Shrinkage defect is very harmful for sand castings. It can cause poor dimensional accuracy, aesthetic damage and structural weakness.
How to minimize shrinkage?
The right pattern
Technical design tools and casting expertise help us to predict the exact degree of solid shrinkage that will occur for a specified casting, so that the pattern can be made fractionally larger than the end product.
The right metal alloy
Alloys have different characteristics as they cool, which will affect shrinkage.
A good running system
The gating and riser system for pouring metal into the mould must be carefully designed to take account of the order in which areas will cool, so that the casting is fully fed with alloy.
The right pouring temperature
Liquid shrinkage may increase if the temperature of the poured alloy is too high. Too low, and the feeding capacity of the risers may fail, restricting the flow of metal.
Therefore, the casting temperature should be calculated accurately according to the ambient temperature and the thermal properties of the metal before casting.
Good casting structure
Careful design can ensure the casting cools evenly, reducing hotspots and therefore helping to manage shrinkage.
How to check for shrinkage?
We perform visual inspections, as well as spectrographic atomic absorption and non-destructive testing, such as ultrasonic flaw detection, so you can be assured that our castings are free from shrinkage defects.
Sand casting in iron foundry
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