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Classification and design of plastic molds
2021-08-20
Main categories:
According to the different molding methods, the types of plastic processing molds corresponding to different process requirements can be divided, mainly including injection molding molds, extrusion molding molds, blister molding molds, high-foamed polystyrene molding molds, etc.
1. Plastic injection (plastic) mold
It is mainly a molding mold that is most commonly used in the production of thermoplastic products. The corresponding processing equipment for plastic injection molds is a plastic injection molding machine. The plastic is first heated and melted in the heating cylinder at the bottom of the injection machine, and then melted in the screw of the injection machine. Or driven by the plunger, it enters the mold cavity through the nozzle of the injection machine and the pouring system of the mold, the plastic is cooled and hardened to form, and the product is demolded. Its structure is usually composed of molding parts, pouring system, guide parts, push-out mechanism, temperature control system, exhaust system, support parts and other parts. Manufacturing materials usually use plastic mold steel modules, and the commonly used materials are mainly carbon structural steel, carbon tool steel, alloy tool steel, high-speed steel, etc. The injection molding processing method is usually only suitable for the production of thermoplastic products. The plastic products produced by the injection molding process are very wide. From daily necessities to various complex machinery, electrical appliances, and transportation parts, they are all molded by injection molds. It is the most widely used processing method in the production of plastic products.
2. Plastic compression mould
It includes two structural mold types: compression molding and injection molding. They are a type of molds mainly used to form thermosetting plastics, and their corresponding equipment is a pressure forming machine. According to the characteristics of the plastic, the compression molding method heats the mold to the molding temperature (generally 103°—108°), then puts the measured compression powder into the mold cavity and the feeding chamber, and closes the mold. The plastic is under high heat and high pressure. It is a softened viscous flow, solidified and shaped into the desired product shape after a certain period of time. The difference between injection molding and compression molding is that there is a separate feeding chamber. The mold is closed before molding. The plastic is preheated in the feeding chamber and is in a viscous flow state. It is adjusted and squeezed into the mold cavity under pressure to harden and form. Compression molds are also used to form some special thermoplastics, such as hard-to-melt thermoplastics (such as polyvinyl fluoride) blanks (cold forming), resin lenses with high optical performance, slightly foamed nitrocellulose car steering wheels, etc. . The compression mold is mainly composed of a cavity, a feeding cavity, a guiding mechanism, an ejecting part, a heating system, etc. Injection molds are widely used for packaging electrical components. The material used in the manufacture of compression molds is basically the same as that of injection molds.
3. Plastic extrusion mould
A type of mold used to mold and produce continuous-shaped plastic products, also called extrusion molding heads, is widely used in the processing of pipes, rods, monofilaments, plates, films, wire and cable coatings, profiled materials, etc. The corresponding production equipment is a plastic extruder. The principle is that the solid plastic is melted and plasticized under the conditions of heating and the screw of the extruder to rotate and pressurize, and the cross-section is the same as the shape of the die through a specific shape of the die. Continuous plastic products. Its manufacturing materials mainly include carbon structural steel, alloy tools, etc. Some extrusion dies will also be inlaid with wear-resistant materials such as diamond on the parts that need to be wear-resistant. The extrusion process is usually only suitable for the production of thermoplastic products, and its structure is obviously different from injection molds and compression molds.
4. Plastic blow mould
It is a kind of mold used to form plastic container hollow products (such as beverage bottles, daily chemical products and other packaging containers). The forms of blow molding are mainly extrusion blow molding hollow molding and injection blow molding hollow molding according to the process principle. , Injection stretch blow molding hollow molding (commonly known as "injection stretch blow"), multilayer blow molding hollow molding, sheet blow molding hollow molding, etc. The corresponding equipment for blow molding of hollow products is usually called a plastic blow molding machine. Blow molding is only suitable for the production of thermoplastic products. The structure of the blow mold is relatively simple, and the materials used are mostly made of carbon.
5. Plastic blister mold
It is a kind of mold that uses plastic plates and sheets as raw materials to form some simpler plastic products. Its principle is to use the vacuum method or compressed air molding method to make the plastic plates and sheets fixed on the concave mold or the convex mold. Under the condition of heating and softening, it is deformed and pasted on the cavity of the mold to obtain the desired molded product, which is mainly used in the production of some daily necessities, food, and toy packaging products. The blister mold is made of cast aluminum or non-metallic materials because of the low pressure during molding, and the structure is relatively simple.
