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Insert moldingis an advanced manufacturing process that has transformed the production of complex and durable parts across different industries. In insert molding, metal and plastic components are integrated into a single part, eliminating the possibility of breakage or separation during use while also providing superior strength, precision and design flexibility. Notably, this is absolutely necessary for industries such as automotive and medical devices, where the reliability and performance of every component is critical. So,what materials are actually used in insert molding?How do these materials affect the final performance and quality of the product?

This article will deeply explore the material selection of insert molding technology, from metal materials, plastic materials to the wide range of applications of other special materials, revealing the scientific principles and process innovation behind it.

What is insert molding?

Insert molding is an injection molding techniquethat integrates inserts, usually metal, into injection molded parts. The process requires placing the insert into the mold cavity before injecting molten plastic. As the plastic cools and solidifies, it firmly encapsulates the insert, turning it into an integral part of the final product.
Insert molding excels at producing parts with high strength, durability and lightweight characteristics. Due to these properties, many industries adopt this method to efficiently create strong yet lightweight components.
LS is an on-demand manufacturerin China that provides custom insert molding services. If you want to start an insert molding project, LS will be your reliable partner.

What Materials Are Used in insert molding？

Insert molding is aninjection molding processin which a preformed part (called an insert) is placed into a mold during the injection molding process and plastic material is then injected so that it tightly bonds with the insert. There are a variety of insert materials used in insert molding, depending primarily on the design requirements and desired functional properties of the product.

1.Thermoplastic

Material	Description
ABS	ABS is one of the most commonly used materials in injection molding. It is widely used in the manufacturing of casings and components for automobiles, home appliances, and electronic products due to its good mechanical properties, impact resistance, chemical resistance, and easy processability.
PC	PC has excellent transparency, impact resistance, heat resistance and dimensional stability. It is often used to make products that require high transparency and high strength, such as optical discs, eyeglass lenses, safety helmets, displays for electronic equipment, etc.
PA	Nylon material has high strength, wear resistance, oil resistance and good self-lubricating properties. It is often used to manufacture bearings, gears, pipes, cable sheaths and other parts that need to withstand mechanical stress and wear resistance.
POM	POM is known for its high hardness, high rigidity and excellent wear resistance. It is often used to manufacture precision parts, gears, bearings, sliding parts, etc.
PET	PET is mainly used to make beverage bottles, food packaging, etc., but in injection molding, it is also used to make some products that require high transparency and good barrier properties.
PMMA	Also known as organic glass, it is often used to make lenses, display boxes, signs, etc. due to its good optical properties, transparency and weather resistance.
PBT and PETG	These materials have good heat resistance, chemical resistance and mechanical properties and are commonly used in the automotive, electronics and home appliance industries.
PPSU and PEEK	These high-performance plastics are used in the manufacture of parts in extreme environments, such as medical devices, aerospace and automotive parts, because of their high temperature resistance, chemical resistance and high strength.
TPE/TPR	This type of material combines the elasticity of rubber with the processability of plastic. It is often used to manufacture seals, hoses, handles and other products that require soft touch and good sealing.

Thermosetting resin

• Phenolic resin:A thermosetting resin with a long history. It has excellent electrical insulation properties, heat resistance and mechanical strength. It is often used in electrical insulation materials, friction materials and other fields.
• Epoxy resin:has excellent adhesion, mechanical properties and chemical corrosion resistance, and is widely used in coatings, adhesives, composite materials and other fields.
• Melamine formaldehyde resin:has excellent heat resistance, water resistance and wear resistance, and is often used to make tableware, floors, etc.
  Urea formaldehyde resin: mainly used to make adhesives, coatings and molded products, etc.

Elastomer

• Natural rubber:has good elasticity, wear resistance and sealing properties, and is widely used in tires, conveyor belts, hoses and other fields.
  Polyurethane: has excellent wear resistance, tear resistance and elasticity, and is often used to make shoe soles, car seats, sound insulation materials, etc.
• Thermoplastic elastomer (TPE):combines the advantages of thermoplastics and rubber, is easy to process, recyclable and environmentally friendly, and is widely used in wires and cables, medical equipment, toys and other fields.

How Does insert molding work？

Insert molding is a sophisticated and complex manufacturing process that involves multiple steps to create complex components with enhanced structural integrity. Here's an overview of how it works:

1.Put the embedded parts into the mold

In theinsert molding process, the first step is the loading of inserts, which can be completed manually or automatically. In an automated loading environment, specialized machinery accurately and quickly places embedded parts inside the mold. The outstanding feature of this automation technology is its high efficiency and accuracy, which is especially suitable for large-scale production occasions. In contrast, the manual loading process relies more on skilled operators. Although this method shows certain advantages in cost management, due to its low work efficiency, it is usually more suitable for the production of small parts.

