What are the characteristics of injection molding parts processing for household appliances?
The processing of injection-molded parts of household appliances is a key link in household appliance manufacturing, and its characteristics are centered on the core dimensions such as precision requirements, material adaptation, production efficiency, surface quality and cost control, and at the same time, the functionality, aesthetics and safety of household appliances should be taken into account. The following are the specific features and technical points:
First, high precision and dimensional stability
1. The demand for precision structural parts is outstanding.
Typical components: air conditioning compressor shell, refrigerator drawer guide rail, washing machine clutch gearbox, etc.
Accuracy requirements:
The dimensional tolerance is usually controlled within ±0.05mm (such as hinge hole position of refrigerator door), and the tolerance of key matching parts (such as gear module) can reach 0.02 mm.
Strict form and position tolerance: flatness ≤0.03mm/100mm (such as TV frame) and verticality ≤0.05mm (such as air conditioning panel mounting column).
Technical realization:
Adopt high-precision mold (tolerance ±0.005mm) and servo motor to drive injection molding machine (position control accuracy ±0.1mm), and cooperate with mold temperature machine to accurately control mold temperature (fluctuation ≤ 1℃) to reduce cooling shrinkage deformation.
Case: A brand of drum washing machine inner cylinder injection parts, through CAE mold flow analysis to optimize the gate position, the size pass rate increased from 85% to 99%.
2. Forming of complex geometric structures
Common structure:
Thin-walled parts (thickness ≤0.8mm, such as air conditioning outlet blades), insert injection molded parts (such as electrical switches with metal terminals), and special-shaped holes formed by multi-slider molds (such as steam holes of rice cookers).
Gear parts should ensure the accuracy of tooth profile (ISO 10 or above), and adopt hot runner die to reduce weld marks and improve mechanical properties.
Second, material diversity and functional adaptation
1. General plastics are dominant, and the proportion of engineering plastics is increased.
Key performance requirements for typical applications of material types
The impact strength of ABS TV shell and electric fan base is ≥ 15kJ/m, and the thermal deformation temperature is ≥95℃.
The inner cylinder of PP washing machine and refrigerator drawer are chemical resistant (resistant to detergent corrosion), and the bending modulus is ≥1200MPa.
PC/ABS air conditioning panel and microwave oven door frame have flame retardant rating of UL94 V-0, and the light transmittance is ≥85% (transparent parts).
Wear resistance (abrasion ≤10mg/1000 cycles) and hardness ≥80HRM of POM washing machine gear and air conditioner oscillating blade shaft.
The modified nylon (PA66+30% GF)) rice cooker handle and electric kettle base have heat resistance (HDT≥250℃) and tensile strength ≥180MPa.
2. Application of special functional materials
Antibacterial material: PP/ABS with silver ion or organic antibacterial agent is used for refrigerator liner and kitchen appliance handle, and the antibacterial rate is ≥99% (such as SIAA certification material).
Low VOC material: environmental protection flame retardant ABS is used for household air conditioner injection molding, and VOC emission is ≤ 10μ g/m, which meets the requirements of GB/T 31107-2014 Climate Chamber Method for Detecting Volatile Organic Compounds in Furniture.
Transparent materials: the water level window of electric kettle and humidifier water tank are made of optical grade PMMA (light transmittance ≥91%) or highly transparent PC (impact resistance is better than PMMA).
Third, efficient production and automation integration
1. High-speed injection molding and multi-cavity mold
Production efficiency index:
Small parts (such as remote control buttons) adopt a 16-cavity mold with a cycle time of ≤15 seconds, and the daily production capacity of a single injection molding machine can reach 200,000 pieces.
For large parts (such as the outer box of washing machine), two-plate injection molding machine (clamping force ≥2000 tons) is used, and the mechanical hand is used to pick up the parts, and the cycle time is ≤90 seconds.
Energy-saving technology: compared with the traditional hydraulic system, the servo motor drive system saves energy by 30%-50%, and the standby power is ≤3kW (for example, a brand of all-electric injection molding machine).
