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1. The ten most common injection molding processes for plastic molding 1molding

Injection molding: also known as injection molding, its principle is to add granular or powdered raw materials into the hopper of the injection machine. The raw materials are heated and melted into a flowing state. Under the push of the screw or piston of the injection machine, they enter the mold cavity through the nozzle and the pouring system of the mold, and harden and shape in the mold cavity. Factors affecting the quality of injection molding: injection pressure, injection time, injection temperature.

Process Features ✦

Advantages:

1. Short molding cycle, high production efficiency, easy to automate
2. Can mold plastic parts with complex shapes, precise dimensions, and metal or non-metal inserts
3. Stable product quality
4. Wide range of applications

Disadvantages:

1. The price of injection molding equipment is relatively high
2. The structure of injection mold is complex
3. High production cost, long production cycle, not suitable for single-piece and small-batch plastic parts production

Application ✦

In industrial products, injection molded products include: kitchen supplies (garbage cans, bowls, buckets, pots, tableware and various containers), housings of electrical equipment (hair dryers, vacuum cleaners, food mixers, etc.), toys and games, various products of the automotive industry, parts of many other products, etc.

2) Insert injection molding

Insert injection molding: Insert molding refers to the molding method of inserting a pre-prepared insert of a different material into the mold and injecting resin, and the molten material is bonded and solidified with the insert to form an integrated product.https://solidcomould.com/product/black-plastic-garden-flower-pot-mould/

Process Features ✦

1. The pre-molding combination of multiple inserts makes the post-processing of product unit combination more rational.
2. The combination of the easy molding and bendability of resin and the rigidity, strength and heat resistance of metal can be used to make complex and exquisite metal-plastic integrated products.
3. In particular, the combination of the insulation of resin and the conductivity of metal is used to make the molded products meet the basic functions of electrical products.
4. For rigid molded products and curved elastic molded products on rubber sealing pads, after the integrated products are made by injection molding on the substrate, the complex operation of arranging the sealing ring can be omitted, making the automated combination of the post-process easier.

3) Two-color injection molding

Two-color injection molding: refers to the molding method of injecting two different colors of plastics into the same mold. It can make the plastic appear in two different colors, and can make the plastic parts present regular patterns or irregular cloud patterns to improve the usability and aesthetics of the plastic parts.

Process Features ✦

1. The core material can use low-viscosity materials to reduce the injection pressure.
2. From the perspective of environmental protection, the core material can use recycled secondary materials.
3. According to different usage characteristics, such as using soft materials for the skin material of thick finished products, using hard materials for the core material or using foamed plastics for the core material to reduce weight.
4. Lower-quality core materials can be used to reduce costs.
5. Expensive materials with special surface properties such as anti-electromagnetic interference and high conductivity can be used for the skin material or core material to increase product performance.
6. Appropriate combination of skin material and core material can reduce the residual stress of the molded product, increase the mechanical strength or surface properties of the product.

IV) 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 complete the molding of the product under a lower and average 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 to form a single-phase solution; then, it is injected into the mold cavity with lower temperature and pressure through a switch nozzle. Due to the decrease in temperature and pressure, the molecular instability causes a large number of bubble nuclei to form in the product, and these bubble nuclei gradually grow to form tiny holes.https://solidcomould.com/product/customized-shape-laundry-basket-mould/

Process Features ✦

1. Precision injection molding;
2. It breaks through many limitations of traditional injection molding, can significantly reduce the weight of the parts and shorten the molding cycle;
3. It greatly improves the warping deformation and dimensional stability of the parts.

Application ✦

Automobile instrument panel, door panel, air conditioning duct, etc.

V) Nano Injection Molding (NMT)

NMT (NanoMoldingTechnology): It is a method of combining metal and plastic with nanotechnology. After the metal surface is nano-treated, the plastic is directly injected and molded on the metal surface, so that the metal and plastic can be formed as one. Nano molding technology is divided into two types of processes according to the location of the plastic:

1. One-piece molding of plastic for non-appearance surface
2. One-piece molding of plastic for appearance surface

Process characteristics ✦

1. The product has a metallic appearance texture,
2. The design of the product components is simplified, making the product lighter, thinner, shorter, smaller, and more cost-effective than CNC processing.
3. Reduce production costs and high bonding strength, and greatly reduce the use 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, PPA;
4. PPS has a particularly strong bonding strength (3000N/c㎡).

Application ✦

Mobile phone shell, laptop shell, etc.

2. Blow molding

Blow molding: It is a method of inserting the molten thermoplastic raw material extruded from the extruder into the mold, and then blowing air into the raw material. The molten raw material expands under the action of air pressure, adheres to the wall of the mold cavity, and finally cools and solidifies into the desired product shape. Blow molding is divided into film blowing and hollow blow molding:

1. Film blowing ✦

Film blowing is to extrude the molten plastic from the annular gap of the extruder head die in the form of a cylindrical thin tube, and at the same time blow compressed air from the center hole of the head into the inner cavity of the thin tube to blow the thin tube into a tubular film with a larger diameter (commonly known as a bubble tube), and then wind it up after cooling.

2. Hollow blow molding ✦

Hollow blow molding is a secondary molding technology that uses gas pressure to blow 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 is divided into extrusion blow molding, injection blow molding, and stretch blow molding according to the different manufacturing methods of the preform.

1) Extrusion blow molding

Extrusion blow molding is to extrude a tubular preform with an extruder, clamp it in the mold cavity while it is hot and seal the bottom, and then introduce compressed air into the inner cavity of the tube to blow it up.

2) Injection blow molding

The preform used is obtained by injection molding. The preform is left on the core mold of the mold. After the blow mold is closed, compressed air is introduced from the core mold to blow up the preform, cool it, and demold it to get the product.

Advantages ✦

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

3. Stretch blow molding

The preform that has been heated to the stretching temperature is placed in the blow mold, stretched longitudinally with a stretching rod, and stretched and inflated transversely with compressed air to obtain the product.

Application ✦

1. Film blow molding is mainly used to make plastic thin molds;
2. Hollow blow molding is mainly used to make hollow plastic products (bottles, packaging barrels, spray bottles, oil tanks, cans, toys, etc.).
3. Extrusion molding (profiles)

Extrusion molding: also known as extrusion molding, is mainly suitable for the molding of thermoplastics, 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 materials from the head with the required cross-sectional shape, and then shape it by the shaper, and then cool it through the cooler to harden it into a product with the required cross-sectional shape.

Process Features ✦

1. Low equipment cost;
2. Simple operation, easy control of the process, and easy to achieve 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 die head.

Application ✦

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