Custom Overmolding Insert Injection Molding Services

Zhongde, a reputable plastic and rubber injection molding company in China, provides insert and over-molding services and produces unique multi-material parts.

Both over-molding and insert molding injection processes by Zhongde, a reliable injection molding supplier, involve putting two types of materials together to make one part, and the inserts can be threaded metal inserts. Overmolding is a two steps process, one to create the substrate and one for the oversold that goes on top of it. China inserts molding is a slightly faster process as it takes only one step that the two materials are molded at the same time.


What Materials are Used in Injection Moulding

In addition to the general materials listed below, Zhongde, a reliable custom rubber injection molding company, can also modify the materials according to the special needs of customers. Our professional engineers will adjust the raw material formula to meet the unique conditions of use. Our production materials for custom over-molding and insert molding range from thermoplastic to elastomer rubber, as well as metal and silicone. We’ve broken down the differences and similarities between the two processes. Let us help you decide which process is right for your project.

Overmolding vs Insert Molding

Overmolding is a process where a single part is created using two or more different materials in combination. Traditionally, over-molding starts with injection molding a hard plastic resin that has a higher melting point. Once that part is cooled, another material is injection molded over the first part, resulting in a single, finished product.

Insert molding combines metal and plastic injection molding services into one single part. It allows the plastic to bond to insert pieces, mostly brass or stainless steel metal component, which go inside a mold cavity. There are many options for the insert that can be placed into the mold. A few examples are warming labels, threaded bushings, wires, batteries, etc.

  • ABS | Acrylonitrile Butadiene Styrene

  • PA 6/6 | Polyamide 6/6, Nylon 6/6

  • PP | Polypropylene

  • LDPE | Low-Density Polyethylene

  • UHMWPE |Ultrahigh Molecular Weight Polyethylene

  • PEEK | Polyether Ether Ketone

  • PMMA | Polymethyl Methacrylate, Acrylic

  • PVC | Polyvinyl Chloride (Shore D)

  • PA 6 | Polyamide 6, Nylon 6

  • POM | Acetal Polyoxymethylene, Delrin

  • PE | Polyethylene

  • HDPE | High-Density Polyethylene

  • PTFE  | Polytetrafluoroethylene

  • PC | Polycarbonate

  • PS | Polystyrene

  • PU | Polyurethane
  • NR | Natural Rubber

  • SBR | Styrene-butadiene Rubber

  • CR | Neoprene Rubber

  • LSR | Liquid Silicone Rubber

  • FKM | Fluorocarbon

  • EPDM | Ethylene-Propylene Diene Monomer Rubber

  • IIR | Butyl Rubber

  • NBR | Nitrile Rubber

  • HNBR | Hydrogenated Nitrile

  • VMQ | Silicone

  • FVMQ | Fluorosilicone

  • FFKM | Perfluorocarbon Rubber

  • IR | Polyisoprene Rubber

  • Aluminum

  • Carbon Steel

  • Brass

  • Stainless Steel

  • Copper

Overmolding VS Insert Molding Type

Bonding The Resin to the Metal

Metal Insert into the Resin

Rubber Onto Plastic

Size of Molding Over & Insert Injection Molding

Below table shows the size of Overmolding & Insert Molding parts we usually make. If you need a larger size, we can also help you achieve it.

Size Metric Inch
Length 2500 98.4
Width 2000 78.7
Height 1500 59

Additives of Overmolding & Insert Molding Injection

Name Description
UV absorbers Absorb UV radiation, slowing down the degradation of the material when used outdoors.
Flame retardants Prevent ignition and inhibits spread of fire.
Plasticizers Increase flexibility and promotes plasticity, reducing brittleness of the material.
Colorants Used to color plastics.
Carbon fibers Increase strength, toughness, and rigidity of the material at the expense of making the material more brittle.
Glass fibers Increase strength, toughness, and rigidity of the material at the expense of making the material more brittle. It is more flexible than carbon fibers.

Surface Finishing of Overmolding & Inserts Injection Molding

For product designers and engineers, the surface finish on molded parts is an important design consideration. Most polish and texture are applied directly to the mold and transferred to the parts during the injection molding process. Following are several surface finish options for molded parts.

Name Description
Glossy The mold is smoothed and then polished with a diamond buff, resulting in parts with a mirror-like finish.
Semi-gloss The mold is smoothed with fine grit sandpaper, resulting in parts with a fine surface finish.
Matte The mold is smoothed using fine stone powder, removing all machining marks.
Textured finish The mold is first smoothed with fine stone powder and then sandblasted, resulting in a textured surface.
As-machined finish The mold is finished to the machinist's discretion. Tool marks may be visible.


Injection Molding

  • Plastic Injection Molding
  • Rubber Injection Molding
  • Overmolding & Insert Molding

Compression Molding

Cast Molding

CNC Machining

  • CNC Milling
  • CNC Turning

Metal Stamping

3D Printing

  • Fused Deposition Modeling
  • Selective Laser Sintering

Material Selection

Color Option

Surface Finishing

Assembly & Packaging

Custom Products

Custom Plastic Parts

  • Plastic Parts
  • Plastic Bonding Metal Parts

Custom Rubber Parts

  • Rubber Parts
  • Rubber Bonding Metal Parts
  • Rubber With Fabric Parts
  • Rubber Bonding Plastic Parts

Custom TPE Parts

  • TPE Parts

CNC Machining Parts

  • Plastic CNC Machining Parts
  • Metal CNC Machining Parts

3D Printing Parts

  • Plastic 3D Printing Parts
  • Metal 3D Printing Parts
  • Assembly Parts

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Related Services

Selective Laser Sintering

CNC Milling

CNC Turning

Fused Deposition Modeling

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Plastic Injection Molding