General problems encountered in Casting – Casting Defects:
Casting is one of the most important step in the ceramic article manufacturing. A number of defects in the ceramic ware can be formed due to improper casting methods and techniques. Defect in ceramic ware is a direct loss on profit margin. It may be true that all the defective wares are not scrap, but still one should not forget the re-work cost required to correct the defect. Hence it is very important to address the root cause of defects and implement necessary corrective measures to prevent such defects.
As mentioned already the main casting methods followed for Ceramic Ware manufacturing are dry pressing and slip casting methods. Both the methods have their own advantages and disadvantages. For instance the dry pressing method is the most quickest method when compared to slip casting method. But the dry pressing method requires that after firing there is no major change to the dimensions and shape of the ware. If the ware expands after firing then it could be re-worked for size reduction. But if the ware shrinks after firing then it is mere scrap. By both means loss will be placed. After firing expansion will consume cost for re-work and after firing shrinkage is a total loss as the item is scraped. Hence it is very important to maintain the shape of wares before and after firing and it is particularly difficult in dry pressing method to obtain the correct dimensions every time to handle this scenario.
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