Rapid prototyping (RP) is a widely used process in the industry to shorten development time.Another advantage of this technology is the ability to create conformal cooling systems, thus not only cooling time and cycle time can be shortened, but also shrinkage, thus warpage can be decreased. The main disadvantage of Rapid prototyping materials is their low thermal conductivity, which strongly influences cooling properties and warpage.The research based on a special developed injection mold for novel rapid prototyping based mold inserts with cooling systems. A method has been introduced to determine the most important thermal parameters for injection molding simulations using rapid tools. Those parameters, which can be measured such as the specific heat and thermal conductivity of the mold materials, are directly implemented into the software. The heat transfer coefficient between the polymer melt and the rapid tool insert surface cannot be measured in a reasonable way, thus simulation software was used to determine that based on indirect calculation 2 derived from real measurements. In the paper, the method was proved with Fused Deposition Modeling (FDM) and Polyjet mold inserts.
With the rapid development of the automotive industry, there is also a significant need to improve the raw materials used. Therefore, the demand is increasing for polymer composites with a focus on mass reduction and recyclability. Thermoplastic polymers are preferred because of their recyclability. As the automotive industry requires mass production, they require a thermoplastic raw material that can impregnate the reinforcement in a short cycle time. The most suitable monomer for this purpose is caprolactam. It can be most efficiently processed with T-RTM (thermoplastic resin transfer molding) technology, during which polyamide 6 is produced from the low-viscosity monomer by anionic ring-opening (in situ) polymerization in a tempered mold with a sufficiently short cycle time. Manufacturing parameters, such as polymerization time and mold temperature, highly influence the morphological and mechanical properties of the product. In this paper, the properties of polyamide 6 produced by T-RTM are analyzed as a function of the production parameters. We determine the crystallinity and the residual monomer content of the samples and their effect on mechanical properties.
Nowadays most research and development concerning injection molded products are focused on their mechanical properties although visual appeal plays an even more important role on the market. There are several standards and recommendations for the testing of mechanical properties, but appearance cannot be quantified easily. The visual aspects are almost completely neglected, and there is not a commonly accepted method for measuring color inhomogeneity.The appearance and color homogeneity of injection molded parts depends on the coloring method itself, the applied technology and several other conditions. The method used nowadays to evaluate color inhomogeneity is based on visual inspection by humans. This research focuses on developing a new and automated method that can replace visual inspection. The functionality and precision of the new method and software have been tested and compared with visual inspection to prove its applicability.
Abstract:The most time-consuming phase of the injection molding cycle is cooling. Cooling efficiency can be enhanced with the application of conformal cooling systems or high thermal conductivity copper molds. The conformal cooling channels are placed along the geometry of the injection-molded product, and thus they can extract more heat and heat removal is more uniform than in the case of conventional cooling systems. In the case of copper mold inserts, cooling channels are made by drilling and heat removal is facilitated by the high thermal conductivity coefficient of copper, which is several times that of steel. Designing optimal cooling systems is a complex process; a proper design requires injection molding simulations, but the accuracy of calculations depends on how precise the input parameters and boundary conditions are. In this study, three cooling circuit designs and three mold materials (Ampcoloy 940, 1.2311 (P20) steel, and MS1 steel) were used and compared using numerical methods. The effect of different mold designs and materials on cooling efficiency were examined using calculated and measured results. The simulation model was adjusted to the measurement results by considering the joint gap between the mold inserts.
Three different nano-and micro-sized ceramic powders (boron-nitride (BN), talc and titanium-dioxide (TiO2)) in 30 vol% have been compounded with a polypropylene (PP) matrix. Scanning electron microscopy (SEM) shows that the particles are dispersed smoothly in the matrix and larger aggregates can not be discovered. The cooling gradients and the cooling rate in the injection-molded samples were estimated with numerical simulations and finite element analysis software. It was proved with differential scanning calorimetry (DSC) measurements that the cooling rate has significant influence on the crystallinity of the compounds. At a low cooling rate BN works as a nucleating agent so the crystallinity of the compound is higher than that of unfilled PP. On the other hand, at a high cooling rate, the crystallinity of the compound is lower than that of unfilled PP because of its higher thermal conductivity. The higher the thermal conductivity is, the higher the real cooling rate in the material, which influences the crystallization kinetics significantly.
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