Designing Considerations for Rotational Molding

Designing considerations for Rotational molding

· Draft Angle: These are required to remove the product from mold. Presuming no rough surface or holes, a draft angle of 1° may work for outside wall. But for inside one, like the inside of a boat hull, the draft angle maybe need to 5°. This is because of shrinkage and possible part warping.

· Structural support ribs: Solid ribs may be desirable and achievable in injection molding and other processes, but for rotational molding, a hollow ribs is best way. A solid rib may be achieved through inserting a finished piece in mold but this increase cost.

· Depth of the recess: Roto-casting molding is good at manufacturing hollow parts. However, we should pay more attention on the depth recess. When it is greater than the width, there would be problems with even heating and cooling.

· Enough room between walls: As we know, rotational molding can produce multi-wall products. It requires enough room to be left between the parallel walls to allow the melt-flow to move smoothly throughout the mold. Or webbing may occur. A desirable parallel wall scenario would have a gap at least three times the nominal wall thickness, with five times the nominal wall thickness being optimal. Sharp corners for parallel walls must also be considered. With angles of less than 45° bridging, webbing, and voids may occur.