A comprehensive collection of ultra-comprehensive rubber and plastic molding process, worthy of coll

Time：2019-11-04 09:10:59 / Popularity： / Source：Other website

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Introduction: Material forming method is an important part of part design, and it is also a problem that manufacturers are extremely concerned about. It is also a key factor in material processing process. Its importance is self-evident.
Following is a detailed introduction to molding process of plastics and rubber.

Plastic molding process

Firstly, injection molding

1. Injection moulding

Injection moulding: principle is to add granular or powdery raw materials into hopper of injection machine, raw material is heated and melted in a flowing state, poured by nozzle and mold under push of screw or piston of injection machine, enters mold cavity through pouring system of nozzle and mold, hardens and shapes in mold cavity.

Injection moulding schematic

Process flow:

Factors affecting quality of injection moulding: injection pressure, injection time, injection temperature
Process characteristics:
Advantages:
1, short molding cycle, high production efficiency and easy automation
2, can form plastic parts with complex shapes, accurate dimensions, with metal or non-metal inserts
3, product quality is stable
4, a wide range of adaptation
Disadvantages:
1, price of injection equipment is higher
2, injection mold structure is complex
3, high production cost, long production cycle, not suitable for single-piece small batch production of plastic parts
Application:
In industrial products, injection molded products are: kitchen supplies (garbage cans, bowls, buckets, pots, cutlery and various containers), electrical equipment shells (hair dryers, vacuum cleaners, food blenders, etc.), various products in toys, games and automotive industry, parts of many other products, etc.

2, insert injection moulding

Insert injection moulding: Insert molding refers to a molding method in which a pre-prepared different material insert is inserted into a mold and then injected with resin, molten material is bonded and solidified to form an integrated product.
Process flow:
In insert molding process, injection moulding machine is usually only part of overall system. Inserts usually require orientation first, and a vibrating table can be used to accomplish this task. Then insert is placed into mold by an arm end tool (EOAT), which can typically be accessed by means of a pre-positioning device. After finished part stage, positioning of ejection is the most important step, and repeatability of injection moulding machine’s mold opening action is crucial here. After being inserted into mold, insert is fixed in a vacuum or mechanically fixed (eg using a slider). At the same time as insert is inserted, the last finished part is ejected.
Technical features:
1. Pre-formed combination of multiple inserts make post-engineering of product unit combination more rational.
2. Resin's easy formability, flexibility and metal rigidity, strength, heat resistance combined with each other, can be made into a complex and sophisticated metal-plastic integrated product.
3. In particular, combination of insulating properties of resin and electrical conductivity of metal can be used to satisfy basic functions of electrical product.
4. For rigid molded product and curved elastic molded product on rubber gasket plate, integrated product is formed by injection moulding on substrate, which can eliminate complicated operation of arranging sealing ring, and make automatic combination of post process easier.

3, two-color injection

Two-color injection molding: refers to molding method of injecting two different color plastics into same mold. It can make plastics appear in two different colors, and can make plastic parts have a regular pattern or irregular cloud-like colors to improve usability and aesthetics of plastic parts.
Process flow:

Technical features:
1. Core material can use low viscosity materials to reduce injection pressure.
2. From perspective of environmental protection, core material can use recycled secondary materials.
3. According to different use characteristics, such as thick pieces of finished leather layer using soft materials, core materials using hard materials or core materials can use foam plastic to reduce weight.
4. Lower quality core materials can be utilized to reduce costs.
5. Cortical material or core material can use expensive and special surface properties of materials, such as anti-electromagnetic interference, high electrical conductivity to increase product performance.
6. Proper cortex material and core material can reduce residual stress of molded product, increase mechanical strength or surface properties of product.

4. Micro-foam injection molding process

Micro-foam injection molding process: It is an innovative precision injection moulding technology that fills product by expansion of pores and completes molding of part under a low and average pressure.
Fundamental:
Micro-foam injection molding process can be divided into three stages: first, a supercritical fluid (carbon dioxide or nitrogen) is dissolved in a hot melt to form a single-phase solution; and then a switch type nozzle is used to inject a mold cavity having a lower temperature and pressure. Since temperature and pressure decrease cause molecular instability to form a large number of bubble nuclei in article, these bubble nuclei gradually grow to form minute holes.
Process flow:

Figure 1. MuCell® Process Flow Chart

Process characteristics:
1. Precision injection moulding;
2. Breaking through limitations of traditional injection molding, can significantly reduce weight of parts, shorten molding cycle;
3. Greatly improved warpage deformation and dimensional stability of workpiece.
Application:
Car dashboard, door panel, air conditioning duct, etc.

