Postmolding Operations

Moldable holes and inserts can complicate molding and may require extra postmolding operations. Thus, the most economical designs are those that minimize the number of holes. With many plastics, both external and internal threads can be molded, but sharp V threads should be avoided because they can cause the plastic to bridge, resulting in incomplete thread fill. Rounded or modified buttress threads will allow improved thread fill. 

Thermosets. The potential of thermosets is not solely a function of mechanical performance. These materials have established themselves as suitable for many demanding environments. The potential must be measured in terms of their ease of fabrication into parts. This is where limitations have existed for reinforced thermosets, specifically polyesters this, in combination with the limitation related to the necessity of postmolding operations to obtain high appearance surfaces. 

Postmolding operations such as final cleanup, trimming to size, or minor repairs can be carried out immediately after the full cure cycle. 

Postmolding operations Finishing—painting Paint chips off easily Finishing—not required... 

When this type of flow pattern is impractical, an alternative may be a through hole or tube formation combined with a postmolding sealing or closing operation by spinning or ultrasonic welding. At the other extreme, consider a 1 /4 in. (0.6 cm) diameter core exposed to a pressure of 4,000 psi (28 MPa) with an allowance for deflection of 0.0001 in. (0.00025 cm) and determine how deep a blind hole can be molded under these conditions. 

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