The various tools and products we use in daily production and life, ranging from the base of machine tools and body shells to as small as a head screw, button and the shell of various household appliances, are all closely related to molds. The shape of the mold determines the appearance of these products, and the processing quality and precision of the mold also determines the quality of these products. Because the materials, appearances, specifications and uses of various products are different, molds are divided into non-plastic molds such as casting molds, forging molds, die-casting molds, and stamping molds, as well as plastic molds.
In recent years, with the rapid development of the plastics industry and the continuous improvement in strength and precision of general and engineering plastics, the application scope of plastic products has also been expanding, such as: household appliances, instruments and meters, construction equipment, automobile industry, In many fields such as daily hardware, the proportion of plastic products is increasing rapidly. A well-designed plastic part can often replace multiple traditional metal parts. There is a growing trend towards the plasticization of industrial and daily products.
General definition of mold: In industrial production, various presses and special tools mounted on the press are used to make parts or products of the required shape from metal or non-metallic materials through pressure. Such special tools are collectively called molds.
Injection molding process description: A mold is a tool for producing plastic products. It consists of several groups of parts with a mold cavity inside. During injection molding, the mold is clamped on the injection molding machine. The molten plastic is injected into the mold cavity and cooled and shaped in the cavity. Then the upper and lower molds are separated. The product is ejected from the mold cavity and away from the mold through the ejection system. Finally, the mold is closed again. For the next injection molding, the entire injection molding process is carried out in a cycle.
It mainly includes a concave mold with a variable cavity composed of a concave mold combination base plate, a concave mold assembly and a concave mold combination card plate. A punch with a variable core composed of side-cut composite panels.
In order to improve the performance of plastics, various auxiliary materials, such as fillers, plasticizers, lubricants, stabilizers, colorants, etc., must be added to the polymer to become a plastic with good performance.
1. Synthetic resin is the main component of plastics, and its content in plastics is generally 40% to 100%. Due to its large content and the properties of the resin often determine the properties of plastic, people often regard resin as a synonym for plastic. For example, polyvinyl chloride resin and polyvinyl chloride plastic, phenolic resin and phenolic plastic are confused. In fact, resin and plastic are two different concepts. Resin is a raw, raw polymer used not only to make plastics, but also as a raw material for coatings, adhesives and synthetic fibers. Except for a very small part of plastics that contain 100% resin, most plastics need to add other substances in addition to the main component resin. 2. Filler Filler is also called filler. It can improve the strength and heat resistance of plastics and reduce costs. For example, adding wood powder to phenolic resin can greatly reduce the cost, making phenolic plastic one of the cheapest plastics, and it can also significantly improve the mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former such as wood powder, rags, paper and various fabric fibers, etc., and the latter such as glass fiber, diatomaceous earth, asbestos, carbon black, etc.
3. Plasticizer can increase the plasticity and softness of plastics, reduce brittleness, and make plastics easier to process and shape. Plasticizers are generally high-boiling organic compounds that are miscible with resin, are non-toxic, odorless, and stable to light and heat. The most commonly used plasticizers are phthalates. For example, when producing polyvinyl chloride plastic, if more plasticizer is added, soft polyvinyl chloride plastic will be obtained. If no or less plasticizer is added (amount <10%), hard polyvinyl chloride plastic will be obtained. .
4. Stabilizer: In order to prevent synthetic resin from being decomposed and damaged by light and heat during processing and use, and to extend its service life, stabilizers must be added to plastics. Commonly used ones include stearate, epoxy resin, etc.
5. Colorants Colorants can make plastics have various bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants.
6. Lubricant: The function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and at the same time, it can make the surface of the plastic smooth and beautiful. Commonly used lubricants include stearic acid and its calcium and magnesium salts. In addition to the above-mentioned additives, flame retardants, foaming agents, antistatic agents, etc. can also be added to plastics.
Molds are basic process equipment in the automotive industry. In automobile production, more than 90% of parts require mold forming. Stamping mold is an indispensable process equipment in stamping production.
Stamping molds are indispensable process equipment for stamping production and are technology-intensive products. The quality, production efficiency and production cost of stamping parts are directly related to the design and manufacturing of molds. The level of mold design and manufacturing technology is one of the important indicators to measure a company’s product manufacturing level. It determines the quality, efficiency and development capabilities of new products to a large extent.
1. Touch test
Wipe the surface of the outer cover with clean gauze. The inspector must wear touch gloves and touch the surface of the stamping part longitudinally. This method of inspection depends on the experience of the inspector. If necessary, you can use a whetstone to polish and inspect the suspicious areas, but this method is a quick and effective one.
2. Oil testing
Wipe the surface of the outer cover with clean gauze. Then use a clean brush to apply the oil evenly to the entire outside surface of the stamping, in the same direction. If the oil-coated stamping parts are placed under strong light, it is recommended that the stamping parts be placed in the position of the valve body. Using this method, it’s easy to spot tiny pits, ponds, and corrugations on the stamping.
3. Flexible gauze polishing
Wipe the surface of the outer cover with clean gauze. The surface of the stamping parts is polished longitudinally with a flexible sand mesh to the entire surface, making it easy to detect any pitting corrosion and indentations.
4. Oil whetstone polishing
1) First clean the surface of the outer cover with clean gauze, then polish it with a whetstone (20×20×100mm or larger), and place it in an arc. The whetstone is relatively small and not easy to wear. (Example: 8×100mm semicircular whetstone)
The choice of particle size depends on surface conditions (such as roughness, galvanizing, etc.). It is recommended to use fine-grained oil stone. The grinding direction of stone is basically longitudinal, which matches well with the surface of stamping parts. Transverse grinding can also be supplemented in some special places.
5. Visual inspection
Visual inspection is mainly used to detect appearance abnormalities and macro defects of stamping parts.
6. Inspection tool inspection
Put the stamping parts into the inspection tool and inspect the stamping parts according to the operating requirements of the inspection tool manual.