Could Slower be better? Assessing Sintering Time, Temperature, and Area Tradeoffs in 3D Printing by Polymer Sintering

3D打印（增材制造）正在实现设计、制造和分销方面的巨大变化。虽然这创造了许多新的机会，但3D打印的材料和性能仍然比传统工艺（如机械加工和注塑成型）有限得多。该奖项支持基础研究，以扩大3D打印过程中使用的材料的范围和功能，通过局部加热（烧结）聚合物粉末（通常使用激光）形成组件。随着可用材料范围的扩大，这些工艺可以得到更广泛的应用。通过改进材料性能、增加材料种类和降低生产成本，增材制造的持续扩张将有助于实现增材制造的全部优势，包括低成本的定制产品、更快的开发时间和更个性化的医疗。通过烧结聚合物粉末的增材制造通常使用扫描激光快速加热材料。紧密聚焦的激光产生较大的热梯度和较短的烧结时间。在这些条件下，很少有材料能够可靠地致密化而不降解。一种单一的材料（尼龙12）构成了所有聚合物烧结成分的绝大部分。然而，一个解决方案可能是使用较低强度的光更长时间。通过使用大的激光光斑尺寸加热更大的区域或通过单次曝光烧结整个层，可以保持或提高构建速度。较长的加工时间将需要从基于能量输入的工艺表征过渡到温度历史。本研究的目的是了解烧结时间、温度和面积对聚合物烧结的影响。这将通过基于加工温度和时间的工艺结果建模来实现，而不是基于光能输入，从而使粘性烧结理论的应用能够指导工艺开发。测试材料的粘度和烧结速率将被测量以校准烧结模型，而加热材料的刚度、强度和粘度测量将被用来确定避免降解的加工窗口。一个投影烧结系统将被开发来测量烧结结果（孔隙度，刚度和强度）与不同的曝光时间，温度和面积。将开发模型来确定加工时间和温度的组合，以达到等效的材料性能。这些模型将用于使用点、线和基于区域的加热方法来预测材料性能、构建速率和替代机器架构之间的分辨率权衡。他们还将加速新型高分子烧结材料的选择和开发。

3D printing (additive manufacturing) is enabling dramatic changes in design, manufacturing, and distribution. While this has created many new opportunities, the materials and the properties available with 3D printing are still much more limited than those available with traditional processes such as machining and injection molding. This award supports fundamental research to enable expansion of the range and functionality of materials used in 3D printing processes that form components by locally heating (sintering) a polymer powder (usually with a laser). As the range of available materials expands, the processes can be used more widely. The continued expansion of additive manufacturing through improved material properties, increased variety of materials, and reduced production costs, will help achieve the full benefits of additive manufacturing including low-cost customized products, faster development times, and more personalized medicine. Additive manufacturing via sintering of polymer powders has typically used a scanning laser to heat the materials quickly. The tightly focused laser creates large thermal gradients and short sintering times. Relatively few materials can densify reliably without degradation under these conditions. A single material (nylon 12) composes a large majority of all polymer-sintered components. However, a solution may be to use lower intensity light for longer time. Build rate may be maintained or improved by heating larger areas using large laser spot sizes or by sintering an entire layer with a single exposure. Longer processing times will require a transition from process characterization based on energy input to temperature history. The objective of this research is to understand the effects of sintering time, temperature, and area in polymer sintering. This will be done by modeling process outcomes based on processing temperature and time, rather than optical energy input--enabling application of viscous sintering theory to guide process development. Viscosity and sintering rates of test materials will be measured to calibrate sintering models while stiffness, strength, and viscosity measurements of heated materials will be used to identify the processing window which avoids degradation. A projection-sintering system will be developed to measure sintering outcomes (porosity, stiffness, and strength) with varying exposure time, temperature, and area. Models will be developed to identify combinations of processing time and temperature that achieve equivalent material properties. These models will be used to predict tradeoffs in material properties, build rate, and resolution between alternative machine architectures using point, line, and area-based heating methods. They will also accelerate selection and development of new polymer sintering materials.