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Injection Molding Technology

1. Of injection molding (core layer injection molding)

Use of injection molding will help observe the unique structure of workpieces. Plastic “A” part of the first injection of charge into the cavity, and then plastic: “B” tight

Followed by “A” injected into the cavity and to maintain the initial pressure field to promote the flow. Core layer under the skin area and the size, the correct ratio of the relevant

Department of measuring the “A” and “B” of the use of feeding amount can be obtained within a core layer “A” looks entirely by the “B” package of workpieces.

In addition, cosmetic applications, a small part of the epidermis “A” material on the “B” material after the injection, so that the gate is fully part of the epidermis

Closed. With 2 different colors of resin injection molding of parts, an easy distinction between the formation of the skin and core interval (recognizing the

Some of the existing injection molding pieces have similar skin and core it is very important. ) If there is no advanced detection technology, is a difficult area

Sub-Surface – core layer of regional and sub-interface.

Coinjection molding is not a new technology. British ici early 70s the company started the application of this technology, and achieved, including base

Theoretical foundation, production machinery and equipment and other products and several patents. ICI is a widely used production process similar to the “sandwich molding”, as molded

The outer skin material and intermediate or core layer of material different, so the two materials must have certain compatibility and core material requires

Highly radiation, foam molding, and 100% recycled and other properties. The selected material should be determined by comparing the number of options. Total Injection Molding

Came 15 years later, really able to popularize. A kind of injection molding with a thick cross-section of teeth lost production.

Non-skin material filled nylon, while the core material is glass – beads material – filled nylon. The core layer of glass beads aggregate shrinkage is very low, with good

Injection molding

Good dimensional stability. Nylon gear teeth to give a good surface lubricity and to avoid the bead pellet is prone to erosion problems.

A total of injection molding based on the basic theory has developed several new types of process improvement methodology. For example, the mode of “painting” and gas-assisted molding

Forming expanded the scope of using this technology. In-mold painting process is used as the outer layer of low molecular weight polymer, while the gas-assisted

Molding is the use of nitrogen or another gas as the core layer (or part of the core layer) material. With the product design and production of continuous processing equipment

Complete improvements to meet a variety of new applications and new technologies demand, total injection will become the rich potential of the industrial mass production process


2. Gas-assisted injection molding

Gas-assisted injection molding technology is designed to reduce weight and (or) to save cycle time and gradually developed.

Usually co-injection molding, the first injection of the outer material, and only partially filled cavity. And gas injection through the nozzle or directly into the mold cavity

Within the cavity of the core layer workpiece location. Liquefied gas can be injected into the core layer to be part of molding products. In general, the gas pressure in the core layer

To promote the flow of molten material forward until completely filled cavity, and to prevent workpiece surface from the mold during the curing stage of parietal sunken, closely linked to the epidermis

The mold parietal, gas is stored in the core layer molded workpiece interval. As the injected gas pressure higher than atmospheric pressure, therefore the pressure of the gas

Before the top of the workpiece must be reduced to avoid became a role model parietal limit movement, resulting in a workpiece deformation.

Highly compressed gas is difficult to control the shape and position of the location of gas core, but with the continuous improvement process and the process will be repeated to produce

Qualified workpiece.

The machine under conditions of control, usually in the process program control. With injection molding the deepening of the basic theoretical research, the controlling party

Act out of control under the pressure of the methods using real process control, the response of the material into the monitoring, regulation and even control. Such as injection

Processing parameters such as radio improved rate of molding products, especially their mechanical properties and surface properties will have a significant impact. Shoot Rod Speed

Degrees and melt injection speed are not equal, it is critical to understand. Viscoelastic material response to the process of inter-related with the water, and a

Be carried out concurrently. In short, like directly observed material response is neither possible nor unrealistic. In the past resulting the reproducibility times

Order processing or control device object. The key step in process is often used in dry cycle measurement equipment. A repetitive mode

Pressure process is of course important, but it should be the highest priority of the melt with reproducible characteristics. As a result, the controller often requires additional auxiliary probe

Device in order to preserve records of plastic melt pressure and temperature, the melt state is an important parameter, but not enough to regulate the materials of non-linear ring

Should be. Complementary regulation and control equipment is used constantly developing a highly complex injection molding workpieces. For example, the mechanical valve gate should be

For the hot runner system, in the flow channel can be a better distribution of pressure control, and can eliminate the weld line and reduce warping.

