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I. Introduction
In recent years, with the development of computer technology, communication technology and numerical control technology and the need for manufacturing automation, DNC technology has been more and more widely used. At present, the concept of enterprise information represented by CIMS has received more and more attention, and DNC has gradually evolved from a single program transmission to an extended DNC that integrates functions such as data management and production information monitoring, becoming a key component of CIMS integration. .
Second, the concept and characteristics of DNC:
The term DNC was originally referred to as distributed numerical control (Distributed Numerical Control), the meaning of which is to use a large computer to control several CNC machine tools at the same time. Later, with the advancement of science and technology, the numerical control system developed from Numerical Control (CN) to Computer Numerical Control (CNC), and each numerical control machine tool was controlled by a computer (CNC system). Therefore, the past concept of DNC has lost its significance.
The current CNC system has been fully functional, and generally supports RS-232C communication functions, that is, receiving or sending processing programs through the RS-232 port. There are many CNC systems that can implement N/C program while cutting machining. This is called DNC (DirectNumericalControl), but not all CNC systems support this function. Some systems only store the received machining programs in the system memory (Memory), but they cannot perform cutting operations at the same time. This type of transmission is generally called Block transmission.
With the rapid development of electronic technology, some CAD/CAM software that can only be run on mainframes or workstations can now be used on very inexpensive microcomputers. This has led to the gradual popularity of CAD/CAM systems. These CAD/CAM systems can generally perform 3-D form surface modeling and generate corresponding N/C codes. These 3-D forms of N/C codes are very long and generally reach several hundred K and several megabytes. Most of the CNC system's memory is difficult to accommodate such a large processing code, then using DNC for transmission processing is the most economical, because for most of the CNC system, the expansion of system memory is very expensive, and the current PC and its Memory expansion is very cheap. Therefore, it is an important means to make good use of NC machine tools to use the RS-232 serial communication port to network the NC machine tools in the workshop.
Third, the current machine tool communication and NC program management status:
1. Status and Problems of NC Program Communication
1) The existing CNC system in the workshop is complicated and the communication procedures used between the systems are different, resulting in the incompatibility of the status quo between each other. This inconveniences the programming and application of technicians and operators and greatly limits the Transfer of parts.
2) The communication program is a one-to-one communication program. It does not have the function of automatic reaction and monitoring of the program. When communicating between a machine tool and a computer, two operators must work at the same time. One machine operates the machine tool in front of the machine tool, and the other computer. The communication software is operated before the terminal, and the two are alternately operated to complete the communication work, so it is very inconvenient. In practice, most factories take the form of placing a computer on the edge of the CNC machine tool, or multiple CNC equipment sharing the form of a computer. Most of the transmission software is software brought by the machine tool factory. Most of the dos version is used. The transmission of the program is performed in an interactive manner. After the machine tool is set to the waiting state, the computer transmits the data again.
3) Remote transmission cannot be achieved, and the working environment of technicians is poor. The noise, dust, oil and gas in the workshop and the environment are poor. The technical staff should be reduced as much as possible to transfer the program between the machine room and the machine tool, and the safety should be programmed in the machine room. The operator should remotely call the machine at the machine side. When debugging the program, the personnel then debugs the program together with the operator. After the program is turned on, the remote transmission function at the machine side is automatically transferred to the corresponding directory or database.
4) The workshop manages the processing procedures of each CNC equipment and uses the disk management method. On the one hand, the disk medium is easily damaged. On the other hand, for a numerical control system without a floppy disk drive, the program on the disk must first be copied to a computer for communication and temporarily connected for communication. Not only is the operation inconvenient, but also it is not convenient to manage the processing tasks of the machine tool, and it is impossible to detect the processing program of the equipment on site. Generally speaking, the workshop is far away from the programming room. Technicians transfer the program by copying the floppy disk or holding a laptop computer. Running back and forth between the two places wastes a lot of time, which is not conducive to improving work efficiency and is frequent. Hot plugging and hot-plugging can easily burn out the machine interface.
5) Various login and machine port information are not recorded and cannot be easily viewed.
6) There is no information feedback on successful or failed program transmission.
7) It is not possible to transfer from any position of the program, such as at the tool changer.
8) The advanced features of some machine tools have not been used, such as ftp, nfs, etc.
9) Some old CNC systems have limited memory space and more than one program. The memory space of the machine tool is not enough, a large number of processing programs have to be deleted and typed repeatedly, and frequently repeated parts preparation wastes a lot of working time. Directly affecting the efficiency of CNC machine tools, repeated programming of the machining program also affects the stability of the program.
10) A unit of CNC machine tools may use a variety of different CNC systems, in accordance with the traditional networking, is generally equipped with 1 PC machine for each machine, using different communication programs for different CNC systems, the drawback is obvious . In addition, many computers are installed in the workshop and the industrial environment is harsh. The life span of the computer is greatly shortened, and it is messy and unfavorable to management. The numerical control equipments are becoming more and more integrated, intelligent, and network-oriented. More and more advanced computers such as PCs are featured. The current numerical control equipments are mostly in the form of a stand-alone operation and need to be networked like a PC. Transformation and realize the sharing of resources.
2. Status of NC program management
1) At present, most technicians take the approach of creating a different directory on the computer for each person. With the increase of personnel, the expansion of the program volume, the existence of chaotic program versions, and difficult search problems, if someone mobilizes or quits, Whether the program can be safely called is indeed a question. Furthermore, the security of the program, the program that it has tuned for itself may be mishandled, or even someone else has no intention of changing your program. These are often problems. However, there is no small matter in the numerical control processing, it is easy to produce batch problems, and the nature is serious.
