Investigation of the Strength of Plastic Parts Improved with Selective Induction Heating

Abstract

The use of selective induction heating of molding surfaces allows for better filling of molding cavities and has a positive effect on the properties of molded products. This is particularly important in the production of parts that include flexible hinges, which are thin plastic layers connecting two or more parts of the product. By using hinges, it is possible to expand the use of injection molding products and their capabilities. They are widely used in the production of parts for the electrical engineering industry and for packaging Fast Moving Consumer Goods (FMCG). The use of hinges also entails specific reductions in wall thickness. Increases in the shear rate can be expected, which can lead to the degradation of polymers and deterioration of mechanical properties of materials. This paper investigates injection molded flexible hinge parts manufactured with selective induction heating to improve their properties. To verify the efficiency of reduction of material degradation due to high shear rates, open/close tests of elastic hinges were performed. The linear relation between the number of cycles the hinges can withstand, mold temperature and injection time was identified, where mold temperature was the more significant factor.

Internal Gas-Assisted Mold Temperature Control for Improving the Filling Ability of Polyamide 6 + 30% Glass Fiber in the Micro-Injection Molding Process

“…These issues can be addressed by directly heating the cavity surface. There are several methods that can support a high heating rate and good predictability without heating the entire cavity volume, for example, induction heating [ 22 , 23 , 24 , 25 ], high-frequency proximity heating [ 26 , 27 ], and gas-assisted mold temperature control (GMTC) [ 28 , 29 , 30 , 31 , 32 ]. The induction heating method has a very fast heating rate, which is a great advantage.…”

Investigations on Temperatures of the Flat Insert Mold Cavity Using VCRHCS with CFD Simulation

“…Nevertheless, increasing the mold temperature will prolong the molding time required for the plastic part (the plastic part must be cooled to the ejection temperature in the mold before the mold can be opened), resulting in unnecessary costs. Poszwa et al [ 32 ] investigated the injection molded flexible hinge parts manufactured with selective induction heating to improve their properties. The linear relation between the number of cycles the hinges can withstand, mold temperature, and injection time was identified.…”

Prediction of Morphology Distribution within Injection Molded Parts Obtained with Fast Cavity Heating Cycles: Effect of Packing Pressure

“…For instance, parts obtained with high cavity temperature show longer durability than parts obtained by conventional processes. [2,3] Lucchetta et al [4] demonstrated that the appearance of acrylonitrile butadiene styrene parts can be significantly improved using high mold temperature during the process. Liu et al [5] proved the improvement of tensile strength in the glass-fiber filled polypropylene specimens.…”

“…[7,8] However, most of the proposed methods show slow heating and cooling rates (10 °C s −1 ), cause excessively long processing time. Induction heating, infrared heating, and high proximity heating [2,9,10] can realize cavity heating with a rate of 50 °C s −1 . [2,11] Although fast, those methods require high investment costs.…”

“…Induction heating, infrared heating, and high proximity heating [2,9,10] can realize cavity heating with a rate of 50 °C s −1 . [2,11] Although fast, those methods require high investment costs. The electrical heating of the cavity surface seems more advantageous than the other techniques since it is simple to implement and integrate with the control loop of the injection molding machine.…”