a great extent circulated in paper form through the production facility.
The function groups and individual modules shown here should be taken as examples but today do nevertheless represent a major part of what a powerful MES system should offer the user. At this point an important issue still needs to be made: an MES should be structured on a modular basis so that it can be introduced gradually as required and progress in familiarization with its functionalities is made easier.
1.5 Vertical and horizontal integration
In the past a two-layer model arose automatically from the two levels of automation and ERP. In most cases information was exchanged manually between the two layers.
The connection between the levels of corporate management and of production was thus a very indirect one and communication cycles were designed with a resolution of several days. With the development of the MES concept, even production management, as seen from the IT side, became a distinct discipline. It has now become possible to assign really specific fields of action to the three levels of corporate management, pro-duction management and propro-duction. In its dealings with ERP or PPS, corporate managements tend to work on a long-term basis with a resolu-tion of weeks or months. Rough producresolu-tion planning deals with a medium-term range of weeks or days, while detailed planning – also known as load planning – acts in the short term in days and shifts. Decisions taken within production management must be made within a time range extending from shifts down to minutes while automation with its machine and plant con-trol systems needs, of course, to react within minutes or even seconds.
The corresponding diagram symbolizes a control characteristic within the different levels whereby the control cycles run within the time resolu-tions shown. There are, of course, no precise boundaries between the three levels of a manufacturing company. Accordingly, between ERP and MES we find the APS (advanced planning and scheduling) functions which, depending on the type of production, tend to be closer to ERP or to MES.
Just as fuzzy is the demarcation between the MES and automation. The presence of functions such as data acquisition and the transmission of ma-chine settings alone creates a tight connection between the two levels which should still nevertheless be regarded as separate levels and whose character tends to be related to planning on the one hand and to technical implementation on the other.
30 1 New ways for the effective factory
In the first sections of this chapter three different types of production are examined. Figure 1.11 seeks to answer qualitatively the question “How much does each production type need MES?”
As we have already said, the functionalities of APS and of system control are located in the overlap areas of the three corporate levels. For the sake of clarity we can also say that in the demarcation between ERP and MES func-tionalities, MES tends to act with a technological orientation and in real time while activities in ERP tend to be commercial and cut to the medium term.
Not only that but the three MES levels of a manufacturing company work with completely different time horizons. Within these time horizons they are autonomous control systems whose control cycle is oriented by the corresponding horizon.
The definition of a discrete type of production indicates that in the proc-esses there are many degrees of freedoms with the aid of which a production order can be channeled through production. Of course, de-grees of freedom also mean many opportunities for long transfer times, waiting times and inefficient order sequences.
Situation- and technology-oriented planning aids are required here which enable production management to react swiftly and appropriately to errors.
An MES covers part of the APS functionalities at this point. At the border with automation the MES permits direct data tapping within production.
The situation is somewhat different with mass production and assembly line production. Here the difference between rough and detailed planning
Fig. 1.11. Requirements for MES penetration within the company
1.5 Vertical and horizontal integration 31 is less than in discrete manufacturing. Relatively long-running orders and lengthy retooling times rule out short-term reactions and thus automati-cally make medium-term production schedules necessary. A major part of short-term activities is handled on the automation level – in other words, in the machine and plant control systems. With this type of production the automation level is very powerfully developed. This reduces the planning portion of the MES to a relatively narrow field which is limited to a short-term and technology-oriented situation presentation and to evaluations relating to times, faults and qualities.
For the make-to-order manufacturer the resolution of large bills of mate-rial is a theme of particular interest. His business is governed by long-running orders. In such a case, a short-term, reactive detailed planning capability will only be of any use in make-to-stock production areas.
A major part of automation is also found in these areas, apart from, of course, complex machining centers in which extensive machining activi-ties are carried out on individual parts. Here the MES part will be limited to the field of small-batch products and to time recording and project time recording inside the plant engineering and construction operation itself.
Different types of production need different MES functionalities and even need MES implementations of different levels of capability. Fig-ure 1.12 shows the extent to which MES functions can be covered by ERP or automation or can extend into these areas.
Fig. 1.12. MES requirements by type of manufacturing
32 1 New ways for the effective factory
With the 3-level structure we have described it has been possible, using the MES as a linking element between corporate management and produc-tion, to achieve vertical integration throughout. In the IT world, with a model of this kind there is now no necessity for any instances of modal fragmentation in which protracted and time-shifted manual recording and data acquisition routines prevent information exchange in real time. Via the MES the ERP level can now supply production with up-to-date information in real time. Via the MES, ERP receives back correctly prepared informa-tion at the right time. However, at this point the MES does supply produc-tion management in real time with the technology- and situaproduc-tion-oriented information which is needed for a timely response to faults and malfunc-tions or to keep fault condimalfunc-tions as short-lasting as possible. Despite the tight coupling afforded by vertical integration the three time levels are de-coupled to the extent that each level can act correctly and the company as a whole can still map time domains ranging from long-term to online.
The attention currently being given to vertical integration shows how im-portant the role of the MES is in the architecture of a company. According to what has already been said, within production management – in other words, in the domain of the MES – there are three function groups: production,
Fig. 1.13. Vertical integration ensures that the different levels in the company are supplied at the right time with information (in the way they need it) from the other levels
1.5 Vertical and horizontal integration 33 personnel and quality. In very few cases indeed are these function groups independent of each other. To manufacture something, the right personnel are needed at the right time and this expensive resource, the individual, should be employed as effectively as possible at the right place. In produc-tion, parts can be produced with different qualities and these need to be in-spected. This short list alone demonstrates that production management, if it is to function effectively, must attend to all three function groups more or less simultaneously. From this arises the demand that these three function groups need to be connected very closely together. According to this, the IT system which maps these functionalities should act in the most uniform manner possible and be based on a single data pool. This prevents duplicated acquisition of data, redundant master data and transaction data.
This so-called horizontal integration is thus an important requirement whereby an MES system provides production management with effective support. The above considerations show how important this integration mechanism (the MES system) is to vertical integration in a manufacturing organization. Vertical integration is an important requirement if a manu-facturer is to enjoy a competitive future.
Fig. 1.14. Vertical integration is important for the effective functioning of the entire company. Horizontal integration in the MES domain is a special instance of implementation and permits effective working with the different function groups in an MES
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1.6 Use of an MES system in the company