3. Low-Pressure Injection Moulding

Low-pressure injection moulding has emerged in recent reports relating to the processing technology. In fact, this is not a new process, but the process used by parties

Injection moulding
Injection moulding

The act will enable better process equipment in the melt with the expected response match. Conventional molding conditions, the injection of the melt initially by over-

Tremendous pressure and destabilizing effects. The resulting sharp increase in viscosity, while the melt due to compression and storage of elastic energy. The low

Injection Molding Process on the contrary, the melt flow through the nozzle and the flow. As the melt viscosity increases with pressure, while the low-pressure injection molding

Low melt viscosity, which can better control the melt characteristics of viscous flow. In addition, the barrel pressure melt faster, more was

Xianchu empty body response is similar to solid-state. Viscoelastic plastic melt from the pure liquid to pure solid-state process, have a broadband response. Melt

Response or relaxation time of the specific characteristics of polymer main chain by the chemical composition of the decision. Avoid sudden changes of flow conditions substantially instantaneous

Degree of change, more conducive to the formation of the required characteristics similar to liquid. In fact, the low-pressure injection molding is to control or regulate the viscoelastic properties of a plastic

Kinds of processing methods. Resin manufacturers generally highly liquid resin to reduce weight in order to reduce the viscoelasticity, which is suitable for the production of thin

Wall products and other needs. With the environmental awareness of the depth of processing, using low-pressure injection molding of plastic will melt more adaptable to the production environment


There are a number of industrial products with low pressure injection molding method. Most design projects have focused on the low-pressure injection and then injecting plastic into

Combined with the use type. Such as automotive door trim molding, is to place the textiles or textile material into the mold, and then directly injected to the mold

Melt. In-mold labeling method is beyond the simple printing of the other molding methods. The beginning of each cycle of production, a separate tag or series of

The film can be converted in-mold position. In addition to printed films, the occasional have a lot of kinetic energy, (such as high anti-line attack, toughened epoxy resin) or

By film may contain additives and stabilizers to protect the surface of molding products.

4. Alternating injection molding

In comparison, alternating injection is a relatively new injection molding options parameter. The technology is the most difficult to change suddenly when the processing conditions

Changes, will appear on the plastic melt little is known about how changes in behavior. The melt rheology of the basic knowledge, not just a fixed shear

Shear viscosity. Rather, the melt response (viscous and elastic behavior) need to express the characteristics of not only the usual steady-state flow rate or shear

Rate and temperature, including pressure and instantaneous flow rate. These features include many elements and very difficult to figure out. However, if

Injection profile to make substantial progress, will need to work out a variety of specific operating procedures of plastic. Another test needs to increase the common tired

Law, in order to get mature and precise control.

In conventional injection molding, the type parietal fixed, in some cases, there are used in the filling and packing movable wall segment depression. 2 can be used

Different ways: mobile type parietal direction perpendicular to the parting line; rotating or sliding parietal. In the filling stage of rotating the core to increase the workpiece

In particular, the epidermal part of the changes in molecular orientation axis. Through this processing, workpiece bending performance and other mechanical properties has been greatly raised

High. Polystyrene drinking cups and polypropylene syringes was obtained using this process to two major changes in breakthrough products.

5. Injection – Compression Molding

Injection – compression molding medium-parietal direction of movement perpendicular to the parting line. Molding using this method, the filling stage, the pressure generated by processes

Driven melt flow, but the depth of a channel can change. In the deeper channel, the pressure drops too low, so that large areas of workpiece

There is no excessive pressure in the melt forming, and to avoid the instantaneous material response, which two kinds of factors that also hinder the flow of the melt. Injection molding over

Process, the cavity depth may be 14% of the final workpiece thickness, the plastic filling roughly 60% -75% of the cavity, the cessation of injection mold cavity

Wall around the same time by pushing the wall until the final workpiece, until the original shape. Workpiece, at this stage to determine the final size.

If the die wall by a cavity filled before the process moving, the kind commonly known as cast molding process. In general, cast molding is a variable

Volume of the cavity with constant pressure on the workpiece for holding pressure. Casting pressure phase is to increase the density of the stage, followed in density between melt and

From the change between the solid plastic. Pressure casting method by forming compact disc, can minimize the residual stress, residual stress on the workpiece can be

Produce variable refraction.

Improved casting molding movable type parietal is a new technology, its curing stage by the injection of all the workpieces through the porous metal type parietal

The “packing” workpieces. This method has been called the external gas-assisted molding method, in fact, this is a misunderstanding, because the gas did not affect

Plastic melt in the cavity flow. Among the conventional injection molding, holding pressure is maintained constant while the cavity volume, the pressure flow

Effect, add in more plastic. Together with the holding pressure in the cavity formed uneven flow of the pressure distribution, there may be poured in by the high-pressure

Location for production defects.

6. Mold cooling

Mold cooling is a key technology. Most of the molding cycle, the process of heat transfer by conduction. Energy transfer from the hot melt

Delivered to the cold mold is because of temperature difference Centre at. Plastic mold side wall surface to effectively isolate the core layer, allowing heat transfer side of this

Type is very inefficient. However, the mold cooling is usually the final stage of the design was able to pay attention. Better cooling design style can be shortened by 20% –

30% or less of the cycle of production time and increase labor productivity.

