Application of Siemens 802S CNC System in High Pressure Water Jet Cutting Machine

I. Introduction:

The high pressure water jet cutting machine is a high pressure water applying special abrasives. It sprays high pressure water jets through nozzles to cut workpieces. It has high cutting efficiency and neat trimming. It is widely used in light industry and other industries. The control system of high-pressure water jet cutting machine generally adopts economical numerical control system to ensure reliable and stable work. Siemens SINUMERIK 802S CNC system adopts 32-bit microprocessor, integrated PLC, separated small-size operation panel and machine control panel. It is an advanced economical CNC system. It is specially developed for the Chinese market with less start-up data and installation and debugging. Convenient and quick; with Chinese and English menu display, easy and convenient operation and programming; with high reliability and strong stability. The high-pressure water jet machine adopts Siemens SINUMERIK 802S CNC system, making full use of the system's rich error compensation functions, such as screw backlash compensation, screw pitch error compensation, feed axis pulse monitoring, etc., greatly improving the high-pressure water jet Machine production efficiency.

Second, the hardware composition of the numerical control system

The CNC system of high-pressure water jet cutting machine mainly includes operation panel (OP020), machine panel (MCP), numerical control part (ECU), step driver (STEPDRIVE C) and stepper motor, PLC module (DI/O), communication port .
1. Operation Panel (OP020)
The keypad layout of the operation panel adopts ergonomic design, which is convenient and flexible. The keys mainly include menu function keys, letter keys, number keys and the like.
2. Machine Tool Panel (MCP)
The machine panel includes universal control keys and dedicated control keys for the high-pressure water jet cutter. The common control keys include the feed axis move button, the numerical control start stop button, the work mode select fold function button, and the feed override select fold band switch. Dedicated control buttons include high-voltage motor start and stop, tool change start stop, cooling, lubrication and so on.
3. Numerical Control Unit (ECU)
The numerical control part mainly includes CPU, ROM, RAM, position control circuit and interface board. The ROM is used to solidify the CNC software. The RAM is used to store variable data such as stack data and control software temporary data. Variable data storage areas such as CNC machining programs and system parameters have a power-off protection function. When the main power supply is not powered, data is not lost.
4. The stepper driver (STEPDRIVE C) and the stepper motor stepper driver (STEPDRIVE C) are single-axis controllers that control five-phase stepper motors. Stepping motor step angle of 0.36 degrees. The drive interface uses a 25-pin D-type socket. Each driver receives three signals, one for the pulse signal, one for the direction signal and one for the enable signal. The pulse sent out controls the operation of the motor. Each rising edge causes the motor to go one step forward. The number of pulses determines the rotation angle of the motor. The pulse frequency determines the rotation speed of the motor.
5. Input/output section (I/O)
The input and output parts mainly include the fast input interface and the PLC module of the numerical control system. Fast inputs include limit proximity switches and NCRDY signals. The NCRDY signal is a contactor emergency stop signal that is used as an NC enable. The PLC module I/O includes high pressure start stop, tool change start stop, cooling switch, lubrication switch and so on.
6. Communication port data communication adopts standard RS-232C, used to receive user program or communicate with computer. It uses a 9-pin D-type socket and the signal names include: RXD-data reception, TXD-data transmission, RTS-transmission request, CTS-transmit enable, DTR-data transmission equipment ready, DSR-data terminal ready, M-signal ground .

