Technical Manual for Sealing Ring Molds: Design and Process Analysis of Four Core Categories

I Core Requirements for Mold Design

1. Structural Design AdaptabilityMold structures shall be optimized according to the application scenarios of sealing parts. Automotive and hydraulic molds adopt modular design, with core inserts that can be quickly replaced to support the switching of multi-specification products, and the delivery cycle is controlled within 12–20 days; electronic and medical molds adopt split mold cavities and guided demolding mechanisms to avoid molding defects caused by complex structures. All molds shall reserve a shrinkage allowance of 0.02–0.04 mm according to the material shrinkage characteristics to ensure the dimensional accuracy of products.
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5. Precision Control StandardsGuide pillars and guide bushes adopt precision matching with a clearance ≤ 0.003 mm to ensure the coaxiality of mold opening and closing; the dimensional tolerance of mold cavities is divided according to application grades, with precision products controlled within ± 0.005–± 0.01 mm and conventional products within ± 0.03–± 0.06 mm. Precision machining with five-axis machining centers and full-size inspection with three-coordinate measuring machines ensure that the mold precision meets the assembly requirements.
6. Material Adaptation PrinciplesSelect mold steel according to the material characteristics of sealing parts. H13 hot work mold steel is used for general scenarios, with a hardness of HRC 58–60; Cr12MoV tool steel is used for high-pressure and wear-resistant scenarios, and its hardness is increased to HRC 60–62 after cryogenic treatment; S136H steel is used for precision scenarios and undergoes nitriding treatment to extend the mold service life.

II Technical Points of Four Types of Sealing Ring Molds

1. Automotive Sealing Ring MoldsFocusing on the sealing needs of key parts such as engines and gearboxes, they need to withstand a temperature range of -40℃–150℃ and a working pressure of 10–30 MPa. The molds adopt a balanced hot runner system, with the mold temperature fluctuation controlled within ± 1.5℃ to ensure the uniform molding of oil-resistant materials such as EPDM and HNBR. The surface of the mold cavity is polished to below Ra 0.2 μm, the dimensional consistency error of products is ≤ 0.03 mm, and the service life of the mold exceeds 1 million mold cycles, adapting to the large-scale production needs of the automotive industry.
2. Hydraulic Sealing Ring MoldsDesigned for high-pressure working conditions, they can adapt to a working pressure of 0–60 MPa, and the V-type sealing ring molds can withstand a maximum pressure of over 60 MPa. A large gate + multi-exhaust groove structure is adopted, with the width of exhaust grooves controlled at 0.015–0.025 mm to solve the material shortage problem caused by the poor fluidity of materials such as fluororubber. The mold core is nitrided to enhance extrusion resistance, and combined with the retainer ring design, it avoids the deformation and failure of sealing parts under high pressure, with the product qualification rate stably above 94%.
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6. Electronic Sealing Ring MoldsMeeting the requirements of miniaturization and environmental resistance, they can mold precision sealing parts with an inner diameter ≤ 5 mm, and the dimensional tolerance of the mold cavity is controlled within ± 0.005–± 0.01 mm. The mold surface achieves a mirror-level roughness (Ra ≤ 0.15 μm) to reduce demolding resistance and product flash. They are suitable for silicone rubber, fluorosilicone rubber and other materials, can withstand a wide temperature range of -60℃–200℃, have good insulation and aging resistance, and meet the waterproof and dustproof standards of electronic equipment.
7. Medical-Grade Sealing Ring MoldsStrictly complying with the requirements of biocompatibility and clean production, they shall be manufactured in a clean workshop above ISO Class 7 (10,000-class), and molds for implantable products shall be equipped with ISO Class 5 laminar flow hoods. The mold surface adopts a dead-corner-free design, and achieves micron-level precision through electrical discharge machining (EDM), complying with the ISO 10993 biocompatibility standard. Anti-adhesion cavity treatment is adopted, suitable for medical materials such as liquid silicone rubber (LSR), to avoid secondary pollution during the demolding process, and the product cleanliness is verified by ATP fluorescence detection.

III Manufacturing Processes and Quality Control

1. Application of Processing TechnologyFive-axis machining centers are used for the precision machining of mold cavities, and electrical discharge machining is supplemented for key parts to improve surface quality; deep hole drilling technology optimizes cooling channels, and the cooling water channels of automotive and hydraulic molds are designed in a conformal way to ensure uniform heat dissipation. The number of cavities of multi-cavity molds can be configured as 4–24 cavities, and the production efficiency is 4–6 times higher than that of single-cavity molds.
2. Surface Treatment ProcessesSelect treatment methods according to application scenarios: electrolytic polishing is adopted for medical-grade molds to ensure no residue; nitriding treatment is adopted for high-pressure molds to enhance surface hardness; mirror polishing is adopted for electronic molds to improve product appearance precision. The surface roughness of all molds is controlled between Ra 0.15–0.2 μm.
3. Quality Inspection SystemBefore delivery, full-size inspection is carried out with three-coordinate measuring machines, focusing on verifying the cavity size, coaxiality and surface roughness; during the trial mold stage, actual working conditions are simulated to test the compression set rate and sealing performance of sealing parts; additional sterile environment tests are conducted for medical-grade molds to ensure compliance with the use standards of medical equipment.
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IV Technical Development Trends

1. Digital Design UpgradeIntroduce CAE simulation technology to optimize mold structures and predict molding defects in advance; adopt digital twin technology to realize the full life cycle management of molds, improve maintenance efficiency and production stability, and shorten the development cycle of new products.
2. Material Innovation and ApplicationPromote the application of environmentally friendly mold steel and coating technology to reduce environmental pollution in the production process; develop molds suitable for new high-performance sealing materials (such as perfluoroelastomer) to expand the temperature and pressure resistance limits to above 300℃ and 60 MPa.
3. Green Production TransformationOptimize mold structures to reduce material waste, and adopt hot runner systems to reduce energy consumption; use recyclable mold materials and modular design to improve the reuse rate of molds, conforming to the low-carbon development trend of the manufacturing industry.