2. Automatic production line integration
Typical process:
Feeding (vacuum suction machine) → drying (hopper dryer, temperature 100-120℃, time 4-6 hours) → injection molding → automatic gate removal (manipulator+water cutter device) → inspection (visual inspection system) → packaging (robot palletizing).
Case: The refrigerator drawer production line of an electrical appliance enterprise adopts a one-mold, two-cavity hot runner mold, with six-axis robot picking and on-line laser marking, the production cycle of a single piece is 45 seconds, and the defect rate is ≤0.3%.
Fourth, the surface quality and post-treatment process
1. High requirements for appearance parts
Surface defect control:
Exterior parts such as TV frame and air conditioning panel need to avoid defects such as weld marks, air lines, shrinkage, etc. Mirror effect can be achieved by in-mold decoration (IMD) or high-gloss traceless injection molding (mold surface roughness Ra≤0.05μm).
Color consistency: ΔE≤1.0(CIE Lab standard), and color master batch metering mixing system (accuracy 0.1%) is adopted to reduce batch color difference.
2. Diversified post-treatment processes
Technical characteristics of process type application scenario
UV paint (curing time ≤30 seconds) is used for personalized coloring of sprayed household appliance shells, with film thickness of 15-20μm and hardness ≥2H.
Electroplating decorative parts (such as air conditioning knobs) is environment-friendly chromium-free electroplating, and the salt spray test is ≥48 hours (such as trivalent chromium electroplating).
The accuracy of screen printing/pad printing function marks (such as key characters) is ±0.1mm, and the adhesive force has passed the 3M tape test (100-grid method ≥4B).
Ultrasonic welding split parts assembly (such as humidifier water tank) welding strength ≥80% parent material tensile strength, welding surface dislocation ≤ 0.2 mm.
V. Cost Control and Lightweight Design
1. Material cost optimization
Thin-walled design: Through CAE analysis, the thickness of refrigerator drawer is reduced from 2.5mm to 2.0mm, the material consumption is reduced by 20%, and the rigidity (bending deformation ≤1.5mm) is maintained.
Utilization of recycled materials: 30%-50% recycled ABS is used for non-appearance parts (such as washing machine base), which must meet the mechanical property retention rate of ≥85% and pass RoHS certification.
2. Die life and maintenance
Long-life molds: The life of household appliance molds is usually required to be ≥ 500,000 times (external parts) to 2 million times (structural parts), and H13 mold steel (hardness 52-56HRC) and coating treatment (such as TD coating, surface hardness ≥ 2,500 HV) are adopted.
Intelligent mold management: install mold temperature sensor and pressure sensor, monitor mold state in real time, and reduce downtime by predictive maintenance (for example, the downtime rate of mold failure in an enterprise is reduced from 8% to 2%).
VI. Industry Standards and Certification
Safety certification:
Parts that come into contact with food (such as turntable bracket of microwave oven) must pass FDA or LFGB certification, and the material migration amount is ≤0.1mg/kg.
Flame-retardant components shall conform to UL94 V-0 (such as the power box of household appliances), and the glow wire test shall be ≥750℃(GB/T 5169.21).
Environmental protection requirements:
Prohibited substances: the content of heavy metals such as lead and cadmium is ≤100ppm(RoHS 3.0), and the phthalate plasticizer is ≤0.1%(REACH regulation).
Recyclable design: component materials are clearly marked (such as ISO 11469 plastic classification mark), which is convenient for disassembly and recycling.
summary
Precision, functionalization and high efficiency are the core of the processing of home appliance injection parts, and it is necessary to balance performance, cost and appearance, and at the same time meet the needs of rapid iteration in the home appliance industry (such as shortening the update cycle of smart home products to 6-12 months). Future trends will focus on micro-foam injection molding (10%-30% weight reduction), application of spray-free materials (reducing post-treatment pollution) and digital twin technology (real-time monitoring of mold state), so as to promote the green and intelligent upgrading of the industry.
