SB7320 semi-automatic precision thread grinder is a precision thread grinder designed and manufactured for the steering gear factory of Yuejin Automobile Group in the late 70s of Hanjiang Machine Tool Plant. It is one of the key equipments of this factory. The machine adopts a numerical control system composed of logic circuits and sequential circuits composed of non-gate elements. The number of printed circuit boards in the numerical control cabinet is as many as 50; the drive circuits of the three stepping motors are analog amplification circuits composed of high-power transistors; Use one or two dials and eight keys to input; the machine control part is a program control circuit composed of relays and contactors. The line of the machine tool is complicated, the reliability is poor, and maintenance is difficult. After more than ten years of use, the grinding machine has fallen behind and has a high frequency of failure. In 1995, our factory modified this CNC grinding machine.
If the numerical control system of the machine tool uses the domestic economical numerical control system at that time, it uses a single board machine as the main control unit, and the number of I/O ports is very small, and the programming is also cumbersome and cannot meet the requirements of this machine tool. If using FANUC, SIEMENS system is very expensive. The SKY CNC system developed by Nanjing Sikai Electronic Enterprise Co., Ltd. is implemented on an ordinary computer platform. It uses 32-bit 80386 CPU, equipped with 270M hard disk, 1.44M floppy drive and 14-inch color display, using a full set of standard computer keyboard as the main control unit, I / O port number can also meet the needs of different program control. When the machine tool is not working, it can also be used as an ordinary computer. The driving element can be a servo motor or a stepping motor. The numerical control system works on the UCDOS Chinese character operating platform and can achieve two-axis or three-axis linkage. Although its price is slightly more expensive than ordinary economical CNC, its performance-price ratio is 3.5 times more than that of general economical CNC system. The SKY CNC system uses the computer's COM1 serial port or an extended serial port to communicate with the outside world. The I/O communication port fully meets our requirements.
We use the F1-MR60 programmable controller and the F1-ER60 expansion unit manufactured by Japan Mitsubishi as the controller of the machine tool. There is a total of 30 communications between the PLC and the NC, which is completed by two serial ports. The execution of the NC program is carried out under the control of the PLC program, which completely accommodates the original functions and operating modes of the machine tool. In order to adapt to the original machine tool operation methods and functions, we use the NC programming method, similar to the method of programming with R parameters, the original machine tool dial, key input NC data operation mode is changed to the CNC system's Chinese character operation screen Above, set/select parameters and select operation methods. We simplifies all the operations. When the system is turned on, it enters the system initialization state. According to the prompt on the display screen, the machine operation interface or machine tool interface can be selected. In the operation explanation interface, we have compiled the operation method and safe operation procedure of the SKY CNC system for machine tools. In the working interface of the machine tool, we put the grinding operation mode of the machine tool (manual/automatic, one-way grinding/bidirectional grinding, rough grinding/semi-finishing/finishing grinding), grinding cycle times, grinding wheel dressing methods (manual/ Automatically), parameters such as coarse and fine grinding feed, number of wheel dressings, and dressing amount are listed on the screen one by one using the menu, and only the ↑, ↓, â†, → cursor keys on the keyboard are used for selection and modification. At the same time on the screen also shows the dynamic size of the workpiece processing.
The driving components of the CNC system are three stepping motors, namely: the grinding wheel feeding motor, the grinding wheel dresser feeding motor and the table transmission screw rod clearance compensation motor. The stepper motor meshes with the transmission ball screw with a pair of gears. Among them, the passive gears are stacked with a pair of 1/2 drive gears with a tooth width, and the two gears use a spring to generate a certain misalignment angle, which can automatically eliminate the meshing gap of the main and driven gears. The headstock of the machine tool rotates the DC motor to use a three-phase asynchronous motor, and uses Mitsubishi's variable frequency speed control system for AC stepless speed regulation. Because the motor and the head frame shaft are connected by belts, according to the working speed range of the machine tool, the proper transmission ratio is selected so that the motor operates between 25 and 60 Hz, which ensures the head frame motor has better mechanical characteristics and good starting characteristics. The rotation of the headstock is constant during the operation of the machine tool, so the adjustment of its speed is only adjusted by the speed control potentiometer.
Due to the large differences in the size of the workpiece blanks, manual grinding is required for some of the larger working blanks, so manual grinding is retained. In the manual mode, in addition to the manual grinding wheel feed, the dressing of the grinding wheel and the compensation of the table screw gap are still automatically fed according to the preset amount.
