Mold concept

In 1992, a new sandwich injection molding concept, called monosandwich, was developed by Jaroschek and Thoma (Ferromatic Milacron). In contrast to the standard sandwich molding process, this technology uses only one injection unit for both skin and core components with an extruder. 

Design product Decide on quantity Decide number of cavities Select molding rrrachine Set mold specifications Screen candidate vendors Issue quote request Review quotes Review mold concepts Finalize product drawing Place order... 

As reviewed in the section on CIIM and included as CSE in Fig. 2-16, there is a computerized shrinkage analysis program (112). This program takes into account processing variables that affect shrinkage (Table 2-10). To do the job, it is designed as part of the total molding concept (TMConcept). 

High-speed-molds should preferably have a design with a take-out process using horizontal handling systems via the shortest route. In the vertical process, the pieces usually fall down onto conveyor belts (that can be directed by a vertical directed breeze). A special design is called the non-open mold concept. In principle, this concept does not... 

Structural reaction injection molding (SRIM) is usually used to produce stiff composites containing polyester or epoxy matrices. In such techniques, the mold consists of a cavity which can be subjected to vacuum. The fiber reinforcement structure in the form of mats or fabrics is placed into this cavity prior to applying vacuum, followed by injecting the two-component polymer. Vacuum, sometimes in combination with pressure, is used to introduce the polymer into the mold cavity and to force it to penetrate the fiber reinforcement structure and form the polymer matrix. For elastomer composite formation, this molding concept is new. The mold development was made because of the higher viscosity in typical two-component elastomers compared to normal polyester- or epoxy-based rigid matrix polymers. 

FIGURE 1.225 Mold concept for joining bearings during the forming process and component with a bearing seat... 

Similar mold concepts are also possible for the integration of bearing elements in thermoplastic fiber-reinforced plastic components [12],... 

The variety of process variations in resin injection also offers more options in the design of the molds. The most important basic functions are similar in all mold concepts. These include compacting of the reinforced semifinished part and contouring of the components, up to curing and demolding [2,13,14]. 

Another very common process (known since 1950) is the resin transfer molding (RTM) process. Filling the cavity is not done through applying vacuum, but through pressure. The basic production process for a component is similar to the vacuum process but is more demanding in terms of the injection mold. In the pressure-sup-ported injection processes, only mold concepts with fixed mold halves can be used. 

With this mold concept, complex mold geometries can also be realized. If the base plate is replaced with a contour plate, as seen in Figure 1.233, a component with a defined bottom side and defined side surfaces can be obtained. The use of a distributer medium is here recommended. 

The venting of the mold can also be important for the process control. In vacuum-assisted processes, the vacuum pump stays active during the entire injection process and is protected from penetrating matrix material by a resin trap. If a plastic tube is used for this venting line, the moment the resin flows out of the mold can be easily recognized. If more lockable exits of a cavity are used, an online flow path control can also be realized in ciosed mold concepts. The construction of a closed injection mold with two fixed moid haives is dependent on which effort for the actual application is justified or necessary for the process-related implementation. 

The manufacture of hollow components can be done with the aid of different processing procedures depending on the component geometry. Here, the aforementioned mold concepts and mold requirements for vacuum and pressure-assisted processes can also retain their validity. New mold requirements arise for the manufacture of the hollow space in the component. 

The use of the hot runner technology allows only certain component geometries and mold concepts. With hot runner systems, gating positions are achieved that cannot be reached conventionally the active movement or complete avoidance of fill lines can be implemented by sequential injection multi-component injection molding can be performed with up to five materials in a mold high-speed stack molds can be built film and fabric can be back injected gas and water injection technology can be implemented multi-cavity molds can be realized clean room production can be optimized and the co-injection technique can be enabled. 

FIGURE 2.71 Mold concept of a LSR mold (company picture DME)... 

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