Molds in the Offer Phase

For molds in the offering phase (Phases 1 and 2), a reasonably accurate but rapid preliminary costing is thus required (supplemented by specified functional costs, if necessary). In the following, the appropriate costing method for this area should therefore be presented first. 

In the offer phase before designing, small changes have to be implemented due to suggestions from mold making. The reason for the changes is generally one of the following ... 

First, the molded part remains on the core after opening the mold. Then, stripper rings 7 and 8 are operated until enough space is created for the molded part to expand. In the next phase, the stripper ring 8 remains on place to allow the strip-over process. A so called 2-step ejector system, which is offered by many manufacturers... 

The unique difference between PPE/PA blends and PPE/HIPS blends is illustrated by (a) the differences in DTUL at 0.45 MPa and the DTUL at 1.82 MPa in glass-reinforced compositions (b) the difference in their relative sensitivity or resistance to chemicals, e.g., some common solvents and automotive fluids (Table 19.26). These differences arise from the facts that (a) polyamide is a crystalline polymer unlike HIPS, which is amorphous and (b) due to the large melt viscosity difference between polyamide and PPE at the normal blend ratios, the polyamide forms the continuous phase. Hence, in the molded parts, the polyamide surface offers resistance to solvent permeation and high softening temperature. In PPE/HIPS blends due to the singlephase amorphous character of the matrix, the solvent resistance is limited, and the heat resistance is limited by the Tg of the blend. Because of these differences, PPE/PA blends have found significant application niches. 

Modern IM processes offer the user numerous, almost confusing settings. Process windows are searched for different times, velocities, pressures, temperatures, forces and paths for the individual phases with respect to their dependencies for each product, the mold used, and the used elastomer mixture. The goal is to produce a product as economically and qualitatively robust as possible. The time required to find optimum process windows is, in spite of technical assistance (e.g., by so-called cure time calculators), still dependent on the experience of the particular user or process engineer and the quality of the resources used (mold, elastomer, machine). 

Table 1 is a partial listing of the comp>ositions of the common p>orous sintered P/M materials. Selected compositions of P/M materials possessing near theoretical full density (>99 %), sometimes called full dense or high-performance P/M materials, are shown in Table 2 [2,9]. Full dense P/M parts are made by liquid phase sintering, powder injection molding, extrusion, or hot isostatic pressing. Important full dense P/M materials include P/M superalloys, P/M tool steels, several P/M aluminum alloys, and many P/M specialty alloys. Owing to their refined microstructure and greater homogeneity, full dense P/M materials offer superior mechanical properties with equal or superior corrosion resistance, compared to their wrought or cast counterparts.

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