What is craft?
In a broad sense, craftsmanship refers to the sum of human behaviors in the process of transforming the objective material world, using natural phenomena or objective laws to process and transform the material world to achieve a certain function or achieve a certain effect. From stone tools in the Paleolithic Age to pottery in the Neolithic Age, from exquisite bronze wares in the Bronze Age to smelting technology in the Iron Age, from Eastern alchemy to Western alchemy... crafts have always accompanied and promoted the development and development of human civilization. progress.
The technology we are discussing refers to the processing technology, also called modern technology, which refers to the
The field of human beings scientifically summarizes and regulates the behavior of transforming the material world, so that it has the standardized part of repeatable mass production of highly consistent products, which belongs to a professional subdivision field in the broad category of technology.
According to the construction method and construction purpose, the processing and manufacturing process can be roughly divided into three major categories: forming process, joining process and surface treatment process.
Injection Molding
Injection molding is an injection-cum-molding molding method that is used to process thermoplastics. It is one of the most important processing methods in production because of its ability to produce products with complex structures and precise dimensions, short production cycles and high automation.
Features
It can produce plastic products with complex shapes, precise dimensions and good consistency in one go, one set of molds can be repeatedly constructed to produce the same products in mass production, the products have excellent appearance and adaptability, they can be applied directly or further modified and processed, the mechanical properties are excellent, the corresponding raw materials can be selected according to different application scenarios, the molding cycle time is short, the mold life is long, and the production can be automated or semi-automated to enhance efficiency.
Applicable materials
Almost all thermoplastics can be molded by injection molding.
Process flow
- Preheating of raw material particles.
- Feed the granular or powdery plastic from the hopper of the injection machine into the barrel for heating and melting (if coloring or modification is required, mixing and stirring should be carried out in advance, and granulation treatment is required in the mass production stage to ensure stability) .
- Under the pressure of the plunger or screw, the material is compressed and moved forward, and injected into the closed mold cavity at a lower temperature at a very fast speed through the nozzle in front of the barrel.
- After cooling for a certain period of time, open the mold and take out the product.
Microcellular Foaming Injection Molding
Microcellular Foaming refers to a molding method in which thermoplastic materials are used as the matrix, and the middle layer of the product is densely covered with closed micropores ranging in size from ten to tens of microns, and then the volume expands to fill the mold cavity to complete the shape replication. Micro-foaming injection molding technology has broken through many limitations of traditional injection molding. On the basis of basically ensuring the performance of the product, it can significantly reduce the weight and molding cycle, greatly reduce the clamping force of the machine, and has small internal stress and warpage. High straightness, no shrinkage, stable size, large molding window, etc., especially in the production of high-precision and expensive materials compared with conventional injection molding, it has become an important direction for the development of injection molding technology in recent years.
Two-color injection molding
Two-color injection molding, also known as dual-material injection molding, is a processing method that consists of two plastic melts, such as soft and hard rubber, or different colors of the same material. The similarity with secondary injection molding products is that the local performance, handfeel or color of individual workpiece is different. The difference between the two is that two-color injection molding does not require the removal of the mold, and is done by two separate injection devices that plasticize and inject two different materials in one. The combination strength and aesthetics are better than secondary injection molding, and can be regarded as an upgrade application of secondary injection molding.
Extrusion molding
Extrusion molding, also known as extrusion molding, is a molding method in which the molten polymer material is forced through the head die under pressure by the extrusion of a screw or plunger to form a continuous profile with a constant cross section. It is used in the molding of pipes, trees, plates, sheets, films, monofilaments, flat wires, wire and cable coverings, etc. It can also be used for powder granulation, dyeing, resin blending, etc. Extrusion molding plastic processing industry occupies a fairly important position, currently China's extrusion molding products account for more than 1/3 of the total number of plastic products.
Features
- Low cost of equipment, small footprint, clean production environment.
- simple operation, easy control of the process, and easy to realize continuous automatic production.
- High production efficiency.
- Uniform and dense product quality.
- By changing the head mouth die, it can form products or semi-finished products of various section shapes.
Applicable materials
Most of the thermoplastic materials, such as PVC, PS, ABS, PC, PE, PP, PA, PMMA, PET, PBT, TPE, TPU, etc.
Co-extrusion molding
Coextrusion is a composite molding process that uses several extruders to supply different molten material streams, which are combined in one composite head to obtain multi-layer composite products. It can make multi-layer materials with different characteristics compounded together in the extrusion process, so that the products have the good characteristics of several different materials, and complement each other in performance, so as to obtain special requirements of performance and appearance, such as oxygen and moisture barrier, coloring, heat insulation, thermoforming and thermal bonding ability, as well as strength, stiffness, hardness and other mechanical properties. These multilayer composites with comprehensive performance have extremely wide applications in many fields. Some of the common co-extruded products in our life are PC lampshades, supermarket price tags (two-color co-extrusion), etc.
Blow Molding
Blow molding is one of the most important processing methods for thermoplastics, in which extrusion and injection methods are used to produce tubular blanks, and then compressed air is passed into the cavity of the thermoplastic blanks to expand them into the desired shape of plastic products. The blow molding process began during World War II with the production of low-density polyethylene vials. in the late 1950s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology was widely used. Hollow containers are available in volumes of up to several thousand liters, and some production has been computer controlled.
Applications
Blow molded products are widely used in various industries, especially in beverage and pharmaceutical packaging industry has been a large number of applications, the toy industry is also widely used, such as: blow baby bottles, hollow floating parts, Christmas lampshades, toy yachts, children's learning car accessories and some large toys, such as slide tracks, bases, etc.
Design points
1. Generally speaking, the corners and corners of blow molding products should be made into R transition, because the inflation ratio at the sharp corner is relatively large, which may cause uneven wall thickness, and the sharp corner is also prone to pressure cracking;2. Depending on the requirements of the product, some structural designs for compression, tension and torsion can also be added;
3. In addition, safety and physical tests (pull, twist, throw and
Consideration of stress cracking), while for container products, more attention is paid to pressure resistance, corrosion resistance and good resistance
Permeability requirements.
Molding
Molding (also known as compression molding or compression molding) is the process of placing powdered, granular or fibrous plastics into a mold cavity at molding temperature, then closing the mold and pressurizing it to mold and cure it.
Applicable materials
Almost all polymer materials can be molded by this method. Considering the characteristics of production efficiency, product size and product use, it is mainly used for molding of thermosetting plastics, rubber products and composite materials.
