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Development of multicolor injection molding machines

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Development of multicolor injection molding machines

Issue Time:2020-10-24

Polycolor injection is, as the name suggests, realized with more than two kinds of plastic injection for a part.The broad multi-color injection molding includes over Molding, which is achieved by two injection molding with an ordinary molding machine. The narrow sense multi-color injection molding refers to the molding manufacturing of two or more different plastics on the same machine by using the multi-color injection molding machine. The most common is the rotary injection molding machine.

Multicolor injection after years of development, not just confined to the rotary machine molding, this technology has expanded the many fixed branch, the sandwich injection molding, cube mold and liquid silicon multicolor injection is also the hot trend of recent years, sandwich injection molding to the secondary consumption of materials, double screw respectively responsible for injection and independent pressure maintaining, in turn, ascension cycle and reducing energy consumption, is currently the most environmental protection of the injection molding process;Cube moulds have unique advantages in terms of efficiency, which are very suitable for thin-walled products such as bottle caps, and have excellent advantages in mass production.Liquid silicon injection, combined with LSR's excellent performance of high and low temperature resistance and corrosion resistance, has excellent characteristics such as stable accuracy brought by injection parts, and has become a hot choice of emerging products.Next, let's make an inventory:

Several common forms of multicolor injection molding:

Vertical rotary table

Vertical turntable (parallel injection table) injection molding machine is the most widely used double injection molding machine, can shape a large number of small and medium-sized products.Usually the tonnage is less than 1500 tons, there are certain requirements on the size and appearance of the mold, can not exceed the loading area.

Mould rotation

After the completion of one injection, the mold core is driven to rotate by the motor, and the prefabricated parts are moved to the next position to complete subsequent processing.In-mold rotation has a very prominent advantage in toothbrush manufacturing and other fields, which can increase the production efficiency by more than 50% and fulfill customized requirements such as multi-color simultaneous production and packaging.

The horizontal rotating injection molding machine can shape large two-color parts, such as TV frames, car sunroof, lampshades, etc., with the maximum tonnage up to 1900 tons.The biggest advantage of horizontal rotary table is that it can produce large-tonnage products, which is incomparable with traditional rotary table equipment.It is widely used in the field of automobile manufacturing.

Monochrome injection molding machine produces two - color products

Monochrome injection molding machine production of two-color products is the first and most basic two-color injection application, the principle is very simple, the first production of semi-finished products, production is completed before the first semi-finished products on the second set of mold coated with glue.The advantage is the production flexibility, the input to the machine is reduced, the disadvantage is to increase the inventory of semi-finished products.It is easier for small injection molding plants to put into production, but this process will be phased out in the context of the increasing degree of automation.

Linkage robot

The linkage manipulator is used to connect two injection molding machines. After the first injection molding machine produces the first product, the manipulator takes the product out and puts it into the second injection molding machine to produce the second product.The principle is the same as manual picking and placing products, but the efficiency is much higher, the dimensional accuracy is more stable, and there is no need for the inventory of semi-finished products.Linkage robot has unique advantages in sanitary ware industry, especially in the processing of shower. The human input is about 60% lower than traditional manufacturing. However, it needs two machines to match production, so the production flexibility is not high.

Combined with LSR

Liquid silicone rubber LSR is suitable for the demanding occasions, because of its good electric insulation, heat resistance, cold resistance and light fastness were excellent, and harmless to human body, therefore, in the medical, electronics and other fields have a wide range of applications, the current in the field of two-color injection molding is also extensive use of LSR with double-color plastic processing to meet various needs.

The hardness range of liquid silicon is very wide, which can well replace TPU, TPE and other thermoplastic elastomers, and at the same time can produce a very good tactile texture.Liquid silicon also meets the requirements of many extreme environments.Therefore, in recent years, liquid silicon material has become a new and popular choice in various industries, gradually stepping into People's Daily life.

Sandwich injection molding

Sandwich injection molding, also known as sandwich injection molding or surface-core processing technology, can inject a material completely into the surface material.Can be filled back, hardness and toughness, as well as the product center of gravity adjustment in different areas of demand, improve the product performance requirements and to ensure the appearance of the surface requirements.

