| Nowadays,it's widespread to produce parts with high-tech Computer Numerical Control(CNC)equipment in manufacturing industry.With the improvement of people's living standards,and the demand of the market for commodities diversification,flexible manufacturing system with five axis machining tools comes into being with more variety,smaller batch features.In the increasingly competitive market,time,quality and cost are three key factors of the flexible manufacturing system.In order to adapt to the inevitable developing trend of intelligent manufacturing,it's of great academic significance and valuable applicability to carry out research on the relationship between manufacturing accuracy and cost,and achieve error control and cost optimization during the flexible manufacturing process based on Stream of variation(Sov).The main purpose of this paper is to present a way to introduce on-machine detection fixture for the manufacturing process of flexible production line with automatic exchange pallet.The production cost of parts is affected by the presented way which is researched to compensate work piece and fixture assembly deviation error from the machining tool,and change the manufacturing process variable error.The detection error and cost are integrated into the error control and cost optimization of the manufacturing process.The relationship between product quality and cost is analyzed to achieve the minimum cost with parts under its processing quality with the method of establishing the error transmission model which is affected by the detection error and the total cost model which is affected by the detection cost.In order to achieve this goal,the research contents of this article are divided into the following three parts,and they are as follows:1.Modeling of error transmission for serial-parallel hybrid multistage process with five axis CNC machine toolsThe formation mechanism of the error stream in the process of serial-parallel hybrid multistage machining process with automatic exchange pallet is analyzed.And a multistage machining process error transmission model is established based on the theory of error stream in the case of an undetected fixture including the fixture error,the reference error and the five axis machining error.A multistage machining process error transmission model is established based on the theory of error stream in the case of the detected fixture including the detection error,the datum error and the machine tool error.2.The total cost model for parts with its life cycleLife cycle of parts is taken as the research object.The cost factors in the parts manufacturing stage are analyzed,and the tolerance cost model together with detection cost model are built.The cost factors in the product using stage are analyzed,and the cost model of quality loss is established.The various cost factors are integrated to establish a total cost model considered the whole life cycle of parts.3.Error control and cost optimizationThe process capability index of the multistage machining process is analyzed to establish the mathematical relationship between product quality and tolerance.Independent variable of the cost function is unified for deriving the error cost function about tolerance.The error cost function is taken as the target function,the quality function of the error transmission is taken as a constraint condition,and a cost optimization model is established to realize the error control of manufacturing parts based on its cost.At the end of the paper,two different kinds of parts are used to simulate,and verify that using the method of on-machine detection fixture which indirectly changes the manufacturing process variable error,benefits to reduce the multistage machining error of parts and the production cost of parts.Moreover,the simulation results show that the method of on-machine detection fixture effectively balances the processing quality and cost of the parts. |
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