1 Introduction
Grinding machine is an important working machine in the metal cold processing industry. With the development of industry, the requirements for machining precision and surface roughness of mechanical parts are increasingly increasing, and grinding processing becomes more important. In the automotive, power, marine, metallurgy, military, aerospace and other industries, domestic CNC grinding machines are playing an increasingly important role. Cylindrical grinding machines are the most widely used, capable of machining a variety of cylindrical and conical outer surfaces and shaft shoulder face grinding machines. The Universal Cylindrical Grinding Machine also has an internal grinding attachment that grinds the inner and outer taper surfaces of the inner bore and the larger taper. The degree of automation of the cylindrical grinding machine defines the machining efficiency of the grinding machine and thus determines the processing scale of the grinding machine.
2 Grinding process
Grinder belongs to the metal workpiece surface precision machining machine. The basic principle of grinding machine is to use grinding wheel or oil stone (cutting tool) to do shallow depth micro-cutting on hardened surface of parts. The depth of cut during grinding is small, and the metal layer that can be removed in one stroke is thin. Abrasive tool rotation is the main movement, and the movement of the workpiece or grinding tool is the feed motion. Grinding machine with high precision, surface roughness Ra value is small. Grinding is a widely used cutting method. Because of the unique grinding structure principle, the biggest feature of the grinding machine compared to other metal cold-working machines is that the cutting speed can reach as high as 30m to 50m per second, and the grinding temperature can reach 1000. "C ~ 1500oC, the grinding process is as short as only one ten-thousandth of a second. Therefore, the grinding process can obtain higher machining accuracy and a small surface roughness value. Grinding can not only process soft materials, such as unquenched Steel, cast iron, non-ferrous metals, etc., but also can be processed hardened steel and other tools can not be processed hard materials such as ceramics and hard alloys.
When the part is processed, it is mainly the movement of two axes. One is the worktable shaft and the other is the grinding frame axis; the worktable travels by servo motion, and the work rests on the workbench, so the feed size is the size of the grinding, the upper and lower material cylinders are mounted on the workbench, and the magnetic card Disk, dresser. Magnetic chucks use strong magnets to hold parts as they are machined, requiring magnetic unloading before feeding and discharging. The dresser moves with the workpiece table. The dresser is used to dress the grinding wheel. The lift is controlled by hydraulic pressure. Grinding wheel mounted on the grinding wheel, the movement of the grinding frame is also controlled by the hydraulic pressure, and the deceleration valve to control the speed of movement in different processes. In addition to the two axis motion related components there are also some auxiliary mechanisms such as grinding fluid, lubricating fluid, measuring frame and so on.
3 Electric Control System Design for Delta Ball Bearing Grinding Machine
3.1 Overall Design
High efficiency is the purpose of the company, and high efficiency means high speed. Speed ​​is an important indicator for evaluating the electronic control system of the outer ring raceway grinder. The electric control project of the grinding machine selected Zhongda EH2 series high-speed PLC and ASD series AC servo system, and optimized the program structure under the premise of safety and precision, which greatly increased the production speed of each workpiece and the processing speed of each basic part. Control within 6-7 seconds. Only a small number of necessary buttons are set on the electronic control panel. Most of the other operations are implemented on the touch screen. It takes full advantage of the interactive dialogue with a huge amount of interactive information on the touch screen, plus intelligent formula and alarm management functions. It is more intuitive and the touch screen is also displayed. The status and time of each step is used as a reference adjustment, so that the part processing is not operated under manual control as much as possible. Most of the processing steps have a strict order. When a non-alarm emergency occurs, an emergency reset button can be used and the system will transfer Rapid security exit process. Electric control panel design shown in Figure 1.
Delta-based systems are:
(1) PLC: DVP40EH00T2 (40-point host, 24DI/16DO (relay), 4-way 200K input/output AC power supply);
(2) PLC expansion unit: DVP32HP00R (32 points expansion machine, 16 points into, 16 points out (relay), AC power);
(3) Inverter: VFD022M43A (• Mini mute 7-speed control and simple PLC automatic program operation, high-speed communication interface, automatic acceleration and deceleration optimization control function);
(4) true color touch screen: AE10THTD (10.4' high-brightness 512K bytes SRAM comes with 3 communication port online function, can simultaneously connect 3 different communication format controllers, structure multi-machine connection network; back provides function card slot, support Printer, follow-up development of other extended feature cards; innovative online/offline simulation capabilities, allowing designers to program edit and debug during program development; support for SMCCard access to man-machine data; conforms to IP65&NEMA4 specifications; 7MB FM);
(5) AC servo driver: ASD-B1521 (AC servo driver built-in PID control, power frequency switching sequence, power failure deceleration stop control function).
