Machine control system

The machine control system was set in accordance with the parameters determined during simulation prior to delivery to the site. Following re-routing and hook-up of the piping, the compressors were run to a maximum flow at 2.71 bar (absolute) and 480°C. The generator was disconnected from the grid and the expander tripped accordingly. 

In addition to the building parameters, there are often some requirements from suppliers of processes and equipment to make sure their parts function properly. This may mean that the requirements for the equipment decide the target levels (e.g., in pharmaceutical and electronics industries). In other cases there are restrictions on deviations from the target levels (e.g., on temperature for machine control system or on humidity and vibration for optical measure nient systems). ... 

Darius, I.H. Rule based control, a new tool, Proc.2nd Int.Conf.Machine Control Systems, pp.121-128, May 1987. 

As well as continuous development of machine design and especially machine control systems, there has been considerable development of molds. These may be quite simple or very sophisticated, with multiple cavities, moving parts. Since the molding of RTPs is essentially a question of the control of heat transfer, advanced temperature control systems are frequently used, which can repay their additional cost by... 

The safety level was defined as category 2 according to standard NF EN ISO 13849 (PL d ). In category 2, the safety function is controlled at suitable intervals by the machine control system. The occurrence of a fault can lead to loss of the safety function in the interval between two checks. The MTTFd is hi and the diagnostic coverage is average . Common cause failures are taken into account. 

Fig. 3 shows a block diagram of a washing machine control system. You can see that this is quite a complex closed loop system using feedback to keep a check on water level, water temperature, and drum speeds. 

Maco, Machine control systems, Barber-Colman Co., Industrial Instruments Div. 

Not all control systems are capable of operating a number of axes simultaneously. The most basic machine control system will only move the axes on a linear path on X and Y and then operate the Z axis separately and is referred to as... 

For any CNC machine to operate, it must be provided with information regarding the operations it will be required to perform. This information is provided by a part program, which is a series of step-by-step instructions, written in sequence, in a format which the machine control system will read, interpret and execute. The control system will first read, interpret and execute the very first command in the program. Only then will it go to the next command then read, interpret and execute. The control will then continue to execute the program commands in sequential order until it reaches the end of program. 

Machine control systems are equipped with a verification system which enables a dry run to be made to confirm the correctness of the part program as well as an editing facility so that any mistakes can be rectified. 

As already stated, the part program is a sequence of instructions which describes all the machining data necessary to be carried out on the workpiece, in a format required by the machine control system. The machining data will include ... 

Before running a program, the machine control system needs to know where the machine axes are positioned and establish their relationship to the workpiece and the tool change position, i.e. the machine co-ordinate system and the machine control system must be synchronised. 

When a CNC machine tool is first turned on, it does not know where the axes are positioned in the workspace. Home position is found by the power up/restart sequence initiated by the operator. This power up/restart sequence drives all three axes slowly towards their extreme limits of travel, which can be -X, +Y, h-Z. As each axis reaches its mechanical limit of travel, a limit switch is activated. This signals to the control system that the home position of each axis has been reached. Once all three axes have stopped moving, the machine is said to be homed. The machine co-ordinates are synchronised with the machine control system. 

The position of the part zero can now be determined relative the home position and is entered into the machine control system as an offset. 

Part programming for a lathe follows the same word address system as described for milling with the same use of words and blocks, read, interpreted and executed sequentially, by the machine control system. Common word addresses for the lathe include ... 

When setting up the machine, the operator needs to determine the distance that different tools are from the home position to part zero. Each tool is manually touched off the face and diameter and their distance from the home position is saved as values of X and Z in the tool offset page of the machine control system. 

This refers to the machine control systems of earth moving vehieles. It calls for requirements to be stated for the foreseen environmental conditions and for a risk analysis to be carried out. Some test eriteria are listed as, for example, relative humidities of 30% and 90%, temperatures of —25 °C and +70 °C with temperature ehange eriteria. 

Hydraulic drives. A special pump or else the injection moulding machine s own hydraulic system is used to power a hydraulic drive. The drive system comprises a pressure regulator (the pressures used are 2-8 MPa, depending on the manufacturer) and hydraulic manifolds. The injection machine control system is normally used to control the drive the injection signal is used to open the nozzle and the end of holding phase signal to close the nozzle. Special time relays may also be used to provide control in a different seqnence. 

How to analyse the functional safety of a programmable electronic machine control system and to educe the seriousness of faults involving safety. 

This paper describes a project covering the development of a program system for the failure mode and effects analysis of plant and machine control systems in several steps. The project leader was Mr. Demski of the TOV Rheinland. The result also takes account of the experiences gathered by Dr. Germer, BIA, and Mr. Six, Technische Universitat Braunschweig, when using PASS I in practice. 

Within the fuel route there are 4 main centres of plant control and interlocking, namely the fuelling machine (the control system is carried "on board"), the irradiated fuel dismantling cell, the ponds and the maintenance cells. Because of its varied duties the fuelling machine control system is the largest and most complex of those listed and is considered in detail in this paper. The same philosophy and methods, however, have been applied to all 4 systems. 

Figure 3 Fuelling Machine Control System Structure...

The conventional method for the reliability analysis of electronic systems is a component level failure mode and effect analysis (FMEA) which involves assessing the potential effects on the system of each mode of failure of each component. Because of the large numbers of components involved, the internal complexity of the integrated circuit components themselves and the time-dependence of internal states in a programmable system, this approach is impractical for the fuelling machine control system. 

Hedberg, J Soderberg A. Tegehall X, 2011. How to design safe machine control systems—a guideline to EN ISO 13849-1, SP Technical Research Institute of Sweden, SP REPORT 2011 81, ISBN 978-91-87017-14-8, ISSN 0284-5172. 

E.g. fire and gas protection systems, tripping of large electrical drives or power switchovers. Machine control systems. 

---