Towards a Mill-Wide System Including Modernization of Sheet Finishing Process

Copyright © IFAC Instrumentation and Automalion in the Paper. Rubber. Plastics and Polymerization Industries .

Ohio. USA . 1986

TOWARDS A MILL-WIDE SYSTEM ... INCLUDING MODERNIZATION OF SHEET FINISHING PROCESS A. Nomoto jlljo PalHr Co .. 1.lhil/oll/alii '\/ill. 2-2-1. ,"al/ko-rl/(). I.Ihil/oll/alii City. 986 jalHIII

Abstract. The automation of sheet finishing process seems to be most backward, but it is different from Process Automation applied to the other pulp and paper continuous processes . We built a new finishing room introducing the techniques broadly known as Factory Automation (FA) at discrete processes, which have made rapid progress in Japanese assembly industries recently . The information system of this process is complex and difficult, but it is important for mill-wide production management system . Now we are constructing a mill-wide computer system in our mill, which has new concepts and designs including sheet finishing process. The system has a horizontal and distributed structure, and it consists of the operator workstations and section computers .

Keywords. Paper industry; sheet finishing process; factory automation; mill-wide system; production management; communication network.

DELAYS IN IMPLEMENTING FA AT SHEET FINISHING PROCESS

a. be familiar with the design of a wide variety of facilities, b. have a fresh approach to problems free of established ideas and c. be capable of configuring a unique control system. However, at present there is a shortage of mill engineers with such a wide range of knowledge and experience, and it is necessary to rely on equipment manufacturers.

The sheet finishing process which involves sheet inspection, sorting and wrapping has traditionally been done by hand, and has the largest number of workers in the pulp and paper mill. But implementation of automation in this process has been delayed for the following reasons. Complexity of the process

Sluggish growth This process is often assumed to be very simple because of its labor intensiveness, but it is quite complex. a. The final products must pass through various stages. b. At each stage, various intermediate products are produced. c . The above products are manually transported between each stage. d. Complex quality information is required at each stage. e . Measurement is difficult at each intermediate

The Japanese pulp and paper industry has enjoyed a steady, albeit low, growth and has never faced such drastic changes of consumer needs as other faster growing industries. Most investment has been in pulp and paper ma king departments, to expand the produ c tion. Consequently, investment in the finishing process has been rare. As a consequence of the two oil crises of the 1970's, most non-expansionary investment has been going into efforts to reduce costs represented by energy savings. On the other hand, FA introduced in other industries has extended to the finishing process to reduce costs through the increased efficiencies inherent in automation.

process.

It is therefore quite difficult to measure and directly manage the production status of the process.

Lack of automated quality control systems Lack of trained engineers The finishing process is, in brief, an inspection or sorting process and has been long undervalued, co mpared to paper making. It is very difficult, once produced and mixed, to identify and remove defect paper from the process and much labor is necessary with no substantial productivity

The finishing process is conventionally beyond jurisdiction of engineers who are in charge of Process Control . In addition to knowledge of operation management, quality control and plant maintenance, an FA engineer should:

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results. This was the situation before the age of quality. As labor costs increased, it became essential to introduce a quality assurance system in its true meaning, that is, the policy was adopted that no defect paper should go to the next stage and the slogan uno sorting U was used. As a result, paper quality has been rapidly improved and the foundation for FA has been established. Lack of a universally applicable system Generally speaking, the operational characteristics of such a system would be determined by mill size, product mix and raw material conditions. The problem is further complicated by the fact that various old stories become entangled. Therefore, it is necessary for system configuration to be based on a large-scale survey, requiring a lot of money, time and manpower. Equipment manu f acturers have appeared, at least so far, to avoid co mmitting themselves to improvement in the finishing process, because not much is gained for them in the absence of a universally applicable system. They have become ready to contribute their resources, only recently, with rapid progress of mechatronics technology available at an economical expenditure. However, a wide automation system based on computers might cost too much because of a need for extensive software development.

