Experimental Study On The Stiffness Characteristics Of Hob Shovel Grinding System

Shovel grinding is the most important process for precision machining of hobs,which determines the tooth shape accuracy and surface quality of hob production.During shovel grinding,the surface of the grinding wheel and the side shovel surface of the hob always maintain linear contact,and this contact line will constantly change with the progress of shovel grinding,which causes the grinding force of shovel grinding to also constantly change,leading to vibration in the hob shovel grinding processing system.For the relief grinding of hobs,the vibration of the system becomes the main factor restricting the efficiency and quality of hob machining.Therefore,exploring the influence of shovel grinding process on vibration and improving the stiffness of shovel grinding machine system has become an urgent problem to be solved.This article takes the CM5840 shovel grinding machine from Hanjiang Tool Factory as the research object,starting from its system stiffness characteristics,and completes the following research work:1)Analyzed the principle of roller blade grinding,pointed out the main reasons for the vibration of roller blade grinding,and proposed a research method for the stiffness characteristics of the roller blade grinding system;In response to the proposed research method,the calculation methods of dynamic stiffness and modal parameters were derived,and the calculation principle of overall dynamic stiffness was explained;2)By conducting force hammer excitation tests on various components of the shovel grinding machine,the modal parameters and dynamic stiffness of each component of the machine were identified and calculated.The components with relatively weak dynamic stiffness of the roller shovel grinding machine were identified,among which the dynamic stiffness of the grinding wheel spindle was the smallest;Based on the coupling relationship between the dynamic stiffness of each component and the overall dynamic stiffness of the shovel grinding machine,the dynamic stiffness of the entire machine of the roller shovel grinding machine was calculated;3)A method of increasing the diameter appropriately to improve the dynamic stiffness of the grinding wheel shaft,which has the weakest dynamic stiffness,was proposed.The dynamic stiffness of the optimized finite element model of the grinding wheel shaft was calculated using ANSYS,and the optimized results were verified;4)By using multiple sets of different combinations of process parameters and using a relief grinding machine to perform relief grinding on the hob,the frequency spectrum of machine tool vibration signals under different process parameters was analyzed and compared,revealing the influence of each process parameter on the relief grinding of the hob;The research results indicate that the dynamic stiffness of the grinding wheel shaft,workpiece spindle,and grinding wheel frame of the CM5840 shovel grinding machine is relatively weak,with the grinding wheel shaft having the weakest dynamic stiffness.The average dynamic stiffness in the X direction is 21901.5N/mm,the average dynamic stiffness in the Y direction is 9948.2N/mm,and the average dynamic stiffness in the Z direction is 6487.4N/mm;By increasing the diameter of the grinding wheel shaft through finite element simulation optimization,when the diameter of the grinding wheel shaft changed from the original 20 mm to 25 mm,the dynamic stiffness of the grinding wheel shaft in the X direction increased by 2268.8N/mm,a year-on-year increase of 10.4%,the dynamic stiffness in the Y direction increased by 1287.4N/mm,a year-on-year increase of 12.9%,and the dynamic stiffness in the Z direction increased by 1749.6N/mm,a year-on-year increase of 27%;The rotational speed of the grinding wheel in the process parameters is the main factor causing the forced vibration of the machine tool itself.When the rotational speed of the grinding wheel reaches 35m/s,the amplitude of the forced vibration reaches 0.028 mm,and the Y and Z directions of the shovel grinding machine increase by 285.7% when compared to 25m/s;The grinding depth and the feed speed of the grinding wheel are the main factors that affect the chatter of the machine tool during the shovel grinding process,with the grinding depth having a smaller impact and the feed speed having the greatest impact.When the grinding depth changes from 0.02 mm to 0.06 mm,the amplitude in the Y direction of the shovel grinding machine increases by 14.9% and the Z direction increases by 16.7%;When the feed speed of the grinding wheel changed from 1080mm/min to 1440mm/min,the amplitude of the shovel grinding machine in the Y direction increased by 233.3% and in the Z direction increased by 498.5%.