• Copper and its alloys (e.g. CuZn, CuSn, CuBe): high conductivity, ideal for contacts
   
• Brass and bronze: easy to form, dimensionally stable, and corrosion-resistant
   
• Steels and stainless steels: rust-free, dimensionally strong, hygienic
   
• Electroplated steel (e.g. DC01): economical and versatile
   
• Aluminum: lightweight, corrosion-resistant, easy to form, with a high degree of thermal conductivity
   
• Nickel: extremely resistant to corrosion, abrasive media, and high temperatures
   
• Titanium: extremely corrosion-resistant, lightweight, and bio-compatible
   
• Bi-metals: material combinations consisting of two different metals (e.g. copper and aluminum or steel and aluminum) for robust or visible components

• PA6 / PA66 GF: tough and heat-resistant – perfect for technical components
   
• PBT / PPS: dimensionally stable, resistant to chemicals and temperature – ideal for electrical engineering
   
• PC / ABS / PC-ABS: for robust or visible components
   
• TPE / TPU: elastic, ideal for seals or flexible elements
   
• PEEK / LCP: high-performance plastics for extreme requirements

• Everything from a single source: from development through our in-house toolmaking to series production
   
• Reduced interfaces: less coordination effort and faster implementation
   
• Sophisticated components: a metal basis plus functional plastic, including finishing
   
• Economical production: automatable, reliable, and ideal for large-scale production
   
• Tailored process and material combinations: perfectly adapted to your technical requirements
   

The benefit to you: less effort, more integration.

The choice of material plays a central role in plastic injection molding. The formed parts do not just have to provide the necessary mechanical properties – they must also form a stable bond with the plastic. 

The most frequently used materials include:

• Stainless steel: with its excellent corrosion-resistance and high strength, stainless steel is ideal for applications that are exposed to severe environmental conditions. In medical technology, food, and chemicals industries in particular, stainless steel makes durable components.
• Aluminum: aluminum has a good ratio of strength to weight, making it ideal for lightweight construction in the automotive industry.
• Copper: copper has excellent electrical and thermal properties. It is suitable for electronic components and contacts that require rapid heat dissipation and reliable electrical conductivity.
• Brass: brass is both very strong and very easy to work. It is particularly suitable for fine mechanical parts and precision components, which are used in hybrid parts such as connecting pieces and seals.
   

Titanium, bronze, nickel silver and other metals are also suitable for use as components for plastic injection molding.

The injection molding material (plastic that surrounds the metal part) is important to the function and service life of the finished part. Different plastics are available for different applications.

• Polyphenylene sulfide (PPS): polyphenylene sulfide is a high-performance plastic that can withstand temperatures of up to 260°C and has good mechanical and chemical resistance. It is used for parts that are subject to high stress in the automotive and electronics industries.
• Polybutylene terephthalate (PBT): a thermoplastic polymer. It is often used in areas where electrical insulation and good mechanical properties are important.
• Polyamide (PA): polyamide, also called nylon, is known for being highly robust and resistant to wear. PA is also very resistant to high temperatures and chemical substances. Polyamides are frequently used in mechanical parts that are exposed to high loads and friction, such as automotive components, mechanical engineering parts or electrical devices.
• Thermoplastic polyurethane (TPU): TPUs are plastics characterized by their flexibility and durability. They are ideal for applications where flexibility and elasticity are important. TPUs can be produced in varying degrees of hardness, which makes them hugely versatile.
• Filled thermoplastics: these materials come with high proportions of filler (up to 65%). Glass- or mineral-filled plastics such as glass fiber-reinforced polyamide provide improved mechanical properties, higher rigidity and reduced shrinkage. Filled thermoplastics are particularly suitable for technical applications that require high dimensional stability and strength.
   

Choosing the right injection molding material is crucial to the durability, stability, and performance of hybrid parts. STÜKEN is happy to help you select the right material and find the optimal solution for your project.

The correct preparation of metal surfaces is vital for ensuring that plastic adheres successfully. The procedures below help to activate the metal surface and achieve a better bond between the metal and plastic.

• Cleaning: a thorough cleaning of the metal part removes dirt, oil or oxidation that may affect the bond. Chemical cleaning agents or abrasive techniques are often used to clean the surface.
• Etching: etching involves treating the metal with an acidic solution that creates a microscopic texture to improve adhesion.
• Plasma treatment: this involves treating the metal surface with plasma, which increases surface energy and improves the adhesion between the metal and plastic.

Here, plastic-hybrid parts are commonly used for smaller components such as door handles, locks, fastening elements, dashboard fixtures or cable ducts. These components, which were previously often produced purely from metal, benefit from the combination of metal and plastic. It makes for lighter, more stable components that meet the safety, durability, and performance requirements for vehicle operation.

For this industry, we produce parts such as plug connectors, housings, and insulation. Materials: PAs, PPS, PES or PEKK. They provide high strength and lasting protection in high temperatures. 

Areas of application include mechanical components and functional parts such as supply lines, containers, panels and crates.

In mechanical engineering, metal-plastic parts are used to produce components with high mechanical strength and flexibility. Examples include gearwheels, couplings and guides. The combination of metal and plastic makes for components with a high load carrying capacity and low frictional properties.