5, Nano Molding Technology (NMT)

ZTE Grand S EXT

NMT (Nano Molding Technology): It is a combination of metal and plastic technology. After metal surface is nano-treated, plastic is directly injected and formed on metal surface, so that metal and plastic can be integrally formed.
Process flow:

Nano Molding Technology is divided into two types of processes based on location of plastic:
1. Integrally moulding that Plastic is a non-design surface
2. Integrally moulding that Plastic is a design surface
Process characteristics:
1. Product has a metallic appearance texture.
2. Design of product machine components is simplified, making products lighter, thinner, shorter and smaller, and more cost-effective than CNC machining method.
3. Reduce production costs and high bonding strength, significantly reduce use of related consumables.
Suitable metal and resin materials:
1. Aluminum, magnesium, copper, stainless steel, titanium, iron, galvanized sheet, brass;
2. Adaptability of aluminum alloy is strong, including 1000 to 7000 series;
3. Resin includes PPS, PBT, PA6, PA66, PPA;
4. PPS has a particularly strong bond strength (3000 N/cm2).
Application:
Mobile phone case, laptop case, Lenovo notebook.

Second, extrusion molding (profile)

Extrusion: Also known as extrusion molding, it is mainly suitable for molding of thermoplastics, and is also suitable for formation of thermosetting and reinforced plastics with better fluidity. Molding process uses a rotating screw to extrude heated and melted thermoplastic material from a machine head having a desired cross-sectional shape, then shaped by a sizing device, and chilled and hardened by a cooler to obtain a product of a desired cross section.

Extrusion schematic

Process flow:

Process characteristics:
1. Low equipment cost;
2. Operation is simple, process is easy to control, and it is convenient to realize continuous automatic production;
3. High production efficiency; uniform and compact product quality;
4. Products or semi-finished products of various cross-section shapes can be formed by changing die of machine head.
Application:
In the field of product design, extrusion has a strong applicability. Extrusion products include pipes, films, rods, monofilaments, flat belts, nets, hollow containers, windows, door frames, plates, cable clads, monofilaments and other profiles.

Third, calendering (sheet, film)

Calendering: A method in which a plastic material is passed through a series of heated press rolls to join a film or sheet under extrusion and stretching.

Calendering schematic

Process flow:

Process characteristics:
Advantages:
Good product quality, large production capacity, and automatic continuous production;
Disadvantages:
Equipment is large, precision is high, auxiliary equipment is large, and width of product is limited by roller length of calender.
Application:
Mostly used in the production of PVC soft film, sheet, sheet, artificial leather, wallpaper, floor leather and so on.

Forth, blow molding

Blow molding: a molten thermoplastic raw material extruded from an extruder is sandwiched into a mold, then air is blown into raw material, molten raw material is expanded by air pressure to be bonded to wall surface of mold cavity, finally cooled and solidified into a desired product shape.
Blow molding is divided into film blow molding and hollow blow molding.

1. Film blow molding

Film blowing is to extrude molten plastic from a circular thin tube in annular gap of die of extruder head, while blowing compressed air from center hole of machine head into inner cavity of thin tube to inflate into a larger diameter tubular film (commonly known as a bubble tube), and is taken up after cooling.

2. Hollow blow molding

Hollow blow molding is a secondary molding technique in which a rubber-like parison closed in a mold cavity is inflated into a hollow product by means of gas pressure, and is a method for producing a hollow plastic product. Hollow blow molding has different manufacturing methods for parisons, such as extrusion blow molding, injection blow molding, and stretch blow molding.
1) Extrusion blow molding: Extrusion blow molding is to extrude a tubular parison by an extruder, sandwich it in a mold cavity and heat bottom, then inject a compressed air into inner cavity of tube blank to form a blow molding.

