Exploring Insert Injection Molding: Integration Perfected

Table of Contents

Plastic injection molding is an incredible method for manufacturing components that offer splendid benefits. However, there’s a more innovative side of injection molding that you might not know about. 

Insert injection mold operation

This type is employed in manufacturing components that provide enhanced performance and better part durability. It’s known simply as insert injection molding, an innovative technique that offers manufacturers so much benefit.

Insert injection molding incorporates plastic injection molding with pre-formed inserts to manufacture mechanically solid parts that offer an array of benefits, including streamlined production. Let’s delve deeper for a better understanding of this insert injection molding. We’re ready whenever you are. 

Insert injection mold operation 3

1. Understanding Insert Injection Molding

1.1 Overview of Insert Injection Molding Process

Insert injection molding is an interesting yet optimally functional method of part production. 

To understand insert injection, think of it as the filling rolled in your pie that’s then wrapped up and baked at a controlled temperature, for a specified time before you get your tasty chicken pie. 

In the case of insert injection, a pre-formed part is inserted into the mold and held properly in place before injecting the molten plastic to form around the pre-formed part. However, the pre-formed inserts could be of different materials ranging from ceramics, metals, or even other plastic materials. 

A typical example of parts made with insert injection molding is your toothbrushes, drill handles, and screw holes in your electrical sockets. 

Furthermore, the shape and size of these inserts could vary as it is dependent on the required project specifications. During this production process, the insert is placed in the mold before it is closed for the injection of the molten plastic around the insert. 

Once this is done, cooling and solidification come next taking the intended shape around the insert thereby offering better functionality and improved mechanical properties. Like innovations such as 3D printing technology, Insert injection molding is great for manufacturing complex designs at cost-saving rates. 

1.2 Advantages of Insert Injection Molding

Having examined the process of insert injection molding, it’s paramount to establish the numerous advantages of the process. 

The most obvious and the first benefit of insert injection molding is part strength due to the integration of the insert in the mold. The introduction of inserts creates a form of reinforcement that boosts part durability and mechanical property. This makes for two different materials in one component. Performance is enhanced and resilience is assured in the part produced.

In addition to part strength is the streamlining of the process itself into faster and simpler steps. With this simplification, there is no further need for post steps such as drilling and tapping the plastic injection molded part to insert the additional materials. This in turn helps manufacturers save time, reduce the cost of production, and enable smooth production flow. 

On top of that, there is design flexibility and dimensional accuracy. Insert injection molding promotes the incorporation of multi-complex designs in a single part which ensures accuracy in dimensions as it is placed in the mold before injecting the molten plastic. This guarantees proper alignment and less displacement or distortions in formation. What’s more, with these advantages, the piecing together of components becomes easier. 

Insert injection mold application

2. Applications of Insert Injection Molding

2.1 Automotive Industry

Various industries including the automotive industry have hugely benefited from insert injection molding with numerous parts made with much precision and excellent aesthetics. 

The integration of high-quality mold manufacturing and suitable materials is key in creating amazing high-quality automotive parts. From the engine and body components to the sleek interiors, it can be ascertained that insert injection molding has not only found a foothold in this industry but also revolutionized it. 

One of the many ways insert injection molding has been a bonus to the automotive industry is in manufacturing automotive connectors. As a result of the reliability and compactness in design, it requires top-level skill in ensuring accurate connectivity and mechanical stability. It requires inserting metal contacts into the plastic casing, fostering functionality. 

On top of that, insert injection molding is employed in making electrical components such as switches, sensors, and connectors. Its working principle aids the smooth infusion of metal pins and terminals. 

Moreover, when you enter into your automobile you love the interior parts. Those parts are a result of a manufacturing advancement in insert injection molding. So, the next time you are in awe of the beauty your car interior exudes, it’s all thanks to insert injection molding. 

Let’s not forget the fasteners. These fasteners allow automotive components to fit compactly, and it cancels out the need to drill to fit them in post-production.