3.3 CNC machining process design
Figure 2 shows the automatic flow block diagram. If the auto-run condition is satisfied, the start-up machine is cycled during the auto-run until the stop flow is entered or the auto-run terminates when an important alarm or emergency reset occurs.
Servo-controlled motion directly affects the finished product specification and quality. Fig. 3 is the motion curve of the workpiece stage that the AC servo driver: ASD-B1521 servo drags. The speed and amount of each step will vary depending on the actual material or size, achieving fast, efficient, and accurate.
Grinding wheels (tools) Automated trimming is an important and necessary CNC function. When the grinding wheel continuously grinds the parts, the grinding wheel itself will be worn and the size will change. Therefore, the technical dressing of the grinding wheel needs to be added to the automatic grinding of the parts (after grinding several parts automatically and dressing the primary grinding wheel), the size of the grinding wheel Change, the starting point of the part's grinding has to follow the change, under normal circumstances, the grinding wheel will be trimmed to wear the diameter of the wheel when the automatic operation stops, prompting a new grinding wheel. In addition to the technical finishing in the automatic process, continuous dressing is also necessary. Continuous dressing allows the grinding wheel to be trimmed directly to the specified size. The process of automatic wear compensation for the grinding wheel is shown in Figure 4.
The outer ring raceway grinding machine project has been successfully developed at a grinding facility in Wuxi. The project used Zhongda products and automated solutions to produce various types of grinding machines and sold them all over the place. The operation conditions were good. It has been proved that Zhongda's integrated products are sufficient to meet the system control requirements and can give full play to the performance of the equipment.
Grinding machine is an important working machine in the metal cold processing industry. With the development of industry, the requirements for machining precision and surface roughness of mechanical parts are increasingly increasing, and grinding processing becomes more important. In the automotive, power, marine, metallurgy, military, aerospace and other industries, domestic CNC grinding machines are playing an increasingly important role. Cylindrical grinding machines are the most widely used, capable of machining a variety of cylindrical and conical outer surfaces and shaft shoulder face grinding machines. The Universal Cylindrical Grinding Machine also has an internal grinding attachment that grinds the inner and outer taper surfaces of the inner bore and the larger taper. The degree of automation of the cylindrical grinding machine defines the machining efficiency of the grinding machine and thus determines the processing scale of the grinding machine.
2 Grinding process
Grinder belongs to the metal workpiece surface precision machining machine. The basic principle of grinding machine is to use grinding wheel or oil stone (cutting tool) to do shallow depth micro-cutting on hardened surface of parts. The depth of cut during grinding is small, and the metal layer that can be removed in one stroke is thin. Abrasive tool rotation is the main movement, and the movement of the workpiece or grinding tool is the feed motion. Grinding machine with high precision, surface roughness Ra value is small. Grinding is a widely used cutting method. Because of the unique grinding structure principle, the biggest feature of the grinding machine compared to other metal cold-working machines is that the cutting speed can reach as high as 30m to 50m per second, and the grinding temperature can reach 1000. "C ~ 1500oC, the grinding process is as short as only one ten-thousandth of a second. Therefore, the grinding process can obtain higher machining accuracy and a small surface roughness value. Grinding can not only process soft materials, such as unquenched Steel, cast iron, non-ferrous metals, etc., but also can be processed hardened steel and other tools can not be processed hard materials such as ceramics and hard alloys.
When the part is processed, it is mainly the movement of two axes. One is the worktable shaft and the other is the grinding frame axis; the worktable travels by servo motion, and the work rests on the workbench, so the feed size is the size of the grinding, the upper and lower material cylinders are mounted on the workbench, and the magnetic card Disk, dresser. Magnetic chucks use strong magnets to hold parts as they are machined, requiring magnetic unloading before feeding and discharging. The dresser moves with the workpiece table. The dresser is used to dress the grinding wheel. The lift is controlled by hydraulic pressure. Grinding wheel mounted on the grinding wheel, the movement of the grinding frame is also controlled by the hydraulic pressure, and the deceleration valve to control the speed of movement in different processes. In addition to the two axis motion related components there are also some auxiliary mechanisms such as grinding fluid, lubricating fluid, measuring frame and so on.
