1964 Volume 13 Issue 128 Pages 287-290
The fabrication of final products in sheet plastics are generally performed by means of vacuum and blow forming methods. Now it is considered that if the conventional process for sheet metal press working operations is applied to the forming of sheet plastics, the working cycle will become more efficient, and then it will contribute to the reduction of production costs. In recent years the studies on this subject have been made by some researchers.
The present study deals with the performance of the stretch and deep drawing operations for the hard PVC sheet by means of the similar tooling as is used in sheet metal pressing. For this purpose, first as the fundamental procedure of the forming condtions, several mechanical and forming characteristics were tested, such as the mechanical properties based on the uniaxial tensile testing, the flow and softening properties, using the Koka-type flow tester, the stretch formability, using the Erichsen testing machine provided with a heating unit, and the deep-drawability by means of the cupping apparatus having conical dies.
From the results obtained in these tests, when cylindrical shells are deep-drawn from a flat blank by means of a conical and a flat-formed dies respectively, the maximum successful drawing ratios achieved in a single pressing were examined. In warm press drawing, it was found that the deep-drawability of PVC sheet within the proper forming temperature range from a minimum value of 56°C to about 90°C was preferable. And also, the deformation mechanism in deep-drawing work of PVC sheet could readily be traced in a similar way to the plasticity analysis for sheet metal drawing, then, the forming limit calculated theoretically was shown in satisfactory agreement with the data given by the drawing experiment. In spite of the excellent drawing formabilty, high anisotropy on the radial draw deformation was generated at the cylindrical part, and as a result of the wide allowance of the thickness of PVC sheet the unsteady forming conditions freqently occurred.