2.2 Electronics and Consumer Products

The electronics and consumer product industry has witnessed a massive improvement in the electronic parts produced simply by applying the insert injection molding technique. If you don’t believe it, just examine the electronic enclosures, switches, connectors, and other wearable devices and observe the precision and versatility they are made with. 

The synergy between the high-quality mold manufacturing industry insert injection molding has helped electronic products significantly. They’ve been able to find expressions in the accurate alignment of components within the plastic shells that boost connectivity.

Majorly, switches, and sensors utilize the insert injection molding precisely because of its component placement. Certain sensitive electrical components can be safely placed without compromising on efficiency, reliability, and connectivity. 

Even so, the consumer products sectors likewise experience the same merits. Hinges, buttons, and many other consumer products are inserted during molding to avoid unnecessary cost increments without any need for post-production processes. 

The easy enveloping of metal components under or within the plastic part secures the component, especially during usage. Users are adequately protected from short circuits that are likely to occur. Insert injection molding has been an invaluable method of producing reliable parts in the electronic world. A feature lots of manufacturers are delighted to incorporate for its benefits.

2.3 Medical and Healthcare Devices

If the automotive and electronics industry can benefit from insert injection molding, you can bet others like the medical sector would also not be left out. 

The production of medical devices such as drug-delivery systems, surgical instruments, and in-brief medical components that are safe, bio-compatible, and of splendid performance is created using insert injection molding. 

Medical devices manufactured by insert injection molding are placed under intense scrutiny to maintain and adhere to strict industry qualities. And this means that the materials used must be biocompatible to eliminate any reactive consequences when interacting with the human body. 

The suitability of this method for producing medical tools lies in the combination of multiple components to work as a single unit. That’s the specialty of insert injection molding as it ensures streamlined sterilization and makes the medical device user-friendly and patient-centric for medical practitioners while limiting the risk of product failure in deployment. 

Furthermore, insert injection molding is well-known to mix both abilities to create complex geometries and remain aesthetically outstanding is a task it can effortlessly attain with manufacturing medical parts. It presents functional design components and enables medical professionals to deliver patient-centric services. 

Insert injection mold

3. Design Considerations for Insert Injection Molding

3.1 Insert Selection and Compatibility

For every project and their underlying manufacturing process, manufacturers, and designers alike have a responsibility to count their costs before embarking on any production run. 

A part of counting the cost entails understanding the design considerations for insert injection molding. And that is where factors such as material compatibility, adhesion properties, as well as mechanical features come into play. Selecting the best materials possible to get the best outcome is your top priority. 

Material compatibility now goes beyond aesthetically pleasing. The more crucial concern here is selecting the best material with the best bonding properties with the plastic mold to be inserted. The resin injected must agree and work in tandem with the insert to be placed within the mold

A perfect example is a metal insert. They may be treated with surface treatments or coatings to enable proper adhesion while eliminating delamination. 

Mechanical compatibility is the added strength the insert provides to the plastic resin for injections. Consequently, mechanical features may include the rigidity of the insert and the coefficient of thermal expansion. With this in consideration, factors such as distortion or irregularities in parts are avoided either during production or part usage. 

More importantly, the mechanical characteristics of the insert are expected to match that of its accompanying plastic resin. This agreement between both the insert and plastic injected would result in an improved final product, with accurate placement of the insert within the mold to avoid detachment.

3.2 Mold Design and Tooling

Typically, careful consideration should be factored in on the mold design and tooling to effect a successful insert injection molding process. Aspects such as mold gating, insert placement, venting, and part ejection are paramount to this innovative method of part production. Let’s consider some of these factors.

