What should be paid attention to in injection molding of precision rubber and plastic components in medical field?

The core requirements of injection molding of precision rubber and plastic components in the medical field are to meet the standards of medical regulations, ensure the accuracy and consistency of products, control the risk of biocompatibility, and give consideration to the traceability of the production process. The following are key considerations for dimensioning:

First, raw material control: medical grade material selection and compliance

Compliance of material selection

Medical certified rubber and plastic materials, such as medical grade PP, PE, PC, ABS, silica gel, fluororubber, etc., must be selected, and the materials must meet ISO 10993 (biocompatibility), USP Class VI (United States Pharmacopoeia), FDA 21 CFR and other standards.

Avoid using recycled materials or non-medical grade additives. Additives (such as release agent, stabilizer and masterbatch) should meet the requirements of medical grade, and the supplier's material certificate (COA) and compliance report should be provided.

Storage and treatment of raw materials

Raw materials should be stored in partitioned isolation, strictly separated from non-medical materials to prevent cross-contamination; The storage environment should be moisture-proof, dust-proof and light-proof, and the temperature and humidity should be controlled (for example, the humidity of plastic particles should be lower than 0.02%).

Before injection molding, materials should be accurately dried to avoid defects such as bubbles and crazing, and drying parameters (temperature and time) should strictly follow the requirements of material suppliers.

The material batch should be traced back to the whole process, and the incoming batch, consumption and corresponding product batch should be recorded to ensure that problems can be traced back.

Second, mold design and manufacturing: precision and clean orientation

Requirements for high-precision molds

The mold accuracy should be controlled within * * 0.005 ~ 0.01 mm * *, and it should be adapted to the tiny size of medical components (such as catheter connector, valve component and sensor seal). The mold cavity and core should be made of wear-resistant and corrosion-resistant mold steel (such as S136 and H13), and mirror polished (Ra≤0.2μm) to reduce the risk of material residue and bacterial growth.

The mold should be designed with runner and gate without dead angle to avoid weld marks, shrinkage marks and other defects, and the gate position should be far away from the key functional areas of the product; For thin-walled precision parts, it is necessary to optimize the cooling water path to ensure uniform cooling and prevent product deformation.

Clean and pollution prevention design

Anti-sticking treatment (such as hard chromium plating and nitriding treatment) should be done on the surface of the mold to reduce the use of release agent; Mold structure should be easy to disassemble and clean, so as to avoid hiding dirt and accommodating filth.

Equipped with mold state monitoring devices (such as pressure sensors and temperature sensors) to monitor mold temperature and clamping force in real time to ensure the stability of injection molding process.

Third, injection molding process parameters: precise control and stability

Fine control of core parameters

Temperature control: the barrel temperature and nozzle temperature should be set accurately in sections to avoid material degradation (for example, the barrel temperature of medical PC should be controlled at 260 ~ 300℃); Mold temperature needs to be constant (error 1℃), which affects the dimensional stability and surface quality of products.

Pressure and speed: the injection pressure should be adapted to the mold filling requirements of precision parts to prevent flash or under-injection; The injection speed needs to be adjusted in stages to reduce the molecular chain fracture of the material caused by shear stress; Holding pressure and time should be accurately matched to eliminate shrinkage cavity and warpage of products.

Cycle control: strictly control the consistency of injection cycle (error ±0.5s) to ensure that there is no difference in size and performance of each batch of products.

Process verification and curing

Before mass production, process verification (PPAP) is required, and the optimal process parameter window is determined by DOE (experimental design) and solidified into standard operation instruction (SOP). It is forbidden to adjust the parameters at will.

Key process parameters need to be recorded in real time and incorporated into the production traceability system.

Iv. production environment: cleanliness level and pollution prevention and control

Clean workshop requirements

The injection molding of medical precision rubber and plastic components should be carried out in a clean workshop with a class of 10,000 or 100,000 (depending on the use of the product, for example, the class of implanted components should be above 10,000), and the workshop should be equipped with a HEPA to control the number of dust particles and microorganisms.

The workshop needs to maintain a positive pressure environment to prevent external pollutants from entering; The floor, wall and ceiling shall be made of seamless and easy-to-clean materials (such as epoxy resin and stainless steel).

Cleaning of personnel and equipment

Operators should wear sterile anti-static work clothes, masks, gloves and shoe covers, and they should be dusted by air shower before entering the workshop. Personnel shall receive regular health training and health examination.

Injection molding machine, manipulator and other equipment should be made of stainless steel or easy-to-clean materials, and the surface of the equipment should be disinfected regularly; Medical-grade lubricating oil should be used for equipment lubrication to avoid oil pollution to products.

V. Quality inspection and traceability: whole process control

Online and offline detection

On-line inspection: equipped with visual inspection system, real-time inspection of product size and appearance defects (such as flash, lack of materials, bubbles), and automatic elimination of unqualified products.

Off-line inspection: use CMM, projector and other precision equipment to inspect the precision of key dimensions of products; Biocompatibility test (cytotoxicity, sensitization, irritation) and physical properties test (tensile strength, hardness, tightness) were carried out by batch sampling.

Whole process traceability

Establish a batch traceability system, and record the raw material batch, mold number, injection molding machine platform, process parameters, operators, test results, finished product delivery information, etc., to ensure the traceability of the whole product life cycle.

The inspection records and production records shall be kept for at least 2 years after the expiration date of the product, which meets the requirements of document retention in the medical industry.

VI. Compliance and Certification: Meeting regulatory requirements

Production system certification

The factory must pass the ISO 13485 medical device quality management system certification, which is the basic threshold for the production of medical products; For export products, it is necessary to comply with the laws and regulations of the target market (such as US FDA QSR 820 and EU CE MDR).

product certification

The finished products need to apply for corresponding certification according to their uses. For example, the implanted components need to pass FDA 510 (k) or PMA certification and EU CE certification, and a complete process verification report, material compliance report and test report should be provided during the certification process.