CNC punch press feeder program

Punching machine in addition to the application of plastic molding of mechanical devices, but also as the body of many special equipment and the mother machine for the screen, cushion mesh, shields and other punching and shearing process. Punching machine is belongs to the point control machine tool, in the middle of the stroke is not processed. As a result of the general processing of a single product, the mold is not often replaced, so in the traditional control of the punch press is generally used in relay control, feeding is generally used to manually feed, this way there is a series of problems in terms of low efficiency, slow speed, precision can not be guaranteed, there are hidden dangers of safety. China's township enterprises and small and medium-sized private enterprises, due to financial management and other restrictions, simple stamping equipment used more, the vast majority of its feeding is by manual feeding, the lack of protection devices. With the development of China's industrial and stamping parts type, the complexity of the process and the humanization of production requirements, manual feeding of stamping production due to the existence of a series of problems in terms of efficiency, speed, accuracy, safety, etc., stamping production of manual feeding has been gradually out of the automatic feeding mechanism to replace, so as to further satisfy the automation of stamping production to improve the speed of production and accuracy of the requirements.

1 CNC press feeding system status

1.1 The type of existing feeding system

CNC press feeding system belongs to the mechatronics products, which includes mechanical parts, control parts, power sources, detection parts and execution components. The existing automatic feeding system, according to the structural form of the control system, according to the different controller, can be roughly divided into the following categories:

1) Specialized CNC system. Foreign CNC systems such as Farnack, Siemens, etc.; domestically produced Wuhan Huazhong, Guangzhou CNC, etc.. Specialized CNC systems have high control accuracy, programming capabilities, high system reliability, to be developed more functions, but for the punch press because it is a point control, control is relatively simple, if the selection of expensive specialized systems is undoubtedly a waste of resources, but also for the specific significance of the feeding device whose control does not necessarily have the advantage.

2) relay control. Relay logic control is a significant feature of low cost, but it has obvious shortcomings, because in modern production equipment, there is often a need for a large number of switches, digitizers, pulses, and analog control devices, such as motor start and stop, solenoid valves open and close, product counting and so on. This control program is more complex wiring, large size, power consumption, once the system is composed, and then want to change or increase the function is very difficult, in addition to the limited number of relay contacts. Therefore, the flexibility and scalability are poor; secondly, in the control speed, relay control logic relies on the mechanical action of the contacts to achieve control, low operating frequency, the natural control speed is very slow, and mechanical contacts will also appear jitter phenomenon, the work is not stable.

3) microcontroller control. Microcontroller has a simple structure, easy to use, inexpensive and other advantages, it is better at data calculation and data processing, generally more widely used in data acquisition and centralized control room control, completely controlled by the microcontroller. In particular, the motion console is also controlled by the microcontroller to send pulses directly, this way, the load of the microcontroller is particularly heavy, in addition to the industrial site of the electromagnetic equal to the disturbing signals, will produce a strong interference with the microcontroller, so the use of the microcontroller winnable into the field control of its anti-jamming treatment is also a problem that has to be considered.

4) PLC control. This is also the current automatic feeding system is more commonly used a control method, the program is simple, hardware optional wide range of software programming is easy, debugging generally does not appear too big a problem. But this program also has some unavoidable shortcomings, such as flexibility is relatively poor, for a specific application, it is difficult to choose a set of completely compatible with the application of the system, often resulting in a waste of system resources, and in the case of some special applications, some technical details are difficult to achieve.

1.2 Execution Components

The existing automatic feeding system is more commonly used stepper motor as the drive execution components. Stepping motor and drive circuit composed of open-loop CNC system, both simple, cheap. And very reliable. But the stepper motor can not directly use the AC power supply and DC power supply, their own noise and vibration, with inertial load capacity is poor, and there are oscillations and out of step phenomenon, the control accuracy is not high, if the control is not properly easy to produce *** vibration, it is difficult to run to a higher speed.

2 Improved program

With the development of China's stamping industry, the performance of stamping equipment in line with the world, stamping production automation to further improve the degree of stamping production feeding technology also put forward more and more high requirements to meet the matching with the stamping equipment.

2.1 Embedded CNC Press Feeding System

According to some deficiencies of the current automatic feeding system, an ARM-based embedded CNC press feeding system is proposed. From a broad perspective, embedded computer systems have the following main advantages:

1) Specialization. Embedded systems are usually oriented to specific applications, so embedded CPUs are mostly for specific user groups designed in the system, usually characterized by low power consumption, small size, high integration.

2) Real-time response. According to the definition of embedded systems, it is used in some kind of technical process of the core processing link, to meet the time limit requirements of the technical process, naturally has the characteristics of real-time processing.

3) Robust and reliable. Embedded products are used by non-computer professionals, the use of environmental conditions are more severe, its robustness and reliability is a must for this type of product.

2.2 servo motor selection

The system uses linear motors to drive the X, y-axis feed. In the machine tool feeding system, the use of linear motor drive and the original rotary motor drive the biggest difference is the elimination of all mechanical intermediate links from the motor to the table (drag plate), the machine tool feeding transmission chain length is shortened to zero (this transmission is known as "zero transmission"). This "zero transmission" mode, brings the original rotary motor drive mode can not achieve the performance indicators and advantages

1) High-speed response. As the system directly canceled some of the response time constant of the mechanical transmission parts (such as screws, etc.). So that the entire closed-loop control system dynamic response performance greatly improved, the response is exceptionally sensitive and fast.