To ensure the safe operation of the machine tool, we have set up a safety protection system and a forced interrupt function. If you want to interrupt the program during grinding, the operator simply presses the "Grind Back" button and the wheel quickly retracts and stops the program. The operator presses the "Esc" key to exit the CNC. The machine tool is in the "manual adjustment" mode, after making the necessary adjustments, the machine is in the grinding initial state. After typing in the "7320" file name, re-enter the "automatic grinding" state to continue working. 30 communication signals between PLC and NC, in the debugging or maintenance, can use the DEBUG statement on the computer of the numerical control system to check whether the data communication is correct, and bring convenience to the maintenance. This machine was delivered to use in April 1995.
If the numerical control system of the machine tool uses the domestic economical numerical control system at that time, it uses a single board machine as the main control unit, and the number of I/O ports is very small, and the programming is also cumbersome and cannot meet the requirements of this machine tool. If using FANUC, SIEMENS system is very expensive. The SKY CNC system developed by Nanjing Sikai Electronic Enterprise Co., Ltd. is implemented on an ordinary computer platform. It uses 32-bit 80386 CPU, equipped with 270M hard disk, 1.44M floppy drive and 14-inch color display, using a full set of standard computer keyboard as the main control unit, I / O port number can also meet the needs of different program control. When the machine tool is not working, it can also be used as an ordinary computer. The driving element can be a servo motor or a stepping motor. The numerical control system works on the UCDOS Chinese character operating platform and can achieve two-axis or three-axis linkage. Although its price is slightly more expensive than ordinary economical CNC, its performance-price ratio is 3.5 times more than that of general economical CNC system. The SKY CNC system uses the computer's COM1 serial port or an extended serial port to communicate with the outside world. The I/O communication port fully meets our requirements.
We use the F1-MR60 programmable controller and the F1-ER60 expansion unit manufactured by Japan Mitsubishi as the controller of the machine tool. There is a total of 30 communications between the PLC and the NC, which is completed by two serial ports. The execution of the NC program is carried out under the control of the PLC program, which completely accommodates the original functions and operating modes of the machine tool. In order to adapt to the original machine tool operation methods and functions, we use the NC programming method, similar to the method of programming with R parameters, the original machine tool dial, key input NC data operation mode is changed to the CNC system's Chinese character operation screen Above, set/select parameters and select operation methods. We simplifies all the operations. When the system is turned on, it enters the system initialization state. According to the prompt on the display screen, the machine operation interface or machine tool interface can be selected. In the operation explanation interface, we have compiled the operation method and safe operation procedure of the SKY CNC system for machine tools. In the working interface of the machine tool, we put the grinding operation mode of the machine tool (manual/automatic, one-way grinding/bidirectional grinding, rough grinding/semi-finishing/finishing grinding), grinding cycle times, grinding wheel dressing methods (manual/ Automatically), parameters such as coarse and fine grinding feed, number of wheel dressings, and dressing amount are listed on the screen one by one using the menu, and only the ↑, ↓, â†, → cursor keys on the keyboard are used for selection and modification. At the same time on the screen also shows the dynamic size of the workpiece processing.
The driving components of the CNC system are three stepping motors, namely: the grinding wheel feeding motor, the grinding wheel dresser feeding motor and the table transmission screw rod clearance compensation motor. The stepper motor meshes with the transmission ball screw with a pair of gears. Among them, the passive gears are stacked with a pair of 1/2 drive gears with a tooth width, and the two gears use a spring to generate a certain misalignment angle, which can automatically eliminate the meshing gap of the main and driven gears. The headstock of the machine tool rotates the DC motor to use a three-phase asynchronous motor, and uses Mitsubishi's variable frequency speed control system for AC stepless speed regulation. Because the motor and the head frame shaft are connected by belts, according to the working speed range of the machine tool, the proper transmission ratio is selected so that the motor operates between 25 and 60 Hz, which ensures the head frame motor has better mechanical characteristics and good starting characteristics. The rotation of the headstock is constant during the operation of the machine tool, so the adjustment of its speed is only adjusted by the speed control potentiometer.
Due to the large differences in the size of the workpiece blanks, manual grinding is required for some of the larger working blanks, so manual grinding is retained. In the manual mode, in addition to the manual grinding wheel feed, the dressing of the grinding wheel and the compensation of the table screw gap are still automatically fed according to the preset amount.
To ensure the safe operation of the machine tool, we have set up a safety protection system and a forced interrupt function. If you want to interrupt the program during grinding, the operator simply presses the "Grind Back" button and the wheel quickly retracts and stops the program. The operator presses the "Esc" key to exit the CNC. The machine tool is in the "manual adjustment" mode, after making the necessary adjustments, the machine is in the grinding initial state. After typing in the "7320" file name, re-enter the "automatic grinding" state to continue working. 30 communication signals between PLC and NC, in the debugging or maintenance, can use the DEBUG statement on the computer of the numerical control system to check whether the data communication is correct, and bring convenience to the maintenance. This machine was delivered to use in April 1995.
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