Views:3 Author:Site Editor Publish Time: 2021-08-31 Origin:Site
The processing and use of plastic molding machines is an engineering technology that involves various processes that transform plastics into plastic products. During the transformation process, one or more of the following situations often occur, such as the rheology of the polymer and changes in physical and chemical properties.
1. Press molding
The main equipment used for compression molding is a press and a mold. The most frequently used presses are self-contained hydraulic presses with tonnage ranging from tens of tons to hundreds of tons. There are down-pressing presses and up-pressing presses. The molds used for compression molding are called compression molds, which are divided into three categories; overflow molds, semi-flush molds, and non-overflow molds. The main advantage of compression molding is that it can mold larger flat products and can be mass-produced. Its disadvantages are long production cycle and low efficiency.
2. Injection molding
Laminate molding is usually operated by a laminator, which is equipped with a multi-layer floating hot plate between the dynamic pressure plate and the fixed pressure plate. The commonly used reinforcement materials for lamination are cotton cloth, glass cloth, paper, asbestos cloth, etc. The resins include phenolic, epoxy, unsaturated polyester and some thermoplastic resins. Injection blow molding, extrusion blow molding, stretch blown film coating, hot melt deposition, fluidized spraying, flame spraying, electrostatic spraying, plasma spraying.
3. Extrusion molding
Extrusion molding is also called extrusion molding or extrusion molding. It is a method in which materials are continuously passed through a die in a flowing state by heating and pressing in an extruder. The extrusion method is mainly used for the molding of thermoplastics, and can also be used for some thermosetting plastics. The extruded products are all continuous profiles, such as tubes, rods, wire sheets, films, wire and cable coatings, etc. In addition, it can also be used for mixing, plasticizing, granulating, coloring, blending, etc. of plastics. The extrusion molding machine is composed of extrusion device, transmission mechanism, heating and cooling system and other main parts. There are two types of extruders: screw type (single screw and multi-screw) and plunger type. The extrusion process of the former is continuous, and the latter is intermittent. The basic structure of single screw extruder mainly includes transmission device, feeding device, barrel, screw, head and die. The auxiliary equipment of the extruder includes three types of material pre-processing equipment (such as material conveying and drying), extrudate processing equipment (formation, cooling, traction, cutting or roll) and production condition control equipment.
Pultrusion is one of the molding methods of thermosetting fiber reinforced plastics. It is used to produce profiles with a fixed section shape and unlimited length. The molding process is to pull out the continuous fiber impregnated with resin glue through a heating die, and then further solidify the resin through a heating chamber to prepare a unidirectional high-strength continuous reinforced plastic profile.
There are three types of resins commonly used for pultrusion: unsaturated polyester, epoxy and silicone. Among them, unsaturated polyester resins are used most. The pultrusion machine is usually composed of fiber arrangement device, resin tank, preforming device, die and heating device, traction device and cutting equipment.