What are the Design Requirements for Medical Injection Molds?

The design of medical injection molds must meet multiple requirements, including high precision, biocompatibility, wear resistance, reasonable demolding, advanced processing technology, and strict environmental control. The following is a detailed introduction:

1. High-Precision Design Requirements

Critical Dimension Control: The critical dimensions of medical injection molds must be controlled within an extremely small range. For example, the inner diameter tolerance of the syringe barrel can be controlled within ±0.02mm to ensure accurate injection dosage.

Relationship between Mold Dimensions and Part Dimensions: Mold dimensions can be obtained by adding the shrinkage rate to the part dimensions. Therefore, it is necessary to consider the main factors affecting the shrinkage rate, such as injection pressure, resin temperature, and mold temperature, to ensure that the actual dimensions of the part are within the dimensional tolerances required on the drawing.

Parting Surface Design: The parting surface should be selected so that the part remains in the moving mold during mold opening, facilitating ejection and preventing ejector pin marks from being visible on the exterior surface. Simultaneously, the parting surface should be selected in a location that does not affect the appearance, and any resulting flash should be easily eliminated or trimmed.

2. Biocompatibility Requirements

Mold Material Selection: Mold materials must possess good biocompatibility. For example, commonly used mold steel S136, after special treatment, meets the ISO 10993 biocompatibility standard, effectively preventing adverse reactions in the human body.

Surface Treatment: Mold surface treatment has a significant impact on the quality of medical consumables. Processes such as mirror polishing, nitriding, and hard chrome plating can improve the surface hardness, smoothness, and corrosion resistance of the mold, reduce impurity precipitation, and ensure the safety of medical consumables.

3. Wear Resistance and Lifespan Requirements

Mold Material Wear Resistance: Due to the large-scale production of medical consumables, molds need to withstand prolonged injection pressure and friction. Therefore, mold materials should have high hardness and good wear resistance, such as 718H steel, which can meet the needs of mass production and extend the mold's lifespan.

Mold Structural Rigidity: The mold structure should have sufficient structural rigidity to withstand the high pressure and high temperature during the injection molding process, preventing mold deformation and damage.

4. Reasonable Demolding Design Requirements

Demolding Mechanism Design: Design reasonable demolding mechanisms for medical consumables of different shapes. For products with undercut structures, such as the shells of some medical devices, use demolding methods such as sliders and angled ejectors to ensure smooth demolding without deformation or damage.

Draft Angle: The draft angle of precision injection molded parts is generally small. To prevent deformation, appropriate technical requirements must be set for the demolding area, and the surface roughness of the molded parts in the enveloping portion of the plastic part should be appropriately reduced.

5. Advanced Machining Process Requirements

Ultra-precision Machining Technology: Utilize ultra-precision machining equipment, such as ultra-precision grinders and EDM machines, to ensure the machining accuracy of key mold components. For small medical injection molds, the machining accuracy of the cavity and core can reach ±0.002mm.

Mold Flow Simulation Verification: Verify the mold design using mold flow simulation software, analyze the flow of molten plastic in the mold cavity, identify potential problems, and propose optimization solutions to improve mold quality and efficiency.

6. Strict Environmental Control Requirements

Cleanroom Requirements: Medical injection mold production must be carried out in a clean environment, generally requiring a Class 10,000 or higher cleanroom standard. Air filtration systems and personnel purification facilities are used to control the number of dust particles in the production environment, preventing impurities from contaminating the molds.

Temperature and Humidity Control: Stable temperature and humidity are crucial for mold manufacturing precision. Temperature control at 22±2℃ and humidity control at 45±5%RH can reduce thermal expansion and contraction of the mold materials caused by temperature and humidity changes, ensuring processing accuracy.

Qingdao Xueyu Molding Products Co., Ltd. is mainly engaged in the design and manufacturing of injection molds, injection molding and secondary processing (spraying, pad printing, ultrasonic welding, stamping), etc. For more information about medical injection mold, please contact us.

Website: www.xyzmould.com

Address: No.18 Henan Head Road, Henan Head Community, Jihongtan Street, Qingdao Industrial Park, Shandong Province, China

Email: wangmiaotian8@163.com