NEW FINISHING FACILITIES AT ISHINOHAKI MILL Jujo Paper Co. Ishinomaki Mill manufactures 600,000 tons/year of mainly wood-contained and wood-free printing paper including coated paper. One-third of the production or approximately 200,000 tons/year is shipped in sheet form. Out of sheet products, 75 - 90 ~ is produced at the mill and the remainder is subcontracted to converters in order to .oderate demand fluctuations. To cope with an increasing demand for sheet, one of four finishing rooms was rebuilt recently. FA technology was vigorously introduced at the new finishing room. The plant came on stream January 1985 and has been produ cing about 6,000 tons/month of mainly wood-contained printing paper since April 1985. Concept of new finishing room The basic concept and restrictions of the plant are following. (1) Rolls for sheeting are supplied from several paper machines and the rate of supply of these rolls changes sharply, because the production schedule of paper machines is given priority. (2) An existing room between a paper ma c hine and the finishing room is available for storing rolls. Rolls are fed from there to the finishing room manually. (3) Two new cutters are operated in three shifts to keep the maximum production and to decrease the amount of relatively expensive subcontracts.

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(4) The inspection of sheeted stacks is generally done by women operators only in the daytime in Japan, but men are inspecting in three shifts in this room. (5) After the inspection, uno defect U material and Ueasily fixed u material are sent to the automatic ream wrapping machine. (6) As a result, the material requiring sorting is removed from lines and carried to manual sorting corners where it is sorted by women in the daytime so as to concentrate inspection and sorting works. Outline of the facilities The new finishing room has a floor space of 4,800 rrf in a one storied building. Outline of the facilities are following along with the production line. (See Fig. 1) (1) Rolls for the two cutters are supplied from a roll storage manually and stand by on two conveyer lines. Therefore, one set of rolls is ready for each cutter beforehand. (2) According to order from an unreel-stand operator, rolls on the co nveyer are sent to the appointed unreel-stands one by one automatically. (3) There are two sets of 9 roll un reel-stands for one cutter(total four sets). One is in operation, and new rolls are meanwhile loading in the other. When one is finished cutting, the travel platform on which two sets of unreelstands are installed moves in parallel and the other unreel-stands come i nto use. (4) Rolls are carried by loading travel trucks in unreel-stands and chucking of rolls to each unreel-stand is fully automatic. (5) The two 2,100 mm width cutters which have automatic stack change system are made by Jagenberg (West Germany) with maximum cutting speed at 300 m/min. (6) Sheeted stacks are carried to inspection stages by a traverser and slat conveyers automatically. There are three inspection conveyers a nd six storage conveyers for each cutter. Thus, uncertain inspection time can be absorbed due to buffering storages. (7) According to judgement at the inspection stages, sheeted stacks are directly carried to wrapping ma chi nes or discharged out of lines automatically. (8) The two a utomati c ream wrapping machines are made by Wrapmatic (ItalY), GRM type. They are capa ble of wrapping a maximum of 17 ream/min. and useful for absorbing fluctuations of their pre- and post-processes. They have automatic stack change system. (9) Wrapped stacks are further wrapped by stretch film and carried to a product warehouse. (10) The handling facilities are all automatic and made by Hitachi Metals. The new automatic roll chucking equipment at unreel-stands was specially developed jointly by Jujo Paper and Hitachi Metals. Characteristics of the facilities (1) From the roll storage to the product

To",ards a !\Iill-wide System warehouse, the handling system is all automatic to achieve labor saving and data tracking. (2) There are adequate buffers from one process to the other to maximize the productivity. So the whole operation in which cutters take a leading part, runs smoothly and allows increasing production. (3) It takes about 7.5 minutes to start cutting new rolls by the quick travel platform after the cutter is stopped, and 17 minutes to load 9 rolls to the unreel-stands by the loading travel truck and the automatic roll chucking equipment. (4) Safety is assured by means of introducing not a hoist but special travel trucks when rolls are carried to unreel-stands. (5) 6 palletizers and 2 depalletizers are installed in cutters and wrapping machines in order to eliminate the periodical manual works. In particular, palletizers with numerical control have been introduced to the cutters and they are operating automatically reasonably well. (6) Soft starting and stopping of conveying equipments by inverter drive units prevents sheeted stacks from slipping. (7) FA technology brings good results in positioning at conveying equipments. In particular, the travel trucks at unreel-stands run at a speed of 30 m/min. and stop at an accuracy of ± 1 mm by means of DC servomechanism. (8) Various automatic operations above-mentioned are achieved by many programable logic controllers. (Total 33 sets)

