Custom Injection Molding
The technology of customized injection molding is widely used in various fields such as electronics, automobiles, home appliances, medical equipment, daily necessities, etc. It can produce complex parts and meet diverse needs.
Medical injection molding provides countless advantages and application areas and is a method that can produce durable and reliable medical-grade components that meet standards. So this process is now the preferred procedure for manufacturing the most advanced medical equipment. It is both cost-effective and has excellent accuracy and consistency, and will come in handy when there is a large production volume and a need for high-precision construction.
The application of medical custom injection molding is diverse. Medical suppliers adopt this process because products can easily meet the specified quality and safety standards under this process. In addition, medical injection molding processes play an increasingly important role in the fields of dental X-ray equipment, orthopedics, components and equipment used for drug delivery, laboratory supplies (such as test tubes, beakers, and other containers), surgical instruments and their preparation equipment, as well as the casing of medical and laboratory equipment.
The Advantages of Medical Injection Molding
The medical injection molding process surpasses other similar production processes in the industry. With its smooth and seamless high-precision operation, this process provides many advantages, including:
- Multiple Material Options
The injection molding program is the most widely used process for material selection. Although medical injection reduces the range of injection materials, there are still many materials suitable for manufacturing high-precision medical-grade components.
- Cost Effectiveness
The process of medical injection molding plays an important role in reducing unnecessary injection molding costs through setting methods. Mass production delivery and mass manufacturing help to maximize the quality and quantity level of the process. Therefore, whenever a large number of medical injection components are produced, the injection molding process can reduce the cost of each component to improve cost-effectiveness.
- Durability
The most important requirement for plastics used in injection molding is to have excellent durability. These materials provide excellent strength and outstanding environmental adaptability. Therefore, the products of this process can effectively cope with the negative effects of heat, dullness, and vibration without any cracks or damage. In addition, when they are sterilized in high-pressure sterilizers, they will not yield to high temperatures.
- Excellent Accuracy
In the injection process of the medical device industry, excellent accuracy is essential. Due to the strict tolerance range of its products, every inch, millimeter, or centimeter can affect the entire molding development. In addition, proficient injection equipment must be used to achieve product development with high precision requirements.
- Resistance to Pollutants
The materials used in this production process must be able to resist the invasion of pollutants. Due to not requiring too much disinfection to maintain sterility, this material easily meets the requirements of FDA standards and other regulations.
Materials Selection and Precautions for Medical Injection Molding
The medical injection molding process is very critical, with high precision requirements and a high probability of failure. Therefore, before and during the design, planning, and operation of the program, some factors need to be considered, including but not limited to:
Materials Selected for Medical Injection Molding:
- Polypropylene (PP): Its firmness and durability make it one of the most commonly used plastics in the industry. Polypropylene contains strong chemical bonds and is an excellent material for manufacturing medical devices such as beakers and test tubes.
- Polyethylene (PE): This material is the main component of the thermoplastic industry. It includes many industrial and commercial mechanical components with different levels of stiffness. It has many variants with different durability levels, including LDPE<HDPE and UHMV. UMHV is a part of most hip, leg, and other joint prostheses.
- Polystyrene (PS): This is a type of plastic that is nonelastic and very strong, with almost no elasticity. It is inflexible and exhibits high levels of impact resistance and plasticity. Mainly used for surfaces that are easy to customize, with good dimensional stability and aesthetics.
- Polyether Ether Ketone (PEEK): It is a thermoplastic known for its high performance and excellent mechanical properties. It has extremely strong wear resistance, radiation resistance, traceability, and thermal degradation.
- Organic Silicon: When medical device components require good flexibility, this is the preferred material. Its ability to provide parts with great durability and biocompatibility is unparalleled in the industry. In mass production, it can also withstand and improve cost-effectiveness.
Precautions for Selecting Materials for Medical Injection Molding:
When selecting medical injection molding materials, corresponding materials should be selected based on specific product requirements, such as usage scenarios, liquid types, performance requirements, etc. In addition, attention should be paid to whether the selected materials comply with relevant national standards and regulatory requirements to ensure their biocompatibility and safety. The main requirements include but are not limited to:
- FDA Requirements
For medical component manufacturing, FDA requirements are the highest target standard in all processes. The regulations for sterility and cleanliness are very strict and need to be strictly followed. At all stages of production, ensure that material selection and other inputs meet or exceed specified standards. For medical-level certification, factories must pass the standards in the components and production process.
- Withstand the Sterilization Process
The sterilization process is the minimum requirement for medical products, but it is a very important mandatory requirement. All shell equipment, facilities, or equipment components that come into contact with the human body must be pollution-resistant. They should also withstand the disinfection process without being damaged.
- Operating Environment
The ability to withstand adverse conditions is a key consideration for plastic molding materials. They must be reliable and durable when subjected to heat, corrosion, liquids, vibration, and other human movements. Most of the plastics used in this process stand out in this requirement.
