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Processing steps of plastic products

Update:17 Oct 2019

Plastic processing is also known as plastic molding. It […]

Plastic processing is also known as plastic molding. It is a general term for various processes for converting synthetic resins or plastics into plastic products and is a large production department in the plastics industry. Plastic processing generally includes the formulation, molding, machining, joining, modification and assembly of plastics. The latter four processes are carried out after the plastic has been formed into a product or a semi-finished product, also known as plastic secondary processing.

Raw materials used in plastic processing, in addition to polymers, generally add various plastic additives, such as stabilizers, plasticizers, colorants, lubricants, reinforcing agents and fillers, to improve the molding process and product performance. Or reduce the cost of the product.

The key part of plastic processing is molding. Various forms of plastics, such as powders, pellets, solutions, dispersions, etc., are formed into articles or blanks of the desired shape. There are more than thirty methods of forming, and its choice depends mainly on the type of plastic, thermoplastic or thermosetting; the starting form and the shape and size of the product.

Commonly used methods for processing thermoplastics include extrusion, injection molding, calendering, blow molding, and thermoforming. The processing of thermosetting plastics is generally carried out by molding, transfer molding, and injection molding.

Machining is the use of metal and wood processing methods to produce plastic products of very precise or small quantities. It can also be used as an auxiliary process for forming, such as sawing of extruded profiles. Because the properties of plastic are different from those of metal and wood, the thermal conductivity of plastic is poor, the coefficient of thermal expansion and the modulus of elasticity are low. When the clamp or tool is too pressurized, it is easy to cause deformation, it is easily melted by heat during cutting, and it is easy to adhere to the tool. on.

Therefore, when the plastic is machined, the tools used and the corresponding cutting speeds must be adapted to the plastic characteristics. Commonly used mechanical processing methods include sawing, shearing, punching, turning, planing, drilling, grinding, polishing, and threading.

Joining is the joining of plastic parts into welding and bonding. The welding method is hot air welding using electrodes, hot melt welding using hot poles, and high frequency welding, friction welding, induction welding, ultrasonic welding, and the like. The bonding method can be classified into a flux, a resin solution, and a hot melt adhesive according to the adhesive used.

The purpose of surface modification is to beautify the surface of plastic products, usually including mechanical modification, that is, using enamel, grinding, polishing and other processes to remove burrs, burrs, and size corrections on the parts; finishing, including coating the surface of the parts with paint, Use a solvent to brighten the surface, apply a patterned film to the surface of the product, etc.; apply color, including painting, printing and hot stamping; metal plating, including vacuum coating, electroplating, and chemical silver plating.

The hot stamping is to transfer the colored aluminum foil layer (or other film layer) on the hot stamping film to the workpiece under heating and pressure. Many household appliances, building products, daily necessities, etc., use this method to obtain patterns such as metallic luster or wood grain.

The assembly uses bonding, welding, and mechanical joining to assemble the finished plastic parts into a complete product. For example: plastic profiles are assembled into plastic window frames and plastic doors through steps such as sawing, welding and drilling.