INFORMATION SYSTEM AT SHEET FINISHING PROCESS There are many operators involved with this process. As the number of brands tend to increase and the lot size of orders tends to get smaller, we urgently require an information system for production management at this section. Problems of information system In designing an information system, however, many problems were pointed out. (1) As rolls for sheeting are produced on a large scale, it is difficult to control the historical information on all rolls collectively. (2) Rolls are not always stored in a fixed warehouse or sent to a fixed cutter. Accordingly we have to built a system for the whole mill. (3) The current fault detectors do not indicate the fault position in cross direction in detail. When the fault position coincides with the slitting point, fault markings are left on both si6e rolls or sheets. Therefore, a fault is not always at a fault marking point. (4) It is difficult to adjust the starting point of each roll for sheeting at unreel-stands, hence fault positions become staggered. (5) Not only fault detectors but also control systems must be installed on all paper machines, whereby the fault data can be communicated to winders so as to stop automatically at the fault position in machine direction. (See Fig. 2)

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Actual infor.ation system An information system, which collectively controls fault data of all rolls for cutters and picks necessary data out of them at cutter's request, must be very large and difficult to build. Inevitably we gave up construction of such information system at an early implementing phase. As a matter of fact, operators are experienced in current methods and it is confirmed that the more complicated the procedures become, the more important the information attached to actual goods becomes. It was reasoned that the best choice would be to excute the procedures with minimum mistakes. We at first constructed the system which is supporting the actual procedures. In the system the slips attached to sheeted stacks and to wrapped stacks are issued automatically. System terminals are installed at three finishing rooms and data communications between them are fulfilled by means of optical fiber cable devices. ~ni~Elng

process in mill-wide system

In going any further improving the information system, we must consider it with all other information systems of the pre- and postprocesses simultaneously, that is, in mill-wide system. Mill-wide systems in the pulp and paper mill have been much talked of and written about in Japan, but they are not yet clearly defined. The system ought to be built based on a fundamental recognition that production management is its base. In case of roll products with production processed by winders and roll wrapping machines, data management is not so difficult. For sheet products, processing is very much complex as discribed above, making its management difficult. However, this process is most important in production management system for following reasons. a. Historical data required for production planning must be obtained accurately and quickly from this process. b. Performance data from the process are the basis for costing, efficiency, yield and profit & loss. c. This is the point where products are delivered to customers and is the origin of shipment control. Therefore, in order to realize a mill-wide system it is necessary to catch information at an appropriate level in a complex flow. Finishing and its pre- and post-processes still require a degree of manual control and manual data input. Our task is to create a new mill-wide system which, keeping the human factors involved in mind, can be tailor-made to each mill.

CONCEPT OF MILL-WIDE SYSTEM In other industries such as assembly industries complete Factory Automation systems have been thoroughly introduced. In the iron and steel industry large-scale computer systems known as

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"Total production management systems" were com pleted about ten years ago. ~e have studied closely the mill-wide systems of Scandinavian pulp and paper mills. However, early discussions about the aims and objectives were inconclusive. We could not see the benefits necessary to justify the large investment. In comparison with foreign countries or other industries, commercial practices, management methods and operation systems are different . Pulp and paper mills vary in mill size, production mix and raw materials . It is therefore impossible to apply the others' systems just as they are. In Scandinavia mill-wide systems were particularly developed in pulp mills or paper mills manufacturing roll products such as newsprint paper. We are intending for the process including the above-mentioned sheet products where the complexity goes beyond the limit of human control. Now we have begun to construct a mill-wide computer system which is original and appropiate for the complex processes in our mill. Production management

