Manufacture of polyurethane foam parts for automotive industry using FDM 3D printed molds

Abstract

Metal molds have traditionally been used in the manufacture of polyurethane foam parts. This type of molds presents several disadvantages: have a high cost; need a long time for their manufacture; involve the use of release agents during the demolding operation. As an alternative, the use of molds manufactured by fused deposition modeling is proposed. These 3D printed molds have a poor surface finish, which complicates the demolding operation. To overcome this handicap, materials that can be chemically polished have been studied: acrylonitrile butadiene styrene and high impact polystyrene. Acrylonitrile butadiene styrene can be polished by exposure to acetone vapors and high impact polystyrene by immersion in limonene. This post-processing operation allows to reduce the surface roughness of the 3D printed mold. To simulate the industrial use of the mold, seven molding-demolding cycles have been performed. To measure the ease of demolding of each material, a pull-off test has been used. The results indicate that and high impact polystyrene has less affinity with polyurethane foam than acrylonitrile butadiene styrene. In addition, although release agent is used in cycle 1, with high impact polystyrene specimens, it is not necessary to use it in cycles 2, 3 and 4; this means a saving of release agent. Furthermore, the chemical polishing of high impact polystyrene by immersion in limonene has several advantages: it is performed in a short time; it allows to obtain an excellent finish regardless of the initial surface roughness; it is done using a biodegradable solvent of organic origin. To experimentally demonstrate the viability of the proposed solution, a mold for the back of a car seat has been printed in high impact polystyrene via fused deposition modeling and chemically polished by immersion in limonene (1 min); the geometrical deviations generated were less than 1 mm