Demoulding of precast member without damage to either the components like lifter or mould is critical to successful replication process for the particular complicated design. During mould design, the designers concentrate to make minimum draft (nearly 10 ) on mould to wherever the possible to minimize demoulding force and resultant stress on lifters and prevent on weaker part of the precast member.
For Example,
CONTRIBUTORS DURING DEMOULDING WITHOUT SLOPE
The above picture shows influencing factors for demoulding force. In this case the resultant DEMOULDING forces like vacuum & friction (Area of contact, Coefficient of friction & Normal contact Pressure) along with self-weight of precast will increase demoulding force. If the demoulding force exceed the lifter capacity limit leads to fail the lifters. So, we can’t able to lift this precast member. To eliminate this type of failure. We need to provide slope where contact pressure or interface adhesion develop.
CONTRIBUTORS DURING DEMOULDING WITH SLOPE
The above picture shows the effect of demoulding slope. Where the 10 slope didn’t affect too much the original shape of precast, but considerably minimize the demoulding force. The slope reduces the frictional force & provide passage to air enter where vacuum force develops.
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