Research On Auxiliary Device Of Hand-held Grinding Tools For Reducing Vibration

Manufacturing occupies an important position in the development of the country,auxiliary tools play an essential role in the workshop manufacturing process.The emergence of different kinds of tools has replaced manpower,improving the productivity and product quality,hand-held tools account for a large proportion among them.Hand-held tools including electric tools and pneumatic tools,used for grinding,polishing,drilling and so on.These tools have been widely used because of the advantages of lightweight and portable,but they also cause other problems.These tools produce vibration during the working process,it will cause discomfort of the hands and even occupational diseases.Especially in intensive polishing and grinding workshop,health problems caused by vibration is particularly prominent.Therefore,this paper focuses on the vibration control of hand-held grinding tools in intensive polishing and grinding workshop.The work is supported by the National Key technologies Research&Development program-"Research on protection technology and equipment for occupational hazards in labor-intensive industrial enterprises"(No.2016YFC0801700)and National Science Foundation project-"Hybrid Energy Flow Method for Prediction of Broadband Vibration and Acoustics in Extra Large Structures Such As High-Speed Train Carriages"(No.51675306).In this paper,the design of the auxiliary device for vibration protection of the hand-held grinding tool is carried out according to the idea of "The proposal of vibration problem?Analysis of vibration characteristics?Research on vibration control method?Vibration control design ?Simulation and experimental verification".The main points of this paper are listed as follows:Firstly,the equivalence of the angle grinder is established on the basis of structural analysis.The characteristics of vibration source are analyzed,the vibration is mainly caused by the unbalance of the rotating parts and the contact force between the rotary grinding disc and the rough surface workpiece.The vibration test is carried out according to the relevant standards,the test result shows that the vibration of the angle grinder belongs to broadband vibration,and there are many vibration peaks at certain frequencies of low frequency.Vibration control is carried out on the basis of the cause of vibration,the natural frequency of the system and the magnitude of vibration in three directions.Secondly,the vibration peak is reduced by the method of dynamic vibration absorption,and the influence of the parameters and layout of the dynamic vibration absorber on the damping effect is analyzed,the damping scheme suitable for this subject is determined.A cantilever type dynamic vibration absorber is designed,which consists of a cantilever beam and a mass block,the natural frequency can be adjusted by changing the position of mass block.The feasibility of the equivalent stiffness calculation method of cantilever beam is verified by finite element method simulation and modal experiment,the effectiveness of the vibration reduction is verified by dynamic simulation and experiment.Multiple frequency vibration peaks can be reduced at the same time,when a plurality of cantilever type dynamic vibration absorbers are arranged.Thirdly,based on the characteristics of the elastic wave band gap of the phononic crystal,the vibration among low frequency domain is reduced,and the damping ring structure adapted to the structure of the angle grinder is designed.The periodic arrangement of the damping rings forms the local resonant phononic crystal structure and produces the vibration band gap.The frequency range of the band gap is obtained by theoretical calculation,and the effectiveness of the vibration reduction is verified by finite element method simulation and experiment.Finally,two kinds of vibration reduction measures of dynamic vibration absorber and phononic crystal is combined,the effect of vibration reduction is verified by simulation and experiment.The result shows that the cantilever vibration absorber and the periodic damping rings have their own damping effect respectively,the weight acceleration of the hand transmitted vibration of the angle grinder is reduced from 0.9 m/s2 to 0.3 m/s2 after adding the damping auxiliary device.The damping measures suitable for the angle grinder are given,and the vibration reduction effect is verified by the simulation and experiment.The results of this study have guiding significance and reference value for the vibration control of hand held grinding tools and the prevention of occupational diseases.