What is LSR (Liquid Silicone) Injection Molding: Applications, Advantages, and Factors Affecting its Molding Process
- What is LSR (Liquid Silicone) Injection Molding: Applications, Advantages, and Factors Affecting its Molding Process
- What is LSR (Liquid Silicone Rubber)?
- What is LSR (Liquid Silicone Rubber) injection molding?
- The specific workflow of LSR (liquid silicone rubber) injection molding
- The difference between liquid silicone rubber and silicone rubber
- Key advantages of liquid silicone rubber (LSR) injection molding process
- Six key factors influencing the success of an LSR molding project
- Future Development and Market Opportunities of LSR Injection Molding Technology
- Applications of liquid silicone rubber molding
- Elimold Liquid Silicone Injection Molding Service
- in conclusion
- FAQ
Are you using LSR (Liquid Silicone Resin) for injection molding? If so, this article is for you. It will focus on the molding process, applications, and factors that affect its performance. After reading this article, you will have a better understanding of this process.
LSR injection molding is similar to other plastic injection molding processes. They all use the same materials and follow the same procedures. However, there are still some key differences to be aware of. These include pressure rate, injection rate, and material properties. Therefore, it would be helpful if you also have general knowledge of plastic injection molding. Now, please read on for details.
What is LSR (Liquid Silicone Rubber)?
LSR is short for liquid silicone rubber. Liquid silicone is a transparent liquid silicone raw material (abbreviated as LSR). Besides possessing basic properties such as safety, non-toxicity, and water resistance, its unique fluid form allows for process precision that traditional solid silicone cannot achieve. Furthermore, its high transparency enables the production of products with equally high-transparency appearances. It is also a material suitable for numerous industries. Its unique composition makes it an ideal choice for manufacturing various products. Its chemical composition endows it with unique physical properties.
In addition, LSR is an elastomer composed of multiple molecules. Unlike other elastomers, it has higher strength and greater heat resistance. It is a good electrical insulator and has good chemical stability. The properties of LSR make it suitable for a variety of applications. It is heat-resistant and water-resistant.
What is LSR (Liquid Silicone Rubber) injection molding?
Liquid silicone injection molding (LIM) is a novel and highly efficient method for molding silicone rubber, developed in the late 1970s. It combines the superior performance and equipment of liquid silicone rubber, enabling precise and stable injection molding. This new silicone rubber molding technology, consisting of only two components (which may also include auxiliary components such as color matching), requires only loading the equipment, and the entire process from feeding, metering, and mixing to forming is fully automated. This molding technology simplifies the process, reduces processing time, saves materials, and improves efficiency. Furthermore, the production process generates virtually no waste, which is environmentally friendly.
The basic process of liquid silicone rubber injection molding is as follows: Two liquid silicone rubber materials, A and B, are precisely metered and fed into a mixing injection unit via a metering device; the two components are completely mixed in the mixing unit and then transferred to the injection molding machine. The mixture is injected through the molding machine or into a preheated multi-mold head and evenly distributed into each cavity; in the hot cavity, the silicone rubber material is heated and rapidly vulcanized to form the product; after vulcanization, the mold automatically opens; then the injection molding cycle begins. The entire molding cycle takes from tens of seconds to several minutes, varying depending on the size of the product. We will now explain this process in detail.
The specific workflow of LSR (liquid silicone rubber) injection molding
As a professional silicone product manufacturer, we will explain in detail the injection molding process of liquid silicone rubber (LSR).
Raw material preparation and mixing stage
Liquid silicone rubber consists of component A and component B, which need to be mixed in a precise 1:1 ratio. A precise metering device and static mixer are used to ensure uniform contact and full reaction between the two components. Furthermore, appropriate amounts of colorant can be added according to product design requirements and thoroughly mixed with the silicone raw material.
Plasticizing and Injection Stage
After rigorous mixing, the liquid silicone material enters the plasticizing system. Due to the low viscosity and shear thinning properties of liquid silicone, the injection molding equipment must be capable of precisely controlling temperature and pressure to maintain stable material properties.
Mold preparation and injection molding
Whether it is a hot runner LSR mold or a cold runner system, the mold temperature must be maintained between 170 and 200°C to ensure that the liquid silicone can quickly undergo a vulcanization reaction and solidify after being injected into the mold.
