Design of Ventilation System for TWS Earphone Housing Plastic Mold
2026-05-26 13:59:24
Plastic Mold
TWS earphone housings are small precision plastic parts with thin wall thickness, complex structure and high appearance requirements. During the injection molding process, gas entrapment in the cavity can easily cause defects such as burns, gas lines, incomplete filling and weld lines, which seriously affect product quality and yield. Therefore, the design of the mold ventilation system is particularly critical.
Characteristics of TWS Earphone Housing and Ventilation RequirementsTWS earphone housings are usually made of ABS, PC/ABS or high-gloss PC materials, with a wall thickness of 0.8 to 1.2 mm, belonging to typical thin-walled parts. The product structure is complex, with many small holes, grooves, buttons and charging interface positions, and the melt flow path is long and narrow. The appearance requires a mirror finish without any surface defects, which puts forward high requirements on the mold ventilation system. The key ventilation areas include the melt flow ends, weld line positions, deep ribs, small holes and thin-wall corners. Poor ventilation in these areas will lead to gas entrapment and various defects.
Types and Design Principles of Mold Ventilation StructuresParting Surface Ventilation
The parting surface is the most common and convenient ventilation position. Segmented exhaust grooves are set along the outline of the earphone housing, especially at the melt flow ends and weld line positions. The depth of the exhaust grooves for ABS and PC/ABS materials is generally controlled at 0.01 to 0.015 mm to ensure that gas can be discharged smoothly without causing flash. The width of the exhaust grooves is 5 to 10 mm, and they are connected to the atmosphere through a 0.5 to 1 mm deep expansion groove to facilitate gas discharge. The exhaust grooves should be continuous and unobstructed, avoiding dead ends.
Insert and Core Pin Ventilation
For small holes, deep ribs and blind hole positions that are difficult to ventilate on the parting surface, ventilation can be achieved through the gaps between inserts and core pins. The fit clearance between the insert and the mold plate is controlled at 0.005 to 0.01 mm to form a ventilation channel. For deep rib positions, a venting insert with a clearance of 0.01 mm can be used to guide the gas to the outside. The fit clearance of core pins is also an important ventilation channel, and the surface of the core pin should be kept clean to avoid blocking the ventilation gap due to carbon deposits or dirt.
Ejector Pin VentilationThe ejector pin clearance can be used as an auxiliary ventilation channel, especially for products with multiple ejector pins. The fit clearance between the ejector pin and the mold plate is controlled at 0.005 to 0.01 mm to allow gas to escape. For products with large ejector pin spacing, additional ejector pins can be added at the gas entrapment position to improve ventilation. The ejector pin should be designed with a ventilation slot or a step structure to enhance the ventilation effect.
Breathable Steel VentilationFor complex structures such as narrow grooves and dead corners where other ventilation methods are difficult to implement, breathable steel can be used. Breathable steel has a large number of tiny pores, which can allow gas to pass through while preventing melt from leaking. It is suitable for gas entrapment positions in small earphone housings. The breathable steel is embedded in the mold at the gas entrapment position, and its surface is flush with the mold surface. The use of breathable steel should pay attention to regular cleaning to avoid blockage caused by dirt.
Key Points of Ventilation System Design for TWS Earphone Housing MoldComprehensive Ventilation LayoutAccording to the melt flow simulation results, predict the gas entrapment positions and design a comprehensive ventilation system. Combine parting surface ventilation, insert ventilation, ejector pin ventilation and breathable steel ventilation to ensure that all gas entrapment positions have effective ventilation channels. The ventilation system should be designed before mold manufacturing, and the exhaust grooves should be reserved during the mold processing stage to avoid modifying the mold later.
Control of Ventilation Groove Size
The depth of the exhaust groove is the key to balancing ventilation and flash. For ABS and PC/ABS materials, the depth of the main exhaust groove is 0.01 to 0.015 mm, and the expansion groove depth is 0.5 to 1 mm. The width of the exhaust groove is set according to the size of the product, generally 5 to 10 mm, and the spacing between exhaust grooves is 20 to 30 mm. For gas entrapment positions at the melt flow end, the exhaust groove should be widened and deepened appropriately to improve the ventilation effect.
Ventilation of Weld Line Positions
Weld line positions are prone to gas entrapment, which will lead to weak weld lines and surface defects. Exhaust grooves should be set at the weld line positions to guide the gas to escape. The exhaust grooves can be designed in a fan shape to increase the ventilation area. For products with multiple weld lines, the ventilation effect of each weld line position should be checked to ensure that the gas is completely discharged.
Cleaning and Maintenance of Ventilation SystemDuring production, the exhaust grooves are easily blocked by carbon deposits, dirt and decomposition products of the material, which will reduce the ventilation effect. Therefore, the ventilation system should be cleaned regularly, usually once a day or once a shift. The exhaust grooves can be cleaned with a copper brush or compressed air, and the breathable steel can be cleaned with ultrasonic cleaning equipment. For molds that are not used for a long time, the ventilation system should be kept dry and rust-proof.
Verification and Optimization of Ventilation EffectAfter the mold is manufactured, the ventilation effect should be verified through trial runs. Observe whether there are burns, gas lines, incomplete filling and other defects on the product. If defects occur, the exhaust grooves can be appropriately deepened or widened, or additional ventilation structures can be added at the gas entrapment position. The ventilation effect can also be verified by pressure sensors installed in the mold to monitor the pressure change in the cavity during filling and adjust the ventilation system accordingly.
SummaryThe design of the ventilation system is a key part of the TWS earphone housing mold design, which directly affects the product quality and production efficiency. A comprehensive and reasonable ventilation system design can effectively eliminate gas entrapment defects and ensure the appearance and performance of the product. In actual production, the ventilation system should be designed according to the product structure, material characteristics and melt flow simulation results, and verified and optimized through trial runs. At the same time, regular cleaning and maintenance of the ventilation system are required to ensure long-term stable ventilation effect.
