With the rapid development of the automobile industry, people are increasingly demanding various performances of tires, which greatly promotes the development of tire mold manufacturing technology. In the past, the surface pattern of the tire mold was simple, and now the surface of the tire mold has many patterns with the same or different unit bumps arranged according to a certain regularity. Since the pattern precision and quality on the tire mold will directly affect the quality and performance of the tire, Therefore, in the processing of tire molds on an EDM machine, in order to manufacture these regular patterns, the mold must be accurately indexed. 2 Process requirements The tire mold electric spark forming machine can produce various tire molds with a tire mold inner diameter of 500 mm to 1200 mm and a fraction of 2 to 500 patterns, and the table rotation accuracy is not less than 0.017°. In the centering mode (adjusting the center of the mold to coincide with the center of the table), the table rotation speed is 0 to 0.5 rpm; in the manual adjustment mode, the table rotation speed is 0 to 0.5 rpm; in the automatic machining mode, the table is The turning speed is 0 to 0.25 rpm. All working parameters can be adjusted and set from the man-machine interface. 3 automatic indexing system, hardware configuration and hardware and software design 3.1 Automatic indexing system Under the premise of ensuring the test requirements, choose a solution with high cost performance, reliable operation and short development cycle. After comprehensive consideration, the touch screen is adopted as the design scheme of the upper computer and the PLC as the lower computer. Data transmission is completed by RS-232 serial communication. The system block diagram is shown in Figure 1: Next page Sink Kitchen Mixers,Kitchen Mixer Faucet,Single Handle Faucet Wenzhou Yili Sanitary Ware Co., Ltd. , http://www.cn-faucet.com
The touch screen is specially designed for PLC applications. It is different from some simple instrument type or other simple PLC control equipment. It is powerful, easy to use and strong in anti-interference ability, which is very suitable for the increasingly large workload of modern industry. The need for functionality, it is increasingly becoming one of the essential equipment for modern industry. The lower position machine programmable controller has the advantages of convenient expansion, simple control, strong anti-interference ability and low price; PLC as the lower position machine completes the functions of indexing control, processing control and collecting encoder feedback data.
3.2 Hardware configuration of the control system According to the performance requirements, from the economic point of view, select the main components:
(1) The touch screen uses the MT508S of EASYVIEW. In addition to the functions of the general human-machine interface, this series of human-machine interfaces also provides many unique features:
a) 6 pop-up windows can be opened at the same time.
b) You can have the same taskbar and quick selection window as Windows 95/98.
c) Using a powerful 32-bit RISC processor (Intel's StrongARM), the MT508 has faster processing speed.
(2) The rotary encoder adopts the Japanese NEMICON company's precision 5400P/R product, which feeds back the position signal of the workbench to the PLC, and then controls the stepping motor by the PLC to process the data, so as to achieve precise control of the position of the table. purpose.
(3) PLC adopts FBE-20MC of FB series of Yonghong Company. There are two main reasons for using this series of PLCs: a) Hardware High Speed ​​Counter (HHSC) with hardware circuit, the highest counting frequency is 20 kHz, and it is a 32-bit high-speed counter. B) The counter of the PLC comes with a 4x frequency circuit, and the encoder signal is subdivided into 4 to improve the system accuracy.
The feedback pulses of the encoder are counted using a set of hardware high speed counters. Each set of hardware high-speed counters of FB-PLC has 8 counting modes to choose from. We choose MD7, that is, the input signal is two pulse signals with phase difference of 90°, counting the rising and falling edges of the two signals separately. Thus, the high-speed counter counts 4 pulses, as shown in Figure 2. The accuracy of the original encoder feedback signal is 360 ° ÷ 5400 = 0.067 °, which obviously does not meet the requirements, but after the subsequent circuit level conversion and PLC 4 times frequency circuit subdivision, without adding any hardware premise The resolution of the encoder is increased to 360° ÷ 5400 ÷ 4 = 0.017°. In the indexing control system, we compare the number of pulses fed back by the encoder with the number of target pulses calculated by the PLC. If the feedback value is less than or greater than the target value, the workbench has not reached the target position. If the two values ​​are equal, This indicates that the workbench has reached the target position. In this way, closed-loop control of the table position is achieved.
(4) FBE-20MC is the core device of the control system, and its input and output signal distribution is shown in Figure 2: 
1 Introduction