  • Insert Placement: The appropriate placement of the insert in the mold cavity can tip in two ways. It is either properly placed and an excellent finished product is achieved or erroneously placed and warping or detachment is the result. But to have a flawless finished product it is crucial to appropriately place the insert to achieve success.
  • Mold Gating: Mold gating is another important consideration. The gate where the molten plastic is to flow through to surround the perfectly placed insert is crucial to maintaining steady flow and evenness. And as the mold gate determines the flow pattern, it in turn determines the outcome of the final product. Accurately placed mold gate ensures consistent part quality that is void of voids.
  • Venting: Adequate venting system permits the release of air and gasses to avoid internal stress in the mold. Effective venting assists with improved surface finish and dimensional accuracy
  • Part Ejection: The last step in injection molding determines the quality of the part expected after removal. A predetermined ejection system must be in place to ensure no damage is found on the part.

4. Material Selection for Insert Injection Molding

4.1 Plastic Resin Considerations

Once the design considerations are completed, deciding what material would fit into the production plan is next. Since insert injection molding is to reinforce the plastic material, there are major considerations to selecting the appropriate plastic resin. 

  • Mechanical properties: With insert injection molding the plastic mold usually takes in preformed material. Its adaptability to such material is important as it directly impacts the functionality of the material. Qualities like strength, impact resistance, and rigidity of the material to hold the insert in place are necessary considerations in selecting the right resin. Acrylonitrile Butadiene Styrene (ABS), polycarbonate (PC), and Nylon are some of the plastic resins that offer such capabilities. 
  • Temperature resistance: some materials may be exposed to a higher level of heat during the application of the component, and materials that can retain their qualities irrespective of the temperature are crucial factors when considering durability. Heat-resistant plastic resins such as PEEK and PPS are plastic resins that offer such qualities. 
  • Chemical compatibility: Industries that work with chemicals and other brutal substances require components that can withstand these harsh conditions. Chemical-resistant materials are vital to such industries and these qualities are typically exhibited by polypropylene (PP) or PVDF.
  • Aesthetics: Aesthetics may also be considered due to its color presentation that attracts consumers to acquire such products, especially consumer products. A wide array of plastic resins that are aesthetically suitable for insert injection molding are available for manufacturers to select from. 

4.2 Overmolding and Multi-Shot Injection

Insert injection molding isn’t the end of design possibilities especially for designers and manufacturers. Overmolding and Multi-shot injection take it a step further by creating room for further designing and functional capacities while retaining its eye-catching powers. You can simply refer to them as a technique of insert within inserts as they form a layer on top of an insert. 

The use of overmolding in insert injection molding allows manufacturers to cover inserts with another layer of plastic materials specific to the project requirements. Overmolding creates a soft-touch quality to the component or enhances its aesthetics amongst other qualities it offers. Overmolding also promotes the customization of products according to the customer or company’s designs with a better finish than computerized manufacturing like high-quality CNC Machining

Multi-shot injection as its name implies maintains multiple shots of different materials at different spots of the same mold. Multi-shot injection permits the creation of sleek and colorful designs with the injection of various materials in the same mold. color schemes, enhanced functional features, and design flexibility are all embedded in this advanced method of injection molding. 

Material selection is essential in getting the best out of insert injection molding. Now when techniques such as overmolding and multi-shot injection are applied, that changes everything.


In a nutshell, the power of insert injection molding is limitless in creating sleek, yet outstanding performance tools. Its impact is experienced in major industries if not all because of its cost benefits, streamlining of the process to save time and cost, and the optimal functionality it provides. 

Additionally, insert injection molding is present in the automotive sector in manufacturing trim parts and interiors, in medical devices in manufacturing surgical components and drug delivery tools, and in consumer products used in manufacturing enclosures and connectors. 

Nonetheless, the design considerations factored in mechanical and material compatibility, mold design, and tooling to achieve a successful production run. 

Finally, material selection enables manufacturers to choose from a wide range of materials that suits the application requirement. And with overmolding and multi-shot injection in the mix, design flexibility is increased, and performance and mechanical properties are likewise enhanced. 


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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