Multi-variable Thermal Energy Control And Thermal Error Compensation Of Dry Hobbing Machine Tool

Dry hobbing is a promising gear hobbing process,which has a good market prospects,due to its environmental friendliness.In dry hobbing,compressed air is applied to cool the cutting zone,which makes the thermal balance and thermal deformation errors characteristics of dry hobbing machine tool different from traditional wet hobbing machine tool.In the last twenty years or so,dry hobbing has been applied in industrial mass production.At present,there is a lack of systematic researches on the thermal balance control and thermal deformation error compensation of dry hobbing machine tool.Although dry hobbing is used for rough machining of semi-finish machining,thermal accumulation and thermal deformation of dry hobbing machine tool still has a great adverse influence on machining precision,productivity and applicability.Therefore,it is urgent to solve those problems in industrial production and academic researches.Thus,under the support of National High Technology Research and Development Program of China,special project of the State Key Laboratory of Mechanical Transmissions,and the National Natural Science Foundation of China,the thermal characteristics of dry hobbing process and dry hobbing machine tool are analyzed.Furthermore,thermal balance control and thermal deformation error compensation of dry hobbing machine tool are studied.Relevant experiments are also presented.The main contents of this thesis are as follows:Cooling patterns,machine tool structures,and components of dry hobbing machine tool,which are different from those of traditional wet hobbing machine tool,are analyzed.The heat generation and sink of dry hobbing machine tool that cause by motors,machined workpiece,chips,compressed cold air,air flow,motor coolant,lubricant,hydraulic oil,convection between dry hobbing machine tool surface and ambient,and radiation are analyzed.The mathematical relation model between them and thermal accumulation are obtained.Furthermore,the multi-variable driving thermal balance model of dry hobbing machine tool is established.The relations between temperature,velocity and mass flow rate of compressed air at nozzle exit and parameters of compressed air cooling system are mathematically modeled and analyzed.Furthermore,the thermal balance control method which is balance on compressed cold air cooling system optimization,is proposed.Combined with experiments,the thermal deformation errors of dry hobbing machine tool is proposed as a criterion to judge accuracy of the multi-variable driving thermal balance model and the effectiveness of the thermal balance control method.Thermal deformation errors of workpiece that machined by dry hobbing machine tool is analyzed,and it can be obtained that both machine tool thermal errors and workpiece thermal deformation errors can be compensated by machine tool thermal error compensation system.With analysis and modeling of relations between compensation value of workpiece thermal deformation errors and temperature of machined workpiece,the thermal error compensation model of dry hobbing machine tool and workpiece is obtained.Experiment system are developed to meet the demands of the research.Hardware of the experiment system is mainly composed of National Instruments’ hardware modules.Software of the experiment system is developed based on the LabVIEW System Design Software.The physical parameters that can be measured by this experiment system are temperature,displacement,power,mass flow rate,pressure,etc.The experiment system provides the equipment support for the experiment in this thesis.