注塑模具设计毕业外文翻译.docxVIP

The Injection Mold —The design of Runner The basic The runner is a channel machined into the mod plate to connect the sprue with the entrance(gate) to the impression. In the basic two-plate mod the runner is positioned on the surface while on the more complex designs the runner may be positioned below the parting surface The wall of the runner channel must be smooth to prevent any restriction to flow. Also, as the runner has to be removed with the molding, there must be no machine marks left, which would tend to retain the runner in the mod plate. To ensure that these points are met, its desirable for the mod designer to specify that the runner(channel) is polished fin line of draw1. There are some other considerations for the designer to bear in mind: (i) the shape of the cross section of the runner, (ii) the size of the runner. Runner cross-section shape The cross-sectional shape of the runner used in a mod is usually one of four forms (Figure 4.2): fully round (a), trapezoidal (b), modified trapezoidal (c) and hexagonal (d). The reason why these particular forms are used in preference to others are outlined below. The criterion of efficient runner design is that the runner should provide a maximum cross-sectional area from the standpoint of pressure transfer and minimum cross-sectional area to periphery will, therefore, give a direct indication of the efficiency of the runner design; the runner section are giver in Figure 4.3. As can be seen, the various types of standpoint; whereas the ratios exhibited by the semicircular and rectangular types make their use generally undesirable. Unfortunately, the square runner is not very satisfactory either, but for another reason: it is difficult to eject. In practice, because of this, an angle of 10°is incorporated on the runner well, thus modifying the square to the trapezoidal section. The volume of the trapezoidal runner is approximately 25% greater than that of a round runner with coiTesponding dimensions (W=D, Figure