What is Injection Molding?

Injection molding is the process of injecting molten plastic into a mold cavity, rapidly cooling it, then ejecting the solidified plastic part. It is the most widely used manufacturing process for plastic parts and the most affordable route to mass production. Once the metal mold or tooling has been made, hundreds, thousands, or millions of plastic duplicate parts can be made in a short timeframe, with the effective cost-per-part reducing with each additional molding as the cost of the mold is amortized. Injection molding is compatible with a very wide range of materials — including thermoplastics, thermosets, and even metals — which can be easily mixed with color pigments and other additives to tweak the function and appearance of the moldings. Furthermore, the injection molding process offers excellent consistency between units, as the tooling remains constant throughout.

At 3ERP, we offer a range of injection molding services, from affordable low-volume prototyping to part production, using thermoplastics, thermosets, or metals. Our team of experienced molding specialists can guide you to the right solution, whether you need rapid aluminum tooling for a fast prototype or a more durable solution for larger production runs. Unlike many molding companies, we do not specify a minimum order quantity.
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Our Injection Molding

We are always ready for the challenges of all types of injection molding parts, such as tight tolerances, thin wall, small draft angle, undercuts, complex part geometry, non-defect surface finishes, etc.
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Plastic Injection Molding Service

The most popular custom plastic injection molding process, thermoplastic, is suitable for consumer products, automotive components, and many other applications.

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Liquid Silicone Rubber Molding Service

Inert and biocompatible, liquid silicone rubber can be used for molded medical items such as fluid management and respiratory devices

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Metal Injection Molding Service

Suitable for small and detailed metal parts, MIM is cost-effective in large volumes and wastes less material than CNC machining.

Looking for Quick-Turn Molding and Parts?

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Quick-Turn Injection Molding

Get an instant quote and have your prototype parts made parts in as little as 7 business days through 3ERP’s ultra-fast plastic injection molding service.

Injection Mold Classes

We can fabricate injection molding tooling in aluminum — ideal for rapid low-volume prototyping — or tool steel. Molds adhere to SPI mold classification, which specifies the durability of tooling and for how many cycles it is suitable.

SPI Mold Classification
Max. Number of Units

SPI Mold Classification:  101
Max. Number of Units:  1,000,000+
Description:  Mass production-ready mold made from best tool steel or other materials

SPI Mold Classification:  102
Max. Number of Units:  1,000,000
Description:  Production-ready mold suitable for large production runs and abrasive materials

SPI Mold Classification:  103
Max. Number of Units:  500,000
Description:  Medium-quality mold suitable for fairly large production runs

SPI Mold Classification:  104
Max. Number of Units:  100,000
Description:  Mold suitable for small production runs and non-abrasive materials

SPI Mold Classification:  105
Max. Number of Units:  500
Description:  Mold suitable for low-volume prototyping

Addition Injection Molding Options

Besides basic injection molding services, we also offer two variants of the process - overmolding and insert molding. Both of these can be useful in specific situations.
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Overmolding uses injection molding to create a part from multiple materials. This process adds an injection molded layer of material over an existing injection molded component. The overmolding process produces chemically bonded parts made from multiple materials.
The overmolding process can be cheaper than creating and assembling components separately. The process can build layered parts from scratch or add a resistant outer layer to existing plastic parts and tools. An example overmolded product is a toothbrush with a solid plastic body and rubberized grip.
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Insert Molding

Insert molding is similar to overmolding, but the substrate is not necessarily plastic and does not have to be produced via injection molding. For example, the process can be used to add a plastic coating to a pre-fabricated metal part.
Common parts made with insert molding include sharp handheld tools, such as scalpels that consist of a metal blade partially housed within a plastic handle. This manufacturing process is also frequently used to create parts with bushings, clips, and fasteners, which can be placed within the mold.

How Custom Plastic
Injection Molding Works

Injection molding uses an injection molding machine made up of three sections: the injection unit, the clamping unit, and the mold or tooling. Such machines are large, expensive, and require expert operators.
During the injection molding process, plastic material in the form of small pellets or granules is fed into a large hopper. The machine moves the pellets from the hopper to a heated barrel, where they melt down into a liquid. Within the barrel, a reciprocating screw — which functions as a kind of plunger — pushes the molten plastic towards the check valve. When enough material is ready to be injected, high pressures are applied, and the material is forced into the mold through a network of channels called sprues and runners. The plastic solidifies, taking the shape of the mold cavity, and is then ejected from the mold with the aid of ejector pins. The process then repeats, with cycle times ranging from a few seconds to upwards of a minute.
When ordering custom injection molding parts from 3ERP, we will first review your design and send a quotation. When quantities and pricing have been agreed, we will quickly fabricate the tooling and, if required, send a sample molding before starting production.
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Injection Molding Materials,
Surface Finishes and More

Im Materials

Mold Tooling and Molding Materials

Wide range type of industrial-grade materials can be used for mold tools and moldings, giving you lots of material selection options to complete prototypes and production runs. Tooling materials such as aluminum and steel, and molding material in common plastics such as ABS, PC, PP, PA or temperature resistance plastics like PEI, PPS, etc.


Surface Finishes

3ERP offers wide variety high level surface finishes. We only list some of the common finishing options. There are more finish options for custom injection molded parts.

Wall Thickness In Injection Molding

Discover More About Injection Molding

Here we present some further information about injection molding, such as what is injection molding, steps to get injection molded parts, what are the 4 stages of injection molding process, the advantages compared to other manufacturing processes such as CNC machining, 3D printing, laser cutting.

Injection Molding Applications

Injection Molding FAQ's

The first step in our injection molding service is to design the injection mold tool. How long this takes will depend on the complexity of your project. The usual timeline can be as short as a week and as long as a couple of months.

The plastic pellets are melted and then inserted in liquid form into the mold tool, where it cools and takes the required shape. The process allows for high precision and tight tolerances because it can be replicated exactly each time.

Injection molding can use almost any type of plastic that can also be combined together. This unmatched versatility makes injection molding so popular and suitable for some of the most demanding industries in the world. You can check out the selection of available materials and finishes our injection molding service handles on this page.

Injection molding is one of the most affordable ways to manufacture large quantities of parts, especially for bigger production runs. Even though design for manufacturing and creating the mold can take time, the process then becomes very affordable and efficient.

Why Use 3ERP Injection Mold Services?

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Endless Options

Choose from millions of possible combinations of materials, finishes, tolerances, markings, and certifications for your order.
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Easy to Use

Get your parts delivered right to your door without the hassle of sourcing, project management, logistics, or shipping.
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Vetted Network

We are ISO 9001:2015, ISO 13485, and AS9100D certified. Only the top shops that apply to become Suppliers make it through our qualification process.