Evaluation of processing variables in polymer projection sintering
Evaluation of processing variables in polymer projection sintering
复制标题
聚合物投影烧结工艺变量的评估
作者：
J. Nussbaum;N. Crane
目的
介绍了一种利用大功率投影仪同时对大面积聚合物粉末进行选择性烧结的系统--投影烧结。本文旨在评估激光烧结（LS）工艺参数对投影烧结的适用性，因为它使用比传统LS低得多的强度，更长的曝光时间和更大的面积。
设计/方法/方式
通过创建具有不同曝光时间和光强度的单层组件来评估烧结结果中的权衡。对其中一些组件进行了横截面分析，并评估了致密化程度，同时测量了其余组件的单层厚度和最大拉伸力。
结果
较短的曝光时间和较高的强度可以产生较厚的，因此比当在较长的曝光上施加相等的能量时更强的部件。这与LS不同，在LS中，能量输入（安德鲁数）被接受为可靠的过程变量。这种差异可能是因为在暴露时间期间从烧结区域损失了大量热能-导致峰值温度降低。这些热损失可以通过增加曝光时间或光强度赋予额外的能量来抵消。
实际影响
大多数用于评估LS工艺参数的方法，例如能量熔化比和安德鲁数，从基本工艺参数估计能量输入。这些方法不考虑热损失，并假设粉末吸收所有入射光。这些方法对于使用可见光的投射烧结变得越来越不准确，其中曝光时间高得多（> 1秒），并且大部分光从粉末表面反射。了解适当的烧结标准对于长时间暴露烧结的发展至关重要。
独创性/价值
介绍了一种选择性烧结大面积的新方法，该方法可以通过实现更长的烧结时间来烧结更广泛的材料，并且可以相对于LS提高生产率。这项工作表明，新的工艺参数需要投影烧结传统LS工艺参数是不够的。
Purpose
Projection sintering, a system for selectively sintering large areas of polymer powder simultaneously with a high-power projector is introduced. This paper aims to evaluate the suitability of laser sintering (LS) process parameters for projection sintering, as it uses substantially lower intensities, longer exposure times and larger areas than conventional LS.
Design/methodology/approach
The tradeoffs in sintering outcomes are evaluated by creating single layer components with varied exposure times and optical intensities. Some of these components were cross-sectioned and evaluated for degree of densification, while the single-layer thickness and the maximum tensile force was measured for the rest.
Findings
Shorter exposure times and higher intensities can create thicker and therefore stronger parts than when equal energy is applied over longer exposures. This is different from LS in which energy input (Andrew’s Number) is accepted as a reliable process variable. This difference is likely because significant thermal energy is lost from the sintering region during the exposure time – resulting in reduced peak temperatures. These thermal losses can be offset by imparting additional energy through increased exposure time or light intensity.
Practical implications
Most methods for evaluating LS process parameters, such as the energy melt ratio and Andrew’s Number, estimate energy input from basic process parameters. These methods do not account for thermal losses and assume that the powder absorbs all incident light. These methods become increasingly inaccurate for projection sintering with visible light where exposure times are much higher (>1s) and a larger portion of the light is reflected from the power’s surface. Understanding the appropriate sintering criteria is critical for the development of long-exposure sintering.
Originality/value
A new method of selectively sintering large areas is introduced that could sinter a wider variety of materials by enabling longer sintering times and may increase productivity relative to LS. This work shows that new processing parameters are required for projection sintering as traditional LS process parameters are inadequate.
DOI：
10.1016/j.jmatprotec.2015.10.010
发表时间：
2016-03-01
影响因子：
6.3
作者：
Akande, S. O.;Dalgarno, K. W.;Pallari, J.
通讯作者：
Pallari, J.