Mechanical Engineering - Workshop Technology - Discussion

When the pattern is removed from the mould, the parallel surface to the withdrawal direction is slightly damaged and converted into slightly tapered surfaces. These parallel surfaces on the pattern are slightly tapered to compensate for these changes (nearly 1 -2 degrees).

This allows for easy removal of the pattern from the mould while having no effect on the casting process. Draft allowances are the changes made to the pattern surface to protect it from damage.

Shrinkage allowance - As hot metal is poured into mold when it cools its size decreases. To avoid this mold pattern is made a bit larger.

Draft allowance - We can't simply take out pattern without disturbing sand. So a slight taper is produced for easy removal without causing damage to mold.

Shrinkage allowance is nothing but when removing pattern from the mold pattern is extended is called as shrinkage allowance.

Small tapper is provide at edges in order to easy withdraw of pattern with damaging the mold is called as draft molding.

Draft allowance provided for easy to removal of pattern without damaging mold.

Machining allowance is giving some allowance for machining surface or part.

The contraction allowance on the pattern is provided to take care of.

The tool used for lifting the pattern from the mould is called?

Castings are designed with rounded edges and corners so as to.

What is the minimum draft angle for draft allowance?