Injection molding
The plasticized liquid silicone is rapidly injected into the preheated mold cavity, completing the filling and vulcanization process in a very short time. Within the mold cavity, the liquid silicone undergoes a chemical reaction triggered by heat, forming a three-dimensional structure to achieve the desired shape and size.
Curing and cooling
After molding, silicone products need to be kept in the mold for a period of time to allow them to fully cure and achieve the desired physical and mechanical properties. The mold is then opened to obtain the final silicone product.
Post-processing
After the final silicone product is removed from the mold, it still needs to undergo post-processing steps such as trimming burrs and quality inspection. For products with special requirements, secondary processing may be required, such as surface treatment or assembly of other accessories.
The difference between liquid silicone rubber and silicone rubber
It’s important to note the differences between silicone and LSR. Subtle differences exist between liquid silicone rubber and silicone, making it difficult to distinguish between their products. Liquid silicone rubber (LSR) is a liquid fluid, while silicone is a solid with no flow properties. Furthermore, LSR and regular silicone have different applications. Industrial products, such as automotive parts, are typically made using silicone. LSR, on the other hand, has a wider range of applications, including baby products, various kitchen utensils, and even medical supplies. Their molding processes also differ. Silicone is compression molded, which is less safe; while LSR is injection molded, which is safer.
Key advantages of liquid silicone rubber (LSR) injection molding process
As an advanced rapid prototyping and manufacturing technology, liquid rapid silicone rubber (LSR) molding is playing an increasingly important role in accelerating innovation across industries. With its high efficiency, design flexibility, and ability to quickly deliver precision parts, LSR molding technology helps companies turn concepts into reality faster. Below are the key advantages of liquid silicone rubber (LSR) injection molding.
Good raw material transparency
Because liquid silicone raw materials are simple to process, without the addition of extra crosslinking agents or other auxiliary agents, they are transparent and pure in texture, and are sealed in a sealed package, which can isolate them from dust and dirt from the external environment. They can be said to be the purest raw materials.
Process Automation
Liquid injection molding is an automated process, which effectively reduces quality issues caused by human error. Furthermore, reducing manual intervention significantly improves production efficiency, reduces labor time, and saves costs.
Accuracy and complexity
One of the main advantages of LSR injection molding is its ability to produce highly fine and precise parts. Because silicone is liquid before curing, it can easily flow into even the smallest areas of the mold, enabling complex designs and shapes that are difficult or impossible to achieve with other materials.
Faster production cycle
Compared to traditional rubber molding processes, LSR injection molding significantly shortens the production cycle. The rapid and efficient curing process of liquid silicone materials helps to shorten the overall cycle and produce a large number of parts in a short time, which is highly advantageous for high-demand applications.
Minimal post-processing
LSR injection molding technology minimizes the need for post-processing. Parts produced typically require almost no trimming, cleaning, or other finishing. This technology produces parts with smooth surfaces and sharp edges immediately after molding. This reduces labor costs and helps streamline the production process, ultimately saving time and resources.
Flexibility and durability
LSR materials exhibit high flexibility and durability even under extreme conditions, maintaining their integrity within a temperature range of -50°C to +250°C, making them ideal for high-temperature applications. Furthermore, LSR materials can be used to produce products with UV resistance, ozone resistance, and chemical resistance. Additionally, the flexibility of LSR allows parts manufactured from it to withstand mechanical stresses (such as tension or compression) without changing their shape.
Biocompatibility and safety
LSR material is commonly used in industries such as healthcare and baby products due to its biocompatibility. This non-toxic material is safe for contact with human skin or tissue, making it ideal for medical devices, surgical instruments, and baby care products such as pacifiers and bottle nipples. Furthermore, LSR meets international safety standards, including FDA and ISO certifications.
Environmental benefits
LSR material is also an environmentally friendly option. It is recyclable and generates very little waste. Furthermore, LSR modules typically have a longer lifespan compared to other materials, helping to reduce replacement needs and waste. The process itself is highly efficient, making it an environmentally friendly manufacturing method for companies focused on sustainability.
Six key factors influencing the success of an LSR molding project
What factors typically influence the success of an LSR molding project? Are structure, temperature, etc., all included? If these factors are ignored, will they affect the production process? When you want custom LSR components that meet your requirements, the following are the reasons why you need to carefully understand the relevant influencing factors. This will save you time and money and bring you the best results.
