In the every manufacturing process defects is mandatory. Defect is condition of the casting when its finalized. And that must be removed by several process otherwise it will categorized to the rejection. There are many types of casting defect which resulted from many cause. It can be removed by proper die design. proper pouring method proper gate and riser design and proper coating cycle. Defect is lost casting quality.
Dependencies of casting defects and discontinuity
1) Mould Design.
2) Pattern Gate Design.
3) Pattern Assembly Design.
4) Coating Cycle and Precoat Viscosity.
5) Melting speed and its temperature.
6) Yield Method
There are many types of casting defect as we discussed below.
1) Hole of Gas
It exists on the casting surface in inside area also. Its shape is irregular like oval, round like this. If it is appear on the casting surface than it can be solves by welding process, but when gas hole is in side the material than it is inspected by the various test. However it appear only after machining. It cause s due to low temperature of metal and pouring speed is very slow.
Gas hole also happen when ceramic mould is not preheated perfectly. It can be solved by increasing temperature of pouring metal, proper preheating of Ceramic Mould. and remove slog from surface.
Gas hole also happen when ceramic mould is not preheated perfectly. It can be solved by increasing temperature of pouring metal, proper preheating of Ceramic Mould. and remove slog from surface.
 |
| Gas Hole |
.
2) Shrinkage
This is a most common defect in many manufacturing are. In this field there are two types of shrinkage is a) wax shrinakge 2) Metal shrinake. Wax shrinkage gets solved from the mould. But metal shrinkage is very crucial problem. When the gating system is not proper than its happen. The gate of pattern should be proper draft angle. Below fig shows a draft of gate.
 |
| Draft Angle |
Shrinkae defect occure when metal feed is very slow. In this there are two types of shrinakeg open shrinkage in which when freezed cast contract its size in atmoshphere and close shrinkage is porosity in metal. Especially shrinake is occure where the casting is enter from gate.
 |
| Shrinkage |
3) Mismatch
This defect cause due to improper assembly of wax mould and parting line gets mismatch.
 |
| Mismatch |
4) Sandwash
Sandwash defect cause to sharp corner of wax pattern. In coating cycle precoat is first layer. Due to very small size of sand particles sand is trapped on wax edge and its exists on casting edge. To resolve this remove sharp edge of pattern make a radius on it.
 |
| Sandwash |
5) Penetration
When the sand size grains is larges, the molten fuses into the sand These casting defects appear as an uneven and rough surface of the casting. and solidifies giving us metal penetration defect. It is caused due to large grain size, low strength and high permeability. Because of this the molten metal penetrates in the molding sand and we get rough or uneven casting surface.
 |
| Penetration |
6) Bulge
Bulge is cause due to shell is very thin, deform in dewaxing, Molten metal pressure is very high. In this defect some of surface area is blooming. Tor resolve this decrees the pressure of metal and height poring height.
 |
| Bulge |
