The insert molding is a pertinent technology in present-day production. It is used in attaching metal or other elements to plastic. The process offers a unified, tough, and strong component. As an alternative to the step-by-step technique of having to assemble pieces after molding them, the insert molding technique fuses them. This will save on labour, time, and enhance the quality of the product.
China is a mammoth in the insert molding. It provides cost-efficient production. High-level factories and skilled labor have been established in the country. China is a producer of all-purpose materials. It leads global production.
This paper will discuss insert molding, its process, insert types, materials, design, available guidelines, its usage, advantages, and comparison with moulding processes in contemporary production.
What is Insert Molding?
Insert molding is a process of plastic moulding. A part that has been assembled, usually a metal part, is placed into a mold. The next step is molten plastic injected around it. When plastic becomes hard, the plastic insert becomes a component of the end product. The technique is used in electronics and automotive industries, and also in the medical equipment industry.
The large advantage of the insert molding is strength and stability. Metal-inserted plastic parts are stronger in terms of mechanical strength. They can also be threaded and worn less as time progresses. This is especially essential in those parts that should be screwed or bolted many times.
Types of Inserts
The inserts used in insert molding have different varieties, which are used according to the purpose.
Metal Inserts
Metal inserts are the most widespread ones. These are either steel, brass, or aluminum. They are used on threaded holes for structural or mechanical strength.
Electronic Inserts
Electronic components that can be molded to appear in the form of plastic are sensors, connectors, or small circuits. This guarantees their safety and the reduction of assembly processes.
Other Materials
Some of the inserts are made in ceramics or composites to be utilized for special purposes. They are used in instances where heat resistance or insulation is required.
Choosing the Right Insert
It would depend on the part role and the type of plastic to make the decision. The major ones are compatibility, strength, and durability.
The Insert Molding Process
Single-step molding entails the incorporation of a metal or other element with a plastic tool. The insert is inserted into the ultimate product. This is a stronger and faster process compared to the assembly of parts that follows.
Preparing the Insert
The insert is rinsed in order to extract all the dirt, grease, or rust. It is also occasionally overcoated or rugged so that it becomes glued to plastic. It will not be destroyed by hot plastic when it is preheated to 65-100 °C.
Placing the Insert
The insert is placed with much care in the mold. Robots can insert it into large factories. Pins or clamps hold it firmly. The positioning of the right will prevent movement when the molding is taking place.
Injecting Plastic
This is accomplished by injecting the molten plastic to surround the insert. Their temperature range is between 180 and 343°C. Pressure is 50-150 MPa. To be strong, the holding pressure should be 5-60 seconds.
Køling
It is a solidification of the plastic. Smaller components take 10-15 seconds, and larger components take 60 seconds or above. Cooling channels prevent the warming up.
Ejecting the Part
The mold and ejector pins force the part out. Small finishing or trimming could then follow.
Important Points
The expansion of metal and plastic is not the same. Preheating and constant controlled mold temperature decreases the stress. This is done by the use of sensors in modern machines to achieve uniformity in the results in terms of pressure and temperature.
Key Parameters:
| Parameter | Typical Industrial Range | Effect |
| Injection Temperature | 180–343 °C | Depends on plastic grade (higher for PC, PEEK) |
| Indsprøjtningstryk | 50–150 MPa (≈7,250–21,750 psi) | Must be high enough to fill around insert surfaces without displacing them |
| Injection Time | 2–10 s | Shorter for small parts; longer for larger components |
| Holding Pressure | ~80% of injection pressure | Applied after fill to densify material and reduce shrinkage voids |
| Holding Time | ~5–60 s | Depends on material and part thickness |
Types of common injections to be shaped
Various types of inserts applied in injection molding exist, and they rely on the use. Each of the types contributes to the strength and performance of the final part.
Threaded Metal Inserts
Threaded inserts can be steel, brass, or aluminum. They allow the potential of screwing and bolting a number of times without the plastic being broken. The latter is common in automobiles, home appliances, and electronics.
