Research On The Rapid Die Replacement System For FET1200 Skin Stretch Forming Machine

The stretch forming process is one of the basic forming methods for aviation skin parts.Because the aircraft skin parts include numerous species,and being produced in small batch and multiple batches,frequent die replacements are required during the actual stretch forming production.The existing die replacement method presents the characteristics of complicated procedures,time consuming and low degree of automation.During the die replacement and the quenching process of skin parts,the stretch forming machine is shutdown,which seriously decreases the work efficiency of skin stretch forming production.The contradiction between the low efficiency of skin stretch forming production and the rapidly growing demand for aircraft skin parts is becoming increasingly prominent.Therefore,a rapid die replacement system is designed to improve the work efficiency and forming quality of skin stretch forming production,which can promote the development of aviation industry in our country.Firstly,the research status of the skin stretch forming technology and equipment,the Single Minute Exchange of Die technology and application are summarized.Based on the investigation of the structure principle,working characteristics,die types and replacement methods of FET1200 skin stretch forming machine,the main reasons affecting the work efficiency and forming quality of skin stretch forming production are analyzed.Then,a rapid die replacement system is proposed for the FET1200 skin stretch forming machine.Secondly,the detailed design is completed aiming at each component unit of the rapid die replacement system.A moving worktable is designed based on the working characteristics of the skin lateral stretch forming machine.A hydraulic synchronous jack-up system based on the pulse width control is designed to overcome the unbalanced loading problem in the jackup process of the moving worktable.Aiming at the problems of the gantry hydraulic press,including low machining precision,poor anti-eccentric load performance and hydraulic vibration and shock,a combined frame hydraulic press is designed to improve the forming quality of the skin parts.Then,the static analysis and modal analysis of the frame hydraulic press is completed using ANSYS Workbench software,and the corresponding displacement deformation,stressstrain diagrams,natural frequencies and vibration modes of the frame hydraulic press body structure are obtained.The analysis results show that the mechanical performance of the frame hydraulic press meets the practical requirements,and its natural frequency is far greater than the working frequency,which will not easy induce resonance phenomenon.Finally,analyses are carried out using AMESim software,aiming at the displacement synchronization performance of the synchronous jack-up system and the dynamic performance of the hydraulic system of frame hydraulic press.Some analytic curves are obtained,including the corresponding displacement curve,displacement deviation curve,speed curve,working pressure change curve,and so on.The analysis results show that the displacement synchronization precision of the synchronous jack-up system and the dynamic performance of the hydraulic system of frame hydraulic press meet the expected design goals and the practical requirements.The die rapid replacement system designed in this paper presents the characteristics of high efficiency of die replacement and high degree of automation.The stretch forming work of other batches of skin parts can be conducted synchronously during the die replacement and the quenching process of skin parts,which reduces the downtime of the skin stretch forming machine,and significantly improves the work efficiency and forming quality of the stretch forming production.