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The production management system forms the foundation of our mill-wide computer system. The main feature in brief, is that the system is to collect every moment production data accurately and automatically from each part of the mill. Where necessary, manual data will be input by the operator's hands at that spot. The purpose of this information is to fulfill on-line and realtime management. Information about production and quality of all sections is given to operators directly, so they can execute the fine management at that spot thoroughly. We improve the management of materials flow and i nformat io n flow in the whole mill. Consequently we can achieve universalization of information and simplification of management. Horizontal and distributed sturucture A mill-wide system aims at achieving the rationalization not of operation as before, but of management. The mill management is car ried out under the hierarchical organization. The millwide system must correspond to the management structure. The management organization is hierarchically classified by the time-span of decision-making in general. (See Fig. 3) That is, the time-span of the relevant information becomes longer as one rises through the layers of the organization structure. Operators require every moment information from the process. Foremen deal with partiably arranged information, for instance every five minutes. Section heads deal with hourly information excepting for sudden abnormalities. Production managers and mill manager require every shift or daily information of the whole mill as speedy as possible. By condensing the information succesively for higher layers of the organizaton structure, the amount of information decreases and the load of communication reduces. So a distributed struc-

ture composed of many computers may be chosen . (See Fig. 4) This system is quite different fro. a large, fast and centralized computer system in general use. It is considered to be more appropriate for the mill production management system . As the time-span of handling data varies with the stages of organization, large data-base is not always advantageous for the system. Here we must take notice that the structure of management sections differs from that of materials flow. The every moment information of all the processes and particularly adjacent ones should be provided for all operators even beyond the bounds of their own management sections.

Our system structure composed of many computers is not constituted hierarchically, because the communication between them becomes far more complicated when the system has more layers. So our system structure is not hierarchical but horizontal and distributed. Operator work-station The basic computer of this system is the newly named "operator work-station" with high intelligence. It is to be installed for every operator at each part, above all for every lift truck driver carrying intermediate products, wrapping materials such as pallets, or final products. Needless to say, it is installed at each part of the above-mentioned finishing process. Every operator can see the state of all processes through the CRT of the operator work-station. The effective informations are expected to improve his management actions. As a result, the rationalization of management will be achieved. In this regard we have noted the experiences of Stora Kopparberg, Skutskar Mill. As they have realized, the managers are normally present at daytime from Monday to Friday. This is only about 20 % of the total production time. The system must be managed for the remaining 80 % without the stuff managers. A new position of the production planner in shift was created at Skutskar. Our system makes operators perform the role of the production planner. Especially, in Japan the bounds and the responsibilities of duties are vague. Operators are in chage of not only operations, but also quality control, facility maintenance and production management. If the relevant information is offered to them, their management decisions will be improved remarkably. When an operator knows something wrong in some other section, he ca n take necessary measures

quickly and help voluntarily depending on the situation . As a result, the confusion will be settled earlier and off-grade products in particular will be minimized. If the production schedule is changed suddenly, all operators will be able to cope with it flexibly and quickly. Large benefits which are difficult to estimate precisely are expected through this facility. The operator work-stations have several types suited to various uses, for field operators, foremen, stuffs and managers. They are personal

TO\\Oards a l'vlill-\\'ide System

terminals of computer system with high intelligence or auxiliary ones with slight functions in all branches of a mill. The section computers and the host computer for production management shown in Fig. 4 are only communication and file servers. As there are few computer engineers in our mill, we can not

look after them carefully. Consequently, the actions to the computers are usually done through the operater work-stations in our system.