Calculation of shrinkage rate
Shrinkage can affect the final accuracy of LSR components. In most cases, shrinkage occurs after heating and molding. Although the shrinkage rate of LSR material itself is not high, it does occur after demolding and cooling. The shrinkage rate of the liquid is approximately 2.5% to 3%. This can alter the intended shape of your product and even its intended thickness.
In addition, certain components within the mold can also cause shrinkage. For example, temperature. Temperature causes the mold to shrink more. Pressure within the mold cavity also contributes to shrinkage. Furthermore, the higher the degree of plastic compression, the greater the shrinkage. If recuring is performed, the expected shrinkage rate will be even higher, approximately 0.5% to 0.7%. Therefore, it is crucial to pay attention to shrinkage issues.
Correct selection of mold materials
The quality of the mold determines the final molding result. For oil-resistant LSR, the mold should be made of a higher-strength material. You also need to consider the internal components of the mold. The mold cavity determines the appearance of the product. If you want to make a transparent product, use polished steel for the inner surface of the mold. This will yield better results.
Accuracy of temperature control
Temperature control is essential for producing any type of LSR component. Uneven heat distribution leads to inconsistent product quality. Therefore, you must ensure uniform heat distribution. This will ensure the cured LSR parts reach their optimal state. If the temperature is too low, product quality will be affected because the curing speed will be slower. Problems may occur during product demolding. Temperature control is crucial. Excessive temperature can cause air leaks.
Selection of flow channel system
The cold runner system is crucial to the molding results of liquid silicone rubber (LSR). An effective cold runner system can reduce material waste, lower labor intensity, and sometimes shorten molding operation time. Furthermore, it occupies little space and enables large-scale production. The temperature of the cold runner needs to be kept balanced. Too high a temperature will lead to vulcanization, while too low a temperature will result in incomplete vulcanization.
Exhaust design
Venting refers to the removal of air after LSR parts are molded. The venting process is crucial. Compressed air must be vented after molding. Otherwise, compressed air will remain in the mold, causing white edges on the product and resulting in defects. Therefore, compressed air must be vented after molding. Maintaining a vacuum within the mold is optimal. This helps the mold close and initiates injection pressure. Some devices can more easily vent air while preventing rubber from overflowing or expanding.
Parting line design
To successfully produce LSR custom parts, the parting line must be defined. Furthermore, the parting line must be precise to avoid over-bonding. The importance of the parting line to the venting groove lies in its location. The venting groove is crucial; it must be located at the final stopping point of the rubber. That is, it must be within the injection pressure range. This helps prevent air bubbles from forming inside the rubber and minimizes the loss of adhesive strength. Additionally, the location of the parting surface determines the location of the breakage surface. Plastic chamfering helps achieve uniform bonding.
Future Development and Market Opportunities of LSR Injection Molding Technology
Industries such as medical, electronics, automotive, and aerospace are increasingly focused on developing smaller, more efficient, lighter, and more environmentally friendly products, driving market demand for high-precision LSR injection molded parts. Specialized manufacturers can capitalize on this trend by investing in more advanced LSR molding technologies to produce lightweight parts that meet increasingly complex market demands. Furthermore, the aging populations and strained healthcare resources worldwide present significant opportunities for the medical device industry, as LSR injection molding is ideally suited for producing medical components that must meet stringent safety and performance standards.
Furthermore, significant opportunities exist in the development of electric vehicles (EV) due to the growing demand for lightweight, durable, and high-performance components. As EV manufacturers seek to reduce vehicle weight and improve efficiency, the demand for LSR components with high heat resistance and excellent sealing performance is expected to increase. The ongoing development of smart and wearable medical devices also presents opportunities for LSR in the form of biocompatible, flexible components that can be seamlessly integrated into advanced healthcare technologies. The LSR molding machine market is well-positioned to benefit from these emerging trends, particularly as the industry pursues more advanced and sustainable manufacturing solutions.
