摘要
砂型3D打印过程中铺砂工艺严重影响成形砂型的质量。砂粒的粒径处于微米量级,分子力对颗粒间的相互作用明显,经典的Hertz接触模型不能很好地描述添加了固化剂的湿砂颗粒间黏附作用,颗粒之间的黏附力在砂粒铺设过程中容易造成对已成形砂型的破坏,形成砂型缺陷。本文采用离散单元法中的JKR(Johnson-Kendall-Roberts)接触模型模拟预先混合固化剂的砂粒之间的黏性接触问题,通过设计砂粒铺设试验研究了固化剂添加量和铺砂速度对成形砂层致密度的影响规律,并与仿真结果进行对比,修正了JKR接触模型的表面能参数,得到精确的砂粒铺设过程的离散元模型。此外,借助砂粒铺设过程的离散元模型,研究了砂粒铺设过程中固化剂添加量、铺粉速度以及刮刀形状对已成形砂型作用力的影响规律。结果表明,砂粒中固化剂添加量越大,铺砂速度越快,铺砂过程中刮刀对已成形砂型的影响越大。此外,具有-30°倾角的刮刀在砂粒铺设过程中对已成形砂型的影响最小。仿真结果具有较强的工程应用价值,为砂型3D打印铺砂工艺提供了理论指导。
The coating parameters in the process of sand mold 3D printing are critical to the quality of forming sand molds.The magnitude of the sand particle size ranges from several microns to several hundred microns.Molecular forces are of obvious advantage in particle interactions.The classical Hertz contact model did not accurately describe the adhesive attraction among sand particles premixed with curing agent.The adhesive forces not only impact the quality of the sand layer but also break the formed sand mold with lower initial strength.In this paper,the Johnson Kendall Roberts(JKR)contact model in the discrete element method is used to simulate the viscous contact between sand particles with premixed curing agent.The influence of the content of the curing agent and coating velocity on the compactness of the sand layer has been experimentally researched.Through comparison of trial results and simulation results,the surface energy factor of the JKR contact model has been modified.A precise simulation model of the coating process was built.Using this simulation model,the effect of the content of the curing agent,coating velocity and scraper shape on the formed sand mold was researched.The simulation results show that higher content of curing agent and higher coating velocities have larger influence on the formed sand mold by the scraper during the coating process.In addition,the scraper with a-30°dip angle has little influence on the formed sand mold during the coating process.The results have significant engineering value and provide a theoretical guide for the process optimization of sand mold 3D printing.
作者
张敬骥
郭智
王超
冉跃龙
ZHANG Jingji;GUO Zhi;WANG Chao;RAN Yuelong(Beijing Jinyu Polytechnic,Beijing 102403,China;Beijing National Innovation Institute of Lightweight Ltd.,Beijing 100044,China;Key Laboratory of Electromechanical Integration Application Technology of Yunnan,Kunming 650031,China)
出处
《铸造技术》
CAS
2023年第12期1130-1138,共9页
Foundry Technology
基金
云南省科学技术厅重点研发计划(202103AA080018)。
关键词
砂型3D打印
砂粒铺设
离散单元法
固化剂添加量
铺砂速度
sand mold 3D printing
sand coating
discrete element method
content of curing agent
coating velocity
