MANUFACTURING PROCESS SIMULATION

Abstract: The present invention provides apparatus and a method for assessing the commercial and practical viability of a manufacturing process having a plurality of steps. The apparatus includes a computer programmed to simulate the process making use of performance and other data relating to some but not all of the steps. Physical equipment carries out at least one step when required by the computer and display means displays data relating to the results of the simulation.

Description: MANUFACTURING PROCESS SIMULATION FIELD OF THE INVENTION This invention relates to manufacturing processes and, more particularly, to the simulation of manufacturing processes to enable their commercial and practical viability to be assessed. BACKGROUND OF THE INVENTION There is frequently a need to establish whether a proposed manufacturing process is both practicable and commercially viable, before the expense and effort has been incurred in putting the process into full manufacturing effect. This can sometimes be achieved by operating the process on a reduced scale and assessing the consequences of scaling up. For some processes, enough is known about each individual step, and the effect of modifications of that step on other steps in the process, for the entire process to be simulatable by means of a suitably programmed computer, the computer then producing data, for instance data relating to the overall time of the process or the costs involved, which can be reasonably fully relied upon. However, some manufacturing processes are such that a reduced scale "model" is not feasible or does not give results which apply to the full-scale operation. Furthermore, at least some of these processes are not capable of total computer simulation because, for instance, certain of the steps are too complex for simulation or the data relating to these steps is simply not available. A particular type of manufacturing process which is not susceptible to analysis of practical and commercial viability by small-scale modelling or computer simulation concerns the nuclear fuel industry. In this industry, fuel elements are manufactured for use by nuclear power stations. A fuel element comprises a multiplicity of fuel rods held within a skeleton of grids. A fuel rod is made up by loading a carrier tube with fuel pellets which are arranged in an end-to-end relationship within the tube. In order to manufacture (or assemble) a fuel element, a complex series of manufacturing steps has to be performed. A fuel element manufacturing facility may be required to manufacture fuel elements for use in different types of reactors. For instance, the fuel elements for different light water reactors vary one from another, including those for Pressurised Water Reactors, Boiling Water Reactors and the East European VVER reactor. In addition, there are different requirements for Heavy Water Reactors. There is a need for a manufacturing facility which is flexible in a number of different ways. For instance, there should be a capability of rapidly changing from one fuel type to another and there should also be an ability rapidly to expand both the plant and the equipment within the plant. When orders for fuel are received by the manufacturing facility, various matters will be specified including the type of reactor and, increasingly nowadays, the fuel makeup within each rod which forms part of the fuel element. So-called multi-zoned stack makeup is an increasing requirement for any manufacturing facility. In order to be able to tender for a given fuel order, considerable design work may have to be undertaken to ensure that the required fuel elements can be manufactured within a certain time, below a certain cost and maintaining the required safety levels. Frequently, there are steps in the manufacturing process which involve so-called risk technology, which means that all the viability and other outcomes of the use of this technology are not entirely predictable in the circumstances of a particular manufacturing operation. STATEMENTS OF INVENTION According to the present invention there is provided apparatus for assessing the commercial and practical viability of a manufacturing process, the process comprising a plurality of steps, the apparatus comprising a computer programmed to simulate the process making use of performance and other data relating to some but not all of the steps, physical apparatus for carrying out at least one of the steps, means for controlling the physical equipment for carrying out said at least one step when required by the computer, and display means for displaying data relating to the results of the simulation. The present invention also provides a method of assessing the commercial and practical viability of the manufacturing process, the process comprising a plurality of steps, the method comprising using a computer programmed to simulate the process making use of performance data relating to some but not all of the steps of the process, operating physical equipment for carrying out at least one of the steps, deriving at least some of said performance and other data as a result of said operation, and displaying data relating to the results of the simulation. Preferably the control system of apparatus in accordance with the present invention comprises an operator interface, an alarm handling function and a