What should be paid attention to in the production and processing of precision rubber and plastic components and their extended products?

The production and processing of precision rubber-plastic components and their extended products should be carried out around four core dimensions, namely, material characteristics, process accuracy, environmental control and quality inspection, covering the whole process from raw material preparation to finished product delivery. The specific precautions are as follows:

Raw material pretreatment and control

Drying treatment: Engineering plastics (such as PA, PBT and LCP) are easy to absorb moisture. Before processing, they need to be dried by a dehumidifier, and the moisture content should be strictly controlled (for example, the moisture content of PA should be ≤0.2%), otherwise, bubbles, crazing and mechanical properties of the products will be reduced. Rubber raw materials need to be plasticated in advance to ensure uniform hardness, and compounding agents (vulcanizing agent, reinforcing agent and antioxidant) need to be accurately matched according to the formula, so as to avoid impurities from mixing.

Batch management: There are differences in melting index and hardness of different batches of raw materials, so they need to be stored separately and processed separately, and the identification should be traced to prevent product performance fluctuations caused by mixed use.

Environmental compliance: Give priority to raw materials meeting RoHS, REACH, FDA and other standards, especially products in medical, food and electronic fields, and avoid harmful substance residues.

Precise control of molding process

Injection molding process: For precision rubber and plastic components, it is necessary to control injection pressure (usually 80–150 MPa), shooting speed, holding time and mold temperature to ensure that the rubber compound fully fills the cavity and avoid lack of rubber, shrinkage and deformation. The tolerance of the mold cavity should be controlled within ±0.005-±0.01mm, the parting surface should be closely fitted, and the depth of the exhaust groove should be ≤0.02mm to prevent flash and bubbles.

Vulcanization process: Vulcanization of rubber products should strictly follow the three elements of "temperature-pressure-time", and the parameters of different rubber types are significantly different (for example, the vulcanization temperature of NBR is 150-160℃ and FKM is 170-180℃), so as to avoid under-vulcanization (lack of elasticity) or over-vulcanization (increase of hardness and brittleness). Pressure should be applied evenly during molding vulcanization to prevent uneven thickness of products.

Extrusion and encapsulation process: the extruded products need to control the matching of screw speed and traction speed to ensure the stability of cross-section size; The surface of metal insert (degreasing, sand blasting and primer coating) should be treated for rubber-coated products to improve the bonding strength between rubber and metal and prevent peeling.

Production environment and equipment maintenance

Cleanliness control: electronic and medical precision components need to be produced in a class 10,000/class 100,000 clean workshop, so as to control dust and static electricity, and avoid particle impurities from adhering to the surface of products and affecting sealing or insulation performance. The temperature and humidity in the workshop should be stable (temperature 20-25℃, humidity 40%-60%) to prevent moisture absorption of raw materials or deformation of products.

Equipment precision maintenance: regularly calibrate the pressure sensor and temperature control system of injection molding machine and vulcanizer, and regularly polish and clean the mold cavity to prevent product size deviation caused by wear. Equipment should be equipped with anti-static devices to avoid electrostatic damage to electronic products.

Post-treatment process specification operation

Trimming and shaping: Freeze trimming or laser trimming is preferred for precision products to avoid mechanical trimming scratching the lip and sealing surface; Deformed products need to be shaped by special fixture to eliminate internal stress.

Cleaning and drying: use ultrasonic cleaning+neutral cleaning agent to remove surface oil stain and release agent, and dry at low temperature (40-60℃) to avoid rubber aging and plastic discoloration caused by high temperature.

Surface treatment: coating (such as lubricating coating and anti-static coating) and plasma treatment are carried out as required to improve the wear resistance, sealing or adhesion of products, and the coating adhesion should be tested after treatment.

Whole process quality inspection

On-line inspection: monitor the product size (using two-dimensional and three-dimensional measuring instruments) and weight in real time during the production process, and adjust the process parameters in time; Rubber products should be tested for hardness (Shore A/D), tensile strength and elongation at break.

Performance test: The sealing performance (water pressure/air pressure test), temperature resistance, medium resistance (oil, acid and alkali) and aging performance of finished products shall be sampled by batches to ensure that the requirements of working conditions are met.

Traceability system: establish production batch files, record raw material batches, process parameters and test data, so as to facilitate the traceability of quality problems.

Packaging and storage

Packaging protection: precision products are packaged independently in antistatic bags and blister boxes to avoid collision and friction scratches; Deformable products need to be fixed by setting fixture.

Storage conditions: Store in a dry, dark and ventilated environment at normal temperature, away from heat sources, oil stains and chemical solvents. The storage period of rubber products generally does not exceed 6 months, following the principle of "first in, first out".