2.Mold injection after melted plastic

During this process, we use injection equipment to inject pre-melted plastic into the interior of the mold. When there is a pressure difference between the injection device and the mold cavity, the plastic will enter the mold cavity through the injection hole and finally solidify. Injection equipment ensures that plastic can be filled accurately and directly into every part of the mold. Then, during the cooling and solidification stages, pressure is applied to the plastic and it interacts with the inner walls of the mold. In order to ensure that every channel in the mold can be completely filled with plastic, this process must be completed under high temperature and high pressure conditions. Therefore, plastic can be effectively prevented from flowing out of each channel and causing pollution. In addition, the high temperature and high pressure environmental conditions can also effectively promote the smooth removal of excess air in the mold through the exhaust port, thus ensuring that all components inserted into the mold can be tightly adhered to the surface of the mold, thereby constructing a complete product structure.

3.Start that mold

Once the molten material has experienced sufficient cooling and solidification within the mold, the mold can be opened. For some products with complex structures, a robot specially designed for injection molding can be used to achieve the above actions. This operation can be done manually or by automated tools. Before opening the mold, it must be ensured that all parts can be fully heated to the required temperature and that the entire structure can work properly. When the mold is opened, it is necessary to confirm whether the insert has been perfectly integrated with other parts of the mold to form a complete system.

4.Separate molding components from gates

During the mold formation process, the gate serves as the main supporting part, ensuring the integrity and stability of each part of the mold. If the gate design is unreasonable or defective, it may cause the entire mold to fail to work properly. It is a common situation during the molding process that the first molded part often forms a tight connection with the gate.
Next, this step becomes particularly critical, as it involves separating the gate from the molded part to facilitate subsequent operations and handling. During this process, special attention should be paid to the cleaning of the gating system and the removal of surface defects. In this critical step, the operation process must be very delicate to prevent improper operation from causing cracks or damage to the molded parts, which will have a negative impact on the quality of the final product.

5.Post- processing

The specific steps for insert molding are determined based on the type of product you wish to achieve. When post-processing becomes an integral part of the production process, surface treatment and final quality inspection become routine operations.

What are the applications of insert molding?

Many industries use insert molded products because their products are more functional, more cost-effective, more durable, and all the other advantages they offer. The following are well-known industries where insert-molded parts are widely used:

1.Aerospace field

The aerospace industry is also an important application area forinsert injection molded parts. The industry has successfully achieved weight reductions in aircraft through the use of insert injection molding technology. Components manufactured using this technology include key components such as controls, communications equipment, seat components and door handles.

2.Automobile manufacturing

Before the advent ofinsert injection molding technology, many automotive parts were generally made of metal, making them rather bulky. However, many automotive components are now smaller and lighter thanks to the introduction of insert molding technology. Products such as electronic device casings, dashboard switches, and door handles are often carefully crafted using insert injection molding.

3.Consumer electronics

Insert injection molding technology is very popular in the field of consumer electrical and electronic products, mainly due to the excellent insulating properties of plastic materials. Without the support of insert injection molding technology, many products would not be able to be used normally, or their safety would not be guaranteed. Wall sockets and screwdrivers are prime examples of this technology being used in everyday applications. In the field of electronic products, this technology is widely used in the manufacturing of remote controls, smartphones, laptops and other equipment.

4.Medical device field

The continuous advancement of medical device technology relies heavily on the functional advantages of insert molding technology. This technology allows the medical device industry to develop components that are lighter and easier to clean and sterilize. Through insert molding technology, metal and plastic can be perfectly combined in test tubes, surgical instruments, oxygen masks and other medical devices.

What are the advantages and disadvantages of insert molding?

Insert injection molding is a molding process in which a pre-formed part, usually a metal part, is embedded into a plastic injection molded part. This technology combines the plasticity of plastics with the rigidity, strength and heat resistance of metals, which brings many advantages to product design and manufacturing, but also has some disadvantages.

Advantage

1. Complementary performance:The plasticity and elasticity of plastics are complemented by the rigidity, strength and heat resistance of metals, which can be made into complex and delicate integrated metal-plastic products while reducing the size and weight of the products.
   
2. Functional diversification:Using the combination of plastic insulation and metal conductivity, the products made can meet the basic functions of electrical products, and can also meet some special requirements, such as magnetic permeability, wear resistance and fastening.
   
3. Improved strength:The addition of metal inserts to plastics can significantly increase the strength of plastic parts and make them more durable.
   
4. Design flexibility: Insert injection molding increases product design flexibility, opening up new possibilities for combining plastic and metal with other parts, helping designers create more diverse products.
   
5. Simplified production processes:Insert injection molding can reduce assembly time and costs by eliminating secondary operations such as hot melt, welding, and riveting.
   
6. Insert materials:Inserts are not limited to metal, but can also be cloth, paper, wires, plastics, glass, wood, coils, electrical parts and plastic parts and other materials, providing more choices for product design.
   
7. Improved product reliability:Since it is a combination of molten plastic and metal inserts, the gap of metal inserts can be designed to be narrower than that of press-in molding, etc., and the product reliability is higher, making it easier to pass vibration and other tests.
   
8. Automated production:The combination of vertical injection molding machine, manipulator, insert product arranging device, etc., makes most of the insert injection molding can realize automatic production and improve production efficiency.

