Investment casting gating system design is different from ordinary sand casting, because it is not only guide the liquid metal into the cavity of the channel, but also act as the bearing function on the wax module and shell and the channel guiding pattern material in and out of the cavity.So it is extremely important to design investment casting gating system.If the design is not reasonable, it will not only affect the quality of module assembly and demoulding, and will directly affect the quality of cast iron castings, to cause the casting defects such as shrinkage cavity, porosity, slag inclusion,cracks,ect.
In general,we should follow below demands when designing investment casting gating system:
1)When introducing the liquid metal into cavity,for easy oxidation alloys,we should fill smoothly as much as possible to avoid oxidation and involving in gas.For investment castings with thin wall thickness,we should ensure good filling and do not produce cold insulation and misrun phenomenon.
2)As the gating system also act as the riser role,so we must ensure that the castings will get directional solidification to the gating section and fully feeding in the casting solidification process,so as to avoid shrinkage cavity or shrinkage in investment castings.
3)Because the gating system will bear the module and the shell,so it should has sufficient strength,in order to prevent casting off in the shell making process.
4)The gating system will guide the mould material in and out of the cavity,so we should be keep it smooth to remove mold material.
5)When design gating system,we should simplify the structure of pressure type,and make investment casting process like molding,compound,shell making,cutting convenient.
6)Under the premise that ensure the quality of investment castings, should reduce the metal weight of pouring system as far as possible,in order to improve product rate of investment castings.