Otomatik transfer hatları ve PLC destekli bir işlem hücresi
Automatic transfer lines and a PLC controlled manufacturing cell in the valve industry
- Tez No: 39518
- Danışmanlar: PROF.DR. MUSTAFA AKKURT
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 206
Özet
ÖZET Bu çalışmada, teknolojinin NC (nümerik kontrollü) sistemlerinden; CNC (kompüterli nümerik kontrollü), DNC (direkt nümerik kontrollü), insansız (robotlaşmış) tam otomatik fabrikalara ulaşmasında önemli bir rol oynayan otomatik transfer hatları ve nümerik sistemlerde kullanılan programlanabilir lojik kontrol sistemleri incelenmiştir. Bir programlanabilen lojik kontrol sistemi (PLC) binary (ikili) düzenindeki giriş (input) sinyallerini işleyerek, direkt olarak çeşitli teknik prosesleri, operasyonları ve sıralamaları etkileyecek çıkış (output) sinyalleri üretir. Bu sebeple otomatik üretim ve transfer hatlarında, son yıllarda yaygın olarak kullanılmaktadır. Karışık tezgâhlarda, tezgâh sistemlerinde ve karışık işlemlerde programlanabilir kontrol sisteminin kullanılması yeni bir iş veya imalât değişikliğinde sistem, kolayca değiştirilebilir; esneklik kazanır. Boole cebri ile elektroniğin bir sentezi olan. bu sistemler, CAD (kompüterlerle konstrüksiyon), CAM (kompüterlerle imalât) gibi disiplinlerin gelişmesinde ve CNC-DNC-CIM kompüterlerle imalât integrasyonuna katkıda bulunmuştur. Transfer hatları, üretilecek parçanın teknolojik operasyon sırasına göre sıralanmış ve parçayı tamamen işlenmiş hale getiren tezgâhlar grubudur. Transfer hatları çeşitli üretim hücrelerinden (tezgâh gruplarından) meydana gelebilir. Parçanın getirilmesi, tezgâhtan tezgâha veya hücreden hücreye taşınması, tezgâha bağlanması ve çözülmesi, ana kontrolü, son kontrolü ve hattan uzaklaştırılması otomatik olarak yapılır. Transfer hatları rijit ve esnek olmak üzere iki gruba ayrılır. IX
Özet (Çeviri)
SUMMARY AUTOMATIC TRANSFER LINES AND A PLC CONTROLLED MANUFACTURING CELL IN THE VALVE INDUSTRY An automatic transfer line is a machine tool group which is arranged according to a technological operation flow and carry out the workpiece completely finished. The automatic transfer lines could be also formed by different manufacturing cells. On this type of manufacturing systems the loading operation of workpiece to the machine tool, transport of the workpiece from machine to machine or from cell to cell, the fastening and unfastening operation, the main and finish control and unloading operation is made fully automatic and under the control of many programmable logic controllers (PLC). These PLC's communicate between each other and are controlled by a main computer which is run a SCADA (Supervisory Control And Data Acquisition) software. There are two types of automatic transfer lines: flexible (the ones mentioned above) and rigid manufacturing systems. In recent years drastic changes have taken place in the field of control and automation technology. Where in the past, relay and contactor circuits were applied to cope with control problems, today an increased use of computer systems can be noticed. Conventional controls - also known as hard-wired programmed controls - are gradually replaced by programmable logic controllers (PLC). This development can easily be explained by the completely different method of signal processing bringing advantages to the PLC compared to the designs with contacts. In conventional controls the signal processing is determined by the wiring between the signal generators and the final control elements. When the tasks for the system change, causing changes in the processing logic, the wiring has to be altered, and if it comes to the worst, a new installation of circuit parts is necessary. In a PLC the wiring is replaced by a program which isstored in a memory module of the computer and processed by micro processors. Alterations in the program can be carried out easily; the problem of rewiring is eliminated. For the PLC the resulting advantages are: - alterations in control problems can be carried out at any time - elimination of long down-time periods - extensive use of mechanical processes are reduced - reduction of interferences in complex units. Thus, installations controlled by PLC are more reliable and economic. The move towards the implementetion of PLC's even in simple systems has been promoted by the development of micro processors and the decline in prices for hardware components of an installation. The basic components of a control are to be found in a programmable logic controller as well. The processing element, the core of the control, is the PLC. It consists of a central control unit, its program memory and the input and output modules. Central control unit and memory are often defined as“computer”. Each module contains a fixed number of inputs and outputs which are able to assume the binary values 0 and 1. Sensors, PLC and actuators make up the control device, which influence the controlled action. The input and output modules set up the connections between the central control unit and sensors/actuators. The central control unit controls the signal flow through the control device: Signals sent out by the sensors to the central