Injection molds are designed and manufactured according to different product requirements and shapes. Depending on the product type and structure, the injection molding process and mold used are also different. Medical device molds are used to produce medical devices and medical equipment, such as injection molding devices, infusion sets, surgical instruments, etc. Medical device molds require a high degree of precision and sterility to ensure the safety and reliability of the product. The manufacture of medical device molds needs to comply with relevant regulations and standards in the medical industry. Generally, according to different molding methods, plastic processing mold types corresponding to different process requirements can be divided, mainly injection molding molds, extrusion molding molds, blister molding molds, high-foam polystyrene molding medical plastic injection molding, etc.
Main classification of medical plastic injection molds
Medical injection molds are key tools in the manufacture of medical devices. They are characterized by high precision, high quality and high efficiency, and can meet the strict requirements of medical devices for precision and reliability. Therefore, different injection molded parts need to be made with different injection molds to meet different medical product needs. There are many types of medical injection molds that can be used to manufacture medical devices, including injection molding molds, extrusion molding molds, vacuum molding molds, high foam polystyrene molding medical plastic injection molds, etc. The following is a brief description of various commonly used medical product injection molds.
- Medical plastic injection molding: including two types of structural molds: compression molding and injection molding. They are a type of mold mainly used to mold thermosetting plastics, and the corresponding equipment is a pressure molding machine. The compression molding method is based on the characteristics of the plastic, and then the measured compression molding powder is placed in the mold cavity and the feeding chamber, the mold is closed, and the plastic is softened and viscous under high heat and high pressure. After a certain period of time, it is solidified and formed into the desired product shape.
- Plastic extrusion medical injection mold: a type of medical plastic injection molding used to form plastic products of continuous shapes, also known as extrusion molding, is widely used in the processing of pipes, rods, monofilaments, plates, films, profiles, etc. The corresponding equipment is a plastic extruder. Its principle is that solid plastic is melted and plasticized under heating and extruder screw rotation and pressure conditions, and a continuous plastic product with the same cross-section as the die shape is made through a specific shape of the die.
- Plastic blow molding medical injection mold: a mold used to form various packaging containers such as plastic container hollow products (such as medicine bottles). The forms of blow molding mainly include extrusion blow molding hollow molding, injection blow molding hollow molding, injection stretch blow molding hollow molding, multi-layer blow molding hollow molding, sheet blow molding hollow molding, etc.
- Blister medical plastic injection mold: a mold that uses plastic plates and sheets as raw materials to form some simpler plastic products. Its principle is to use vacuum expansion method or compressed air molding method to deform the plastic plates and sheets fixed on the concave or convex mold under heating and softening conditions and stick them to the mold cavity to form the required molded product.
- High foam polystyrene molding medical injection mold: a medical plastic injection molding that uses expandable polystyrene (beaded material composed of polystyrene and foaming agent) raw materials to form various required shapes of foam plastic packaging materials.
Types of medical injection molding processes
Depending on the purpose, medical devices are only allowed to use plastic materials that meet the pharmaceutical method and international ISO13485 quality standards. Only resin materials that have withstood the sterilization and sterilization treatment of ultraviolet irradiation and gamma ray irradiation and passed clinical trials such as human blood coagulation reaction and allergic reaction can be used. Therefore, the types of injection molding processes commonly used in medical products are mainly the following.
- Standard injection molding: This is the most common type of injection molding, used to manufacture a variety of plastic parts and products.
- Two-color injection molding: This process involves injecting two different materials into the same mold to make a single part. This is often used to make parts with multiple colors or to combine different materials with different properties.
- Insert injection molding: This process is to put metal inserts into the same mold to make a single part, most of which are used for connectors.
- Overmolding: This process involves injecting a second material onto a previously molded part to make a finished product. This is often used to create grips, handles, and other functional features on the product.
Plastic injection mold structure and style
Basic structure and composition
Medical injection molds are mainly composed of two parts: the concave mold and the convex mold. The concave mold usually includes a concave mold combination base plate, a concave mold component, and a concave mold combination pallet, while the convex mold includes a convex mold combination base plate, a convex mold component, a convex mold combination pallet, a cavity truncation component, etc. The coordinated changes of these components enable the mold to adapt to the production of plastic products of different shapes and sizes.
