Study On Development And Cutting Performance Of Ultrasonic Cutting System For Nomex Honeycomb Core

Nomex Honeycomb cores is a typical porous material,which is difficult to be machined.The stiffness of the hexagonal grid is weak.Honeycomb core in the molding process is prone to many quality problems,such as deformation of hexagonal grid,tearing,crushing,and more surface burrs after processing.Based on Nomex honeycomb core materials,Honeycomb sandwich structure is made.It has many advantages such as light weight,low density,high strength,high rigidity,good insulation performance,excellent chemical inertness and heat insulation.On the basis of combining the properties and structural characteristics of honeycomb core materials,honeycomb core processing methods and processes have been constantly exploring.The method of modeling honeycomb core includes high speed milling,ultrasonic cutting,Band saw cutting and so on.As a new type of processing technology,ultrasonic cutting technology has the advantages of high processing efficiency,good molding surface quality and less dust pollution in the field of honeycomb core processing.Some companies of Europe and the United States make this ultrasonic cutting technology apply to the honeycomb core material processing.They developed the corresponding machine automation equipment.Some domestic research institutes are also developing ultrasonic cutting system.But the overall technology is not mature enough,which has not yet formed a complete system.In the paper,the design and cutting performance of ultrasonic vibration system for cutting honeycomb core are studied.The main contents are as follows:In order to study the ultrasonic machining technology for processing of Nomex honeycomb cores,an ultrasonic horn with high displacement amplification is designed.The profile of the horn is composed of a cone,a cylinder,and Bézier curves.The ultrasonic horn and disc cutter are considered integrated.Depending on the structure of the ultrasonic horn and the wave equation which presents the fluctuation of the ultrasonic in the variable section bar,the overall design concept is proposed.A design method of the horn using NSGA and finite element analyses is aimed at optimizing the profile.And then modal and harmonic response analysis is performed to complete the design of an entire wavelength composite ultrasonic horn.Longitudinal vibration tests are carried out to evaluate the resonance vibration performance of the ultrasonic horn and disc cutter.The results demonstrate that after the installation of the disk cutter,this innovative ultrasonic system is adjusted to the longitudinal resonant state.The amplitude of the end surface of the knife discs can reach 45.5 ?m when the driving voltage is 300 V.The vibration of the whole system is stable.And,the amplitude is large enough.Which can verify the rationality of the ultrasonic cutting system.In its process of Nomex Honeycomb cores,the cutting force has a significant impact on the quality of processing and fixture.Ultrasonic cutting by disc cutter is a new method in honeycomb cores processing.In order to achieve an optimized processing of ultrasonic cutting procedure,enhance the machining efficiency and achieve a better machining quality,the research on the variation law of impact factors affecting the cutting force is needed.In this study,the experiment platform of honeycomb cores cutting was set up.The cutting force was measured during the process.The honeycomb core samples were cut in the ultrasonic cutting system to obtain the cutting force at different amplitudes and cutting depths with the same feed rate.By means of regression analysis,the experimental data of cutting force was fitted to an empirical formula with the error between the fitting results and experimental data lower than 10%,the cutting force Fy,Fz are in good linear relationship with the cutting depth ap,the amplitude of the bottom of disc cutter A.The surface morphologies of machined honeycomb cores were observed and analyzed.The results demonstrated that the surface of the honeycomb core was better and with less burr after ultrasonic cutting,which could provide a reference for the processing research on ultrasonic cutting honeycomb core by disc cutter.