三维陶瓷零件低温沉积过程挤压力建模及自适应控制

Modeling for Extrusion Force and Adaptive Control in the Freeze Deposition Process of Three Dimensional Ceramic Components

在CNC机床上开发出一种新的三维陶瓷零件增材制造装置,在低于材料凝固点的温度下,将高固相膏体状陶瓷进行分层沉积成型,形成三维陶瓷材料零件。但在该三维零件沉积成型过程中,配置好的Al_2O_3材料由于挤压作用,会产生结块。当结块分解,膏体中气泡释放以及储料器中材料不断减少时,导致沉积过程的挤压力不断变化,使得成型过程不稳定,成形零件质量差。在分析三维陶瓷零件沉积成型过程的干扰因素的基础上,根据试验,建立了沉积过程中挤压力的动态模型,采用递推最小二乘方法进行系统辨识,完成了自适应挤压力控制器的设计,并进行了低温沉积控制过程仿真和实验。结果表明:该动态模型可以有效的描述陶瓷零件沉积过程的挤压力变化,所设计的自适应控制器可以有效的跟踪不同种类的参考挤压力的变化,实现稳定的三维陶瓷零件沉积过程。

A novel additive manufacturing equipment built on CNC in an environmentally friendly fashion has been developed for manufacturing three dimensional ceramic components, on which a high solid ceramic colloidal paste below the temperature of solidification point is deposited layer-by-layer by extruding an aqueous. Due to the release of the bubble, the formation of agglomeration, the breakdown of material agglomeration and reducing of material in stocker at the deposition process of three dimensional components, the extrusion force of deposition process is changed with the ceramic paste status and the deposition process is unstable, therefore, the quality of deposited parts is hardly guaranteed. Analyzing on the various process parameters and disturbance affected on the deposition process of ceramic-based components, based on the plentiful of experiments, the dynamic model for deposition process is constructed in this paper and the recursive least squares （RLS） method is used to systematiccly identify, the adaptive extrusion force controller is designed to conduct the experiment and simulation of freeze deposition process. The results demonstrate that the dynamic model can effectively describe the extrusion force change in the freeze deposition process and the adaptive controller can well track the different kind of reference extrusion force and promote stability in the deposition process of three dimensional components.