Press-Fit Inserts
The press-fit inserts are those that are installed in a molded component without any additional attachment. As the plastic cools, it holds the insert and stabilizes it very well and powerfully.
Heat-Set Inserts
This is followed by the process of heat-setting inserts. When allowed to cool, the hot insert will fuse with the surrounding plastic to some extent, creating a very strong bond. They are generally used in thermoplastics, e.g., nylon.
Ultrasonic Inserts
In a vibration, ultrasonic inserts are installed. The plastic melts in the region surrounding the insert and becomes hard to create a tight fit. It is a precise and fast method.
Choosing the Right Insert
The choice of the right and left is according to the type of plastic, part design, and the load that is anticipated. The choice of metal inserts has been made based on strength, and the special inserts, like the heat-set inserts and ultrasonic inserts, have been evaluated on the basis of precision and durability.
Design Rules in the Industry of Insert Injection Molding
The design of parts to be inserted by use of molding should be properly planned. The accurate design ensures that there is high bonding, precision, and permanence.
Insert Placement
The inserts will be inserted where they will be in a good position to be supported by plastic. They must not be very close to walls or thin edges because this can result in cracks or warping.
Plastic Thickness
Always make sure that the walls that surround the insert are of the same thickness. Due to an abrupt thickness change, uneven cooling and shrinkage can be experienced. The insert will typically have a 2-5 mm thickness, which is sufficient as far as strength and stability are concerned.
Materialekompatibilitet
Take plastic and stuff it with adhesive materials. An example is a nylon that can be used with brass or stainless-steel inserts. Mixes that become excessive in heat must be avoided.
Formdesign
Add a good gate position and cooling arrangements to the mold. The plastic must be capable of moving freely about the insert and must not entrap air. The temperatures are stabilized by channels and prevented from warping.
Tolerancer
Correct tolerances of the insert components of the design. It only takes a small space of clearance of 0.1-0.3 mm in order to perfectly fit the insert without being loose or hard.
Reinforcement Features
The insert should be underpinned using ribs, bosses, or gussets. When used, these properties become widely distributed, thereby preventing cracking or movement of inserts.
Unsuitable Overmold Materials to use in an insert-molding process
The ideal process is the insert molding; however, the plastic is readily melted and easily flows throughout the process of molding. The plastic should also be attached to the insert to create a robust part. Preference is given to thermoplastics because they possess the correct melting characteristics and flow characteristics.
Styrene Acrylonitrile Butadiene Styrene
ABS is not only dimensional, but it is also easy to work with. It is best applicable to consumer electronics among other products that demand a high level of accuracy and stability.
Nylon (Polyamide, PA)
Nylon is strong and flexible. It is usually welded to metal inserts to a structural commodity, e.g, automotive bracketry or building component.
Polykarbonat (PC)
Polycarbonate is not only crack-free but also tough. It is applicable mostly in the provision of electronics enclosures and medical equipment, and other equipment that requires durability.
Polyetheretherketone (PEEK)
PEEK has a competitive advantage over the heat and chemical. It would apply to the high-performance engineering, aerospace, and medical fields.
Polypropylen (PP)
Polypropylene is not viscous, and neither does it respond to a high number of chemicals. It is used on domestic and consumer goods, and on automobile parts.
Polyethylen (PE)
Polyethylene is cheap and also elastic. The primary use of this is in lighting, e.g., packaging or protective cases.
Thermal plastic Polyurethane (TPU) and Thermoplastic Elastomer (TPE)
TPU and TPE are rubber-like, soft, and elastic. They are perfect in over molding grips, seals, or parts that require impact absorption.
Choosing the Right Material
The choice of the overmold material is dictated by the part functionality, the task of the insert, and its functioning. It should also be a good flow plastic bonding the insert, besides providing the required strength and flexibility.
Part Geometry and Insert Placement:
This feature applies to all parts.
Part Geometry and Insert Placement:
It is a feature that could be applied to any part.
