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The Process Of Injection Molding Of Optical Components

During the injection molding of optical components, the molding process has an impact not only on its geometry but also on the internal performance of the components. Research on component quality has shown that the change from injection molding to injection-compression molding can only slightly increase the geometry of the components. However, its optical properties are probably able to improve the seven factors, so only by testing the geometric parameters to evaluate the optical properties of components is not enough. It is thus proven that injection molding - compression molding is a suitable method for processing optical components. Optical Products Component Injection Molding During the pressurization process, the pressure phase is applied directly after the compression phase. The pressure is applied to the surface of the part at a pressure equal to the homogeneous distribution. As an example of a different variant associated with conventional injection-compression molding, injection-compression and expansion-compression molding will be described below.

Optical Parts Injection Molding: Conventional Injection Molding - Compression Molding

Compared with standard injection molding, injection molding - compression molding allows the mold to have a flow path / wall thickness ratio of up to 500: 1. It is important that there is no conversion of the flow mark on the surface of the optical component. So each individual process and movement in a cycle must be continuous.

In the filling phase, the mold only opens 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 the screw position as a function. Since the mold is open, the internal pressure decreases or even completely disappears during the injection molding process. The compression stage is initiated by a positionally adjustable screw. Before the cavity is fully filled, Optical Products Component Injection Molding the plastic melt flows along the end of the flow path and is compressed by the subsequent compression stage, which also compensates for the shrinkage of the plastic.

If the cavity is filled with the end of the filling phase, the compression phase begins directly. With the use of some machines, the plastic melt can also be pressed back into the plasticizing unit in the opposite direction to the screw pressure at this stage. In this way, it is possible to produce a member (a wall thickness ratio SA / SI? 3, such as a concave mirror or a negative meniscus scattering lens, Optical Products Component Injection Molding which has a high demand for welds without any welds or selectively transferred to the component edge region ).

Expansion - compression molding

The expansion-compression molding achieved by the use of a mold clamping unit is more suitable for the production of components where the wall thickness remains constant at the cross-section. The advantage of this processing method is that after the molding, the stress is not introduced into the production part, since the pressure is not applied by the screw during the injection molding, but by the mode-locking. So that the pressure in the mold cavity is uniform, and the plastic melt can be cooled almost without stress, thereby obtaining a member having a uniform microstructure.

As with the standard optics component injection molding, the plastic melt filling process of this method is also done in a closed mold. In the expansion phase, Optical Products Component Injection Molding

 molds where the mold clamping force is likely to decrease is opened by means of a screw to a defined and precisely repeatable position. The accuracy achieved by this position control is a key factor in producing components with reproducible wall thickness. The compression process moves the compression core of the mold to the compression position.

When the position is reached (measured directly on the mold), the compression process begins and the filling process stops immediately. The compression and containment stages consist of a multi-stage clamping force / compression force distribution.

Both expansion compression molding and injection-compression molding can vary the compression ratio by compressing the mold core instead of the machine's clamping unit. Optical Products Component Injection Molding However, this only makes sense if the part needs to be partially compressed. Depending on the concept of injection molding the mechanical mode-locking unit, the compression process may also be done only by means of a core. The complete hydraulic lever clamping unit provides the user with the most flexible choice.

In the production of optical components, the 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 desired product. This requires precise process control, that is, the known mold state and the existing process. These speculations require knowledge of cavity pressure. Because the cavity pressure accurately reflects the filling, compression and packing stages during injection molding, these information are helpful during process optimization and for processing and quality monitoring.


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