communication function. More preferably the communication function communicates with at least one programmable logic function. Most preferably, the programmable logic function controls the physical equipment. Examples of physical equipment controlled by the programmable logic function include fuel assembly process equipment, a tray retrieval unit and a robot, and a visions system and a servo motor. Preferably the apparatus includes an error recovery system for detecting faults and error conditions in the physical equipment or in the operation thereof. Preferably the computer contains means for providing a range of indicators of commercial and practical viability including a profit forecast, a risk analysis and an investment appraisal. Additionally or alternatively, the computer may contain means for utilising information on capital and operating costs, information on plant design and information on the cost of finance in its analysis. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, showing an embodiment of the present invention by way of example only, there are the following Figures:- Figure 1 illustrates the main aspects of apparatus according to the present invention; Figure 2 illustrates the relationship between the computer system software packages and the development equipment of the apparatus shown in Figure 1 ; and Figure 3 shows the physical equipment used in connection with the apparatus of Figure 1. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION The present invention, of which the apparatus shown in the drawings represents an embodiment, is concerned with the use of computer technology and ethernet/internet communication to integrate financial analysis in a virtual world environment with "high technical risk" physical hardware to determine at the early stage of development the costs associated with the use of the manufacturing facility over a period which might be the whole of its lifetime and also to minimise the risks associated with the proposed investment. As a result of the use of the present invention, it is possible to reduce the time for designing a manufacturing facility which is capable of being rapidly adapted to meet differing manufacturing requirements and also capable of being expanded (or contracted) in accordance with the manufacturing requirements. Apparatus of the present invention will enable plant to be designed having taken into account all possible problems in the operation of the plant including bottle-necks, buffering and the down time of machinery. In operating the apparatus, those aspects of the plant which represent "risk technology" will be eliminated. This embodiment of the present invention makes use of advanced 3 -dimensional stochastic processes and a virtual world plant simulation is used to scheme and optimise a manufacturing facility. Typically, a number of concept plant design solutions is developed to meet the requirements for a multiplicity of sales projections from start up to maximum throughput. The solutions will determine the additions in plant and equipment required to meet increasing production throughput. From this concept plant design, the capital and operating costs for the lifetime of the facility can be generated. A high-level factory control system is electronically integrated with simulation software and development equipment. The concept of inserting the physical test equipment into the virtual world environment and operating the combined system as a manufacturing facility is an important aspect of the present invention. The combined facility generates, tests and validates the real manufacturing capacity and plant operability in connection with production works orders generated from customers' orders and delivery dates. Referring to Figure 1 of the accompanying drawings, apparatus according to the present invention includes a factory control system 1 which provides higher level management information, control and production scheduling, allowing strategic level control of the operations in the plant as well as maintaining traceability. The factory control system consists of two layers. The lower layer 3 provides SCADA facilities such as an operator interface and alarm handling. These facilities are provided by a software package which is a real time control and data acquisition system. The lower layer communicates with programmable logic controllers (PLCs) and the simulator part of the system via ethernet. This level also contains application software which drives the physical machines by means of the PLCs and populates the application specification part of the database. The upper layer 5 of the factory control system 1 includes a software package which provides production scheduling facilities. Management information is stored in an Oracle database. There are three PLC systems 7 which provide tactical level control of the machine and servo drives within the plant 9. Each PLC has a small panel providing a man/machine interface. All three PLCs communicate directly with the plant via direct input/output. Communication between the PLCs is achieved by means of appropriate software. The simulator 1 1 can be used to simulate the entire plant or just those parts which are not demonstrated with the physical equipment. The plant is modelled using a package called Quest together with a further package 12 called Syslink which drives the interface