The insert retention is dependent on the shape of the part. The insert positioning should be such that of adequate plastic around it. One should not have insurance too close to edges or narrow walls, as this can crack or bend.
The plastic surrounding the insert should be smooth in thickness. A sudden change in thickness can result in either nonuniform cooling or contraction. In the case of the insert, a normal 2-5 mm of plastic is sufficient in regard to strength and stability.
The design features that can be used to support the insert are ribs, bosses, and gussets. As it is used, they help in the dispersion of stress and the inhibition of movement. Once the insert is correctly installed, one is assured that the part is in place and that the part works effectively.
Technical Comparison of Thermoplastics for Insert Molding
| Materiale | Melt Temp (°C) | Mold Temp (°C) | Injection Pressure (MPa) | Tensile Strength (MPa) | Impact Strength (kJ/m²) | Shrinkage (%) | Typical Applications |
| ABS | 220–260 | 50–70 | 50–90 | 40–50 | 15–25 | 0.4–0.7 | Consumer electronics, housings |
| Nylon (PA6/PA66) | 250–290 | 90–110 | 70–120 | 70–80 | 30–60 | 0.7–1.0 | Automotive brackets, load-bearing parts |
| Polykarbonat (PC) | 270–320 | 90–120 | 80–130 | 60–70 | 60–80 | 0.4–0.6 | Electronics enclosures, medical devices |
| PEEK | 340–343 | 150–180 | 90–150 | 90–100 | 15–25 | 0.2–0.5 | Aerospace, medical, chemical applications |
| Polypropylen (PP) | 180–230 | 40–70 | 50–90 | 25–35 | 20–30 | 1.5–2.0 | Automotive parts, packaging |
| Polyethylen (PE) | 160–220 | 40–60 | 50–80 | 15–25 | 10–20 | 1.0–2.5 | Packaging, low-load housings |
| TPU/TPE | 200–240 | 40–70 | 50–90 | 30–50 | 40–80 | 0.5–1.0 | Grips, seals, flexible components |
The Advantages of the Insert Moulding
Strong and Durable Parts
An insert molding process involves the combination of plastic and metal into a single entity. This makes the components tough, robust, and can be used over and over again.
Reduced Assembly and Labour
The insert will be inserted into the plastic, and no additional assembly will be required. This conserves time and labor and reduces the possibility of mistakes during assembly.
Precision and Reliability
The insert is firmly attached to the moulding. This guarantees that the dimensions are the same and that the mechanical strength is increased to increase the reliability of parts.
Design Flexibility
The fabrication of complex designs through the assistance of insert moulding would be difficult to produce through conventional assembly. It is possible to have metal and plastic being used in a novel combination to fulfil functional requirements.
Cost-Effectiveness
Insert molding will also reduce waste of materials, as well as assembly costs in large volumes of production. It improves effectiveness and overall quality of products, therefore long-term cost-effective.
The applications of the Insert Moulding
Bilindustrien
The automobile industry is a typical application of Indsatsstøbning. Plastic components have metal inserts, which provide the component, like brackets, engine parts, and connectors, with strength. This will render assembly less and durability more.
Elektronik
Electronics. The benefit of insert molding here is that it is possible to add connectors, sensors, and circuits to a plastic casing. This will guarantee the safety of the fragile components and make the assembly process relatively easy.
Medicinsk udstyr
The technology of insert molding is highly used in medical apparatuses that demand a high degree of accuracy and longevity. This is applied in the production of surgical equipment, diagnostic equipment, and durable plastic-metal combinations.
Forbrugerprodukter
Consumer goods like power tools, appliances, and sports equipment are mostly molded with insert molding. It reinforces and simplifies the assembly of the process, and it makes ergonomic or complex designs possible.
Industrial Applications, Aerospace.
Den Indsatsstøbning is also used in heavy industries and aerospace. High-performance plastics that are filled with metal have light and strong components that are heat-resistant and wear-resistant.
Materials Used
The action of the insert mode of molding requires the appropriate materials for the plastic and the insert. The choice will lead to power, stability, and output.
