Silicone mold structure
A. The upper limit of the mold thickness is tentatively set at 250mm, the size can reach 500X500, and the product can be up to 400X400 in the mold area. The mold structure is generally divided into upper mold, lower mold, bottom plate, top plate, ejector rod, mold core, hinge and other auxiliary parts. When designing silicone products, attention should be paid to the characteristics of its mold and production process.

B. Demoulding: The demoulding of silicone products can be directly and strongly released. For products without design defects, the size requirements for forced release are mainly the ratio of the circumference of the largest part of the mold core to the smallest closing part during demolding. For products below 55°, it can be 2-3 times longer. The parts that require forced demolding are not There may be cracks and sharp corners at the opening. Because vulcanization requires a temperature of 180 degrees Celsius, the demolding work is almost all manual except for the upper and lower separation of the mold itself. Therefore, the convenience and quickness of removal should be considered when designing parts. So as not to affect the vulcanization quality and production efficiency of the parts due to too long demoulding time. Since the mold release method of silicone is mainly manual, the movement stroke of the top plate is also very small, so the silicone mold has no inclined top compared with the plastic mold. Generally, core pulling is not provided.

C. Fixing of the mold core:
Different from plastic molds, the cores of silicone molds are usually removed together with the product parts when the mold is opened and the parts are taken. Therefore, it is more difficult to handle the fixing and accurate positioning of the mold core than the plastic mold, and the rigidity of the mold core is higher. Generally, the mold cores are made together, and all the mold cores are fixed at one time. Or pass the mold core through auxiliary tools to enable it to be positioned quickly. Because there is a lot of pressure during the mold clamping process, it is necessary to strictly prevent the mold core from moving.

D. Core-pulling: Generally, it cannot move automatically, but it can be forced off. Core-pulling is only used for small-sized structures. The setting of core pulling is similar to that of plastic mold, but it is manually taken out when the mold is opened. In addition, the core pulling occupies a relatively large space in the mold, which is not only complicated to process in a silicone mold with more than one mold, but also has a low utilization rate of mold space. So do not pull the core as much as possible.

E. Shape: Silicone products are very tough when the surface is intact, but once there are cracks, the cracks will expand rapidly under the action of external force. In other words, silicone products are very sensitive to cracks. Taking these issues into consideration, attention should be paid to the design of silicone parts: no sharp corners at all positions to avoid cracks due to stress concentration. The R angle at the opening should not be less than 0.5F. Self-demolition: The main function of self-demolition: to accommodate excess rubber; to facilitate mold exhaust; to facilitate trimming of flash. The self-dismantling edge generally consists of a thin edge at the parting surface of the part and the corresponding relatively strong torn edge. The thickness of the thin edge part is generally 0.1~0.2, the thickness of the torn edge part is generally 0.8, and the width is generally 1~2MM.

G. Inserts: Various types of inserts can be placed in silicone products, but several issues should be paid attention to: First, the surface of the embedded parts should be pre-treated, mainly surface vulcanization or surface activation. Otherwise, it will be difficult to connect the insert and the rubber firmly. The second is the fixing and positioning of the insert. It can be fixed in one direction in the vertical direction, but it must be fixed in all directions in other directions. So as not to move the insert during the full mold process. The third is the thickness of the glue around the insert. For parts that are fully encapsulated (all surfaces are encapsulated, so the insert cannot be positioned), at least 0.5mm of glue thickness should be used around the insert. For inserts with positioning, the thickness of the peripheral adhesive layer should be above 0.4mm.