Mold style
There are many forms and classification methods of injection molds. According to the installation method on the injection molding machine, it can be divided into mobile (only for vertical injection molding machines) and fixed injection molds; according to the type of injection molding machine used, it can be divided into injection molds for horizontal or vertical injection molding machines and injection molds for angular injection molding machines; according to the number of mold cavities, it can be divided into single-cavity and multi-cavity injection molds; according to the size of the molded product, it can be divided into large, medium and small injection molds. The overall structural characteristics of injection molds are divided into the following types:
- Single parting surface injection mold: Single parting surface injection mold is also called two (double) plate injection mold. It is the simplest and most commonly used standard structural form of injection mold. One part of the cavity is on the movable mold, and the other part is on the fixed mold. For single parting surface injection molds used in horizontal or vertical injection molding machines, the main runner is set on the fixed mold side, and the branch runner is set on the parting surface. After the mold is opened, the product and the runner condensate are left on the movable mold side. The movable mold is provided with an ejector device to eject the product and runner condensate. This mold has a simple structure and reliable operation, and is often used for large box and shell products.
- Double parting surface injection mold: Double parting surface injection mold refers to a mold in which the pouring system and the product are taken out from different parting surfaces, also called a three-plate injection mold. Compared with the single parting surface mold, a movable middle plate (also known as a gate plate) is added. The mold consists of a fixed runner plate, a movable middle plate with a runner or cavity, and a movable mold plate with an ejector device, a core mold and other components. When the mold is opened, the middle plate is separated from the fixed mold plate and the movable mold plate, and the product and the pouring system cold material are taken out from both sides of the middle plate. Therefore, this injection mold has two parallel parting surfaces.
- Injection mold with movable inserts: Due to the special requirements of the product, the mold is provided with a movable threaded core or lateral core and a half slider. When the mold is opened, these parts cannot be simply separated from the product along the mold opening direction. When demolding, they must be moved out of the mold together with the product, and then separated from the product by hand or simple tools. When this movable insert of the mold is installed in the mold, it should be reliably positioned to avoid accidents that cause product scrapping or mold damage.
- Automatic thread removal injection mold: When products with internal or external threads require automatic demolding, a rotatable thread core or ring is provided on the mold. The product is ejected by using the rotation or reciprocating motion of the injection molding machine, or by installing a special prime mover (such as an electric motor, hydraulic motor, etc. and a transmission device to drive the threaded core or ring to rotate.
- Runnerless injection mold: Runnerless injection molds include hot runner or insulated runner injection molds, which use the method of heating or insulating the runner (the condensed plastic outer layer in the runner acts as an insulation for the molten plastic in the center of the runner) to keep the plastic from the nozzle to the gate in a molten state.
- Horizontal parting core-pulling injection mold: When the product has side holes or side recesses , in the automatically operated mold, there is a transverse core pulling mechanism such as an inclined guide column or an inclined slider. When the mold is opened, the mold opening force is used to drive the side core to move horizontally to separate it from the product. There are also oil cylinders or air cylinders installed on the mold to drive the side core to do transverse parting and core pulling.
- An ejector is set on the fixed mold side: Generally, after the injection mold is opened, the product is left on the movable mold side, so the ejector is also set on the movable mold side. However, sometimes due to special requirements or shape restrictions of the product, the product is left on the fixed mold (or may be left on the fixed mold), and an ejector is set on the fixed mold side.
Development Trends
With the continuous advancement of medical technology and changes in market demand, medical injection molds are developing towards higher precision, higher efficiency and more intelligent directions. At the same time, with the application of new materials and new technologies, the performance of medical injection molds will be further improved. Medical injection molds play an important role in the manufacture of medical devices. By continuously optimizing the design and manufacturing process, we can expect more efficient, more precise and safer medical injection molds to bring more innovation and development opportunities to the medical industry.