Research on Online Monitoring System of CNC Machining

Research on CNC Surveillance Online Monitoring System of Journal of Hebei University of Science and Technology Wang Shigang Chen Ji Ma Yulin 2 2. Harbin Institute of Technology Modern Production Technology Data Machine and Microcomputer Dedicated Communication Interface and System Software. For the CNC machine! The research on automatic compensation in step modification and quality assurance systems provides the necessary technical support.

271: The essence of A numerical control technology is to implement data driving and software control, which makes the manufacturing industry undergo a qualitative change. In the early 1980s, the development of modern control technology promoted the development of numerical control technology, and flexible manufacturing appeared internationally. Units (FMC) and Flexible Manufacturing Systems (FMS), which are considered to be the necessary stages and foundations for implementing Computer Integrated Manufacturing Systems (CIMS). From the structural point of view, the FMS system includes structural subsystems such as machining system workpiece flow system, tool flow system, and assembly system monitoring system. The monitoring system is the key link for the realization of quality assurance function.

The processing size online monitoring system mainly takes various size parameters in the processing process as the object, real-time detection, real-time processing, and corresponding quality control feedback to ensure product quality; at the same time, the recovery of the processing process interruption also needs to be collected through the monitoring system. And store historical data of the product during processing to analyze the quality information of the process.

Based on the development and implementation of the system, this system constructs an on-line monitoring system based on microcomputer with strong anti-interference ability and real-time multi-task parallel processing. The online monitoring system consists of the following components: Contact probe sensor: when it is in contact with the workpiece, it sends a switch signal; X/Y direction linear displacement sensor and related secondary instrument (GX-A type developed by the Chinese Academy of Sciences); used to record X/Y direction coordinate values, and BCD code format is transmitted to the computer; 32-channel BCD code interface board); used to transmit the size information of the raster to the computer; Fund project: Specialized communication interface (13.1.1) funded by the National Defense Science and Technology Commission's "Ninth Five-Year Plan" pre-research project ( SCIC) (self-design and development); according to the instructions of the control computer, drive the movement of the probe, complete the information transmission between the computer and the machining center; the computer-related monitoring software: used to control the operation of the machining center on the computer, it is based on the microcomputer The core of the monitoring system. The structural principle of the whole detection system, as shown in Fig. 2 The hardware system and interface structure of the monitoring system are in the computer control system. In order to realize the control of the production process, various measured parameters of the production site should be transmitted to the computer in the required manner. After the calculation process, the result is output as a number, and at this time, the output is also converted into a control amount suitable for the production process. Therefore, between the computer and the production process, information transmission and transformation devices must be set up. This connection device is called the output input process channel. Journal of Hebei University of Science and Technology This system is divided into a forward channel interface and a backward channel interface forward channel. : It is a signal input channel that connects the measured object and the system; in this channel, it is mainly a sensor-related signal conditioning and conversion circuit, also called a sensor interface channel; the triggering probe, the grating and its interface belong to the forward channel Backward channel: It is the output channel of the control object to realize the structure principle of the operation monitoring system. Its structure is closely related to the control object and control Fig.2Structuralprindples task. It generally completes small signal output, high power control function XY to AC servo drive power supply and its The interface with the microcomputer belongs to the working principle of the backward channel 2.1 grating and the working principle of the installation of the 21.1 grating ruler. On the high-precision CNC machine tool, the grating is used as the position detecting device, which converts the mechanical displacement or analog quantity into a digital pulse, and feeds back The numerical control device realizes closed-loop control. Due to the development of laser technology, the precision of grating fabrication has been greatly improved. Now the grating accuracy can reach micron level, and the resolution of subdivision circuit can reach 0.1m or even higher.

Coupling, so that the ground potential of the two circuits is completely isolated, so that even if the ground potential is different, it will not cause interference into the resistance row. The pull-up resistor makes the circuit in a high-resistance state in the case of the optocoupler unreachable, and the conduction signal passes. The 74Ls14p integer filter circuit forms a regular signal into the buffer memory. When the computer command passes through one of the four-selected function circuits of b) and strobes one of k1, k2, k3, k4, the signal in the corresponding buffer is sent to the buffer 245. Under the control of the enable signal k5 from the computer, the output of the final signal is completed. 2.3 The numerical control device of the CNC machine tool and the upper control computer communication interface bed needs to carry out data transmission and information communication with the following devices; data input and output device; external machine control panel General hand crank pulser; feed drive line and spindle drive line With the development of factory automation (FA) and CIMS, the numerical control device acts as a layer in the FA or CIMS structure, in addition to being connected to data input and output devices. Communicate with the upper control computer, so it should also have the function of communication between the computers with the function of network communication. In most cases, control commands cannot be transmitted through the serial port (RS-232C). Therefore, in order to achieve full communication between the upper control computer and the machining center, a dedicated communication interface unit must be developed. The author's initialization module implements various initialization parameters, such as: pulse when ~ quantity (PULEQU), timer 1 and timer 2 work break query module in the detection process, because the trigger signal of the probe is random, according to the system The requirements, when the trigger signal is generated, should be: 1) the computer can accept and recognize the signal; 2) control the machine tool in each axial stop after receiving the signal; 3) simultaneously read the transmission signal of the grating ruler, and carry out In order to achieve the above objectives, three working modes are adopted: First, a soft interrupt with an interrupt number of 0 x 72 is intercepted, and the interrupt signal input port is queried by the interrupt before the control signal is sent. The feedback direction is used to determine the execution direction of the program. Second, using the internal timer interrupt of the computer, since the microcomputer system performs the clock hard interrupt (IRQ1) at 18.2 times per second, and then the soft interrupt is called, then it can be used at a frequency of 18.2 times per second. To activate the memory resident program, perform the timing background query, and the software query mode raster display module. In order to form a closed-loop detection control system, the data transmitted by the raster should be displayed in real time and stored in a data file for processing of the test data and adaptive compensation control after completion. The data transmitted by the raster is in the form of BCD code, which is converted into a binary number by the bitwise operation. The functions of the module are: data storage, multi-point display, single-point display and error separation.

Direction control module. According to the actual situation, the feed direction of each axis is set, and each direction corresponds to different parameter setting port operation and timing relationship feed control module. Referring to the control mode and working principle of the speed regulating potentiometer, the sub-functions (such as the control feed rate increase SETFEEDINCRECE) for designing the control feed speed working mode are designed. The timing relationship includes rapid feed control, jog feed control and feedrate override. control.

The spindle speed adjustment module completes the power giant automatic detection module by setting a sub-function that controls the spindle speed operation mode (such as controlling the spindle speed increase SETROTATINCREASE). The detection path is based on the optimization of the interpolation algorithm. Under the premise of not losing steps and not increasing the steps, the interpolation algorithm of the feed rate can be realized as fast as possible to control the trajectory of the real-time speed regulation, and the interpolation is also considered. The positional accuracy and detection efficiency of the output 4 Conclusion This paper has carried out a comprehensive experimental research on the online monitoring technology of numerical control processing. Based on the experience of advanced monitoring at home and abroad, a monitoring system based on microcomputer is constructed, and a special communication interface card is produced. The WINDOWS-based monitoring system software was compiled with VC++, which can realize multi-task parallel processing. The control software of forward and backward monitoring channels was designed and developed by digital pulse technology. Through the operation of the experimental system for many times, a large amount of data was measured. The analysis results of the experimental data show that the actual use of the system is good and the expected research goal is achieved.