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Study on the NC Control System of Frame Cold-bending Machine

Author: ZhouYongQing
Tutor: WangChengFang
School: Wuhan University of Technology
Course: Design and manufacture of ships and marine structures
Keywords: shipbuilding profile process frame bending machine CNC automaticmarking
CLC: TP241
Type: PhD thesis
Year: 2012
Downloads: 25
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Abstract


A review on recent advances and trends on CNC frame cold bending technology is presented at the beginning of this thesis. Based on chord-length measuring method and frame cold bending machine, study on the real-time calculating method of bending angle, handling method for the spring back of the frame, and calculating method of automatic marking parameters is carried out. Improving method of detecting unit and bending dies is presented. Automatic making unit and control software for the CNC frame bending machine are designed, and the control software has been repeatedly tested and constantly improved for a long term. The main contents of this thesis are as follow:Study on the real time calculating of bending angle is carried out. With the real-time calculating method, the bending angle θi at the actual feeding position of the frame is worked out. Comparison of this angle with the angle calculated before processing shows that it is necessary to calculate the bending angle in real time. Processing frame with this angle, influence of feeding error is eliminated and the processing precision is improved.The bending and spring back course of the frame while processed is analyzed and the angles at every stage of the course are recorded. Considering that there is a short time from bending stop command is send out to the frame bending machine stop bending action, handling of spring back is carried out with the deviated angle instead of spring back angle, which is used in gradually approaching method. With this new method, the approaching times are obviously decreased and the frame processing efficiency is improved.Study on the calculating method for automatic marking parameters is carried out. According to marking parameters in offset value coordinate system, installing parameters of the frame bending machine and the detecting parameters in detecting coordinate system, the method to work out the marking parameters in detecting coordinate system are deduced. With the method, control software can work out the control parameters needed by the automatic marking apparatus presented according to the detected coordinates, and drive it to mark out the part name with arbitrary font, start line, end line, waterlines, cutting lines, flooding holes etc. at regulated position on frame surface. So, the bending process and marking of the frame is finished at one process course and the efficiency of the frame process is improved.The mechanic, hydraulic and electrical components of frame bending machine are introduced. A new detecting unit is presented. It can provide data for automatic marking during bending process and solve the problem existed for a long time that the steel wire using for detecting impacts the operation. The reasons of the wave distortion happened at the flange plate of bulb and T bar are analyzed, and then a design plan of bending dies to avoid this distortion and improve the shaping equality of the frame process is presented.According to the hardware components and control system of the frame cold bending machine, the control software is developed. And its functions, developing environment, automatic control interface, manual operation interface, calibrating interface and setting interface are introduced. The phenomenon occurred in feed-in process that bulb head runs out of bending dies and is heavily scraped and the phenomenon occurred in bending process that there is heavy noises and the surface of web plate is heavily scraped are analyzed. The reasons of them occurred are found out and the control software is made improvement to eliminate them. So, the safety of automatic process and surface equality of the processed frame are improved, and the radial force acted on the central clamp hydraulic cylinder is reduced.Some reseach advancement about the CNC control of frame bending machine in theory and engineering application are achieved in this thesis. In theory, the real time calculating method of bending angle, the calculating method of automatic marking parameters and the handling method of spring back are presented. In engineering application, the detecting unit, bending dies, automatic marking apparatus and the control software has been put into practical use. And the software has been constantly improved in the long time test and application.Accompanied with the application and popularizing of CNC frame bending machine, the results of this thesis has been widely used to practical production of frame automatic process in shipyards.

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