Design Of The Control Sysytem And Process Test Based On Wedm-LS

Wire electrical discharging machining-low speed(WEDM-LS)is one kind of processing method,which uses the moving metal electrode as the tool.It is widely used in aerospace,automobile and die manufacturing industries because of high processing precision and good stability.Pulse power supply and motion control system are two key technologies of WEDM-LS machine and the pulse power control system is the core factor that affects process indexes of WEDM-LS.The experiments on 06Cr25Ni20 stainless steel were carried out by designing the adjustable duty ratio pulse power supply,besides,the machining process was monitored online by the acoustic emission(AE)technology.The main research contents and results are as follows:(1)The hardware circuit and corresponding software realization method of the adjustable duty ration pulse power supply based on STC89C51 were designed.A new fuzzy self-adaptive PID dynamic control method was used to adjust the pulse parameters,and the pulse width control model was established,as well as the simulation test.(2)The mathematical model was established after systematically analyzing the numerical relationship between the duty ratio and the surface roughness of the workpiece.And it can be known that there is a power function relationship between the duty cycle of pulse signals and the surface roughness of WEDM.(3)The experiments on 06Cr25Ni20 stainless steel were carried out to verify the rationality and reliability of the mathematical model established in(2),utilizing different combinations of pulse width and pulse interval parameters.(4)The datas in(3)were fitted based on OriginLab software,and the fitting results show that the mathematical model between the duty ratio and the surface roughness of the workpiece is reasonable and the maximum error is 6.2%.(5)The AE signal was de-noised by wavelet transformation,then the peak value and the mean square value were calculated.It can be known that the peak value and the mean square value of AE signals increase with the increase of the surface roughness of the workpiece.The peak value and the mean square value grow faster with the increase of the surface roughness of WEDM-LS.(6)By analyzing the frequency spectrum of AE signals based on Fourier transform,it can be known that when the frequency of AE signals is close to the pulse signal frequency of the pulse power supply during WEDM-LS process,the energy of AEsignals is larger,and the distribution of the signal is more concentrated.(7)The energy percentage of AE signals in each frequency band is calculated by using wavelet packet spectrum algorithm.After analyzing the variation of the energy of AE signals in different frequency bands under different duty cycle pulse parameters,we can know that the energy changes of AE signals on each frequency band can reflect the pulse parameters changes,which can be used to on-line monitor the pulse parameters.Meanwhile it can forecast the changing trend of the surface quality of WEDM-LS.