Lipstick, a small and exquisite object, is highly dependent on an extremely precise mold system for its perfect shape. Although these mold parts are small, they integrate modern material science, precision processing technology and rigorous design. Below we will analyze the core elements of lipstick precision mold parts in depth.
Design: From concept to blueprint
Product requirements definition: Design begins with a deep understanding of the lipstick product itself, including: target shape (pointed bevel, square, special shape, etc.), size (diameter, length), weight (affecting injection volume), rotation structure requirements (rotation smoothness, limit), surface effect (high gloss, matte, texture) and demolding feasibility.
Effect (high gloss, matte, texture) and demolding feasibility.
Structural design:
Core: The inner cavity shape of the lipstick paste. The design needs to consider the demolding slope (usually 0.5°-2°), surface finish requirements, cooling water channel layout, and precise matching with the cavity.
Cavity: The outer surface shape of the lipstick. The design focuses on perfect replication of surface details (logo, texture), high polishing requirements, exhaust groove design (to prevent idle air), and cooling efficiency.
Rotation system: Including thread core, gears, bearings, transmission structure, etc. The design needs to ensure smooth rotation, no jamming, and precise positioning (spin-out/spin-back position).
Ejector system: responsible for ejecting the molded lipstick base (usually a plastic part) out of the mold cavity. It is necessary to design ejectors, push plates, etc. to ensure smooth ejection, no damage, and accurate positioning.
Cooling system: optimize the water channel layout to ensure uniform temperature of the mold core and mold cavity, shorten the molding cycle and reduce deformation.
Casting system: design the flow channel and gate for the molten plastic (lipstick base) to enter the mold cavity, which affects the filling efficiency and appearance quality.
Constraints of material selection on design: The processing performance (such as wire cutting, polishing, etching), heat treatment deformation, wear resistance, etc. of the selected material must be considered during design.
The life of mold accessories directly determines the production cost and efficiency. Lipstick molds are subjected to high temperature plastic melt (180-300°C), high pressure (tens to hundreds of MPa), friction and wear (mold release, rotation), and possible corrosion for a long time. The longest service life (plastic decomposition, mold release agent) is the material selection that needs comprehensive consideration:
- High wear resistance: resists friction and wear between paste and plastic during demoulding and rotation.
- High corrosion resistance: resists erosion by plastic additives, demoulding agents, and environmental moisture.
- High polishability: achieves mirror-grade finish (Ra s0.008 um) to ensure a flawless lipstick surface
- Balance of high hardness and toughness: ensures wear resistance while preventing brittle cracking.
- Good thermal stability: reduces thermal fatigue deformation and maintains dimensional accuracy.
- Excellent processing performance: facilitates precision processing, heat treatment, and polishing.
Material selection for lipstick precision mold accessories.
The “longest life” choice: S136/2083 high-grade stainless steel is undoubtedly the first choice for the pursuit of extreme life. Its perfect combination of corrosion resistance, wear resistance and polishing properties makes it the most durable and stable in the harsh lipstick production environment. NAK80 has an advantage in avoiding heat treatment deformation and has a very long life.
Cost and performance balance: 420 series is a widely used economical choice, and it can also achieve a long service life through good heat treatment and surface treatment. H13 is used on parts that require special emphasis on toughness and thermal fatigue resistance.
Multiplication of coating technology: Regardless of the substrate selected, physical vapor deposition (PVD) or diamond-like carbon coating (DLC) is the key to further extend the life of key components (such as mold cores, thread cores). These ultra-hard, low-friction, highly corrosion-resistant coatings can significantly reduce wear, reduce demolding force, prevent corrosion and sticking, and extend mold life several times.
The cornerstone of precision: strict tolerance requirements
The precision of lipstick molds is reflected in micron-level tolerance control:
Mold core and mold cavity match: This is the key to molding. The matching clearance is usually required to be between 0.005-0.02 mm. Too large a gap will cause flash (burrs); too small a gap will increase friction, accelerate wear and even bite. Accurate temperature expansion compensation calculation is required.
Dimension tolerance: The tolerance of key dimensions such as lipstick paste diameter, length, base size, etc. must be controlled within +0.01-+0.03 mm.
Geometric tolerances: Concentricity, roundness, parallelism, verticality, etc. are extremely demanding, especially in rotating structures and ejection systems, usually within the range of 0.005-0.015 mm.
Rotating structure tolerances: The thread core and nut, gear meshing clearance, etc. need to be precisely controlled (usually 0.01-0.03mm) to ensure smooth rotation without shaking and accurate positioning
Ejector system: The clearance between the ejector and the guide sleeve is extremely small (about 0.005-0.015 mm) to ensure smooth ejection without jamming or scratching.
Standard reference: DINISO 2768-mK or stricter internal enterprise standards are often used.
- Notes: Details throughout the entire process.
Design stage:
Demolding slope: must be sufficient (especially the paste part) to prevent strain and deformation,
Avoid sharp corners: All corners need to be rounded (R angle) to reduce stress concentration, improve material flow and extend mold life.
Balanced cooling: The waterway design must ensure uniform mold temperature to prevent deformation and stress caused by temperature difference.
Sufficient exhaust: Reasonably set the exhaust groove position and depth (usually 0.015-0.03mm deep) to avoid trapped air burning and insufficient filling.
· Material and heat treatment:
Material purity: Select high-quality and pure materials (such as ESR electroslag remelting steel),Reduce internal defects, heat treatment process: strictly control the quenching and tempering process to achieve the target hardness and minimize deformation and residual stress. Cryogenic treatment is sometimes used to improve dimensional stability and wear resistance. - Stress relief: After rough machining, before fine machining, and after EDM, stress relief and surface treatment are required:
- Precision machining: Rely on high-precision CNC machining center (CNC), wire cutting (WEDM
- LS), precision grinder, coordinate grinder.
Conclusion
Lipstick precision mold parts are the crystallization of modern precision manufacturing technology. Its success depends on the pursuit of excellence: precise design guided by product needs; selection of high-performance materials such as S136 and NAK80 supplemented by advanced coatings; implementation of strict micron-level tolerance standards; pursuit of perfection in key processes such as material processing, precision machining (CNC, WEDM-LS) grinding and manual mirror polishing; and implementation of a rigorous attitude of rust prevention, damage prevention, precision assembly and standardized maintenance throughout the entire process.
Only in this way can we forge the precise “behind-the-scenes heroes” who can stably produce hundreds of millions of perfect lipsticks, and show the pinnacle of industrial manufacturing art in a small space. Mold makers need to deeply understand that every micron of precision improvement, every perfect polishing, and every proper heat treatment directly translates into more lasting, more stable, and more economical productivity on the assembly line.
