Packing Molds Application Article: Design and Manufacturing of Special Molds for Foundation Pump Head Housings-News

Packing molds are the core equipment for forming cosmetic packaging components, and their precision and stability directly determine the product's appearance texture, assembly adaptability, and mass production efficiency. As a key packaging component of high-end cosmetics, the foundation pump head housing not only undertakes the functions of protecting the pump body and transmitting pressing force but also needs to have excellent appearance texture, chemical resistance, and structural sealing performance, imposing strict requirements on the mold's forming precision, surface treatment, and detail control. Traditional molds struggle to balance the forming of complex buckle structures and mirror-like appearance requirements, while special packing molds can achieve dual compliance of product performance and aesthetics through optimized design and precision manufacturing. Taking the 30ml foundation pump head housing as the target product, this article elaborates on the application details, technical points, and practical value of packing molds, providing a reference for the development of similar cosmetic packaging molds.

I. Product Characteristics and Core Mold Requirements

The foundation pump head housing focused on in this article has a stepped cylindrical structure with an overall size of Φ28mm×45mm and a main wall thickness of 1.2mm. It integrates a pressing platform on the top, a pump core installation cavity and a snap-fit fixing structure inside, and a sealing groove reserved at the bottom. The appearance surface needs to present a mirror effect without scratches, shrinkage marks, flash, or other defects, and must be compatible with the glass bottle mouth thread, with the assembly gap controlled within 0.05mm. The product is made of food-grade ABS resin, complying with GB 4806.7-2016 "Standards for Cosmetic Contact Materials", featuring excellent alcohol and grease resistance, and no fracture or deformation after more than 1,000 pressing cycles.

The core requirements for the corresponding packing mold are clear: cavity dimensional tolerance of ±0.01mm to ensure the adaptability of key structures such as buckles and sealing grooves; the appearance cavity requires mirror polishing (Ra≤0.15μm) to restore the product's high-gloss texture; multi-cavity design is adopted to improve production capacity while ensuring product consistency among all cavities; a precise gating and cooling system is equipped to avoid appearance defects and deformation; the mold material must be easy to polish, wear-resistant, free of impurity precipitation, and meet the hygiene requirements of cosmetic packaging.

II. Key Design Points of Packing Molds for Pump Head Housings

The mold adopts an overall two-plate structure suitable for horizontal injection molding machines, designed with an 8-cavity symmetrical layout. Each mold cycle can produce 8 pump head housings, balancing mass production and forming precision. The mold material is S136 stainless steel, which is subjected to solution treatment and nitriding treatment to improve polishing performance and service life. The core design points are as follows:

Parting surface and cavity design: The parting surface is set along the maximum contour line of the housing, avoiding key areas such as the pressing platform and sealing groove. A curved parting structure is adopted to reduce the impact of parting line marks on the appearance. The cavity adopts an integral structure, and the internal core is precisely processed according to the pump core installation cavity and buckle structure. A 0.03mm pre-deformation compensation is made at the buckle part to adapt to the shrinkage characteristics of ABS material and avoid assembly jamming. The inner wall of the cavity is mirror-polished, and a 0.05mm draft angle is reserved to ensure smooth demolding of the product without scratching the surface.

Gating and cooling system: A hot runner + submarine gate gating system is adopted, with a main sprue diameter of 8mm and symmetrically distributed branch runners. Each cavity is equipped with an independent hot runner nozzle, with a temperature control accuracy of ±1℃, reducing gate waste and marks and ensuring uniform filling of molten plastic. The cooling system adopts an annular water channel design, fitting the outer wall of the cavity and the inside of the core, with a water channel spacing of 6-8mm. The mold temperature is controlled at 50℃ and precisely regulated by a constant temperature machine to ensure consistent cooling rate of each cavity, shorten the forming cycle to 15s, and avoid product shrinkage marks and deformation.

Ejection and exhaust system: A combined structure of ejector pins and ejector plates is adopted. Ejector pins are evenly distributed on the non-appearance surface of the housing, and the ejector plate is attached to the edge of the bottom sealing groove, ensuring uniform ejection force and avoiding ejection marks on the product surface. Micro exhaust grooves (width 0.02mm, depth 0.01mm) are set at the root of the buckle and the highest point of the cavity to quickly discharge air and molten plastic volatiles in the cavity, prevent air holes and burning defects, and ensure the integrity of the product appearance.

III. Mold Manufacturing Process and Quality Control

The manufacturing of packing molds for pump head housings follows the principle of "high-precision machining + multi-process inspection", with the process flow: material pretreatment → CNC milling → EDM precision machining → mirror polishing → assembly and debugging → mold testing and optimization → finished product acceptance. The whole process is controlled around the dual cores of appearance and precision.

High-precision machining link: After quenching and tempering treatment, S136 steel is processed into cavity and core blanks by 5-axis CNC milling, with a machining accuracy of ±0.003mm, focusing on ensuring the dimensional accuracy of buckles and sealing grooves; EDM (Electrical Discharge Machining) is used to process complex structures inside the buckles, using copper electrodes for discharge forming, reducing the surface roughness to Ra≤0.1μm; Wire cutting is used to process precision parts such as ejector pins and positioning pins to ensure uniform fit gaps of all components without assembly jamming.

Mirror polishing and assembly: A composite process of "mechanical polishing + chemical polishing" is adopted, grinding step by step from 800# abrasive wheel to 12000# polishing paste, finally achieving a mirror effect of Ra≤0.15μm on the inner wall of the cavity with no residual polishing texture. During assembly, an optical projector is used to calibrate the coaxiality of each component, ensuring the ejection mechanism moves smoothly without jamming. Food-grade silica gel is selected for seals to prevent hydraulic oil leakage and product contamination, meeting the hygiene requirements of cosmetic contact.

Mold testing and optimization: A Haitian MA1600/500 injection molding machine is selected for mold testing, with the plasticizing temperature set at 210-230℃, injection pressure at 70-80MPa, holding pressure at 50-60MPa, and cooling time at 15s. After mold testing, a coordinate measuring machine is used to detect key dimensions, and an optical projector is used to check appearance quality. The holding time and mold temperature are adjusted to solve slight shrinkage marks, and the qualified rate of optimized products reaches 99.8% with 100% assembly adaptability.

IV. Application Value and Practical Effects

After the packing mold is put into production, the single-shift output reaches 38,400 pump head housings, doubling the efficiency compared with traditional 4-cavity molds, and reducing the unit product mold sharing cost by 25%, adapting to the mass production demand of 5 million bottles of high-end foundation per year. The mold has excellent stability, with a service life of up to 4 million cycles under normal production conditions, greatly reducing the frequency of mold replacement and production costs.

Practical application verification shows that the pump head housings formed by the mold meet the mirror-like appearance requirements with no obvious defects. After assembly, they fit closely with glass bottles and pump cores, featuring good sealing performance, smooth pressing without jamming, and no discoloration or cracking after 72 hours of alcohol resistance testing. Meanwhile, the mold is suitable for food-grade material forming, and the products can directly meet cosmetic packaging standards without additional grinding, shortening the production chain and helping brands improve product competitiveness.

Conclusion

The design and manufacturing of special packing molds for foundation pump head housings accurately meet the core requirements of the cosmetic industry for packaging aesthetics, precision, and mass production. Through scientific cavity structure design, efficient gating and cooling system configuration, and full-process quality control, the dual compliance of product appearance and performance is successfully achieved. With the upgrading of the cosmetic industry towards high-end and personalized development, packing molds will further optimize structural design and surface treatment processes to adapt to more complex shape and functional requirements, providing core technical support for improving the quality and efficiency of cosmetic packaging.