Structural Design And Research Of Special-Shaped Ultrasonic Machining Systems

Ultrasonic vibration aided machining(UVAM)as a hybrid processing method is widely used in hard and brittle materials machining as well as difficult processing materials machining.UVAM has a plenty of merits,such as reducing cutting force,improving finished quality,extending tool life,facilitating chip removing and so on.At the same time,the shape and direction of ultrasonic vibration which is decided by ultrasonic booster or structure of machining tool would affect the machining quality.Therefore,different 2D or 3D ultrasonic vibration boosters which are based on Sandwich ultrasonic transduce were design in this paper.According to practical machining,spiral structure cutting tool was proven that these structure could influence the vibrational direction and then influence the machining results.(1)Ultrasonic vibration turning(UVT)device could not process deep concave surfaces because of the interference between booster and workpiece.Therefore,a freeform booster was design in this paper.Using finite element analysis and three-dimensional modeling,the design of the new freeform booster is optimized.(2)Because of the special structure of the freeform booster,it could produce an elliptical ultrasonic vibration through a longitudinal vibration.It also could ameliorate 1D vibration turning problem that diamond tool and workpiece could collide during machining.(3)According to rotary ultrasonic assisted drilling and milling experiments,the structures of cutting tools would directly influence machining results,and change with altering vibration frequencies.Especially for spiral structure tool,when exerting an axial vibration on the top of cutting tool,the end of tool would produce a longitudinal and torsional vibration.(4)According to the results of finite element analysis,the vibration direction of tool would be alter with the changing of vibration frequency,from 1st and 3rd quadrants to 2nd and 4th quadrants.These changes would influence practical cutting angle of tool.Besides,through setting up a series of local coordinate system,we could find that any point on the cutting edge could seem as an elliptical vibration cutting on cross section of cutting edge.Therefore it is possible to use elliptical vibration cutting model to explain cutting process.(5)Since current rotary ultrasonic assisted grinding are based on 1D longitudinal vibration,when grinding the side of workpiece,the ultrasonic vibration effect is not obvious.Therefore,a longitudinal and torsional rotary ultrasonic assisted machining apparatus was designed,and 1D axis vibration is changed to 3D longitudinal and torsional vibration through altering the structure of ultrasonic booster.(6)Through combining finite element analysis with three-dimensional modeling,slot type longitudinal and torsional ultrasonic booster was designed and optimized.Theoretically,longitudinal and torsional ultrasonic vibration could extend the tool life and improve surface roughness effectively.Finally,a longitudinal and torsional ultrasonic vibration assisted grinding contrast experiments was conducted to illustrate that it could reduce the cutting force.