Accurate numerical simulation of material extrusion additive manufacturing requires reliable tracking of evolving material interfaces while preserving mass conservation. Inaccurate mass conservation can lead to significant discrepancies between simulated and deposited strand geometries, undermining the predictive capability of the model. In this work, we investigate the mass conservation performance of the conservative level-set (CLS) method in extrusion-based 3D printing simulations. A systematic parametric study is conducted to quantify the influence of the interface thickness and reinitialization parameters on mass conservation, using the steady-state cross-sectional area of deposited strands as a quantitative metric. Simulated cross-sections are compared against reference values obtained from analytical mass balance relations. The results show that reducing both the interface thickness and the reinitialization parameter improves mass conservation accuracy, although diminishing returns and increased computational cost are observed beyond certain thresholds. In addition, appropriate tuning of the interface thickness can relax mesh refinement requirements while maintaining acceptable accuracy. The proposed parameter selection strategy is validated across a range of printing conditions, materials, and nozzle geometries, including multilayer deposition of viscoplastic fluids. The simulations show reasonable agreement with experimentally validated data from the literature, confirming that careful CLS parameter tuning enables accurate and computationally efficient prediction of strand geometry in extrusion-based 3D printing.

翻译：对材料挤出增材制造进行精确数值模拟，需要在保持质量守恒的同时可靠地追踪演变的材料界面。质量守恒不准确会导致模拟与沉积线材几何形状之间存在显著差异，从而削弱模型的预测能力。在本研究中，我们探究了保守水平集（CLS）方法在挤出式三维打印模拟中的质量守恒性能。通过系统参数化研究，以沉积线材稳态横截面积为量化指标，量化了界面厚度和重新初始化参数对质量守恒的影响。将模拟的横截面与通过解析质量平衡关系获得的参考值进行比较。结果表明，减小界面厚度和重新初始化参数均能提高质量守恒精度，但超过特定阈值后会出现收益递减和计算成本增加的情况。此外，适当调整界面厚度可在保持可接受精度的同时放宽网格细化要求。所提出的参数选择策略已在多种打印条件、材料和喷嘴几何形状（包括粘塑性流体的多层沉积）中得到验证。模拟结果与文献中经实验验证的数据具有较好的一致性，证实了通过仔细调整CLS参数，可在挤出式三维打印中实现精确且计算高效的线材几何形状预测。