to the higher level system. As indicated in Figure 1, PLC 1 has associated with it two systems 13, 15 which control particular aspects of the physical machinery operation. Similarly, PLC 2 has two further systems 17, 19 concerned with other aspects of the control of the physical apparatus. These will be discussed in more detail below. In addition, an error recovery system 21 , based on the G2 Al system, monitors the states of the input/output devices on each PLC using ethernet. Error recovery system 21 detects fault and error conditions on the plant and provides advice to the operator on one or more possible methods of correcting the problem. It operates in real time and provides an expert system for handling error monitoring and recovery. It includes a library of errors and associated causes and remedies and it is capable of building up this library as and when a new condition occurs and is remedied. Before describing the apparatus shown in Figure 1 in further detail, reference is made to Figure 2 which shows the relationship between the computer system software packages and the development equipment used to evaluate manufacturing options. In order to understand the use of the apparatus of the present invention more fully, the physical equipment associated with the apparatus will now be discussed by reference to Figure 3. The apparatus shown in Figure 3 represents demonstration equipment identified as being the risk technology steps in the manufacture of nuclear fuel elements. Broadly, the steps in manufacturing a nuclear fuel element might start with the retrieval of the required nuclear fuel pellets from storage positions. These required nuclear fuel pellets are delivered to equipment for making up columns of pellets for weighing and loading into carrier tubes to make fuel rods. The completed fuel rods are inserted into a skeleton of grids to form the fuel elements. The apparatus shown in Figure 3 includes equipment for demonstrating some of the stages in the manufacturing process. This equipment includes a tray retrieval unit 31 for delivering trays of pellets to the region where they are made up into columns or substacks. Trays 33 from the tray retrieval unit are delivered to an index table 35 and a robot 37 removes pellet retaining end bars from the tray. The tray 33 is then moved to the position indicated by 39 in Figure 3 where a control system 41, including a vision system, finds rows of pellets on the tray and builds a substack of the required length. The substack is located on a stack weigh beam 43 which, when loaded with pellets, is moved from the position indicated in solid lines to the position indicated by broken lines (see arrow in Figure 3). From this latter position, the pellets are pushed through a pellet load head 45 and pneumatic seal 47 into a fuel tube 49. Further operations are carried out on the rod (the loaded fuel tube) by means of the simulator rather than using actual physical equipment. When building a fuel element, the system requests the simulator to provide a rod. The simulator will then instruct the control system that it has provided the rod. An operator will load a rod onto the fuel rod pusher device 51 and this device will then be operated to load the fuel rod into a fuel skeleton 53 located on positioning equipment 55. The equipment will load the rod into an appropriate position in the fuel assembly and, when all the rods have been loaded, the simulator takes over the remaining operations. Referring again to Figure 1, the systems 13, 15, 17 and 19 can now be described with reference to the physical demonstrator. The vision system 17 is a PC based system which is used to identify the positions of pellets on the pellet trays and to measure substacks. It communicates with PLC 2. The servo control system 19 manages the motion control systems for the whole demonstrator. It is used to move the drives on the index table, the pellet pusher and the rod load machine. Systems 17 and 19 are shown linked to PLC 2. Accordingly, PLC 2 controls substack build, stack weight and the loading of pellets into tubes. It also controls the vision system and the servo unit. System 13 is a tray retrieval unit control system, controlling the machine which delivers the pellet trays from a store of such trays to the tray index table. It removes them again when they are no longer required. This system is under the control of PLC 1 using digital I/O for communication. System 15 controls the robot which removes the end bars from the tray of pellets after a tray has been placed on the index table and so that pellets may be transferred from the table. This system communicates with PLC 1. Accordingly, PLC 1 controls the loading and unloading of pellet trays on the index table via the tray retrieval unit. It also controls the movement of the tray index table and the removal of the tray retainers. Finally, PLC 3 controls the fuel assembly process. In operation, apparatus of the present invention will operate in accordance with a Works Order which requires various resources, such as raw or part finished materials, machines and tools, in order for it to take place. There are two types of Works Order, a Rod Works Order and a Fuel Works Order. A Works Order is defined by the operator by means of the production scheduling package on the control system. Use of this scheduling system allows short term production