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

3D打印(加法制造)正在使设计、制造和分销发生巨大变化。虽然这创造了许多新的机会，但3D打印可用的材料和性能仍然比机械加工和注塑等传统工艺的材料和性能有限得多。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，3D打印过程中使用的材料通过局部加热(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。通过改善材料性能、增加材料种类和降低生产成本，添加剂制造的持续扩张将有助于实现添加剂制造的全部好处，包括低成本定制产品、更快的开发时间和更个性化的药物。通过烧结聚合物粉末进行的添加剂制造通常使用扫描激光来快速加热材料。紧密聚焦的激光产生了较大的温度梯度和较短的烧结时间。在这些条件下，能够可靠致密而不会降解的材料相对较少。一种单一的材料(尼龙12)构成了所有聚合物烧结件的大部分。然而，一种解决方案可能是使用较低强度的灯光更长时间。通过使用大的激光光斑尺寸加热更大的区域或通过一次曝光烧结整个涂层，可以保持或提高构建速度。更长的处理时间将需要从基于能量输入的过程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，而不是基于光学能量输入--使得能够应用粘性烧结理论来指导工艺开发。测试材料的粘度和烧结率将被测量以校准烧结模型，而加热材料的硬度、强度和粘度的测量将被用来确定避免退化的工艺窗口。将开发一种投影烧结系统来测量不同曝光时间、温度和面积下的烧结结果(孔隙率、硬度和强度)。将开发模型，以确定实现相同材料性能的处理时间和温度的组合。这些模型将用于预测使用基于点、线和面的加热方法的替代机器架构在材料特性、构建速度和分辨率方面的权衡。他们还将加快选择和开发新的聚合物烧结材料。

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.