3 Electric Control System Design for Delta Ball Bearing Grinding Machine
3.1 Overall Design
High efficiency is the purpose of the company, and high efficiency means high speed. Speed ​​is an important indicator for evaluating the electronic control system of the outer ring raceway grinder. The electric control project of the grinding machine selected Zhongda EH2 series high-speed PLC and ASD series AC servo system, and optimized the program structure under the premise of safety and precision, which greatly increased the production speed of each workpiece and the processing speed of each basic part. Control within 6-7 seconds. Only a small number of necessary buttons are set on the electronic control panel. Most of the other operations are implemented on the touch screen. It takes full advantage of the interactive dialogue with a huge amount of interactive information on the touch screen, plus intelligent formula and alarm management functions. It is more intuitive and the touch screen is also displayed. The status and time of each step is used as a reference adjustment, so that the part processing is not operated under manual control as much as possible. Most of the processing steps have a strict order. When a non-alarm emergency occurs, an emergency reset button can be used and the system will transfer Rapid security exit process. Electric control panel design shown in Figure 1.
Figure 1 Electrical control panel
Delta-based systems are:
(1) PLC: DVP40EH00T2 (40-point host, 24DI/16DO (relay), 4-way 200K input/output AC power supply);
(2) PLC expansion unit: DVP32HP00R (32 points expansion machine, 16 points into, 16 points out (relay), AC power);
(3) Inverter: VFD022M43A (• Mini mute 7-speed control and simple PLC automatic program operation, high-speed communication interface, automatic acceleration and deceleration optimization control function);
(4) true color touch screen: AE10THTD (10.4' high-brightness 512K bytes SRAM comes with 3 communication port online function, can simultaneously connect 3 different communication format controllers, structure multi-machine connection network; back provides function card slot, support Printer, follow-up development of other extended feature cards; innovative online/offline simulation capabilities, allowing designers to program edit and debug during program development; support for SMCCard access to man-machine data; conforms to IP65&NEMA4 specifications; 7MB FM);
(5) AC servo driver: ASD-B1521 (AC servo driver built-in PID control, power frequency switching sequence, power failure deceleration stop control function).
3.3 CNC machining process design
Figure 2 shows the automatic flow block diagram. If the auto-run condition is satisfied, the start-up machine is cycled during the auto-run until the stop flow is entered or the auto-run terminates when an important alarm or emergency reset occurs.
Fig. 2 Automatic processing flow
Servo-controlled motion directly affects the finished product specification and quality. Fig. 3 is the motion curve of the workpiece stage that the AC servo driver: ASD-B1521 servo drags. The speed and amount of each step will vary depending on the actual material or size, achieving fast, efficient, and accurate.
Figure 3 Workpiece table servo control movement curve
Grinding wheels (tools) Automated trimming is an important and necessary CNC function. When the grinding wheel continuously grinds the parts, the grinding wheel itself will be worn and the size will change. Therefore, the technical dressing of the grinding wheel needs to be added to the automatic grinding of the parts (after grinding several parts automatically and dressing the primary grinding wheel), the size of the grinding wheel Change, the starting point of the part's grinding has to follow the change, under normal circumstances, the grinding wheel will be trimmed to wear the diameter of the wheel when the automatic operation stops, prompting a new grinding wheel. In addition to the technical finishing in the automatic process, continuous dressing is also necessary. Continuous dressing allows the grinding wheel to be trimmed directly to the specified size. The process of automatic wear compensation for the grinding wheel is shown in Figure 4.
Figure 4 wheel wear compensation process
The outer ring raceway grinding machine project has been successfully developed at a grinding facility in Wuxi. The project used Zhongda products and automated solutions to produce various types of grinding machines and sold them all over the place. The operation conditions were good. It has been proved that Zhongda's integrated products are sufficient to meet the system control requirements and can give full play to the performance of the equipment.
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