Mold shear edge

Figure 11-118. Matched mold shear edges. The better design is to use the lower angle (left).

Mold construction FRP spray metal, cast aluminum gusket seal, air vents, self-sealing injection port FRP FRP, spray metal, cast aluminum, pinch (land) Metal, shear edge High grade steel shear edge... 

Part trim equipment Generally expected mold life (parts) 3,000 Yes 1,000 3,000 With optimum shear edges, minor trimining only 150.000+ 150.000+ ... 

Once the boundary conditions are applied, the pressure field can be solved using the appropriate matrix solving routines. Note that for mold filling problems, there is a natural boundary condition that satisfies no flow across mold boundaries or shear edges, dp/dn = 0. Once the pressure field has been solved, it is used to perform a mass balance using eqn. (9.144) or (9.145). Once the flowrates across nodal control volume boundaries are known, a simulation program updates the nodal control volume fill factors using... 

Mold design is a decisive factor for the molding success such as dimensioning and location of the sprue gates, dimensioning of shear edges, flow aids, cooling and ejector techniques, etc. 

With backpressure the process is performed in conventional injection molding machines (IMMs) (Chapter 4). The cover stock is inserted and located in an open mold. A shear edge mold permits draw-in of the cover stock during the closing cycle to avoid wrinkles and damage by stretching of the fabric. Molds require special attention. They generally use a hot runner system with its shut-off nozzle(s). All mold elements such as ejector, core pulls, and slides have to be on the injection side mold half. 

Fig. 6-3. Schematic of closed mold using a shear edge around the cavity periphery.

Mold construction FRPt spray metal, cast FRP FRP, spray metal Metal, shear edge High grade steel ... 

To ensure an easy inserting of the reinforcement structure into the cavity, molds with shearing edges are used (Figure 1.240). Exact positioning of the reinforcement... 

FIGURE 1.240 (a) Mold without a shearing edge (b) mold with a shearing edge... 

Situations where the polymer is subjected to shear forces are the ones most commonly considered. Shear forces are imposed on polymer melts by rotating screws and by flow through dies. In theory the polymer touching the metal surfaces is stationary, and hence a vclocit> gradient occurs between fixed and moving parts, and between the center and edges of a die channel or mold runner as shown in Fig. H. 

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