Research On Grinding Burr Formation Mechanism And Deburring Technology Of Precision Working Edge

Burr formation is one of the most common phenomena in the metal cutting process,and it has an adverse influence on processing quality,assembly and application in subsequent processes.Deburring operations are time and money-consuming processes,which badly affect the metal cutting processes.In grinding process,due to the influence of burr size,deburring is different from other processes.In order to improve the processing quality of grinding parts,it is particularly important to understand burr formation mechanism and influence factors in grinding process.Spool valve is composed of valve spool and valve sleeve,and as the power stage of servo valve,it has a high degree of accuracy and is difficult for machining.All edges of servo valve core must be completely defect-free with strict radii.On one hand,the micron burrs of the servo valve core edge are extremely small which has made deburring process more difficult.On the other hand,the final machining dimensional accuracy is also at micron level,namely the sizes of micro defects and the function sizes of precision parts are very close.Therefore the difficulty of deburring is extremely great.The objective of this research is to study the mechanism of grinding micro burr and the deburring technology of servo valve core burr.Through the strict definition of precision working edge,by means of the combination of simulation and experimentations,the burr formation mechanism is analyzed,and a thorough research on size effect and work hardening phenomenon of the precision working edge burr forming process is carried out.The main contents and innovations are as followings:(1)The mathematical models of three types of grinding burrs are established,with comprehensive consideration of abrasive edge radius,equivalent negative rake angle.Grinding burrs can be divided into entrance burr,side burr and exit burr,of which the entrance burr and the side burr can be treated as poisson burr,the exit burr as rollover burr.(2)In burr formation simulation,the grinding burrs forming process is divided into six stages,respectively: continuous grinding stage,burr pre-initiation stage,the plastic distortion point generation stage,the plastic deformation zone formation stage,burr grow stage and burr eventually formed.The influence of different grinding parameters on the burr size is studied.Under the circumstances of same grinding depth,the burr size is bigger in one time grinding than grinding repeatedly.In the actual production process,it is necessary to try to reduce the times of grinding,especially in the fine grinding stage.Aim at face grinding process of precision working edge,through the calculation of cutting paths,a kind of single grain grinding process simulation model is carried out.Deburring by turning process is also simulated.(3)Experimental study work of working edge grinding burrs is put forward based on the simulation research.Combined with experimental results,using the BP neural network,a forecasting model of grinding parameters on the burr height is set up.By using Nano Indenter G200 tests combined with the EBSD technology analysis,in the actual grinding process,the degree of strain hardening is also the most significant in burr root.Grain size of burr root is smaller.It can be found that,with grain size decreases,the grain boundary density increases gradually,the movable dislocation effect boundary of grain boundary becomes stronger,which all contributed to the work hardening.(4)Turning process and single crystal diamond tool are introduced for online deburring of servo valve cores In this paper.Single point diamond turning is a processing technology,by which nanometers of roughness and shape precision can be obtained.Therefore,the method chosen above fully meets the accuracy requirement.The edge radius of single crystal diamond tool can reach to dozens of nanometers or below,and the sharp cutting edge is suitable for removing micro burrs.(5)A reasonable design of online precision micro-burr removal equipment is carried out by integrating precision feeding system,deburring tool system and process control system.Meanwhile,a closed-loop deburring controller is developed to regulate the feed of deburring tool and monitor the effect of deburring by force sensor and laser displacement sensor.By the instrumental investigation in this paper,the micro-burr which is arise from the end-face grinding can be effectively removed,and the accuracy of the working edges is very well guaranteed,so as to improve the production efficiency.