CHARACTERISTICS OF THE SYSTEM Reliable data in pulp and paper mill In the pulp and paper mill the quantitative management is most backward. There are extremely few figures worthy of input to a computer automatically as data for mill management. For example it is difficult to accurately measure the moisture rate of wood, chip, pulp and paper. The most serious problem is that the quantity of pulp can not be measured with enough accuracy for the on-line management data, because the absolute value of pulp consistency is not measurable by means of on-line instruments on the market. In our system the area of paper is chosen as the basis of the production. The wound length on the reel part of paper machines is measured accurately and automatically, and the management system is constituted on the length data equivalent to the area of paper_ In case of roll products the basic data are available from the wound length at winders. For sheet products the number of rolls for sheeting, cutting length and cutting counts at sheet cutters are basic data. In both cases the on-line data are measured automatically. In addition, we must input some data by hands in handling materials and products for inventory control and shipment control. There the operator work-stations may play an important part. Another information with high reliability is quality test data. It is very important for field operators to judge whether the manufactured products come up to the standard or not. In our mill the test samples are sent to and measured at the test room. In this case the computer system distributes the test data to the computer terminals, that is, the test data may be immediately displayed on the operator work-stations installed at many places. The role of automatic control In our system automatic control or regulation is not implemented. Mill-wide systems with hierarchical structure have been introduced or proposed in many papers, in which process computers are allocated to the lowest layer. However, we must consider how many computers are installed and what roles they are performing. Recently some computers become much bigger and faster namely "super" and others tend towards "micro".

In every process many and diverse computers are introduced, for example in a paper machine,

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there are computers for basis weight and moisture control, sectional drive control, dryer ventilation control, fault detector control, and various sequential control . Many facilities now tend to have intelligence for higher effectiveness. The latest winder has many computers for controlling web tention, speed command, wound length, roll tightness, slitter positioning and stoppage at defect point. However, the computer systems are all managed by operators, even if the systems are very big. In process industries the instructions about production are given not by computers directly, but by operators. Then the operator work-station gives and takes necessary information to the control equipments via some communication tools . In our case a process interface unit which is connected to the control equipments. (See Fig. 5) When suppliers or types of computers are different in the methods of the communications, protocol conversion is practiced in the process interface unit. The unit carries out preliminary processing of the field data and the communication so that the program may be standardized. Features of our system There are 9 paper machines, 3 coating machines, 10 winders and 6 cutters in Ishinomaki Mill. We manufacture a great many grades of printing paper, so our production management computer system will be large. Especially, the volume of the software is enormous, so it is a serious problem to minimize the programming costs. We must realize the next two functions in it. One is that every operator can see the state of all processes through the operator work-station. The other is that every moment data must be condensed into every roll, every reel, hourly, every shift, daily and every brand information according to the layers of the organization structure. Our system structure is not a large and centralized computer system, but an original and horizontally distributed system which is considered to be appropriate for achieving the two main functions. The characteristics are following. (1) By distributing and layering the data, the memory capacity decreases and the load of communication reduces.

(2) It is ready for the system to be connected and integrated with all sorts of the computer systems for process control. (3) The software for the same part of processes may be identical and this will contribute to the reduction of the programming costs. (4) As each part of the system is excellent in separateness, the system maintenance is plain. (5) The system consists of the section units, so it is easy to modify and expand it, and it is adequate for a small mill as well as a large one. (6) The total costs of the system may be cheaper than the hierarchical and centralized system. ~e intend to make the program so easy that operators may modify or make a least part of it for themselves. ~e have had favorable experiences with operators making simple graphics by filling in the form.

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A. Nomow CONCLUSION

We are only in the first stage of our project at present, and we are constructing 24 hour continuous system apart from daytime system. Perhaps the number of the operator work-stations will be far more than 100. The complete system will be very large, and it will take a long time to complete the whole system. The performance of computers is making rapid progress with the addition of new convenient functions at regular intervals. Nevertheless, there is still some doubt whether they will be able to satisfy our demands or not. Our essential philosophy is that computers are not only equipments for computer engineers, but also apparatus for various kinds of people, including operators. We intend to develop a more familiar computer system by means of generalizing the concept of the operator work-station. An operator will use it freely in order to improve not only the efficiency higher, but also his work easier. Consequently his working motivation will be heightened. The computeri zation of the pulp and paper industry has fallen far befind the other industries. We must make efforts in order to reduce the gap by utilizing new computer technology. •

Tuwards a Mill- wide System

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