfaces Good for anchoring parts in an

assemblyElectrical Contacts in a plastic part

Disadvantages

FloatingCrushingFlow of Material Into an Open Hole

Through The InsertsFlow of Material Into Blind-hole InsertsProtruding Inserts

Plastic Part Design Standards

Dimensions/Tolerances: Thread dimensions critical. Exterior Dimensions/Knurling not as Critical. Tolerances:

Length +/- 0.010 in. Diameters +/- 0.002 in. Angular +/- 1 degree max.

Minimum Wall Thickness Around Inserts

Dependant Upon Shrinkage of Plastic Coefficient of Expansion (plastic and inserts) Temperature Range of Inserts Moisture Sensitivity of Plastic Resin Design of Insert

Minimum Wall Thickness Around Inserts (cont.)

Try To Keep Wall Thickness Around Inserts Nominal

Put Inserts in Bosses or Gussets

Mold Design Suggestions

Ejectors on the InsertsPost Inside the Mold to Hold InsertsMagnetic Insert Holders

Selection of Metal For Inserts

Refer to Data Sheets from Material Supplier

Essential Due To Coefficient of Expansion

Must Be The Same

Materials Used For Inserts

AluminumBrassCopperCarbon SteelAlloy SteelStainless SteelSilver and Other Precious Metals

Insert Illustrations

Conclusions

Through the use of inserts, a plastic part can be used in applications where once only metal could be used. Good thread, pin, and bushing properties can now be obtained in plastic parts through the use of inserts.

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