Page 48 - Handbook of Plastics Technologies
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INTRODUCTION TO POLYMERS AND PLASTICS


                             1.34                        CHAPTER 1




















                                        FIGURE 1.32 Free-blowing process. 69


































                                      FIGURE 1.33 Matched die thermoforming. 70



                               Multistep forming is used in applications for thicker sheets or complex geometries with
                             deep draw. In this type of thermoforming, the first step involves prestretching the sheet by
                             techniques such as billowing or plug assist. After prestretching, the sheet is then pressed
                                                                        35
                             against the mold. Multistep forming includes the following:




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