Gate design

The  metal  entering  the  sprue  is  directed  into  one  or  more  passages,  or  runners.  Near  the  die  cavity,  the  cross sectional area of the runner decreases to form a gate designed to direct the metal into the die cavity. The main function of the runner and gating system is to deliver molten metal passed into the mould into all section of the molten cavity. Runner and gate are major components in this design system. for the ingate design. Cast material is selected and then cavity volume  is  calculated.  Once  mechanical  properties  of  cast  are  input  and  the  filling  speed  of  molten  material  into  dies  is selected, the gate area is calculated.

Runner Design
The runner is machined entirely in the ejector half and the cover half forms only the flat side of the runner. After the cross sectional area of gate is determined from equation, that of runner can be calculated based on volume constancy point of view. And then the shape of runner is selected from database. The width and depth  of  runner  varies  with  the  volume  of  metal  to  be  injected  into  the  cavity.  Finally,  the  shape  and  numerical  data  are generated. Various shapes of runners are illustrated. Cross sectional shape of runner is inverted trapezoidal, Generally,  the  area  of  runner  is  4~5  times  of  that  of  gate,  the  fraction of  depth  to  width  1:1.5~3.0,  side  angle 10~20°, and corner radius longer than 6mm

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Overflow Design 

Overflows  provide  exits  for  the  air  from  the  casting  cavity  and  serve as  receptacles  for  the  first  metal  entering  the  die cavity during each shot. They provide additional mass to small casting, thereby helping to maintain a satisfactory and stable die temperature. Overflows are closely spaced in the thin sections of the die cavity and around the areas of die cavity that are farthest from the source of hot metal. Venting may also be provided by small grooves cut across the parting plane of the die, or by the clearance around the ejector pins or movable cores and slides. The volume of overflow is determined by equations as above and then the geometry of overflow (the shape of cross section, width and depth) is selected from database. Finally,-overflow is generated.