Third, the control system software

Siemens 802S CNC system is a complex multi-task real-time software, which uses a modular structure, each module in charge of their own tasks, the formation of specific functional modules, the corresponding software is also modular, forming a functional module software structure solidified in the CPU.
The CNC unit of Siemens 802S CNC system is mainly composed of three major modules, namely man-machine communication (MMC) module, numerical control module (NCK), and programmable logic controller (PLC) module.
1. Human Machine Communication (MMC) Module The Siemens 802S CNC system uses human-computer interaction processing technology to interact with the user interface. The user selects the working mode of the CNC system and inputs the corresponding data and commands. The CNC system provides feedback on the user's operations in real time, providing the user with system operation status, providing corresponding operation and learning assistance, and operating errors and systems. In the event of a fault, errors and warnings are generated.
The main menu of Siemens 802S control system includes: 1) processing, 2) parameters, 3) program, 4) communication, 5) diagnosis.
2. Numerical Control Module (NCK)
The numerical control module includes the numerical control core function program, such as the decoding, pretreatment and interpolation processing of the numerical control processing program, and also includes the numerical control processing program editor, processing simulation, tool management, and fault monitoring and diagnosis functions.
3. Programmable controller (PLC) module The programmable controller module handles the logic control of the machine tool electronics and the control of some other switching signals in the NC machining program. Siemens 802S CNC system PLC programming software uses S7-200.

Fourth, the system debugging and should pay attention to the problem:

The application of the Siemens 802S CNC system in high pressure water jet cutting machines is based on a standard lathe system. According to the hardware configuration, the display machine data, general machine data, axis-related machine data, and channel-related machine data are set accordingly.
Modifying the machine data is very important for the machine tool. Incorrect setting of the parameters will cause the machine to be confused. The machine tool modification effectively includes the following four conditions: 1) so - immediate effective 2) cf - valid after confirmation 3) re - reset effective 4) po - powered on. Different levels of machine data correspond to different valid modification settings.
The PLC parameters are entered from the "Diagnosis/Machine Data/General Machine Data" parameter screen of the operation panel according to the configuration of the program. The configuration of the PLC machine hardware corresponds to the setting of the corresponding machine data.

Siemens 802S CNC system application debugging should pay attention to the following questions:
1. The system requires a limit switch in both directions (+/-) for each axis so that the NCK monitors the limit in all modes of operation. After the travel switch is hit, all axes must stop immediately and the system only allows The overtravel axis moves in the opposite direction in JOG mode. Limit switches include hardware limit switches and software limit switches. If the hardware limit switch is exceeded, the PLC informs the NC via IS V380X1000.1/.0 and interrupts the movement of all axes. Each axis has two pairs of software limit switches, which are set in the machine axis system by MD: POS_LIMIT_PLUS, POS_LIMIT_MINUS, POS_LIMIT_PLUS2, POS_LIMIT_MINUS2.
2. Each axis is equipped with a reference point deceleration control switch as required. The X-axis switch is connected to I1.4 and the Z-axis switch is connected to I1.5. A reference point proximity switch (BERO) is connected to the NCK input (X20) to accurately set the reference point.
3. Positioning monitoring is as follows: In order to ensure that the axis reaches the specified point within a predetermined time, the time set in MD: POSITIONING_TIME (positioning delay) is started at the end of a block operation (position amount = 0), and at this time Check whether the movement error is lower than the limit value of STOP_LIMIT_FINE (fine positioning accuracy) after the end of the operation. If the position control gain coefficient is too small, change the position control gain adjustment MD: POSCTRL_GAIN (N) setting value; if the positioning window (precise stop ) Inconsistent with the position monitoring time and position control gain coefficient, change the settings of MD: STOP_LIMIT_FINE (precise stop), MD: POSITIONING_TIME (precise stop delay time), MD: POSCTRL_GAIN (N).
4. In the switch output circuit, the power contactor and the solenoid valve of the strong circuit are controlled through intermediate relays, and a shunt protection diode is added at the same time so that when the coil is cut off, a release circuit is provided for the current to protect the digital control drive circuit.
5. In order to improve the anti-jamming ability of the whole system, the weak current signal and the strong electric driving signal are routed as far as possible in the wiring groove, and the RC arc extinguishers are connected in parallel at both ends of the AC contactor coil. To ensure the reliability of the CNC system.

V. Conclusion

The high pressure water jet machine adopts Siemens SINUMERIK 802S CNC system, which solves the instability of the original domestic machine tool CNC system, and makes full use of the system's rich error compensation function, which greatly improves the reliability of the whole machine and the function of the machine tool.