oneLack of glue

Manifesting as loose, pockmarked, or hollow surfaces (in whole or in part) on the surface, the reasons for their occurrence and prevention methods:

（1） Insufficient feeding amount To ensure that each cavity of the product is not lacking in glue, the amount of material used should be accurately determined, the amount of material added should be sufficient, and reflected in the process documents;

（2） The pressure is insufficient and the amount of glue cannot fill the mold cavity. The pressure should be increased appropriately. 

（3） The flowability of the rubber material is too poor . If the product performance allows, the rubber formula can be adjusted to increase plasticity. Appropriately increase the pressure in the process or apply a layer of lubricant such as zinc stearate or silicone oil on the surface of the mold. 

（4） The mold temperature is too high, causing partial burning of the rubber material and reduced fluidity. The mold temperature during loading should be appropriately reduced, but not too much, otherwise the mold temperature will not reach the vulcanization temperature within the specified time and the entire mold material will be scrapped. Silicone rubber can be loaded at lower temperatures. 

（5） The burning time of the rubber material is too short The formula should be improved to enhance the burn resistance of the rubber material.

（6） charge The mold closing speed is too slow, causing scorching, and the operating technique should be improved.

（7） Improper placement of the blank material makes it difficult for the adhesive to fill the mold cavity. 

（8） Unreasonable mold structure can also make it difficult for the rubber material to fill the mold cavity. For narrow products, it should be convenient for the length direction of the product to be perpendicular to the direction of pressure. 

（9）If the pressure is too fast, the rubber material will be extruded out of the mold before filling the cavity, causing the flash to thicken and the product to be short of material Slowing down the pressurization speed means that the rubber material slowly flows into the mold cavity under pressure.

2.Cracking of the mating line

Manifesting as cracking of the product at the joint of the mold after mold opening, sometimes accompanied by internal shrinkage of the flying edge (commonly known as edge pulling), the cause of the occurrence And prevention methods:

（1）Insufficient pressure or pressure fluctuations  Make the pressure inside the rubber mold cavity greater than the vulcanization pressure during the vulcanization process. If the mold slightly expands, causing the product to crack, the pressure or the cause of pressure fluctuations should be checked.

（2）Excessive sulfurization pressure  The rubber material is severely compressed, and when the mold is opened, the pressure drops sharply. The volume of the vulcanized rubber increases, and other parts of the product cannot expand due to the limitations of the mold. However, the mold can freely expand at the joint line. The internal stress caused by uneven expansion can lead to cracking of the joint line. The vulcanization pressure should be adjusted to an appropriate state to prevent excessive or insufficient expansion. If the flash edge thickens after pressure reduction, the feeding amount can be reduced or the flow gel tank can be increased as appropriate. 

（3）High vulcanization temperature and short time  The main reason for the edge pulling of thick products is due to the external vulcanization of the product, which is caused by the adhesive The heat transfer of the material is slow, and the interior is still in an uncured state. If the pressure is reduced and the mold is opened at this time, the active materials in the internal vulcanization reaction will quickly overflow. At the same time, due to the temperature drop, the rubber material will shrink severely (the shrinkage rate is greater than that of fully vulcanized rubber material). These two factors lead to cracking and edge pulling at the mold line, and the vulcanization strip should be adjusted Parts, using low-temperature long-term vulcanization method or staged heating vulcanization method

（4）Local looseness at the mold line and low bonding strength between the adhesive materials are common causes of local cracking at the mold line See reason. There are many reasons that can cause local looseness, such as poor mold fit and excessive leakage of adhesive from gaps, Improper feeding method. Make a certain part of the mating line have an inconspicuous lack of glue; The mold structure is unreasonable (parallel alignment of the mating direction and the pressure direction is a typical unreasonable structure and should be avoided), and the rubber material is too hard. Analyze specific issues and make improvements accordingly.

（5）Slow pressure too late If the surface of the rubber material has already been vulcanized and then slowly pressed, it often causes cracking of the mating line.

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