Injection molding tooling

Fig. 13.3 (a) Schematic view of injection molding tooling showing the tip of the injection system... 

Fig. 13 Injection mold tool with two cavities for bipolar plate production...

It is an ideal production process with the proviso, that large batches are produced, because the injection molding tool is usually made for a single article only. 

These two demands on the injection molding tool are thus fundamentally different. Therefore, there can also be great structural differences between molds used for the processing of thermoplastics and those employed for the processing of reactive molding compounds. 

A wide variety of ejector designs may be used. The choice depends on the shape of the article, its position within the mold and the force retaining it Figure 4-11 shows a pin system as an example of an ejector in an injection molding tool. 

The cooling time equation has been derived at as a simple approximation for defining heat-transfer within the molding during the cooling process in the injection molding tool ... 

An injection molding tool must fulfill several primary tasks, which in turn give rise to secondary tasks. 

For the geometrical layout of a mold, CAD (Computer Aided Design) systems are available nowadays, with which an injection molding tool cannot only be described by two-dimensional drawings, but also shown as a complete 3-D model. The latter is of particular interest for the description of the often complex, shape-giving mold contours. The input for producing such a model... 

Figure 8-1 Functions of an injection molding tool (splits mold)...

With knowledge of the material temperature, wall temperature, ambient temperature, plus the specification of the article removal temperature, it becomes possible to analyze the energy balance of the overall mold. Decisions on whether and how to provide the mold with thermal insulation arc made at this stage of the layout. The performance of the temperatiue control system is also established at this stage. Figure 8-5 shows the heat balancing of an injection molding tool. 

The plane, in which the injection molding tool separates, when it is opened complex molds must often be provided with additional parting... 

That part of the injection molding tool, against which the nozzle pushes during the injection process to inject the melt. The bore of the sprue bush is cone-shaped and with many single impression molds connects directly into the cavity... 

The machining of press tools of large sheet metal parts such as car parts or injection molding tools of large plastic products needs the removal of a large quantity of material to produce high quality 3D surfaces. Productivity is enhanced by reducing the control of... 

Micromolding, Fig. 10 Example of injection molding tool fabricated using Ni electroplating (a) and the resulting features in COC (b) (From Trichur [20])... 

In-mold decoration. With the broadening use of polycarbonate-based resins in consumer items such as mobile phone handsets and external automotive panels, the need for rapid, paint-free part decoration is beginning to be met via in-mold decorating solutions. In tbis process, a decorative film is placed in the cavity side of an injection-molding tool, the tool closes, and a resin substrate is injected behind the film for rigidity. Due to the broad performance capabilities represented by the various copolymers and blends of polycarbonate, the choices of film and substrate can meet a variety of unique product requirements while still providing the adhesion needed between the two materials. Typically, choices for the decorative film are driven by color, texture, and weatherabihty requirements, while the substrate resin is chosen primarily for processability in order to adequately fill the part without damaging the film. 

Blow mold and extrusion tooling required only—cost is 30-40% of injection tooling cost. Superior for very low volume requirements under 500,000 per year. Must have three core rods for each cavity and an injection mold. Tooling is precise and expensive. However, high price is justified by higher efficiency and is some times indicated by preference for this method. 

The use of a 0.5 mm layer of modified tungsten disulfide in injection molding tools for polymers allows faster demolding from the molds and reduces mold wear, in some cases reducing or eliminating the need for lubricants and release agents. ... 

One must carefully evaluate the overall costs associated with insert dry film molding compared to coating. Dry film molding requires a thermoform tool, a system to place the preformed film in the injection mold, an injection molding tool, and a trim process. 

The design of injection molding tooling is a complex process. In a commercial process the tooling usually contains multiple... 

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