Secondary molding forming
The secondary forming is one of the plastic molding processing method. With plastic material or parison as raw material, make its external force by heating and a method of the shape of the products needed.
Secondary molding is a the piece, pipe, plate, such as plastic material, heating in a kind of rubber state, deformation by external force and moulding for all kinds of simple shape, then through cooling stereotypes and products. Secondary molding including the hollow blow molding, thermoforming, stretching film forming method, such as only applies to thermoplastic plastic molding. Secondary molding is in a molding on the basis of a method.
Mainly includes the following several forming methods:
thermoforming
Hot forming is a thermoplastic plastic sheet is heated to softening, the gas pressure, liquid pressure or mechanical pressure, using the appropriate tooling or jig and make its products a molding method. Plastic thermoforming method are many, generally can be divided into:
Molding using single mode (male die and female die) or to die, using plus mechanical pressure or weight, to make all kinds of products from sheet forming method, it is different from a processing molding. This method is suitable for all thermoplastics.
Differential pressure molding using single mode (male die and female die) or to die, also don't have to die, in the gas under the action of pressure difference, make the heating to soft plastic sheets with mould surface, cooling is made after forming methods of various kinds of products. Can be divided into the vacuum forming and differential pressure molding pressure molding.
Thermoforming especially suitable for thin wall, large surface area of the products manufacturing. The commonly used plastic varieties have various types of polystyrene, organic glass, PVC, ABS, polyethylene, polypropylene, polyamide, polycarbonate, and polyethylene terephthalate, etc.
Thermoforming equipment including clamping system, heating system, vacuum and compressed air system and forming mould, etc.
Biaxial tensile
To make molecular reorientation of thermoplastic film or plate, etc, especially above the glass transition temperature of the bidirectional tensile process. Stretch orientation to between the glass transition temperature and melting point of polymer, after directional tensile and rapid cooling to room temperature, the film or monofilament, on the drawing direction has a lot to improve mechanical properties.
Suitable for directional stretching of polymer are: polyvinyl chloride (PVC), polyethylene terephthalate, polyvinylidene chloride, poly (methyl methacrylate, polyethylene, polypropylene, polystyrene, and some of the styrene copolymer.
Solid phase forming
Solid phase forming is a thermoplastic material or stock under pressure for products with mold the molding method. In the plastic molding process of molten (softening) under temperature (below the melting point at least 10-20 ℃). Solid phase forming. Including plastic of non-crystalline class above the glass transition temperature, melting point below the high elastic area processing is often called thermoforming, and below the glass transition temperature is called cold forming or room temperature molding processing, also often called cold working methods or room temperature plasticity of plastic processing.
The method has the following advantages: short production cycle; Improve the toughness and strength of products; Simple equipment, can produce large and super large products; Cost reduction. Defect is: hard to produce complex shape, the precision of products; It is difficult to control production process, the products easy to be out of shape, craze.
Solid phase forming include: sheet roll, deep drawing or sheet stamping, hydraulic forming, extrusion, cold stamping, roll forming, etc.