Runner and gate design

Beaumont, J. Runner and Gating Design Handbook Tools for Successful Injection Molding Hanser, 2004. 

John, P. B., Runner and Gating Design Handbook. Hanser Pubhshers, Mimich, Hanser Gardner Publication, Cinciimati Ohio (2004). 

Injection moulding and extrusion may be carried out at temperatures in the range of 300-380°C. The polymer has a high melt viscosity and melt fracture occurs at a lower shear rate (about 10 s ) than with low-density polyethylene (about 10 s ) or nylon 66 (about 10 s ). Extruders should thus be designed to operate at low shear rates whilst large runners and gates are employed in injection moulds. 

Since the materials have a very soft plasticity rating, or inches of flow on spiral mold, the materials are all molded in special transfer molding presses and specially designed transfer molds. Because an acid catalyst and glass or mineral fillers are used to make the compound, these materials may have an adverse effect on the hardened steel mold with the result that there may be excessive runner and gate wear. 

Molding method. Compression, transfer, injection, mold designs, part configuration, number of cavities and their location in the mold, and size and location of the runner and gate system. 

A computer prt ram for the design of flow channels has also been developed to get uniform mold filling. This program is known as runner and gate variaticm (RGV). The resin melt can fills all the cavities at almost the same velosity. The program compu-... 

Mould design (Sprue runner and gate geometries)... 

A three-plate mold design (Figure 2.10) features a third, movable, plate which contains the cavities, thereby permitting center or offset gating into each cavity for multicavity operation. When the mold is opened, it provides two openings, one for ejection of the molded part and the other for removal of the runner and sprue. 

The Lost Foam process (Figure 2.36) starts with the 3D-CAD design and production of a precision moulded foam pattern, made from expanded polystyrene (EPS) or PMMA, produced by automated injection moulding machines. These patterns can be made from one piece or by assembling a number of parts by adhesives. Here usually, a number of patterns, dependent on size, are fixed to a runner-down gating system, made from the same material as the pattern, thereby generating a cluster. 

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