Top 10 Plastic Molding Processes：

一 Injection molding

1）Injection molding

Injection molding: Also known as injection molding, its principle is to add granular or powdery raw materials into the hopper of the injection machine. The raw materials are heated, melted and in a flowing state. They are poured through the nozzle and mold driven by the screw or piston of the injection machine. The system enters the mold cavity and hardens and shapes in the mold cavity. Factors affecting injection molding quality: injection pressure, injection time, injection temperature

Process features:

advantage:

1. Short molding cycle, high production efficiency and easy automation

2. Can form plastic parts with complex shapes, precise dimensions, and metal or non-metal inserts.

3. Product quality is stable

4. Wide adaptability

shortcoming:

1. Injection molding equipment is more expensive

2. The injection mold has a complex structure

3. The production cost is high, the production cycle is long, and it is not suitable for the production of single-piece and small-batch plastic parts.

application:

Among industrial products, injection molded products include: kitchen supplies (trash cans, bowls, buckets, pots, tableware and various containers), casings of electrical equipment (hair dryers, vacuum cleaners, food mixers, etc.), toys and games, automobiles Various industrial products, parts for many other products, etc.

2） Insert injection molding

Insert injection molding: Insert molding refers to a molding method in which pre-prepared inserts of different materials are installed in the mold and then resin is injected. The molten material joins and solidifies with the insert to form an integrated product.

Process features:

1. The pre-molding combination of multiple inserts makes the post-engineering of product unit combination more rational.

2. The easy formability and bendability of resin and the rigidity, strength and heat resistance of metal can be combined and complement each other to make complex and exquisite metal-plastic integrated products.

3. Especially by utilizing the combination of the insulation of resin and the conductivity of metal, the molded products can meet the basic functions of electrical products.

4. For rigid molded products and bending elastic molded products on rubber sealing gaskets, after the integrated products are made by injection molding on the base body, the complex work of arranging sealing rings can be omitted, making the automated combination of post-processes easier.

3） Two-color injection molding

Two-color injection molding: refers to a molding method in which two plastics of different colors are injected into the same mold. It can make plastic appear two different colors, and can make plastic parts show regular patterns or irregular moiré-like colors to improve the usability and aesthetics of plastic parts.

Process features:

1. Low-viscosity materials can be used as core materials to reduce injection pressure.

2. From the perspective of environmental protection, recycled secondary materials can be used as core materials.

3. According to different usage characteristics, for example, thick finished products use soft materials for the skin material, hard materials for the core material, or foam plastics can be used for the core material to reduce weight.

4. Lower quality core materials can be used to reduce costs.

5. The skin material or core material can use expensive materials with special surface properties, such as anti-electromagnetic wave interference, high conductivity and other materials to increase product performance.

6. The appropriate combination of skin material and core material can reduce the residual stress of the molded product and increase the mechanical strength or surface properties of the product.

4） Micro-foam injection molding process

Micro-foam injection molding process: It is an innovative precision injection molding technology that relies on the expansion of pores to fill the product, and completes the molding of the product under low and even pressure. The microcellular foaming molding process can be divided into three stages: first, the supercritical fluid (carbon dioxide or nitrogen) is dissolved into the hot melt glue to form a single-phase solution; then the mold with lower temperature and pressure is injected through the switch-type nozzle. Due to the decrease in temperature and pressure, the instability of molecules triggers the formation of a large number of bubble nuclei in the product, and these bubble nuclei gradually grow to form tiny holes.

Process features:

1. Precision injection molding;

2. Breaking through many limitations of traditional injection molding, it can significantly reduce the weight of parts and shorten the molding cycle;

3. Greatly improve the warpage deformation and dimensional stability of the parts.

application:

Car dashboards, door panels, air conditioning ducts, etc.

5） Nano injection molding (NMT)

NMT (Nano Molding Technology): It is a construction method that combines metal and plastic with nanotechnology. After the metal surface is nano-treated, the plastic is directly injection molded on the metal surface, so that the metal and plastic can be formed into one piece. Nanomolding technology is divided into two types of processes based on the location of the plastic:

1. The plastic is integrally formed on the non-appearance surface.

2. The plastic is integrated into the exterior surface.

Process features:

1. The product has a metallic appearance and texture.

2. The design of product machine components is simplified, making the product lighter, thinner, shorter and smaller, and more cost-effective than CNC processing.

3. Reduce production costs and achieve high bonding strength, and significantly reduce the usage rate of related consumables.

