Effect Analysis of Zero Drive Force of a Cross-legged Parallel Machine Tool on Machining Accuracy
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摘要: 研究了交叉杆并联机床驱动力为零对加工精度的影响。根据牛顿—欧拉方程,得到交叉杆并联机床的动力学方程,解得连杆的驱动力,分析了丝杠与螺母之间的间隙对加工精度的影响。研究表明:如果丝杠与螺母之间有间隙,交叉杆并联机床在驱动力为零的位置附近,影响交叉杆并联机床的加工精度;如果预紧丝杠螺母,则不影响并联机床的加工精度,但增加螺旋副的功率消耗和磨损,而且对于经常在驱动力不为零情况下工作的交叉杆并联机床,丝杠螺母的预紧机构是多余的。提出控制一个循环工序的加工时间,使交叉杆并联机床不出现驱动力为零的位置。根据临界加工时间的长短,设置和使用丝杠螺母的预紧机构。Abstract: Machining accuracy of cross-legged parallel machine tool of zero drive force was investigated.Dynamic equation of a cross-legged parallel machine tool was obtained by Newton-Euler approach.Drive force of a leg was solved by the dynamic equation.The effects of clearance between a screw and a nut on machining accuracy were analyzed.The results show that if there is clearance between a screw and a nut,machining accuracy of a cross-legged parallel machine tool will be affected near the zero drive force posotion of a cross-legged parallel machine tool.Machining accuracy of a cross-legged parallel machine tool is not affected by a preload screw nut,but power consumption and wear of screw pair is increased.A preload mechanism of a screw nut is redundant in a cross-legged parallel machine tool which often works under non-zero drive force condition.It was expected that machining time of a cycle process is controlled in order that a cross-legged parallel machine tool does not have the position of zero drive force.A preload mechanism of a screw nut was set and used according to critical machining time.
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Key words:
- parallel machine tool /
- machining accuracy /
- zero drive force /
- clearance /
- critical machining time
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