2) High precision. Linear drive system eliminates the transmission gap and errors generated by mechanical institutions such as screws, reducing the interpolation movement due to transmission system lag brought about by the tracking error. Through the linear position detection feedback control, you can greatly improve the positioning accuracy of the machine tool.

3) High transmission stiffness. Because the "direct drive" to avoid the start, speed and direction change due to the intermediate transmission link of the elastic deformation, friction and wear and backlash caused by the movement of the lag phenomenon, but also to improve its transmission rigidity.

4) Fast speed, acceleration and deceleration process is short. Linear motor used in machine tool feed drive to meet its ultra-high-speed cutting leopard maximum feed speed (required to reach 60-100 m/min or higher) is not the same problem. Also because of the above "zero transmission" of high-speed responsiveness, so that the acceleration and deceleration process is greatly shortened, can be realized at the start to instantly reach high speeds, and high-speed operation can be stopped instantly. Higher acceleration can be obtained, generally up to 2 a 1Og. And the maximum acceleration of the ball screw drive is generally only 0.1 a 0.5g.

5) the length of the trip is not limited. In the guide rail by series linear electrical machine, you can extend its stroke length indefinitely.

6)Quiet movement, low noise. As a result of the abolition of mechanical friction of the drive screw and other components, and the guide can be used rolling guide or magnetic pad suspension guide (no mechanical contact). Its movement noise will be greatly reduced.

7) High efficiency. Because there is no intermediate transmission links, eliminating the mechanical friction when the energy loss, transmission efficiency is greatly improved.

2.3 System Pure Hardware Design

The hardware structure block diagram of the improved system is shown in Figure l. The upper computer is a PC. The upper computer is a PC, through the serial port and the lower ARM communication, the lower computer control touch screen and linear motor.

The control part uses a low-cost, high-performance, low-power microprocessor S3C2410 as the core controller. It is a 32-bit RISC architecture of low-cost, high-performance, low-power emblem processor, the main frequency of 200MHz, containing a LCD controller (support for STN and 'rFT with a touch-screen LCD), SDRAM controller, 3-channel ART, 4-channel DMA, 4 timers with PWM function and an Internal clock, 8-channel 10-bit ADC, touch screen interface, etc. S3C24J O business integration simplifies the application system hardware design and improves the application system reliability and stability. Operation part of the touch screen as the operating unit, human-computer interaction is intuitive and convenient, friendly interface, easy to operate, to achieve feeding automatic, manual, start, stop and other operations and some system parameters set. The X and y axes of the motion part use Kollmorgen's DDL series linear servo motors without iron core, and the stator of the motors adopts the U-type structure, and the rotor adopts the design without iron core. Linear motor structure is simple, safe and reliable, while eliminating the intermediate mechanical links, positioning accuracy is relatively high, the position detection element selected scale, high detection accuracy. The whole system adopts closed-loop control, which greatly improves the system accuracy.

2.4 System Software Design

The system software mainly includes the upper computer software and lower computer software two parts, as shown in Figure 2. The upper computer software is mainly responsible for NC code generation, translation, and communication with the lower computer and other PCs; the lower computer software mainly includes five modules: basic control module, data communication module, motion control module, human-computer interaction module and transaction processing module.1

In the whole software system, the lower computer software is the core of the whole system. We choose to choose the Linux real-time operating system with open source code, good portability and simple learning as the software operating environment, which will complete the management scheduling of the 5 major task modules, and realize the functions of the feeding system by combining the system's hardware equipment. The basic control module manages some basic operations of the system, including the management of device drivers, the management of system hardware initialization settings, etc.; the data communication module is responsible for the reception of data as well as appropriate data processing; the motion control module, including interpolation algorithms, acceleration and deceleration control of motors and position control, is the core of the system control; the human-computer interaction module, including the liquid crystal display and the touch-screen input, etc., and the interface design of this paper is based on the Qt-based embedded graphics. The use of Qt-based embedded graphics library development tools Qt/Embedded. It is a user application and the kernel between a graphics library framework; in order to ensure the integrity of the system, set up a transaction processing module to manage the alarm as well as some of the abnormal transactions.

The communication and scheduling between the 5 modules is done under the management of the operating system. The system specifies each module as a specific task, which is usually referred to as the thread or process approach. The role of the embedded operating system is to decide which process the system should run at a particular moment. General system processes have three states: running state (Running), ready state (Ready) and waiting state (Waitting), the switch between these states is provided by the operating system through the message mechanism, such as mailboxes, semaphores, message queues, etc. to complete, there is no other coupling between the modules. If the system functions need to be increased or decreased, just add or delete modules in the corresponding tasks, then the system can realize multi-functionality and diversification, so that the system has openness and expandability.

3 Conclusion

This paper analyzes the current situation of the existing CNC punch press feeding system from the controller and servo drive two prophecies, and according to the shortcomings of these feeding systems, puts forward a kind of amount of the curtain in the ARM embedded system program, the use of linear motors as the X, y-axis control motors, saving human resources, saving raw materials, reliability has been improved, control accuracy and modernization has been greatly improved. The degree of modernization has been greatly improved.