Design Of Dot-matrix Printer System Based On Touch Screen

Dot-matrix big character printer is an electro-mechanical and hydraulic integrated system which is widely used in product identification. The development of domestic printers lags behind foreign products. At present, domestic printers have many disadvantages such as unstable performance and narrow application range. Foreign products have longer serving life and more stable performance, but the price is higher. In addition, foreign printers cannot adapt to domestic product line directly. Therefore, it is necessary to develop efficient and adaptable printing products.In this thesis, an integrated dot-matrix big character printer system is developed according to the application status of big character printers. This printing system can print 7×5 dot matrix font of ASCII characters. The height of characters can be changed to adjust to different printing requirements. A whole printer system includes mechanical structure, hydraulic system, control system and human-machine interactive system. According to the composition of the printer system, the main content of this thesis is summarized as follows.Firstly, the platform of printer system and XY worktable for nozzles are designed by AutoCAD and manufactured for further study. And the structure of nozzle switch valve is improved.Secondly, the ink hydraulic circuit is developed to provide stable pressure ink for nozzle valves according to hydraulics principle.Thirdly, the forming principle of dot-matrix characters is explained and the new adjustment method of character height is introduced in detail. Then the control circuit is designed based on single chip microcomputer and the programs in the SCM are written to control nozzle valves and step motors of XY worktable.Next, touch screen is chosen as the human machine interface of human-machine interactive system. The HMI is designed by configuration software. Then the communication program of CPU and touch screen is written by Modbus-RTU protocol.Finally, the printing function is debugged based on the complete system designed in this thesis. The optimal turn-on time of nozzle valves should be selected by experiment firstly. Then all characters in the font are printed to observe the printing result and the new adjustment method is tested to change character height. After all of these experiments, the performance and weakness of the dot-matrix big character printer system can be summarized.The innovations of this thesis include three points.The first one is the mechanical structure of nozzle. Nozzle switch valve, which could have a direct impact on printing effect, is the critical component of a printing device. In this thesis, a new complex valve structure is designed to solve the problem of ink leakage according to the principle of ball valve.The second point is the adjustment method of dot-matrix character height. At present, most dot-matrix big character printers regulate the printing angle of nozzles to change the character size. This thesis proposes a new method to change character height by moving nozzles in the height axial. This method can avoid the restriction of dot spacing which is determined by the structure size of nozzles. What’s more, the new method has wider adjusting range than angle adjusting method.Last but not least, the human-machine interactive system is developed with touch screen so that the traditional keyboard, mouse, display and computer host can be replaced. In this way, the size of printing device is smaller and the manufacturing cost can be reduced.