6. High-expansion polystyrene molding die
It is a mold for using expandable polystyrene (beads composed of polystyrene and foaming agent) raw materials to form various desired shapes of foam packaging materials. The principle is that the expandable polystyrene can be steam-formed in the mold, including two types of simple manual operation molds and hydraulic straight-through foam plastic molds, which are mainly used to produce industrial packaging products. The materials used to make this kind of molds are cast aluminum, stainless steel, bronze and so on.
Design elements:
Mold design and manufacturing are closely related to plastic processing. The success or failure of plastic processing depends largely on the effect of mold design and mold manufacturing quality, and the design of plastic molds is based on the correct design of plastic products.
The structural elements to be considered in the design of plastic molds are:
① Parting surface, that is, the contact surface where the concave mold and the convex mold cooperate with each other when the mold is closed. The selection of its location and form is affected by factors such as product shape and appearance, wall thickness, molding method, post-processing technology, mold type and structure, demolding method, and molding machine structure.
②Structural parts, namely sliders, inclined tops, straight top blocks, etc. of complex molds. The design of structural parts is very critical, and it is related to the life of the mold, processing cycle, cost, product quality, etc. Therefore, the design of the core structure of a complex mold requires a higher comprehensive ability of the designer, and the pursuit of simpler, more durable, and more economical is as much as possible. Design scheme.
③Mold precision, namely avoiding jams, precise positioning, guide posts, positioning pins, etc. The positioning system is related to the appearance quality of the product, mold quality and life. According to the different mold structure, different positioning methods are selected. The positioning accuracy control mainly depends on processing. The inner mold positioning is mainly considered by the designer to design a more reasonable and easy-to-adjust positioning Way.
②Gating system, that is, the feed channel from the nozzle of the injection molding machine to the cavity, including the main runner, the runner, the gate and the cold cavities. In particular, the selection of the gate position should be conducive to the molten plastic filling the cavity in a good flow state. The solid runner and gate cold material attached to the product are easy to eject from the mold and be removed when the mold is opened. Except for road model).
According to the different molding methods, the types of plastic processing molds corresponding to different process requirements can be divided, mainly including injection molding molds, extrusion molding molds, blister molding molds, high-foamed polystyrene molding molds, etc.
1. Plastic injection (plastic) mold
It is mainly a molding mold that is most commonly used in the production of thermoplastic products. The corresponding processing equipment for plastic injection molds is a plastic injection molding machine. The plastic is first heated and melted in the heating cylinder at the bottom of the injection machine, and then melted in the screw of the injection machine. Or driven by the plunger, it enters the mold cavity through the nozzle of the injection machine and the pouring system of the mold, the plastic is cooled and hardened to form, and the product is demolded. Its structure is usually composed of molding parts, pouring system, guide parts, push-out mechanism, temperature control system, exhaust system, support parts and other parts. Manufacturing materials usually use plastic mold steel modules, and the commonly used materials are mainly carbon structural steel, carbon tool steel, alloy tool steel, high-speed steel, etc. The injection molding processing method is usually only suitable for the production of thermoplastic products. The plastic products produced by the injection molding process are very wide. From daily necessities to various complex machinery, electrical appliances, and transportation parts, they are all molded by injection molds. It is the most widely used processing method in the production of plastic products.
2. Plastic compression mould
It includes two structural mold types: compression molding and injection molding. They are a type of molds mainly used to form thermosetting plastics, and their corresponding equipment is a pressure forming machine. According to the characteristics of the plastic, the compression molding method heats the mold to the molding temperature (generally 103°—108°), then puts the measured compression powder into the mold cavity and the feeding chamber, and closes the mold. The plastic is under high heat and high pressure. It is a softened viscous flow, solidified and shaped into the desired product shape after a certain period of time. The difference between injection molding and compression molding is that there is a separate feeding chamber. The mold is closed before molding. The plastic is preheated in the feeding chamber and is in a viscous flow state. It is adjusted and squeezed into the mold cavity under pressure to harden and form. Compression molds are also used to form some special thermoplastics, such as hard-to-melt thermoplastics (such as polyvinyl fluoride) blanks (cold forming), resin lenses with high optical performance, slightly foamed nitrocellulose car steering wheels, etc. . The compression mold is mainly composed of a cavity, a feeding cavity, a guiding mechanism, an ejecting part, a heating system, etc. Injection molds are widely used for packaging electrical components. The material used in the manufacture of compression molds is basically the same as that of injection molds.