2) In addition, can the program check the path of the tool before calling it? Can the two versions compare intelligently? Are there any characters that have changed? Are there any mistakes? Can you implement simple address math?
3) The program structure problem, NC program must be associated with the corresponding part model, but also have the corresponding tool list, tool parameters, process cards and other documents, with the popularity of digital cameras, it is best to the processing of key processes, clamping The status, special tool shapes are recorded and stored with the program. The next call is very visual and intuitive.
4) The last one is the status of the program. Some have just been written, some are debugging, some are stereotyped, how to distinguish different kinds of programs, and set different permissions for different people are also very important.
Fourth, the solution:
Using mature and perfect DNC ​​solutions, use a computer for program management and program transmission of multiple CNC machine tools.
Benefits: Solve all the problems in the above-mentioned machine tool communication and NC program management status, which are specifically expressed in:
1) DNC communication software can support various CNC systems and support various communication standards;
2) Support the automatic calling of NC program files in the computer from the machine side;
3) It can package and call multiple NC programs remotely;
4) Support online machining of CNC machine tools, and can realize simultaneous on-line machining of multiple machine tools, support breakpoint transmission function during online processing, and support online invocation of subroutines during DNC online processing;
5) Support automatic download of NC program files from machine tool to computer;
6) Multiple machine tools can call the required machining program at the same time;
7) Automatically generate file transmission information reports to facilitate statistics and verification management;
8) Complete error information report;
9) Provide various ways of comparing different NC programs to facilitate comparison of differences between two or more programs;
10) Can provide powerful NC program editing function;
11) The transmission distance is not limited;
12) Providing program database management functions;
and many more.
V. Several overall solutions for machine networking:
Due to the unequal scale and different work habits of each CNC shop (or factory), the networking solutions of each unit are not the same. It may be a typical connection form or a combination of several forms. But its principle is the same, the following will introduce the most common networking solutions.
1. Intermediate client type
In this scheme, a client uses a multi-channel RS232 interface (or multi-function serial communication card) to control multiple CNC devices. Each client communicates with the server, the plant, the entire plant, and even the Internet via Ethernet. The joints are connected together and their typical structure is shown in Figure 9.
Related images on this topic are as follows:
In this scheme, a client uses a multi-channel RS232 interface (or multi-function serial communication card) to control multiple CNC devices. Each client communicates with the server, the plant, the entire plant, and even the Internet via Ethernet. The joints are connected together and their typical structure is shown in Figure 9.
The advantages and disadvantages of this solution are:
advantage:
a) The cost is low. When the number of machine tools is larger, the average cost per machine tool is lower.
b) The construction of the local area network is not necessary and it does not change much with the original system.
Disadvantages:
a) When a certain hardware or software fails, it will affect the operation of multiple devices.
b) Due to the limitation of RS232 transmission distance, long distance receivers must be added when the distance exceeds 15 meters.
c) More PCs are needed.
2. Multi-serial device server type;
The characteristic of this kind of scheme is to use a multi-serial equipment server to realize the connection of multiple CNC equipment and Ethernet. In this way, any computer on the Ethernet can directly control any machine on the network.
Related images on this topic are as follows:
advantage:
a) The average cost is lower. Compared with the previous scheme, the cost is slightly higher, but when the number of machine tools is large, the cost is still low.
b) Flexibility, because any computer can control any numerical control device, so it has a higher flexibility.
Disadvantages:
a) When multiple serial port device servers fail, multiple devices will be affected.
b) Due to the limitation of RS232 transmission distance, long distance receivers must be added when the distance exceeds 15 meters.
3. Single serial device server type
The feature of this design scheme is that each serial port numerical control device is equipped with a single serial port device server respectively, which enables any device to directly connect with Ethernet, and any computer on the Ethernet can directly control any one of them. Taiwan CNC equipment.
Related images on this topic are as follows:
Single serial device server
Figure 11 Single-serial device server architecture
advantage:
a) The flexibility is good, any computer can directly control any numerical control equipment, which greatly improves the flexibility of the numerical control equipment.
b) High reliability, because this connection is a typical star connection. Even if a single serial port device server fails, it will only affect one device.
c) Not limited by the length of RS232 transmission.
Disadvantages:
a) The need to build a standard LAN.
b) The cost is slightly higher.
Sixth, DNC communication software:
Common two world-class DNC software, XpertDNC communication software of American XpertDNC Company, Europe DIM-Max software of CIMCO Company. Advantages, powerful, mature, are top foreign DNC communications software; shortcomings, prices are relatively high.
In addition, with the development of domestic DNC technology, some powerful companies have developed their own DNC communication software, such as JCSDNS of Beijing Machine Tool Research Institute and DSDNC of Dongsheng Software. Because these companies were originally engaged in the related work of CNC machine tools, so they developed more professional, and some even can be comparable with foreign countries, and their prices are relatively low, is a good choice for SMEs to launch CNC machine tool networking projects .
ã€Abstract】In recent years, with the development of computer technology, communication technology and numerical control technology and the need of manufacturing automation, DNC technology has been more and more widely used. At present, the concept of enterprise information represented by CIMS has received more and more attention, and DNC has gradually evolved from a single program transmission to an extended DNC that integrates functions such as data management and production information monitoring, becoming a key component of CIMS integration. .