Applicable metal and resin materials:

1. Aluminum, magnesium, copper, stainless steel, titanium, iron, galvanized sheet, brass;

2. Aluminum alloys have strong adaptability, including 1000 to 7000 series;

3. Resins include PPS, PBT, PA6, PA66, and PPA;

4. PPS has particularly strong bonding strength (3000N/c㎡).

application:

Mobile phone cases, laptop cases, etc.

- 2. Blow molding

Blow molding: The molten thermoplastic raw material extruded from the extruder is clamped into the mold, and then air is blown into the raw material. The molten raw material expands under the action of air pressure, adheres to the wall of the mold cavity, and is finally cooled. A method of curing into the desired product shape. Blow molding is divided into two types: film blow molding and hollow blow molding:

1）Film blow molding

Film blowing is to extrude molten plastic into a cylindrical thin tube from the annular gap of the die of the extruder head. At the same time, compressed air is blown into the inner cavity of the thin tube from the center hole of the extruder head to inflate the thin tube to a diameter of Larger tubular films (commonly known as bubble tubes) are rolled up after cooling.

2）Hollow blow molding

Hollow blow molding is a secondary molding technology that uses gas pressure to inflate the rubber-like parison closed in the mold cavity into a hollow product. It is a method for producing hollow plastic products. Hollow blow molding depends on the manufacturing method of the parison, including extrusion blow molding, injection blow molding, and stretch blow molding.

1) Extrusion blow molding: Extrusion blow molding uses an extruder to extrude a tubular parison, clamp it in the mold cavity while it is hot and seal it at the bottom, and then introduce compressed air into the inner cavity of the tube parison to blow it into shape.

2) Injection blow molding: The parison used is obtained by injection molding. The parison remains on the core mold of the mold. After closing the mold with the blow mold, compressed air is introduced from the core mold to inflate the parison, cool it, and after demoulding, the product is obtained.

advantage:

The product has uniform wall thickness, small weight tolerance, less post-processing, and small waste corners; it is suitable for producing small refined products in large batches.

3) Stretch blow molding: Place the parison that has been heated to the stretching temperature in the blow mold, use a stretch rod to stretch it longitudinally, and use blown compressed air to stretch and blow it transversely to obtain the product. method.

application:

1. Film blowing is mainly used to manufacture thin plastic molds;

2. Hollow blow molding is mainly used to make hollow plastic products (bottles, packaging barrels, spray cans, fuel tanks, cans, toys, etc.).

3. Extrusion molding (profiles)

Extrusion molding: Also known as extrusion molding, it is mainly suitable for the molding of thermoplastic plastics, and is also suitable for the molding of some thermosetting and reinforced plastics with good fluidity. The molding process is to use a rotating screw to extrude the heated and molten thermoplastic raw material from the machine head with the required cross-section shape, then shape it by the shaper, and then pass it through the cooler to cool and solidify it into the required cross-section. product.

Process features:

1. Low equipment cost;

2. The operation is simple, the process is easy to control, and it is convenient to realize continuous automated production;

3. High production efficiency; uniform and dense product quality;

4. Products or semi-finished products with various cross-sectional shapes can be formed by changing the die of the machine head.

application:

In the field of product design, extrusion molding has strong applicability. The types of extruded products include pipes, films, rods, monofilaments, flat ribbons, nets, hollow containers, windows, door frames, plates, cable cladding, monofilaments and other special-shaped materials.

4. Calendering (sheet, film)

Calendering: It is a method in which plastic raw materials pass through a series of heated pressure rollers and are connected into films or sheets under the action of extrusion and stretching.

Process features:

Advantages: good product quality, large production capacity, and automatic and continuous production;

Disadvantages: huge equipment, high precision requirements, many auxiliary equipment, and product width is limited by the length of the calender roller.

application:

It is mostly used to produce PVC soft films, sheets, sheets, artificial leather, wallpaper, floor leather, etc.

5. Press molding

Press molding: Mainly used for the molding of thermosetting plastics. According to the properties of the molding material and the characteristics of the processing equipment and technology, press molding can be divided into two types: compression molding and lamination molding.

1. Molding

Compression molding, also known as compression molding, is the main method for molding thermoset plastics and reinforced plastics. The process is to pressurize the raw materials in a mold that has been heated to a specified temperature, so that the raw materials melt, flow and evenly fill the mold cavity. After a certain period of time under the conditions of heating and pressurization, the raw materials form products.

Process features:

Molded products have dense texture, accurate dimensions, smooth and smooth appearance, no gate marks, and good stability.

application:

Among industrial products, molded products include electrical equipment (plugs and sockets), pot handles, tableware handles, bottle caps, toilets, non-breakable dinner plates (melamine dishes), carved plastic doors, etc.

