Experimental investigation on the effect of thickness, heating time and extrude direction on thermal shrinkage and thickness variations ABS sheet in vacuum forming process

In vacuum forming process, determining the optimum conditions and selecting the appropriate values of parameters improves the dimensional and physical quality of the components and reduces waste and discarded parts during the manufacturing process. In this research, the ABS sheet with 2 mm thickness was selected and the mold was made from aluminum, then the experimental tests were performed by varying the initial sheet thickness (4 and 5 mm), Six temperature times ("315,"330 ,"345 و"360, "375, "390) and direction of feeding the sheet (vertical or horizontal for extruding). After 3D-measurement of vacuum components, the influence of the values and conditions of the parameters on the thickness and thermal shrinkage changes were studied. Increasing the heating time resulted in improved flow and steady distribution of sheet thickness, While the minimum changes of thickness (up to 2%) for the vacuum of the 4 mm sheet happened in heating time of 345", and for the vacuum of the 5mm sheet occurred in heating time of 390", and minimum thermal shrinkage (0.3%) was seen in heating time of 315" for 4 mm sheet by feeding vertical to the direction of extrudes. By changing the primary thickness of the sheets from 4mm to 5 mm, thickness variations reduced but the thermal shrinkage increased up to 0.9%. The vertical position of extruded materials chained structure with vacuum orientation caused the layers slippage resistance on each other and led to decreased thickness variations from 35% to zero and also reduced thermal shrinkage from 1.2 to 0.3 %.