The most stringent in the injection blow molding process, the operating conditions of the parison mold to withstand the high injection pressure, Therefore, for the manufacture of the mold, we must carefully choose the right steel, which types of molded plastic and production cycle length is two a more important factor.
For example, high density and low density polyethylene are more prone to processing, because of their low intensity, no pressure, in addition, the flash rarely. Plastics such as polycarbonates casein and other higher strength, higher molding pressure, and therefore easily lead to a bending mold parting line or sub-surface deformation. The first case, you can use a lower strength steel, the latter cases, you must use high-strength steel to resist repeated high-pressure role.
Other important factors to consider in select mold steel mold repair and correction. From the standpoint of mold makers, metal materials processing performance is as important as it can wear the highest finish, also chrome plated to prevent adhesion of the resin and polished. Usually four metal Material: chilled cast iron, mild steel, tool steel of quenched and tempered steel and air broken fire.
(A) chilled cast iron
Chilled cast iron and other metal materials, sufficient to meet short-term production, but can not withstand the continuous pressure to repeated impact. In the past, polyethylene containers parison mold widespread use of chilled cast iron. Easy machining cast iron, to achieve and maintain a good finish, the larger problems of repair and correction of difficulties, because of its poor weldability. In addition, unlike other materials as easy to use, now replaced by other metals.
(B) low carbon steel
Easily processing of hot rolled low carbon steel, commonly used in manufacturing polyethylene mold of the secondary and higher intensity, or manufacturing of blow molding soft plastic mold. Low-carbon steel has excellent processing performance, availability, and maintain a high finish, and easy welding, repair and corrected is convenient. In the actual production, the durability equal to or slightly better than chilled cast iron.
(C) quenched and tempered steel
Quenched and tempered steel (Rockwell hardness of R030) is very suitable for the manufacture of polyolefin plastics (including polypropylene and other hard plastic) in the mold of low, medium intensity. Although it is not like a low-carbon steel processing, quenched and tempered steel processing or convenient it has high compressive strength and durability, sufficient to meet most production needs. It can be easier to obtain and maintain a high finish, and easily welded.
(D) air hardening tool steel
Air the haggard fire tool steel has many types, the most widely used in injection blow mold a household JS] Transport: Its specifications are a variety of types and sizes. It may be the most comprehensive performance of the mold material, but also the most expensive materials. Its characteristics in the hardness RolD processing, and then air quenched to at RO45 an 48. Repair or orthodontic, annealing welding process.Secondary heat treatment, the deformation is small, has needed for the production of high strength and durability, in particular, especially after heat treatment stereotypes. In addition, it prevents the deformation and failure of the mold parting line. To compensate for the polypropylene inherently easy to produce a tendency to flash, high strength steel has been widely used in the processing of polypropylene mold manufacturing.