Runner design

An injection moulding is in the form of a flat sheet 100 mm square and 4 nun thick. The melt temperature is 230°C, the mould temperature is 30°C and the plastic may be ejected from the mould at a centre-line temperature of %°C. If the runner design criterion is that it should be ejectable at the same instant as the moulding, eshmate the required runner diameter. The thermal diffusivity of the melt is 1 x 10 m /s. 

Even though a molder has received a mold intended to meet part performance requirements at the lowest cost, it may not be cost-efficient because of a poor runner design. One can simulate the gate and runner design on commercial CAD programs such as Moldflow before the runner system is built. Once it is built, very limited rework can be done. 

Fig. 6.9. RIM runner design. (Courtesy of W. E. Becker (1979). Reaction Injection Moulding, Van Nostrand Reinhold, New York).

Figure R.6 Runner designs. (Ref Monsanto Plastics and Resins Co. also Schwartz, S.S. and Goodwin, S.H., Plastics Materials and Processes, van Nostrand Reinhold, New York, 1982, p. 876)...

John Beaumont, New Runner—Design Concept Boosts Quahty and Productivity, Beaumont Technologies Inc., Erie, Pa., USA. 

Beaumont, J. P., Revolutionizing Runner Design in Hot and Cold Runner Molds, SPE-ANTEC, May 2001. 

Close cooperation between the mold designer and hot runner designer, as early as the planning phase, is essential for a smooth project flow and optimal product quality. Some full-service providers also support the customer in the design, construction, and complete construction of the injection mold, except for the cavity areas. 

More specific demands of the runner design eould inelude the following points ... 

The criteria for efficient runner design is that the runner should provide a maximum cross-sectional area and a minimum contact on the periphery from the point of heat transfer. 

For multi-impression molds, a balanced runner design is preferred generous radii should be incorporated at each runner junction so as to prevent excessive shear heating to the material during mold filling and/or, causing unnecessary pressure drops to occur. 

Case Process conditions Tumber of gates Cold runner design... 

Consider the simple branching runner design with one primary runner with two secondary runners shown in Figure 6 the concepts presented in this paper may be extended to arbitrarily complex runner systems. One of... 

Controlling Intra-Cavitv Melt Flow and Weld Strength Through New Runner Design Technology ANTEC 05. John P. Beaumont... 

Beaumont J, Steward C, Ezzo M, Controlling Intra-Cavity Flow and Weld Strength through New Runner Design Technolo, ANTEC, 2005... 

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