Performance analysis of the incremental sheet forming on PMMA using a combined chemical and mechanical approach

Single Point Incremental Forming (SPIF) has been widely investigated highlighting advantages as low-cost, higher formability and greater process flexibility if compared to traditional processes [1]. Recent works have proven the SPIF feasibility for polymers processing. Experimental researches have been carried out with the aim to investigate the influence of several working variables, i.e. spindle speed, tool diameter, step depth, etc., on the final quality of the formed parts [2, 3]. The processed thermoplastic materials are characterized by glass temperatures close to the room temperature and, therefore, SPIF has been performed without external thermal source, exploiting mostly the friction heat generated during the forming phases. In the proposed work, the attention has been focused on extruded poly(methyl methacrylate) (PMMA) sheets, which are characterized by a glass temperature of more than 100 °C. Because of that, an experimental equipment has been designed and the PMMA sheets have been placed on the top of chamber with controlled temperature before SPIF beginning. The temperature on the upper face of the sheets has been monitored by thermocamera, which has been properly set by matching its readings with the ones extracted by a thermocouple in contact with the sheets. SPIF at different temperatures has been carried out by changing both the heater temperature and the process parameters which have an influence on the workpiece heating. The influence of the highlighted process conditions on the worked parts and on the process feasibility has been investigated. Furthermore, examinations on the quality of the formed parts have been performed pointing out the effects that different process conditions have on surface integrity.