Extrusion blow molding schematic

Injection blow molding: Parison used was obtained by injection moulding. Parison is left on the core of mold, after mold is closed by blow mold, compressed air is introduced from core mold to inflate parison, and after cooling, product is obtained after demolding.

Advantages:
Product has uniform wall thickness, small weight tolerance, less post-processing and small waste corner; suitable for producing small-sized fine products with large batch size.
Stretch blow molding: Parison which has been heated to stretching temperature is placed in a blow mold, longitudinally stretched with a stretching rod, laterally stretched and inflated with blown compressed air to obtain a product.

Application:
1. Film blowing is mainly used to make plastic thin molds;
2. Hollow blow molding is mainly used to make hollow plastic products (bottles, drums, watering cans, fuel tanks, cans, toys, etc.).

Fifth, press forming

Press forming is mainly used for forming of thermosetting plastics. According to properties of forming materials, characteristics of processing equipment and process, press forming can be divided into two types: compression molding and lamination molding.

1. Compression molding

Compression molding, is primary method of forming thermoset plastics and reinforced plastics. Process is to pressurize raw material in a mold that has been heated to a specified temperature, so that raw material is melted and uniformly filled into cavity, and it is formed into a product under a condition of heating and pressurization for a certain period of time.

Features:
Molded product has compact texture, accurate size, smooth appearance, no gate mark and good stability.
Application:
In industrial products, molded products include electrical equipment (plugs and sockets), handles, handles for tableware, bottle caps, toilet bowls, non-breaking plates (Melamine), carved plastic doors, and so on.

2. Lamination molding

Lamination molding: a method in which two or more layers of same or different materials are combined into one body under heat and pressure using a sheet or fibrous material as a filler.
Process flow:
Laminating process consists of three stages of impregnation, pressing and post-processing, and is used to produce reinforced plastic sheets, pipes, rods and model products.
Features:
Texture is compact and surface is smooth.

Sixth, transfer molding

Transfer molding: It is a molding method of thermosetting plastic developed on the basis of compression molding. Process is similar to injection moulding process. During transfer molding, plastic is plasticized in feeding chamber of mold, then enters cavity through casting system, and injection molding is plasticized in the barrel of injection molding machine.
Process flow:

Difference between transfer molding and compression molding:
Compression molding process is to close mold after feeding, and transfer molding generally requires feeding after mold is closed.
Process characteristics:
Advantages: (compared to compression molding)
1. Plastic has been plasticized before entering cavity, and it can produce plastic parts with complex shape, thin wall or large wall thickness and fine inserts.
2. Shorten molding cycle, improve production efficiency, improve density and strength of plastic parts.
3. Since mold is completely closed before plastic molding, flash edge of parting surface is very thin, so precision of plastic part is easy to ensure surface roughness is also low.
Disadvantages:
1. There will always be some residual material left in feeding room, and raw material consumption is large;
2. Trimming of gate marks increases workload;
3. Molding pressure is larger than that of compression molding; shrinkage ratio is larger than that of compression molding;
4. Structure of mold is also more complicated than structure of compression mold;
5. Process conditions are more stringent than compression molding requirements, and operation is difficult.

Seventh, rotational molding

Rotational molding: plastic raw material is first added to mold, then mold is continuously rotated and heated along two vertical axes, so that plastic material in mold is gradually uniformly coated, melted and adhered to entire surface of cavity under action of gravity and heat energy. It is formed into a desired shape, cooled, shaped, demolded, and finally obtained a product.
Process flow:

Advantages:
1. Provide more design space and reduce assembly costs;
2. Change is simple, cost is low;
3. Save raw materials.
Application:
Water polo, floating ball, small swimming pool, bicycle seat cushion, surfboard, machine casing, protective cover, lampshade, agricultural sprayer, furniture, canoe, camping vehicle top, etc.

Eighth, drop molding

Drop molding: It utilizes characteristics of a variable state of thermoplastic polymer material, that is, it has a viscous property under certain conditions and can restore solid state at a normal temperature, uses an appropriate method and a special tool to eject ink, it is molded into a designed form under viscous flow state, and then solidified at a normal temperature.
Process flow:

It mainly includes three stages: gel-dropping-cooling and solidification.
Advantages:
1. Product transparency and gloss are good;
2. It has physical properties such as anti-friction, waterproof and anti-pollution;
3. It has a unique three-dimensional effect.
Application:
Plastic gloves, balloons, condoms, etc.

