Thermoplastics as well as thermosets and elastomers can be processed with the injection molding process, although for cross-linking polymers modified equipment in machines and adequate molds, which are generally heated to 120 to 180 °C, are needed. Due to the large majority of applications, the following covers primarily molds for thermoplastics, with temperature control between 10 to 120 °C, which can go up to 200 °C for “exotic”, highly heat-resistant thermoplastics.
Generally, mold making shows a very broad spectrum of use, and molds are needed for a number of processes in plastics manufacturing. Molds have their special features in all areas; some of these features can be derived from process engineering, and others partly evolved from history (Figure 2.1).
Due to its exceptionally advantageous combination of properties that are of critical importance for tools and molds, steel is the principal material used in the plastic mold making industry. There is now a range of custom steels available for mold making, with the steel undergoing specialised processes at steel manufacturers to achieve the service hardness required for global applications. Another distinguishing feature of steel as a material is that its functional properties can be adapted to special requirements by further appropriate heat treatment and/or surface finishing
As in other areas of activity, the manufacturing of molds is subject to constant change; driven by technological changes in design process, mold construction, programming, processing, and assembly. This requires continuous changes in processes and reorganization of the business to new investment and training. The fact that the manufacture of molds is strongly influenced by knowledge, experience, and information remains unchangeable. The complexity of the “manufacture of a mold” process is shown in the following.
Plastic injection molds are typically special molds and are essentially individual parts, despite all the standardization efforts of the individual components (standards). However, this aspect alone has an enormous impact on the production costs of such a product. But also the other operational services to be provided in connection with the injection mold (e.g., a constructive, qualitatively perfect design, project planning in agreement with the customer, as well as management and distribution of mold) must be mostly based on a single project and a single customer. A digressively effective and balancing cost distribution, as is possible in series production, can mostly not be carried out.
