Molding Technology for Hollow Parts: 3D Suction Blow Molding

General-purpose blow-molding technologies, such as those used for plastic bottles, are constrained to mostly symmetrical shapes because the parison follows gravity when blown up in the mold. In contrast, 3D suction blow molding, as the name suggests, blows up parisons introduced into the mold cavity under suction to create a 3D shape, enabling parts with long and complex shapes to be formed in one shot. In addition, a control mechanism called Radius Wall Thickness Control (RWTC) facilitates even thickness and enables the difference between the inside and outside circumference to be adjusted, irrespective of changes in thickness or increases and decreases in wall thickness for each part. Toray has partnered with Kautex Maschinenbau, a leading German machinery manufacturer, to promote the fusion of material and molding technologies.

In general, blow molding resins require an optimized melt viscosity and retention stability in order to be compatible with the process. In addition, the RWTC control mechanism mentioned above is useful for 3D suction blow molding, and an optimized melt viscosity is desirable for each shear rate optimized for parison shape retention.
With this in mind, Toray has selected matrix polymers to develop and provide optimal materials for a range of environmental temperatures. The figure shows our approach to grade deployment. In particular, PPS resin has high heat resistance that provides high part performance, but the low melt viscosity means it is generally difficult to optimize for 3D suction blow molding. However, Toray's proprietary technology has succeeded in developing ultra-flexible PPS that can handle various processing methods.