An internationally renowned sanitary ware enterprise has introduced sandwich injection molding to optimize the addition of secondary materials, which can save 35% raw materials in a year and reasonably utilize the secondary materials that cannot be added before, greatly enhancing the competitiveness of the enterprise in terms of manufacturing costs.

Cube mold

The cube mold can make full use of the opening time for cooling, thus greatly improving the production efficiency and increasing the capacity of the equipment to the limit.

In the production of thin - walled mass production has a very prominent advantage.The only disadvantage is that the mold input cost is very high, in addition to the need for some customized transformation of the equipment.

In the current multicolor molding process, the cube mold has an unparalleled advantage in terms of efficiency. This process makes full use of the opening and closing mold, ejecting and other time in the molding cycle, and has outstanding advantages in mass production.

Process requirements for multicolor injection molding

Soft and hard glue two-color design:

The melting point of the two materials must have a certain temperature difference. It is generally recommended that the melting point of the two materials should be 60° and above 30°. The melting point of the first shot material should be high, generally the first shot is PC or PC/ABS, and the second shot is TPU or TPE.

Widen the contact area as far as possible, make grooves and so on to increase the adhesive force, or the first shot adopts core-pulling, the second shot part of the material injection into the first shot, the first shot mold surface as rough as possible.

Material compatibility

Two basic compatibility conditions must be met for the matching materials of multicolor injection molding, namely adhesion compatibility and process compatibility.

Transparent and opaque bijective designs

· Birefringence design for small lenses

The first shot does not transparent, the second shot does the lens, the first shot tries to use PC melting point high, the second shot USES PMMA.

· Transparent and non-transparent birefringent design for decoration

The first shot is non-transparent material, the second shot is transparent material, the non-transparent material is commonly used is SABIC PC material temperature high, the second shot is transparent material PMMA or PC.PC needs to be sprayed with UV protection, PMMA can choose UV or enhanced, if there are characters on the surface must choose UV.

Two-color injection mold features

Moving mold is the same, injection process is rotating, need to exchange, so moving mold must be the same.(There are special cases, molding cavity can be different)

After injection molding of the first shot of the mold, the runner can not be left on the mold, it is better to be hot runner, or you can use the manipulator to grab, the worst is also if the latent gate, can automatically fall off, or the second shot on the mold can not be consistent production is also prone to die accidents.

The product is shot twice. After the mold opening, the first shot must be left at the moving mold side. Generally speaking, it is the choice to leave the two shot products at the moving mold side.

Process evaluation of multicolor injection molding:

Two-color injection molding has been a very mature molding process, in the initial stage of mold development, can be through a variety of CAE software analogical analysis, through the analog operation of the model can accurately determine the mold and the formation of each parameter.

Material analysis

Material analysis is a key issue to be considered in the research and development stage of dual-color injection molding. With the increasing market demand, a variety of materials appear in the field of dual-color injection molding. Reasonable material selection has become a very key link in the research and development stage.A more rigorous approach is that CAE software can be used for the simulation test of surface compatibility and binding degree, and data selection can be carried out.

Water analysis

In the mold development stage, the waterway is a crucial link, because in the two-color injection process, if the cooling is not sufficient or unstable, will cause defects in the size and appearance of the product, so in the development stage must do a careful review of th distribution of the waterway.

Analysis in LSR and other fields

In LSR and other emerging domestic forming processes, we can also determine the problem points that may occur in the forming process through some software analysis, so as to reduce the defective rate in the production process.

Above all, multi-color injection molding technology after years of development, the branch of the molding is increasingly perfect, can good application in various fields, high manufacturing efficiency at the same time, the different is able to meet the actual requirements, thus being widely used, in the automotive industry, electronics, medical and other fields has a very good economic benefit, is a technique of great development potential.Among these branches, sandwich injection molding, cube mold and LSR molding have distinct advantages in environmental protection, high efficiency, excellent application performance and other aspects. These technologies have gradually become a hot trend in the industry and gradually come into People's Daily life.We also hope that the multi - color molding process can bring more exciting for our production.