planning which has real time knowledge of what is happening on the plant. The system will not allow a Works Order to be commenced without the necessary resources being available. When a Works Order becomes due, the operator checks that the machine is ready and then instructs the Works Order to commence on that machine. The machine is able to process material when the appropriate material arrives at the machine. As soon as a machine has been started for a Works Order, that Works Order can no longer be rescheduled using the production scheduling system. Once a Works Order has been commenced, the simulator will start to mark carriers used, in order to identify them. It will then plug the rods. If the systems are in full plant simulation mode, fuel will then be made until the Works Order is complete. Otherwise, the simulator suspends operations once it has bottom end plugged a rod. The system then waits for the arrival of a bottom end plugged rod at stack build; this is detected by the stack build PLC via a bar code reading. Further operations are as described above, leading to the production of a fuel element. Once all the rods have been loaded for every required fuel element in the Works Order, then the Works Order is complete. It will have been completed in sequence for each plant area as the last material for the Works Order left it. The next Works Order can start on a piece of equipment as soon as the previous one has terminated. It will be appreciated that, in a full manufacturing facility, there will be one or more separate servo systems for each machine requiring servo control, with communication direct to the relevant PLC. In the apparatus shown in the accompanying drawings, PLC 2 administers one servo control system for the whole plant and this is justified on cost grounds. The use of the apparatus of the present invention provides a robust and structured method for the generation and analysis of investment appraisals for new and existing manufacturing facilities. Research and development is only focused on areas of high technical risk. Development costs are minimised to the high risk areas of development. Financial sensitivity can be evaluated and quantified. In addition, the dynamic three dimensional schematic simulation of the proposed manufacturing facility is "visible" for evaluation by plant managers, both for operability and with regard to safety implications. In general, the design and redesign of capital investment schemes to meet financial targets are minimised. The "lead time" from concept to financial approval for the building of the plant is significantly reduced.

Claims: CLAIMS 1. An apparatus for assessing the commercial and practical viability of a manufacturing process, the process comprising a plurality of steps, the apparatus comprising a computer programmed to simulate the process and make use of performance and other data relating to some but not all of the steps, physical equipment for carrying out at lest one of the steps, at least some of said performance and other data being derived thereby, means for controlling the physical equipment for carrying out said at least one step and display means for displaying data relating to the results of the simulation. 2. An apparatus as in Claim 1 in which the control system comprises an operator interface, an alarm handling function and a communication function. 3. An apparatus as in Claim 2 in which the communication function communicates with at least one programmable logic function. 4. An apparatus as in Claim 3 in which the or each programmable logic function controls the physical equipment. 5. An apparatus as in Claim 3 or Claim 4 in which the or a programmable logic function controls a tray retrieval unit and a robot. 6. An apparatus as in Claim 3 or Claim 4 in which the or a programmable logic function controls a vision system and a servo motor. 7. An apparatus as in Claim 3 or Claim 4 in which the or a programmable logic function controls a fuel assembly process. 8. An apparatus as in any of the preceding claims and including an error recovery system for detecting faults and error conditions in the physical equipment in the operation thereof. 9. An apparatus as in any of the preceding claims in which the computer contains means for providing a range of indicators of commercial and practical viability including a profit forecast, a risk analysis and an investment appraisal. 10. An apparatus as in any of the preceding claims in which the computer contains means for utilising information on capital and operating costs, information on plant design and information on the cost of finance in its analysis. 11. A method for assessing the commercial and practical viability of a manufacturing process, the process comprising a plurality of steps, the method comprising using a computer programmed to simulate the process and making use of the performance and other data relating to some but not all of the steps, operating physical equipment for carrying out at least one of the steps, deriving at least some of said performance and other data as a result of said operation, and means for displaying data relating to the results of the simulation.

Inventors: SAUNDERS JOHN PETER, SAUNDERS, JOHN, PETER
Applicants: BRITISH NUCLEAR FUELS PLC, SAUNDERS JOHN PETER, SAUNDERS, JOHN, PETER
Application year: 1997
Main classification: G05B19
IPC codes: B25J9, G05B19