Disadvantages

1. Complex mold structure:The placement of inserts often complicates the mold structure, lengthens the injection molding cycle, increases manufacturing costs, and makes automated production difficult.
   
2. Inconsistent coefficient of thermal expansion:The coefficient of thermal expansion of the insert is inconsistent with that of the plastic, which is easy to cause internal stress in the final product, resulting in product cracking or deformation.
   
3. Insert pretreatment:Inserts (especially nut inserts) often need to be preheated or dried to reduce internal stress, which increases the production process and cost.
   
4. Insert fixation:The insert must be firmly fixed in the mold, otherwise it is easy to shift or deform under the impact of the melt, affecting the product quality.
   
5. High cost of defective products:Once the insert injection molding produces defective products, such as poor injection molding, missing inserts, poor position, etc., it will cause the entire product to be scrapped and the cost is high.
   
6. Not conducive to product recycling:Insert injection molding products are not conducive to product recycling and scrap disposal due to the combination of multiple materials, which has a certain impact on the environment.

FAQs

1.What material is used in molding?

There are manytypes of materials used for molding, mainly including metallic materials, non-metallic materials and composite materials. Metal materials: Steel, aluminum, copper and other metal materials have good mechanical properties and processing properties and are widely used in the manufacture of various mechanical parts, structural parts and metal products. Non-metallic materials: including plastic, rubber, wood, paper, etc. These materials have different physical and chemical properties and are suitable for manufacturing various packaging materials, insulation materials, sealing materials, building materials, etc. Composite material: composed of two or more materials with different properties, such as glass fiber reinforced plastic, carbon fiber reinforced metal, etc.

2.What are inserts in injection molding?

Inserts in injection molding are mold accessoriesthat are embedded in the mold core of the injection mold. It has very high requirements for precision. Its main functions include: reducing the mold height: the injection mold fixing material is a relatively regular block of steel with a fixed shape. If one place in the mold is higher than other places, it can be reduced by making inserts. the height of this part. Convenient for mold modification: The parts of the injection mold that often need to be modified can be dismantled and made into inserts. In this way, only the inserts need to be replaced when the mold is changed, reducing modification costs. Exhaust: Add inserts where the mold needs to be vented. You can use the matching gaps of the inserts to vent air to prevent trapped air in the mold cavity. Convenient processing: For difficult-to-process parts such as deep bone locations in the mold, inserts can be made to reduce processing difficulty. Extend the life of the mold: The insert is usually a vulnerable part of the mold. Once the insert is damaged, it can be replaced, thereby extending the service life of the injection mold.

3.What material should I use for injection molding?

When selectinginjection molding materials, factors such as the use and requirements of the product, the physical properties of the material, cost, environmental impact, processability, environmental protection, and special requirements need to be considered. Common injection molding materials include: ABS (Acrylonitrile Butadiene Styrene): It has good mechanical properties and processing properties and is suitable for electronic housings, automotive parts, etc. PC (polycarbonate): has excellent impact resistance and heat resistance, and is often used in eyeglass lenses, protective equipment, etc. PP (Polypropylene): With good chemical resistance and low cost, it is suitable for food containers, car interiors, etc. PE (polyethylene): divided into low-density polyethylene (LDPE) and high-density polyethylene (HDPE), which are suitable for films and rigid containers respectively. PS (polystyrene): has good transparency and electrical insulation, suitable for packaging materials and disposable tableware.

4.What is the material of cavity insert and core insert?

Commoncavity insert and core insert materialsinclude: Steel: such as carbon steel, alloy steel, etc., which have good mechanical properties and thermal stability and are suitable for manufacturing high-precision and high-demand molds. Copper alloy: such as copper-nickel-silicon-chromium quaternary alloy (such as MoldMet200), which can improve hardness, strength and conductivity through solid solution and aging heat treatment. It is suitable for cores and inserts of blow molds and injection molds, etc. . Carbide: It has high hardness and wear resistance and is suitable for manufacturing mold parts that need to withstand high load and wear.

Summary

Commonly usedmaterials for insert molding include thermoplastics (PE, PS, PA, PP, ABS), thermosetting resins (phenolic resin, epoxy resin, melamine formaldehyde resin, urea formaldehyde resin), elastomers (natural rubber, polyurethane, thermoplastic elastomer). The insert molding process has a wide range of material options, and reasonable material selection can be made according to different application environments and performance requirements. By selecting appropriate materials and process parameters, insert molding technology can produce high-quality, high-performance integrated products that meet the needs of various industries.

Disclaimer

The content on this page is for reference only.LSdoes not make any express or implied representation or warranty as to the accuracy, completeness or validity of the information. No performance parameters, geometric tolerances, specific design features, material quality and type or workmanship should be inferred as to what a third party supplier or manufacturer will deliver through the Longsheng Network. It is the responsibility of the buyerseeking a quote for partsto determine the specific requirements for those parts.Pleasecontact usfor moreinformation.

LS Team

This article was written by multiple LS contributors. LS is a leading resource in the manufacturing sector, withCNC machining,sheet metal fabrication,3D printing,injection molding,metal stamping, and more.