冷冻砂型数控加工气动辅助精确排砂方法

Pneumatic-Assisted Precise Sand Discharging Method for CNC Machining of Frozen Sand Molds

在冷冻砂型数控(Computerized numerical control,CNC)加工过程中,有效排出切削砂坯产生的砂粒是确保砂型成形质量的关键技术之一。本文基于计算流体力学方法,对环绕阵列式射流喷吹的排砂方式进行了数值模拟,分析了射流流量、靶距、俯角和口径对型腔周围流场的影响。设计数控加工正交实验并对排砂率进行了极差分析,验证了仿真的结果。研究表明,环绕阵列式高速射流在刀具柱面和型腔壁面上会形成稳定贴附,输送砂粒的主要区域为射流在型腔壁面形成的“排砂区”。仿真与实验结果均表明最佳排砂工艺参数为射流流量30 L/min、靶距45 mm、俯角65°和口径2 mm,其中射流流量的影响最为显著,其次是射流喷嘴口径、俯角和靶距。本文结果可为排砂装置及工艺参数优化提供指导。

In the frozen sand mold computerized numerical control(CNC)machining process,the effective discharge of sand particles generated by cutting sand blanks is one of the key technologies to ensure the quality of sand molding.In this paper,based on the computational fluid dynamics method,a numerical simulation of the sand discharge mode of the surrounded array jet is carried out to analyze the effects of flow rate,target distance,pitch angle and aperture on the flow field around the cavity.CNC machining orthogonal experiments are designed and the range analysis of sand removal rate is carried out to verify the simulation results.Highspeed jets form stable attachments on the tool face and cavity walls,and the main area for transporting sand particles is the“sand discharge area”formed by the jets on the cavity wall.Both simulation and experimental results show that the optimal sand removal process parameters are flow rate of 30 L/min,target distance of 45 mm,pitch angle of 65°and caliber of 2 mm,in which the effect of flow rate is the most significant,followed by nozzle caliber,pitch angle and target distance.Results can provide guidance for the optimization of sand removal devices and process parameters.