Secondary forming is one of the methods of forming Shi Ying.  A method of making Shi Ying profiles or parisons into products of desired shape by heating and external force.

 The secondary molding is to heat the Shi Ying profiles such as sheets, tubes and plates obtained from the primary molding to make them in a rubber-like state, deform them into various simple shapes by external force, and then cool and shape the products.  Secondary molding includes hollow blow molding, thermoforming, tentering film molding and other methods, and is only applicable to the molding of thermoplastics.  Secondary forming is a method of forming on the basis of primary forming.