control unit via the input modules are interconnected and the results transmitted to the output modules. The output modules cause the actuators to influence the process within the controlled action. The PLC program determines the method of processing, i.e. which input signals are to be logically connected and to which outputs they should be assigned. XIThe PLC programs contain the rules for the processing of the signals. Each program consists of a series of instructions, each instruction of an operation part and an operand part. The operation part indicates which logic operations are to be carried out. The operand part indicates which input signals are to be used for the logic operation and to which output they should be assigned. It can also be said: the operand part shows where something is to take place, the operation part shows what is to take place. In a running program all instructions are worked up in sequence, i.e. one after the other. Owing to this sequential execution of a program, it is not possible to include all conditions of an installation simultaneously. Therefore, the program is processed cyclically; after the last instruction has been performed the program returns to the beginning and the processing is restarted. The duration of one cycle of the program is a matter of milliseconds, so it seems as if the processing of the signal conditions has taken place in an instant. The PLC programs are stored in the program memory of the central control unit. This code consists of a sequence of binary symbols (the numbers 0 and 1), which only can be understood by the central control unit.. Under these conditions, the creation of a program is very difficult, time consuming and hard to read. Therefore, programming languages have been developed to set up the communication between the programmer and the PLC. These programming languages use mnemo- technical expressions (symbolic codes, e.g.“S”for switch) and graphic symbols to formulate a control instruction. The ladder diagram (LDR) is one of these programming languages, there are also the function chart (FCH) and the statement list ( STL ). The program is developed on an exterior programmer, then translated into machine code and transferred to the program memory. The programmer is not required for the execution of XIIthe program. The ladder diagram (LDR) is a graphic programming language. It was first used as a wiring diagram in the United States and was further developed as a programming language, when the first PLC's were introduced. The structure of the LDR- prog ramming language reflects the original applications as a wiring diagram for circuits with fixed wires. The meanings of the symbols, however, has partly changed. When one compares the DIN 40719 for wiring diagrams to the graphic display of the LDR, it has been rotated 90 degrees. The contact rails are vertical, the individual current paths horizontal. This ladder structure represents the framework for the program. Each of the current paths usually consists of several instructions. The symbols representing the interrogation for the signal conditions at the inputs are drawn in on the left-hand end. On the right-hand end are the symbols of the outputs to be activated. The designations placed above the input and output symbols are referring to the addresses of the inputs and outputs of the PLC. This is identical to the operand part of an instruction. The type of logic operation is defined by the position and the connection of the various symbols on a current path representing a network. The current paths are read from left to right. A reversed signal flow is not allowed. The current paths are numbered starting from the top, this defines the sequence in the program as well. In addition, the structure of the LDR resembles the signal flow through the control device. If we define the input signal as information, whether or not a condition is fulfilled, and the output signal as instruction for an actuator to execute a command, the general structure of a control instruction can be found in a current path as well. Logic control systems are characterized by the fact that input signals can be assigned at any time to output signals. Assignment is caused for the most part by the logic control functions. In a sequence control system, the control is subdivided into several steps. The control is activated step XIIIby step. After step 1 has been completed, step 2 will follow, then step 3, etc. Switching on to the next step is dependent upon certain conditions of time or process. The automatic stellite welding line introduced in this research work is formed by 7 automatic machine tools. In this automatic production line 2 automatic welding machines and 4 elevators are controlled by PLC's. The PLC used to control the welding machine consists of 32 inputs 28 outputs and is the 5TI model of the Texas Instruments. The program written to control the stellite welding machine is in LDR and in STL, and has 397 lines (rows). The program consists of two parts: control part (where the sequence is controlled) and power part (where the outputs are activated). XIV
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