Abstract : Based on the system's working process, the OMRON CP1L PLC was selected to realize manual/automatic control of the film-coating machine. The heating time can be adjusted via an external analog potentiometer, greatly improving production efficiency and ease of operation. Keywords : PLC; analog potentiometer; ease of operation 1 Introduction to Film-coating Machine The film-coating machine is a type of woodworking machinery that performs the function of coating materials such as wood panels. It is divided into single-worktable and double-worktable types, mainly composed of a transmission device, heating device, pressurizing device, and control cabinet, as shown in Figure 1. [align=center]Figure 1[/align] During operation, the motor drives the worktable to feed the wood covered with film into the heating box. After a certain period of heating, the film softens, and then a vacuum pump pressurizes it to tightly adhere the film to the wood board. Finally, the finished product is delivered. The working process is shown in Figure 1. 2. PLC Control of the Vacuum Covering Machine Since the unloading and loading processes are done manually, for a double-worktable vacuum covering machine, unloading and loading can be completed on the other side while one side is working. Therefore, the double-worktable vacuum covering machine saves time and has higher production efficiency than the single-worktable type. This article focuses on the double-worktable design, so that the vacuum covering machine can work either individually or in pairs. 1. Control Process This system design uses the CP1L-M40DR-A manufactured by Omron as the core of the control system. Its features include high automation, convenient operation, flexible programming, strong anti-interference capability, high safety, and convenient use and maintenance. Point 00100 is used as the manual/automatic selection position, point 00101 as the stop position, and points 00102 and 00103 are the start positions for the left and right worktables, respectively. To prevent collisions, the left worktable can only start when the right limit switch of the right worktable is depressed; similarly, the right worktable can only start when the left limit switch of the left worktable is depressed. When the manual/automatic switch is selected in manual mode, the feeding, pre-compression, forming, depressurization, and discharge processes are controlled by corresponding buttons; when the manual/automatic switch is selected in automatic mode, pressing the start button for either the left or right worktable will automatically complete the entire processing from feeding to discharge. When the left worktable is allowed to start, press the left worktable start button. The motor rotates forward and feeds the material into the work box. The heating time is set by TIM000 for a certain period. The vacuum pump solenoid valve is then activated for a brief pre-compression (approximately three seconds, set by TIM001), followed by forming (set by TIM002), a delay (set by TIM003), and finally, the product is delivered. The entire process ends when the left limit switch of the left worktable is pressed down. The right worktable operates in the same way. 2. PLC Program Different materials require different heating times. We can conveniently set the time using the external analog potentiometer of the CP1H without frequently reading and writing programs to change the timer's setting value. Its usage involves applying a voltage of 0-10V to the external analog setting input terminal of the CP1H CPU unit. The input voltage can then be converted from analog to digital, and the current value of the special auxiliary relay A642CH can be freely changed within the range of 0-225. Store the contents of A642CH into D2, convert it to a BCD number, multiply it by a certain factor and store it into D0. Use the value in D0 as the timer setting value. The program implementation is shown in Figure 3. The PLC control programs for the left and right worktables are similar. Here, only the PLC program for the left worktable is given, as shown in Figure 4. [align=center] [/align] 3 System Functional Features (1). Manual/Automatic Selection Considering that manual operation is sometimes required during the production process, the system is set to manual/automatic selection. In automatic working mode, the vacuum coating machine can automatically complete the entire production process, improving production efficiency. (2). Safe and Energy-Saving The heating box is fixed, with minimal heat loss, rapid heating, and energy-saving insulation. Automatic timed heating, pressurization, and depressurization are safe and convenient. An observation port is set in the heating box, resulting in a high yield rate. (3). Adaptability For different materials, such as PVC and wood veneer, the required heating time is different. The time can be set by the potentiometer on the panel without modifying the program. References: [1] Xu Shixu, Gong Shuzhen, Peng Tao. Application Guide for Programmable Logic Controllers [M]. Beijing: Electronic Industry Press, 2007. [2] SYSMAC CP Series Programmable Logic Controller CP1L-CPU Unit Operation Manual. [3] SYSMAC CP Series Programmable Logic Controller CP1L-CPU Unit Programming Manual. Author Biography: Contact Information: Mailing Address: Graduate Student, Class of 2006, School of Automation Engineering, Qingdao University, Qingdao, China (Attn: Li Junjie) Postcode: 266071 Tel: 13864808032 Email: [email protected]