A Method to Characterize the Quality of a Polymer Laser Sintering Process

Abstract

The reproducibility and reliability of quality aspects are an important challenge of the polymer laser sintering process. However, existing quality concepts and standardization activities considering influencing factors along the whole process chain have not been validated experimentally yet. In this work, these factors are analyzed and kept constant to obtain a reliable material data set for different layer thicknesses and testing temperatures. In addition, material qualities regarding powder ageing effects are analyzed using different build heights and layer thicknesses: while an increase of the layer thickness reduces mechanical part strength and density, it also results in a less intense thermal ageing of unmolten powder due to shorter build times.

Design for Additive Manufacturing: Trends, opportunities, considerations, and constraints

“…At the same time, the freedoms of AM reduce the need for, and therefore the importance of, designing for activities such as assembly [149]. AM processes have different batch sizes, production times, and cost drivers than traditional processes [29][148] [275][276] [366] and require different approaches to metrology and quality control [224] [274]. Therefore a new body of knowledge is required to support DfAM.…”

“…The boundary between newly created and existing material can act as an interface where cracks and other types of failure can initiate. Since the discretization in modern AM processes is rarely isotropic, the surface roughness and resulting material properties [113][268] [274] are also usually anisotropic. One common method to address these anisotropies is to modify the part [25][118] [328] or assembly [232] orientation to minimize their impact.…”

Application of Machine Learning Techniques to Predict the Mechanical Properties of Polyamide 2200 (PA12) in Additive Manufacturing

“…The current state-of-the-art [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] describes the importance of part orientation, powder morphology, and machine process parameters as a means towards the control and management of variation in polymer powder bed fusion system. Among the most investigated additive manufacturing (AM) machine process parameters are laser power, scan speed, hatch distance, scan strategy, beam speed, melting temperature, and powder bed temperature [2][3][4][5][6][7]. There is a number of studies [20][21][22] which report that laser power, scan speed, hatch distance, and layer thickness can be used to define the line energy and how their variation may influence mechanical properties of the part.…”

Experimental analysis and modeling of local ageing effects during laser sintering of polyamide 12 in regard to individual thermal histories

“…For high temperatures and long reaction times, the mobility of the molecular chains increases and free carboxyl groups (COOH) connect to free amino groups (NH 2 ) under elimination of H 2 O. Thereby the average molecular weight increases significantly, which can directly be measured via gel permeation chromatography analyses, or indirectly detected via an increased solution viscosity and a decreased melt volume rate (MVR) . While postcondensation in the liquid phase is required for high mechanical properties and interlayer bonding of the produced parts, it is unfavorable in the solid phase (unused powder) .…”

“…Experimental work can be found for both process ageing, artificial (oven) ageing, as well as comparison of both. For example, it has been shown that the powder ageing intensity increases with longer process times, reduced layer thickness, increased build height, and centered location within the part cake . Models to mathematically describe the ageing behavior can be found for specific ageing temperatures and in the liquid phase of the material .…”