Sharp corners in casting design may cause defects in the casting but it helps in strengthening of pattern material.
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Sharp corners in the casting design also produce the problem of sand inclusion in the castings.
In horizontally parted moulds, a draft is required for vertical as well as for horizontal surfaces of a pattern.
In casting design, concave junctions are generally added to avoid the effect of sharp corners in the casting.
In pattern fillets, the size of a fillet is usually determined by its width.
A very large fillet in casting design also may cause shrinkage defects in the casting.
Sharp internal corner of the casting also causes the misrun defect in the casting.
To avoid sharp external corners in casting design, rounding of external edges is done in pattern making that termed as radii.
Finishing allowance to a pattern is generally provided to avoid various defects in the casting.
Finishing also includes removal of scales from the surface of the casting.
Subsequent machining for products finishing does not require extra material to the metal casting, as it removes negligible amount of material from the casting.
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