2. Lamination molding

Laminated molding: It is a method that uses sheet or fibrous materials as fillers to combine two or more layers of the same or different materials into a whole under heating and pressure conditions.

Process features:

The lamination molding process consists of three stages: impregnation, pressing and post-processing, and is mostly used to produce reinforced plastic sheets, pipes, rods and model products. The texture is dense and the surface is smooth and clean.

6. Pressure injection molding

Injection molding: It is a thermosetting plastic molding method developed on the basis of compression molding, also known as transfer molding. The process is similar to the injection molding process. During injection molding, the plastic is plasticized in the feeding cavity of the mold and then enters the cavity through the gating system. In injection molding, the plastic is plasticized in the barrel of the injection molding machine. The difference between injection molding and compression molding: the compression molding process is to add materials first and then close the mold, while injection molding generally requires closing the mold first and then adding materials.

Process features:

Advantages: (compared to compression molding)

1. The plastic has been plasticized before entering the mold cavity, and it can produce plastic parts with complex shapes, thin walls or widely varying wall thicknesses, and fine inserts.

2. Shorten the molding cycle, improve production efficiency, and increase the density and strength of plastic parts.

3. Since the mold is completely closed before plastic molding, the flash on the parting surface is very thin, so the precision of the plastic part is easy to ensure and the surface roughness is low.

shortcoming:

1. There will always be a part of the remaining material left in the feeding room, which consumes a lot of raw materials;

2. Trimming of gate marks increases the workload;

3. The molding pressure is greater than that of compression molding; the shrinkage rate is greater than that of compression molding;

4. The structure of the mold is also more complex than that of the compression mold;

5. The process conditions are more stringent than compression molding and the operation is difficult.

7. Rotational molding

Rotational molding: The plastic raw materials are first added to the mold, and then the mold is continuously rotated along two vertical axes and heated, so that the plastic raw materials in the mold are gradually and evenly coated, melted and adhered to the mold under the action of gravity and heat energy. The entire surface of the mold cavity is molded into the required shape, and then cooled, set, and demoulded, and finally the product is obtained.

advantage:

1. Provide more design space and reduce assembly costs;

2. Easy to change and low cost;

3. Save raw materials.

application:

Water balloons, floats, small swimming pools, bicycle seat cushions, surfboards, machine casings, protective covers, lampshades, agricultural sprayers, furniture, canoes, camping vehicle roofs, etc.

8. Drop molding

Drop molding: It takes advantage of the state-changeable characteristics of thermoplastic polymer materials, that is, it has viscous fluidity under certain conditions and can return to solid state at room temperature, and uses appropriate methods and specialized tools to inkjet. In its viscous flow state, it is shaped into the designed shape as required, and then solidified at room temperature. The process flow mainly includes three stages: weighing - dispensing - cooling and solidification.

advantage:

1. The product has good transparency and gloss;

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.

9. Blister molding

Blister molding: Also called vacuum forming, it is one of the thermoforming methods for thermoplastic plastics. It refers to clamping the sheet or plate-like material on the frame of the vacuum forming machine. After heating and softening, it is vacuum-adsorbed to the mold through the air channel on the side of the mold. After a short period of cooling, the formed plastic product is obtained. .

Process features:

Vacuum forming methods mainly include concave mold vacuum forming, convex mold vacuum forming, concave and convex mold vacuum forming, bubble blowing vacuum forming, plunger push-down vacuum forming, vacuum forming with gas buffer device, etc.

advantage:

The equipment is relatively simple, the mold does not need to withstand pressure and can be made of metal, wood or gypsum. The molding speed is fast and the operation is easy.

application:

Widely used in internal and external packaging of food, cosmetics, electronics, hardware, toys, crafts, medicine, health products, daily necessities, stationery and other industries; disposable cups, various cup-shaped cups, etc.; breeding trays, seedling cultivation trays, degradable fast food box.

10. Slush molding

Slush molding: Pour the paste plastic (plastic sol) into a mold (concave mold or female mold) that is preheated to a certain temperature. The paste plastic close to the inner wall of the mold cavity will gel due to heat, and then the non-gelled plastic will gel. The paste plastic is poured out, and the paste plastic attached to the inner wall of the mold cavity is heat treated (baked and melted), and then cooled to obtain the hollow product from the mold.

Process features:

1. Low equipment cost and high production speed.

2. The process control is simple, but the accuracy of the thickness, quality (weight), etc. of the product is poor.

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