Injection molding and blow molding process is different, blow molding is injection + blowing;Injection molding is injection + pressure;The blow molding must have the head left by the blowing pipe, and the injection molding must have a gate section.
Generally speaking, injection molding is solid core body, blow molding is hollow body, blow molding surface is not flat. Blow molding is blowing.
Injection molding, or thermoplastic injection molding, is to melt the plastic material and inject it into the membrane cavity.Once the molten plastic enters the mold, it is cooled and molded into a certain shape.The resulting shape is often the final product that no longer needs to be processed before it is installed or used as a final product.Many details, such as bulges, ribs, and threads, can be molded in a one-step injection molding process.The injection molding machine has two basic parts: the injection device and the mould device for melting and feeding the plastic into the mold.The function of the mould device is: 1. Make the mold close under the pressure of the injection;2. Take the product out of the injection device and melt it before the plastic injection mold, and then control the pressure and speed to inject the melt into the mold.There are two types of injection devices: screw preplasticizer or two-stage device, and reciprocating screw.The screw type preplasticizer utilizes the preplasticized screw (first stage) to inject the molten plastic into the injection rod (level 2).The advantage of the screw preplasticizer is that the melt quality is constant, high pressure and high speed, and accurate injection quantity control (using the mechanical thrust device at both ends of the piston stroke).These strengths are required for transparency, thin-walled products and high production rates.Its disadvantages include inhomogeneous residence time (resulting in degradation of materials), higher equipment costs and maintenance costs.The most commonly used reciprocating screw injection device does not require a plunger to melt and inject the plastic.
Blow molding: also called hollow blow molding, a rapid development of plastic processing methods.Thermoplastic resin by extrusion or injection molding of plastic parison tube, hot (or heated to softening state), put in split cavity, mold closing immediately after ventilation with compressed air within the parison, make plastic parison swell and clingy wall in the mold, the cooling mold release, the products have all kinds of hollow.Blown film manufacturing technology on the principle and hollow blow molding is very similar, but it does not use the mould, from the perspective of classification of plastics processing technology, molding process is usually included in the extrusion of blown film.The blow molding process was used in the production of low density polyethylene bottles during world war ii.In the late 1950s, with the birth of high density polyethylene and the development of blow molding machine, blow molding technology was widely used.The volume of hollow containers can reach thousands of litres, and some of them have been computerized.It is suitable for blowing plastic with polyethylene, polyvinyl chloride, polypropylene, polyester, etc., and the empty container is widely used as an industrial packaging container.