Precision fixtures for tire bead forming: PP tire bead pad and triangular rubber shaping disc
In the tire manufacturing process, the bead serves as the "skeleton" that carries the weight of the entire vehicle, and its geometric accuracy directly determines the high-speed safety and uniformity of the tire. In the bonding, shaping, and pre vulcanization buffering process between the steel wire ring and the triangular rubber, the tire bead separator is not only an isolation tool, but also a shaping mold that controls the dimensional accuracy of the semi-finished product. With the development of all steel radial tires towards flattening and low rolling resistance, traditional metal separators are gradually being replaced by PP bead separators (polypropylene bead separators), which form high-precision tooling combinations with triangular rubber shaping discs.
1、 Structural Design and Geometric Accuracy Control
The tire bead separator usually adopts a disc-shaped design, with several precisely designed protrusions distributed on the inner sidewall, and a stepped support structure at the bottom. This non planar multi-point contact design aims to reduce the contact area with uncured triangular rubber. Specific data shows that the optimized protruding structure can reduce the contact area by more than 40%, effectively preventing irregular deformation of the rubber material under gravity and stacking pressure.
The triangular rubber shaping plate used in conjunction focuses more on controlling the curvature. Its working surface has a specific cone angle, usually matching the bead angle of the tire design (30 °~60 °), that is, the angle between the inclined surface of the shaping plate and the horizontal plane is mostly controlled between 15 °~25 °. This precise curvature fitting ensures that the "slender" triangular rubber always adheres tightly to the model during the cooling shrinkage process, avoiding defects such as curling and twisting, and strictly controlling the ovality error of the tire bead within ± 0.5mm.
2、 Physical performance data of PP material
The core reason for choosing PP bead separators is the unique physical properties of polypropylene material. The density of PP is only 0.89~0.91 g/cm ³, which means that the weight of a partition of the same size is only 1/7 of that of an aluminum alloy product. In a tire bead production line with a daily output of 5000 pieces, workers transport thousands of times a day. The lightweight PP material significantly reduces labor intensity and minimizes the risk of work-related injuries.
In terms of heat resistance and mechanical properties, the melting point of PP is as high as 164-176 ℃, and the Vicat softening point can reach 135-145 ℃. Although the temperature of the triangular adhesive is usually between 80-100 ℃, PP material can still maintain dimensional stability and does not soften or collapse in environments close to hot plates or high-temperature workshops in summer. At the same time, the bending modulus of PP is between 1300 and 1500 MPa, which is sufficient to withstand the stacking pressure of up to 50 layers of tire beads, and has excellent resistance to bending fatigue (commonly known as "100 fold rubber"), suitable for frequent grabbing and placement on automated production lines.
3、 Anti sticking mechanism and surface characteristics
Untreated rubber has extremely high self adhesiveness and is prone to adhesion with metals or rough surfaces. The surface energy of the PP bead separator is extremely low (critical surface tension of about 30-33 mN/m), and with the smooth injection molding surface, the rubber peeling force is reduced to below 0.5 N/cm. In addition, PP has extremely low water absorption (24-hour water absorption rate<0.01%), and will not contaminate the rubber material with debris due to moisture like wooden or paper partitions, nor will it produce spots on the surface of the tire bead due to rust like metal partitions.
Changshu Yongchengsheng Hardware Products Co., Ltd. specializes in the production and sales of tire bead separators and PP tire bead pads. If you need them, please contact us at+86-13506249539; Contact email: ljd706627@gmail.com
Welcome to consult, Changshu Yongchengsheng Hardware Products Co., Ltd. will provide you with the most professional answers!