Ninth, blister molding

Blister molding: also known as vacuum forming, is one of thermoplastic thermoforming methods. It refers to clamping sheet or plate material on the frame of vacuum forming machine, heating and softening, passing it through air passage of die edge, vacuuming it onto mold, and cooling for a short time to obtain molded plastic product.

Classification:
Vacuum forming methods mainly include die vacuum forming, punch vacuum forming, embossing die vacuum forming, bubble forming vacuum forming, plunger pushing down vacuum forming, vacuum forming with a gas buffer device, and so on.
Advantages:
Equipment is relatively simple, mold does not need to withstand pressure, can be made of metal, wood or gypsum, molding speed is fast and operation is easy.
Application:
Widely used in industry inner and outer packaging such as food, cosmetics, electronics, hardware, toys, crafts, medicine, health products, daily necessities, stationery and so on; disposable cups, all kinds of cups, breeding trays, breeding trays, degradable fast food box.

Ten, slush molding

Sluch molding: Pour plastic (plastic sol) into a mold (female or negative mold) that is preheated to a certain temperature. Paste plastic near inner wall of cavity will be gelled by heat and paste plastic which is not gelled is poured out. Paste plastic attached to inner wall of cavity is subjected to heat treatment (baking), and then hollow product can be obtained from mold by cooling.
Process flow:

Technical features:
1. Low equipment cost and high production speed.
2. Process control is simple, but accuracy of thickness and mass (weight) of product is poor.
Application:
Mainly used for high-end car dashboard and other products with high requirements for visual effects, plastic toys, etc.

Rubber molding process

First, injection moulding

Rubber injection molding is also called injection molding. It is a production method that uses pressure of injection molding machine to directly inject preheated rubber into cavity through nozzle, is vulcanized and shaped.
Process flow:
Feeding→gel softening preheating→injection (shooting)→vulcanization setting→removal of product.

Advantages:
1. Coherence
2, strict tolerances
3, faster production time
4, high cost performance
Application:
It is suitable for production of large, thick-walled, thin-walled and geometrically complex rubber products with high quality and high output.

Second, compression molding

Compression molding: also known as press forming. Semi-finished rubber compound which has been kneaded, processed into a certain shape, weighed and has certain plasticity is directly placed into open mold cavity, then mold is closed, sent to flat vulcanizing machine for pressurization and heating, maintained for a period of time, compound is vulcanized and formed under action of heat and pressure.

Advantages:
1, can produce more complex products
2, less bonding lines
3, low processing costs
4, high production efficiency
5, can handle high hardness materials
Application:
Suitable for production of sealing rings, gaskets, rubber products with inserts, such as handles, cloth tape, tires, rubber shoes, etc.

Third, transfer molding

Transfer molding or extrusion molding. Utility model adopts a mixed and simple shape, a certain limited amount of rubber strip or rubber block semi-finished product into die-casting mold cavity, extrudes rubber compound through pressure of die-casting plug, causes rubber compound to be vulcanized and shaped into mold cavity through pouring system.

Advantages:
1, handle larger products
2, pressure inside mold can do very detailed processing,
3, rapid mold setting
4, high production efficiency
5, low production costs
Application:
Particularly suitable for large and complex, difficult to feed, thin wall and more sophisticated rubber products with inserts.

Fourth, extrusion forming

Rubber extrusion molding is the heating and plasticizing of the rubber in an extruder, which is continuously conveyed forward by a screw or a plunger, then extruded by a rubber molding die, various semi-finished products (profiles, molded articles) of a desired shape are pressed out to complete a molding or other work process.
Process characteristics:
1. Semi-finished quality is even and dense. Wide applications range, fast forming speed, high work efficiency and low cost are conducive to automated production.
2. Equipment has small floor space, light weight, simple structure and low cost; it can operate continuously and has large production capacity.
3. Die-shaped mold has simple structure, easy processing, convenient disassembly and assembly, long service life, easy storage and maintenance.
Application:
1. Preparation of semi-finished products of tires, rubber shoes, hoses and other products.
2. Metal wire or wire, wire rope, etc.

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