Simulation of the shrinkage behavior in Fused Deposition Modeling

该项目的目的是模拟用熔融沉积建模（FDM）制造的部件的收缩行为。通过收缩模拟，可以确定FDM组件的尺寸变化。通过这种尺寸变化，导出了FDM工艺的最佳收缩系数。这些收缩因素显然是高尺寸精度的原因。收缩系数是沿所有轴的缩放，以补偿塑料部件的过程引起的收缩。初步研究表明，一个全局适应的收缩因子（沿着空间方向X， Y和Z）可以显著减少具有恒定标称长度的试件发生的尺寸偏差。通常，在一个复杂的零件中有不同的标称长度。这些标称长度可以是小尺寸≤10mm或更大尺寸（≥100mm）。鉴于优化的收缩系数决定性地依赖于标称长度，应在项目的第二步开发一种方法，如何在组件的设计和施工阶段应用本地适应的收缩系数。为了能够有效和经济地将该工艺用于单个和小批量的生产，第一个组件需要满足产品要求。因此，对于收缩系数而言，工作点优化是不可取的，因为这也会增加机器时间和成本。为了节约资源，应采用仿真技术对FDM零件的收缩行为进行分析。根据研究结果，得出了更高标称长度（高达400毫米）或新材料的最佳收缩系数。因此，为了确定缩水率，在单元格中检查冷却行为，缩水率代表了FDM部件的结构。在此之前，还必须确定加工条件。这些因素对收缩有决定性的影响。从确定的熔化和挤压分析数据出发，确定了冷却模拟结果的输入变量。主要的焦点是温度和收缩模拟，目的是确定最终的尺寸变化。最后，通过实验研究对仿真结果进行了验证和评价。必须对复杂演示部件的特定几何形状或标称长度的局部应用收缩因子的方法进行检查。随后，利用三坐标测量机对部件进行测量，从而对尺寸精度进行分析。

The aim of the project is to simulate the shrinkage behavior of components manufactured with Fused Deposition Modeling (FDM). By using the shrinkage simulation, the resulting dimensional change of FDM components shall be determined. By means of this dimensional change, optimized shrink factors are derived for the FDM process. These shrink factors are evidently responsible for a high dimensional accuracy. The shrink factor is a scaling along all axes to compensate the process-induced shrinkage of the plastic component. Preliminary investigations have shown that a globally adapted shrink factor (along the spatial directions X, Y and Z) can achieve a significant reduction in the occurring dimensional deviations of test specimens with a constant nominal length. Normally, there are different nominal lengths within a complex part. These nominal lengths can be small dimensions ≤ 10 mm or higher dimensions (≥ 100 mm).Whereas the optimized shrink factor is decisively dependent on the nominal length, a method shall be developed in the second step of the project how to apply locally adapted shrink factors already in the design and construction phase of the component. In order to be able to use the process for the production of individual and small series efficiently and economically, product requirements needs to be fulfilled already with the first component. Therefore, an operating point optimization is not desirable concerning the shrinkage factor, as this would increase the machine time and costs as well. In order to save resources, the shrinkage behavior of FDM parts should be analyzed with simulation technologies. Based on the findings optimum shrinkage factors for higher nominal lengths (up to 400 mm) or new materials, for example, are derived. Therefore, the cooling behavior is examined at a unit cell for determining the shrinkage, which represents the structure of a FDM part. Previously, it is necessary that the processing conditions are determined as well. These have a decisive influence on shrinkage. From the ascertained data of the melting and extrusion analysis, the input variables for the cooling simulation result. The main focus is on temperature and shrinkage simulation, with the aim of determining the resulting dimensional change.Finally, the simulation results are validated and evaluated by means of experimental investigations. The approach of locally applied shrink factors on specific geometries or nominal lengths of a complex demonstrator component has to be examined. Subsequently, the components are measured by means of a coordinate measuring machine and thus are analyzed with regard to the dimensional accuracy.