In the production cycle, the mold surface temperature constantly “high – low” periodic changing, when the hot melt to force the pressing die wall, the mold temperature on

High, top of the workpiece, the next injection before the empty cavity of the mold temperature is low. In order to shorten the cooling time to a minimum, it has been exploration

Seek to produce the lowest qualified mold workpiece temperature. Mold temperature is the important role played by impact melt flow cavity, and skin and core layer of

The ratio between the size of the size. The lower mold temperature, the more thick, the cavity surface size greater pressure drop. Pulse line cooling technology is the injection of plastic into the

After the mold cavity, usually within a very cold cycle cooling pipe freezing liquid to adjust the cooling of a technology. Top of the workpiece, if not through

Central, next time shoot material after pouring into the mold cavity, mold temperature on the parietal increased significantly. Using pulse-line cooling, its temperature will be more oriented parietal

High, but lower than the conventional method of detecting mold cooling temperature lower. Pulse line can be widely used in cooling the molding thin-walled workpiece; demands repeat accuracy

Surface of the workpiece shape, and material flow depth range of mutation. Such as reverse flow delay. For the pulse-line processing advantages and its cooling

It is limited to characteristics related to the potential advantages, the cost of cooling the clock line is spending too much debate has become less important.

7. Melt core molding process

Core melt molding method is a relatively new technology methods, facilitate the processing of complex internal cross-channel, groove or notch in the workpieces. Production Pipeline

Fixture, the pump housing and sports goods manufacturers such as small workpiece, who, as early as 15 years ago began to consider whether to adopt the identified

Process the. Recently, automobile manufacturers have adopted the technology of production of large components, such as the light of the power system sample and intake manifold and so on.

The Core is the same as the conventional mold can be folded to the core function of the type style, with a limited type within the parietal insert core. The main difference is that Core

Structure, such cores can not be demolished in the mold can be used to model mechanical things out. In addition, if the core of this type is inductive Melting

Melt away, such as low melting point (138oc) tin – tin-bismuth alloy or other alloys, is in the second operation was (soluble acrylic polymer

Property) line wash. That the melt core molding process using conventional methods, the main difference between the two cores and the thermal properties of different cavity materials.

Core thermal performance directly affects the movement of workpiece surface – thickness of core structure. According to the actual processing conditions, thickness of top and bottom of the epidermis

Different, in some cases, possible warping of the defect, while the other cases, there may be reduced or defective workpiece, fire-prone

Warping phenomenon.

Core melt molding method which, as the die wall cores only. Filling process does not change inserts for solid state. As the metal alloys or polymers Core Core

The thermal properties quite different, so it required a different pressure. Core polymer play the role of isolation wall, and molding products in

Have a very thin fluid surface; metal cores become scattered hot spots formed in the workpiece is relatively thick fluid surface. If the plastic melt out of date

Core surface has melted, will have a flow of fundamental change. Article has been reported as a type of ice core. Liquid film interface in the presence of ice and plastic

Very complex processing problem can be solved, this method is feasible for high-precision workpieces.

8. Computer-aided prototyping

Using computer-aided engineering (cae) on the design and analysis process will help shorten the design cycle and avoid costly mechanical failures. Business

Simulation of the industry code commonly used in the current lane marked size, to balance the melt in the runner system and the cavity flow, while identifying the best open gate

Settings and the number of gates. Calculated tonnage of the injection pressure Harmony module processing according to different conditions and materials may be. Combination of shrinkage and warpage rate

Can accurately estimate the initial flow out. It is important to make this design tools to help skilled analysts in a research design or processing

Operations research to judge the time. The results must be understood as to study the objects and processing / material as the premise. When considering the use of this method is accurate and enter

Data, can be tremendous benefits. In addition, this analysis will enable the economy of the design cycle required for the production of shorter and shorter.

Should be reminded to note that commercial cae procedure is usually not used directly. Fully mimic arguably generate valuable insights, but the results

Must be re-estimated to reconsider its limitations. Injection molding application of modern computer simulation is limited to pure viscous fluid

(Not including the viscoelastic melt plastic). Melt into the mold cavity can predict the actual flow rate announcement on composition and performance, as can be

Viscoelastic analysis of high precision. Currently used by any other processing methods can not reach this advanced level, and in recent years,

Simulation equipment from the leading industry and university research team has made good progress. Several companies are working on simulation technology

Operation, in order to correctly explain the more realistic plastic behavior and processing phenomenon. For example, the polymer main chain orientation on the physical properties and the local

Performance distribution. Physics is a very complicated process, but some of the phenomena of viscoelastic body is still not fully understood, a more perfect and reasonable

Processing methods are now slowly emerging. The more powerful way to get much higher than current design capacity


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