- Durability and Strength
To avoid or minimize biological hazards in the medical field in manufacturing equipment, plastics that are too brittle or fragile should not be chosen. Therefore, each selected material should have satisfactory durability indicators before being put into use. More importantly, they should be able to exhibit high levels of tensile strength and toughness.
- General Use
Always consider the usage area and purpose of the material before making a selection. For example, disposable materials such as syringes, needles, pipes, and connectors should be transparent, flexible, and easy to disinfect. Similarly, the manufacturing of surgical injection components should be lightweight and ergonomic.
- High Biocompatibility
Medical injection materials should meet biocompatibility standards that are non-toxic, nonirritating, nonmutagenic, and nonallergenic to the human body.
Common Technical Types of Medical Injection Molding
- Thin Wall Forming
Thin wall molding is one of the most common processes in plastic injection molding in the medical device industry. It is used to produce tools or effects that involve functionality and patient comfort. The wall of the injection component of medical devices is much thinner compared to other complete components. The wall is usually thinner than 1 millimeter. The equipment produced using this injection molding type includes wearable devices, surgical tools, and catheter ablation tools.
- Gas Assisted Injection Molding
This is a more complex type of molding. In design, manufacturing tools with sharp corners are not suitable for gas-assisted injection molding methods with thicker parts, as if the gas does not flow in a straight line, the pressure will decrease. However, this molding method is more suitable for producing complex parts. Dry or solidify slower towards thinner walls. The reason is that there is not enough pressure to properly package the resin and make it uniform.
- Metal Injection Molding
The use of metal injection molding in medical device manufacturing is also a key process technology. The reason is that metal equipment plays an important role in equipment that requires high density, small size, and mobility. This does not diminish or diminish the many uses and advantages of traditional 3D printing, medical plastic molding, or gas-assisted molding.
- Liquid Silicone Injection Molding
Liquid silicone injection molding is usually most suitable for producing medical devices that are difficult to maintain hygiene, such as tubes and breathing masks. The characteristic of silicone not reacting with biological tissues makes it more suitable for safe implantation. However, this injection molding process requires many steps and is more complex. If the expected performance of the obtained silicone product is high, the liquid silicone molding method is chosen.
The Steps of Medical Injection Molding
Preparation before Medical Injection Molding:
To ensure the smooth progress of medical injection molding and the quality of medical device products, a series of preparatory work such as raw material pretreatment, cleaning machine barrels, preheating inserts, and selecting release agents are required before production.
Medical Injection molding Processing:
The injection process generally includes key punching feeding – plasticization – injection – cooling – demolding.
Feeding: As injection molding is an intermittent cycle process, quantitative (constant volume) feeding is required to ensure stable operation, uniform plastic plasticization, and ultimately obtain high-quality and measurable plastic parts.
Plasticization: The process in which a molded material undergoes continuous heating, compaction, and mixing within the barrel of an injection molding machine, transforming from a loose powder or granular solid to a continuous homogenized melt.
Injection: Starting from the measuring position inside the barrel, the plunger or screw applies high pressure through the injection cylinder and piston to quickly feed the plasticized plastic melt into the closed mold cavity through the nozzle at the front end of the barrel and the pouring system in the mold. Injection can be further divided into three stages: flow molding, pressure holding and contraction, and backflow.
Cooling: When the plastic in the pouring system has frozen, it is no longer necessary to continue to maintain pressure. Therefore, the plunger or screw can be returned to remove the pressure of the plastic melt in the barrel, and new material can be added. At the same time, cooling media such as cooling water, oil, or air are introduced into the mold to further cool the mold. This stage is called cooling after the gate is frozen. The cooling process from mold filling, and pressure holding to demolding begins with the injection of plastic melt into the mold cavity, which includes:
Demolding: The plastic part can be cooled to a certain temperature to open the mold, and under the action of the ejection mechanism, the plastic part is pushed out of the mold.
Medical Injection Molding:
It refers to a model with a certain shape, which is formed by injecting molten plastic into the mold cavity through pressure. The process principle is to melt the solid plastic at a certain melting point, inject it into the mold at a certain speed through the pressure of the injection machine, and the mold solidifies the plastic through a water channel to obtain a product that matches the design mold cavity. Mainly used for the molding of thermoplastic materials, it can also be used for the molding of thermosetting plastics.
Demolding and Subsequent Processing:
Remove the product from the mold. Remove burrs from the product, and perform surface treatment and repair to improve the appearance quality, and performance of the product. And conduct strict quality testing on the size, accuracy, and other aspects of the finished product.
Medical injection molding is a complex and precise process that involves multiple critical steps. Through precise mold design, high-quality material selection, and strict quality control, medical injection molding products that meet the strict standards of the medical industry can be ensured to be developed and produced.
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