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NCK Technology Co.,Ltd

Process Of Injection Molding Of Optical Product Components

In the process of injection molding of optical product parts, the measurement of cavity pressure is limited because it cannot be labeled on its surface. But in order to use this important process parameter for quality control, a non-contact measurement method using a special measuring pin is used to measure the cavity pressure. This does not include the quality of high-end optical components, on the contrary, just to use the highest ...

In the process of injection molded optical components, the measurement of cavity pressure is limited because it cannot be labeled on its surface. But in order to use this important process parameter for quality control, a non-contact measurement method using a special measuring pin is used to measure the cavity pressure. Optical Products Component Injection Molding The flow path is coupled to the Pvt diagram to develop new processing monitoring techniques.

This does not include the quality of high-end optical components, on the contrary, just at the highest level of quality to produce the actual application of optical components. As far as the prism is concerned, not only its geometrical shape and surface structure play an important role, but also the repeatability of production can greatly affect the internal performance of products such as internal stress or molecular orientation. Therefore, in the case of the production process to assess the optical performance of the product, Optical Products Component Injection Molding only by checking the geometrical shape of the parts or to the naked eye to check the surface of the parts is not enough. The measurement of optical properties is more important. For example, the distortion of the wavefront measured by a Shack-hartmann sensor (SHS) can be used as a determinant. Use mathematical methods to push the performance of more important quality functions.

For continuous production processes, such as injection molding, it is difficult to use the above method for optical testing. There is no doubt that the need to place sensitive test devices from the outside is a time-consuming process. And we need to wait a long time in this process until we get the test results. This delays the entire production order, especially at the start. Generally speaking, the machine must stop working in the above time period. Optical Products Component Injection Molding Considering the long production cycle and machine cost, it is unacceptable to produce waste products.

Machining variants for manufacturing optical components

During the injection molding process of optical product components, the molding process not only has an effect on its geometrical shape, but also has an important influence on the internal performance of the components. Research on the quality of components has shown that, for example, plastic injection molding-compression molding can only slightly increase the accuracy of the geometrical dimensions of the parts. However, its optical properties can be improved by about 7 factors, so it is not enough to evaluate the optical properties of a component only by measuring geometrical parameters. Therefore, it is proved that injection-compression molding is a suitable method for processing optical components. In the compression process, the pressure phase is directly after the compressing phase. Optical Products Component Injection Molding Pressure is applied to the surface of the component by a homogeneous distribution of pressure. As an example of the different variants associated with the conventional injection molding-compression molding, Optical Products Component Injection Molding the injection-compression and expansion-compressive moulding is described below.

Conventional injection moulding-compression moulding

Compared with the standard injection molding molding, the injection-compression molding allows the mold to flow/wall thickness ratio up to 500:1. It is important to have no conversion flow marks on the surface of the optical components. Therefore, each independent process and movement in a cycle must be continuously connected.

In the fill phase, the stencil opens only a little. The gap size corresponds to the value of the compression stroke. After the plastic melt is injected into the mold, the compression process begins with a function of the screw position. Because the mold is open, the internal pressure in the injection process decreases or even disappears completely. The compression phase begins with a position-adjustable screw. Before the mold cavity is fully filled, the plastic melt flows along the end of the flow path and is compressed by the subsequent compression phase, which also compensates for the shrinkage of the plastic.

If the cavity is filled at the end of the filling stage, Optical Products Component Injection Molding the compression phase begins directly. Using the settings on some machines, the plastic melts can also be pressed back into the plasticizing unit in the opposite direction of the screw pressure. In this way, a component (a prism, such as a concave or a negative meniscus) that is required to produce a weld mark that is not fused or selectively transferred to the edge area of a part (Sa Si).

Expansion-Compression Molding

The expansion-compression moulding using the Clamping unit is more suitable for the production of parts with constant wall thickness at cross-section. The advantage of the processing method is that the stress is not introduced into the production parts after the molding, because the pressure is not applied through the screw, but through the locking mode. Thus, the pressure in the cavity is homogeneous, and the plastic melts can be cooled almost without stress, thus obtaining a homogeneous microstructure component.

As with the standard injection molding method, the plastic melt filling process of the method is also done in a closed mold. In the expansion phase, the mold may gradually reduce the clamping force through the screw is opened to a limited and accurate repeat position. The accuracy of the position control is a key factor that can produce a reproducible part of the output wall thickness. The compression process moves the compression core of the stencil to the compressed position.

When the position is reached (measured directly on the stencil), Optical Products Component Injection Molding the compression process begins, and the fill process stops immediately. The compression and holding stages are composed of a multi-stage clamping force/compression force distribution.

Expansion compression molding and injection-compression molding can change the compression ratio by compressing the mold core rather than the clamping unit of the machine. However, this only makes sense in cases where parts need to be partially compressed. Depending on the concept of an injection molded mechanical clamping unit, the compression process may be done only through the core. The complete hydraulic lever clamping module provides the most flexible choice for the user.

Process Control with three-dimensional problem field

In the production of optical components, three-dimensional problem areas must be managed: the geometrical, surface and optical properties of the components must be included in the quality assessment of the required products. This requires precise process control, which is to speculate on the melt state and the existing process within the known mold. These conjectures require knowledge of the pressure of the cavities. Optical Products Component Injection Molding Because the cavity pressure accurately reflects the filling, compression and holding stages during injection molding, this information can be helpful during process optimization and during processing and quality monitoring.

In an idealized, pressure-free injection molding, the theoretical cavity is filled with isothermal, and the melt is compressed and then cooled, which means that the specific volume is unchanged at this stage (Fig. 1). However, such a fill operation will require very high pressure, which is not necessarily achievable because the method imposes stress on the mold and the machine.

(1) During the injection phase (1-2), the pressure increases with almost constant temperature (isothermal).

(2) After the filling stage of the fixed volume filling cavity is finished, the compression phase begins. The melt is compressed to ensure a certain reproducibility of the shape of the parts being produced.

(3) When the maximum cavity pressure is reached, the pressure-holding stage begins to run. It compensates for the high temperature shrinkage of polymers by supplementing more materials. In other words, the reduction of the volume of parts is caused by the decrease of temperature.

(4) Solidification of the melt at the gate area (the sealing point). The gradual generation of heat shrinkage provides the possibility of reduced pressure within the cavity to ambient pressure (5). This phase (4-5) is equal capacity.

(5) The internal pressure of the mold cavity reaches the ambient pressure, the contraction process begins.

(6) The component temperature drops to ambient temperature. The specific volume changes in the (5-6) phase correspond to the processing shrinkage.

It is important that during the injection molding process, the pressure is fired from the screw through the gate to the component. The cooling effect solidifies the outer flow direction of the component. This results in a pressure gradient within the component during the compression and retention phase, which leads to the generation of internal stresses.

It is important that the Pvt diagram as a two-dimensional description actually gives only a bit of information. That means that it does not describe the pressure state in the part along the flow direction. However, for optical components, the internal performance stability along its flow direction is very important to its quality. This will not induce internal stress generation.

To determine the actual condition of the part, the Pvt diagram must be extended around the flow path to the three-dimensional diagram. Only in this way can we explain that in the standard injection molding, there is a heterogeneous pressure state in the part, which leads to the formation of internal stress. Optical Products Component Injection Molding The screw is used to compensate the shrinkage of the parts through the gate by point pressure, which makes every one points along the flow path in different pvt state. In the three-dimensional diagram, the machining curve is represented by a surfaces and is used to describe the standard machining along the flow pressure reduction and temperature reduction.

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