3. Plastic extrusion mould
A type of mold used to mold and produce continuous-shaped plastic products, also called extrusion molding heads, is widely used in the processing of pipes, rods, monofilaments, plates, films, wire and cable coatings, profiled materials, etc. The corresponding production equipment is a plastic extruder. The principle is that the solid plastic is melted and plasticized under the conditions of heating and the screw of the extruder to rotate and pressurize, and the cross-section is the same as the shape of the die through a specific shape of the die. Continuous plastic products. Its manufacturing materials mainly include carbon structural steel, alloy tools, etc. Some extrusion dies will also be inlaid with wear-resistant materials such as diamond on the parts that need to be wear-resistant. The extrusion process is usually only suitable for the production of thermoplastic products, and its structure is obviously different from injection molds and compression molds.
4. Plastic blow mould
It is a kind of mold used to form plastic container hollow products (such as beverage bottles, daily chemical products and other packaging containers). The forms of blow molding are mainly extrusion blow molding hollow molding and injection blow molding hollow molding according to the process principle. , Injection stretch blow molding hollow molding (commonly known as "injection stretch blow"), multilayer blow molding hollow molding, sheet blow molding hollow molding, etc. The corresponding equipment for blow molding of hollow products is usually called a plastic blow molding machine. Blow molding is only suitable for the production of thermoplastic products. The structure of the blow mold is relatively simple, and the materials used are mostly made of carbon.
5. Plastic blister mold
It is a kind of mold that uses plastic plates and sheets as raw materials to form some simpler plastic products. Its principle is to use the vacuum method or compressed air molding method to make the plastic plates and sheets fixed on the concave mold or the convex mold. Under the condition of heating and softening, it is deformed and pasted on the cavity of the mold to obtain the desired molded product, which is mainly used in the production of some daily necessities, food, and toy packaging products. The blister mold is made of cast aluminum or non-metallic materials because of the low pressure during molding, and the structure is relatively simple.
6. High-expansion polystyrene molding die
It is a mold for using expandable polystyrene (beads composed of polystyrene and foaming agent) raw materials to form various desired shapes of foam packaging materials. The principle is that the expandable polystyrene can be steam-formed in the mold, including two types of simple manual operation molds and hydraulic straight-through foam plastic molds, which are mainly used to produce industrial packaging products. The materials used to make this kind of molds are cast aluminum, stainless steel, bronze and so on.
Design elements:
Mold design and manufacturing are closely related to plastic processing. The success or failure of plastic processing depends largely on the effect of mold design and mold manufacturing quality, and the design of plastic molds is based on the correct design of plastic products.
The structural elements to be considered in the design of plastic molds are:
① Parting surface, that is, the contact surface where the concave mold and the convex mold cooperate with each other when the mold is closed. The selection of its location and form is affected by factors such as product shape and appearance, wall thickness, molding method, post-processing technology, mold type and structure, demolding method, and molding machine structure.
②Structural parts, namely sliders, inclined tops, straight top blocks, etc. of complex molds. The design of structural parts is very critical, and it is related to the life of the mold, processing cycle, cost, product quality, etc. Therefore, the design of the core structure of a complex mold requires a higher comprehensive ability of the designer, and the pursuit of simpler, more durable, and more economical is as much as possible. Design scheme.
③Mold precision, namely avoiding jams, precise positioning, guide posts, positioning pins, etc. The positioning system is related to the appearance quality of the product, mold quality and life. According to the different mold structure, different positioning methods are selected. The positioning accuracy control mainly depends on processing. The inner mold positioning is mainly considered by the designer to design a more reasonable and easy-to-adjust positioning Way.
②Gating system, that is, the feed channel from the nozzle of the injection molding machine to the cavity, including the main runner, the runner, the gate and the cold cavities. In particular, the selection of the gate position should be conducive to the molten plastic filling the cavity in a good flow state. The solid runner and gate cold material attached to the product are easy to eject from the mold and be removed when the mold is opened. Except for road model).
③ Plastic shrinkage rate and various factors that affect the dimensional accuracy of products, such as mold manufacturing and assembly errors, mold wear, etc. In addition, when designing compression molds and injection molds, the matching of the process and structural parameters of the molding machine should also be considered. Computer-aided design technology has been widely used in plastic mold design.
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