Stamped and stamped-and-bent parts such as metal frames, contact pins, spring contacts and guides are encased in plastic and then used in products such as infusion pumps, surgical instruments and measuring devices.

This unit is responsible for heating up the plastic and injecting it into the mold under high pressure. The injection unit heats up the plastic until it liquefies and then quickly injects it into the mold, where the metal part has already been placed. The pressure ensures that the plastic fills all the cavities in the mold and evenly surrounds the metal part.

There are various types of machines, each of which offers different benefits. The two most common configurations are:

• Vertical injection unit: with this machine configuration, the metal part is placed into the mold vertically. The vertical configuration is particularly beneficial for aligning the metal part precisely during the injection process. These machines are often suitable for smaller or medium-sized series production where accuracy is necessary.
• Horizontal injection unit: with this configuration, the metal part is placed into the mold horizontally. These machines are better suited to larger-scale series production because they offer a higher production rate. They are often more robust and provide greater flexibility when designing the molds required for large-scale series production.
   

The choice of machine configuration largely depends on the product design, cycle times and production volumes. Our cutting-edge systems allow for modular retrofitting, which means we can produce both prototypes and large-scale series production.

This unit ensures that the mold stays closed throughout the entire process. The pressure applied to the mold makes sure the metal part stays in position and the plastic is injected correctly. This unit plays an important role in ensuring the quality of the bond between the metal and plastic.

Plastic injection molding processes often involve automated handling systems that precisely position the metal part in the mold. Robots or automatic handling units help to speed up the production process.

Precise temperature control is vital to the success of the process. The plastic must be kept at a constant temperature so that it liquefies evenly and fills out the mold completely. The mold itself can also be fitted with heating and cooling systems for controlling the plastic curing process and ensuring an even hardness.

There are a variety of different plastic injection molding methods which differ in terms of how the metal part is integrated into the injection molding process. Each of these methods has its own benefits, depending on the applicable production requirements and desired product quantity.

Below you can learn about the methods we use most frequently at STÜKEN.

Punched strip injection molding is a production method in which metal strips that have already been punched are inserted directly into the injection molding tool and plastic is then injected into the mold around them. There is a further distinction between two types of punched strip molding processes.

1. Reel-to-reel process
   The reel-to-reel process is a production process where metal strips or foils are fed into the injection mold. These are continuously drawn through the injection molding tool and the plastic is applied to predefined areas.
   This technique is particularly beneficial for mass production of parts because it provides a high production speed at a consistently high-quality level. It is especially suited to the production of electronic components and packaging. Following the injection molding step, the finished parts are separated from the metal foil or film for further processing.
    
2. Tape-and-reel process
   The tape-and-reel process is similar to reel-to-reel but in this case a metallic strip is used instead of a metal foil. Like the reel-to-reel process, the strip is continuously fed through the injection molding tool with plastic injected around it. This process is very effective for the production of electronic parts and interlinked components. It maintains a constant supply of material and increases production speed. The continuous flow of materials allows for large-scale series production with minimal effort.

In shuttle molding, multiple tools are fitted on a shuttle system that moves back and forth between various stations. The plastic injection molding is carried out at one of these stations, where the metal part is inserted into a mold and plastic is then injected around it. This process lets you combine metal and plastic parts in one step, thus producing stable and functional components.

Carousel molding is another variant that is suitable for large-scale series production. In this method, the form is installed on a rotating carousel with multiple stations. Each station successively processes a component while the carousel continues to turn. This process offers significant benefits if a high-speed production is required. Carousel molding is often used for automotive components, electrical devices, and medical devices.

Plastics are much lighter than metal, which means that the weight of the components is reduced significantly. This is particularly beneficial in the automotive industry, where minimizing weight helps to improve vehicle performance and energy efficiency.

The manufacture of hybrid parts through plastic injection molding is efficient, particularly in comparison to other methods such as welding or the mechanical processing of metal. Since the process involves the direct manufacture of parts in a mold, additional assembly or bonding steps are dispensed with, leading to lower production costs and time savings.

Plastic injection molding allows you to create complex geometries and multifunctional capabilities in a single step, reducing the need for extra components and assembly costs. Plastic also lets you implement complicated designs that would be difficult or unfeasible to achieve using traditional production methods.

Plastic injection-molded parts combine the mechanical stability of metals with the benefits of plastics. Choosing the right materials (glass fiber-reinforced plastics, for instance) lets you develop components with high strength and toughness without increasing weight. 

Metal parts with plastic injection molding are much better protected against corrosion. That provides a crucial advantage for components used in damp or chemically abrasive environments such as those found in the maritime industry, vehicle parts or chemical plants.

Injection molding lets you combine multiple functions in one single part. For instance, you can integrate seals, fastening elements, or guides directly into the mold, which not only reduces assembly costs, but also improves the functionality of the end product and helps reduce the number of parts.

Plastic injection molding can produce parts with a smooth, visually appealing surface finish that fulfills both aesthetic and functional requirements, which is particularly relevant in electronics applications or consumer electronics products where design plays an important role alongside functionality. Plastic can also be designed in different colors and textures to meet the requirements of specific applications.