Applications of liquid silicone rubber molding
LSR are transformed into desired shapes or geometries through different processes. LSR injection molding is widely used across various industries due to its versatility. The following are common industries and related applications.
| Industry | Application Area | Typical LSR Injection Molded Parts |
| Medical & Healthcare | Disposable and reusable medical devices | Seals, gaskets, valves, diaphragms, syringe components, catheter tips |
| Medical & Healthcare | Wearable and implant-adjacent devices | Sensor housings, soft interfaces, cushioning components |
| Automotive | Powertrain and fluid systems | O-rings, grommets, seals, connector seals |
| Automotive | Electronics and lighting | LED lens seals, waterproof connectors, sensor encapsulation |
| Consumer Electronics | Device sealing and protection | Keypads, button membranes, waterproof gaskets |
| Consumer Electronics | Wearables | Watch seals, earbuds tips, charging port covers |
| Infant & Baby Products | Feeding and care products | Bottle nipples, pacifiers, valves, teething components |
| Food & Beverage | Processing and dispensing equipment | Seals, diaphragms, valves, tubing connectors |
| Industrial Equipment | Fluid control and automation | Pump seals, valve seats, membrane diaphragms |
| Aerospace & Defense | Sealing and protection systems | Environmental seals, vibration-damping components |
| Lighting | Outdoor and indoor luminaires | Optical lenses, sealing rings, protective covers |
| Electrical & Energy | Power distribution and insulation | Cable seals, insulating covers, connector overmolds |
| Personal Care & Cosmetics | Packaging and applicators | Valves, seals, soft-touch applicator tips |
Elimold Liquid Silicone Injection Molding Service
Injection molding of liquid silicone rubber (LSR) differs from that of thermoplastics or composites. The low viscosity of LSR necessitates careful consideration and strict control of the process to achieve optimal results. Elimold understands this well and adapts its LSR injection molding services to evolving market demands.
Therefore, we have our own factory in Shenzhen, China, equipped with advanced automated injection molding equipment and a professional mold-making team to meet your various needs. Elimold has over 20 experienced engineers with more than ten years of experience, providing comprehensive injection molding services from design optimization to quality control.
Partnering with Elimold eliminates the hassle of finding custom mold solutions. Our in-house mold manufacturing workshop, equipped with CNC and EDM machining equipment, enables the production of professional LSR silicone molds, enabling the creation of precision and complex molds, thus accelerating your project timeline. If you require injection molding services for LSR parts or products, please send us your design drawings and other specifications.
in conclusion
In conclusion, liquid silicone rubber (LSR) stands out as an ideal choice for numerous industries due to its superior thermal stability, UV resistance, chemical resistance, and biocompatibility. Furthermore, its recyclability and extremely low waste during production make it an environmentally friendly option. With its excellent material properties, efficient molding processes, flexible design space, and broad application potential, it provides a solid foundation and limitless possibilities for innovation across various industries. From life-saving medical devices to the cars that power the future, and to the consumer electronics we encounter, LSR liquid silicone molding technology is writing exciting new chapters in shaping a better, smarter, and more sustainable future with its exquisite craftsmanship.
FAQ
Are liquid silicone rubber (LSR) injection molded parts durable?
Yes, they are very durable due to their excellent resistance to extreme temperatures, UV radiation, and chemicals.
What are the main applications of liquid silicone injection molding?
LSR is used in medical devices, automotive parts, aerospace applications, and electronics, offering flexibility, durability, and high performance.
How does liquid silicone injection molding benefit the medical device industry?
LSR’s biocompatibility, high precision, and ability to withstand sterilization processes make it ideal for medical device components such as seals, gaskets, and implants.
What are the advantages of using LSR in automotive manufacturing?
LSR’s durability, high-temperature resistance, and lightweight properties make it ideal for seals, gaskets, and insulation components in automotive applications.
Why is liquid silicone injection molding important for aerospace?
LSR’s high tensile strength and resistance to extreme temperatures make it ideal for critical aerospace components such as seals and insulation materials.
Is liquid silicone injection molding environmentally friendly?
Yes, LSR is recyclable and durable, reducing waste and environmental impact, making it a sustainable choice for many industries.
What is the role of liquid silicone injection molding (LSR) in electric vehicle production?
LSR is used to produce lightweight, durable, and heat-resistant parts, contributing to improved efficiency and performance in electric vehicles.
How does automation impact the liquid silicone injection molding market?
Automation improves the efficiency, consistency, and precision of the molding process, reduces costs, and increases production capacity.
Is liquid silicone injection molding environmentally friendly?
Yes, LSR is recyclable and durable, reducing waste and environmental impact, making it a sustainable choice for many industries.
What are the key trends shaping the future of liquid silicone injection molding?
Key trends include advancements in molding technology, increasing automation, and the growing demand for sustainable and environmentally friendly materials.