Metal Inserts
The use of metal inserts is normally done because they are rough and durable. It comprises mainly steel, brass, and aluminium. In parts with a load, steel can be used, brass cannot be corroded, and aluminum is light.
Plastic Inserts
Plastic inserts are corrosion-resistant and light. They are used in low-load applications or applications in parts that are non-conductive. Plastic inserts can also be shaped into complex shapes.
The Ceramic and Composite Inserts.
Ceramic and composite inserts are used to obtain heat, wear, or chemical resistance. They are normally employed in aerospace, medical, and industrial fields. Ceramics are resistant to high temperatures, and composites are also stiff yet have low thermal expansion.
Thermoplastic Overmolds
The surroundings of the insert are a thermoplastic that is generally a plastic. Available options include ABS, Nylon, Polycarbonate, PEEK, Polypropylene, Polyethylene, TPU, and TPE. ABS is moldable, stable, Nylon is flexible and strong, and Polycarbonate is an impact-resistant material. TPU and TPE are soft and rubbery materials that are used as seals or grips.
Materialekompatibilitet
Plastic and metal are supposed to grow in ratio to one another in order to eliminate strain or deformation. The plastics must be glued to the insert in case they should not separate. In plastic inserts, the overmold material should acquire adhesive to ensure that it becomes strong.
Material Selection Tips
Consider the load, temperature, chemical, and part design exposure. The metal inserts are durable, the plastic inserts are lightweight, and the ceramics can withstand extreme conditions. The overmold material must have the capability of meeting all the functional requirements.
Cost Analysis
The inserted plastic will enable the saving of the money that would have been utilized in the attachment of the single parts. The decrease in the assembly levels will mean a decrease in the number of labourers and a faster production speed.
Initial costs of moulding and tooling are higher. Multiplex molds having a set of inserts in a certain position are more expensive. However, the unit cost is lower when the level of production is large.
Choice of material is also a factor of cost. Plastic inserts are less expensive than metal inserts. PEEK is a high-performance plastic that is costly in comparison to the widely used plastics, including ABS or polypropylene.
Overall, the price of insert moulding will be minimal in the medium to high volume of production. It will save assembly time, improve the quality of the parts, and reduce long term cost of production.
The problems with the Molding of Inserts
Despite the high efficacy of the insert molding, it has its problems, too:
Thermal Expansion: We will have rate differences and therefore warp in metal and plastic.
Insert Movement: Inserts can move, already in the injection process, unless firmly fixed.
Material Compatibility: Not all plastics can be compatible with all metals.
Small Run Mould tooling and set-up Cost: Mould tooling and set-up can be expensive at very small quantities.
These problems are reduced to a minimum by designing well, mould preparation, and process control.
Fremtiden for indsætningsstøbning
The insert moulding is in the development stage. New materials, improved machines, and automation are being used to increase efficiency, and 3D printing and hybrid manufacturing processes are also becoming opportunities. Its ability to produce lightweight, strong, and precise parts due to the necessity of the parts is that the insert moulding will be a significant production process.
When it comes to Assistance with Sincere Tech
In the case of insert moulding and overmoulding, we offer high-quality, correct, and reliable moulding solutions of moulding at Sincere Tech. Our technology and hand-craft workers will ensure that every part will be as per your specification. We are strong in the long-lasting, complicated, and economical automobile, electronic, medical, and consumer goods moulds. Your manufacturing process is easy and efficient, and this is due to our turnaround times and great customer service. You are moving to Sincere Tech, and with the company will work in line with precision, quality, and your success. Trust us and have your designs come true for us correctly, dependably, and to industry standards.
Konklusion
Insert moulding is a production process that is flexible and effective. It allows designers to employ a single powerful component that is a combination of metal and plastic. The use of insert moulding in industries over the years is due to its advantages that include power, precision, and low cost. But it is getting more confident along with the advancements in materials and automation. The solution to manufacturing by insert molding is time saving, cost reduction, and high-quality products in the context of modern manufacturing.
