Rubber Bushing is one of the most widely used and abundant rubber shock absorber in automobiles. Usually the rubber bushing with inner and outer metal sleeves can be divided into the following categories according to the manufacturing method and characteristics: 1. inner and outer bushing bonding type. 2. inner bushing bonding and outer bushing pressing type. 3. both inner and outer bushing pressing type. The durability of the bushing can be improved effectively by reducing the diameter of certain amount of radial compression for the bushing with both inner and outer bushing bonding types.

Keywords：rubber bushing, shock absorber

How does the shrinkage process improve the durability?

Rubber bushing with both inner sleeve and the outer sleeve bonded to rubber, after vulcanization, the rubber cools and shrinks. The rubber is firmly bonded to the inner sleeve and the outer sleeve. There is no shrinkage space for the rubber to shrink, and tensile stress will be generated between the molecules. The rubber bushing bears external forces during operation, so the stretched state on one side is relaxed, and the stretched state on the other side increases. When the tensile stress between molecules exceeds the strength of the rubber itself, cracks will appear inside the rubber bushing, which will cause early damage to the product. 

If the outer tube is radially compressed after the bushing is vulcanized, a pre-existing stress will be generated between the rubber molecules. When the rubber bush bears an external load during operation, the stress on one side will increase, while the stress on the other side will decrease or return to a free state. Thereby increasing the durability of the product.

What kind of shrinkage processes for production?

Straight cylinder shrink process

Extrude the product from a hole smaller than the outer diameter of the product to achieve radial compression of the outer diameter of the bush.

Advantage: it’s fast and efficient. The appearance of product is well protected. Disadvantage: the shrinkage is small at a time. Products with large diameter reductions need to be reduced in multiple times, which is easy to produce noise during production.

Elastic chuck type shrink process

Put the bush into the elastic chuck, through the radial compression of the elastic chuck to achieve radial compression of the outer diameter of the bush.