Papers by Keyword: Part Quality

Abstract: Fused Deposition Modeling (FDM), a fast growing rapid prototyping technology, is a process for developing physical objects by adding fused layers of materials according to a three dimensional CAD geometry. FDM can be used to produce parts with complex geometries. Hence it gains distinct advantages in industries. One of the major drawbacks of FDM is the reduced part quality measured in terms of dimensional accuracy, surface finish and mechanical characteristics. The major share of research literature related to the field of FDM process parameter optimization focuses on flat and circular surfaces, while only a few studies are available on helical surfaces. This paper is based on a close study conducted to understand the effect of four parameters, namely, layer thickness, raster width, print speed and support material density on dimensional accuracy, tensile strength and surface finish of FDM processed helical surfaces. The experiments were designed by taking three levels of each process parameter selected. Optimum parameter level for improving dimensional accuracy, tensile strength and surface finish simultaneously were obtained by Grey Relational Analysis. The main effect plots were also analyzed.

Abstract: In this paper a new variable forming tool concept and associated numerical methods for calculating optimal actuator layout and estimating CFRP part quality are presented. The concept of the tool features a modular design and active control of the forming process to achieve the desired geometry. Initially the laminate is placed on the flat top layer of the forming tool. There it is fixed and compacted using vacuum bagging. After compacting, it is heated up to increase the performance of the forming process using water based tempering of the forming tools top layer. The heated laminate is then formed, pulling the tools top layer into the desired geometry using the actuators. Finally, the formed laminate is cooled and transferred into a mold for curing. The position of the forming tools actuators on the base plates is variable. Numerical optimization in combination with finite element (FE) technologies is utilized, to approximate the tool surface within given error margins, with as few actuators as possible. In addition, results of a numerical method for part quality estimation are shown. The influence of the forming process on mechanical properties due to fiber waviness is taking into account using a self-developed method that includes manufacturing characteristics in FE modeling of the part. The method is based on mathematical descriptions of fiber waviness, which are implemented into a FE model. Therefore a structure discretization assuming perfect fiber orientations is realized and the expected fiber waviness induced by the forming process is applied element-wise.

Abstract: Sintering temperature influences on sintering process essentially. Laser power and scanning speed determined sintering temperature. Preheat to powder is beneficial to improve the surface temperature uniformity. Stress concentration of part is various in different layer depth. Therefore, the influence of laser power, scanning speed, thickness of spreading layer and preheat temperature on part quality in selective laser sintering(SLS) are main factors. Based on laser energy in Gaussian distribution and mechanism of SLS, with manufactured specimen pieces by molding machine AFS-450, orthogonal experimental design and analysis of variance are adopted to post-treatment. The prototyping sintering parameters are optimized. The result and solution of the experiment are the preheat temperature of 100°C, the scanning speed of 2000 mm/s, the laser power of 24W, the thickness of single layer of 0.2mm for ABS resin. This work can provide optimized parameters in SLS for ABS resin. It will be of benefit to improve the part dimensional precision and strength.