Intended learning outcomes: Explain campaign planning using an example of a process chain in chemical production. Identify campaign cycles for the example and a minimum campaign of one day’s production. Describe how the process stages could be synchronized.
Section 8.1.3 described large lots as a consequence of setup costs due to stopping, cleaning, and restarting processes. The changeover processes for transporting flow resources are of lesser significance. In processor-oriented resource management, the objects concerning capacity management and production control are not equivalent to materials management objects.
- For control, the planning unit is the machine or facility, such as the reactor, which thus also becomes the actual planning object. The technically feasible batch size is calculated by the quantity of goods that should ideally be processed by this facility. The batch thus produced is also used for accounting, stockkeeping, and archiving information for the subsequent lot traceability, for instance.
- From the materials management viewpoint, the emphasis is placed on demand. For technical reasons, a production lot can only be a multiple of a production batch. “Optimum” batch sizes, whether calculated using stochastic or deterministic methods (see Sections 11.3 and 12.3), often have to be rounded up considerably due to the high setup costs and the required utilization of capacity. Such hidden formation of batch sizes results increasingly in block demand for, and thus a decidedly quasi-deterministic form of, materials management.
A campaign is an integer multiple of production batches of a certain item, the batches being produced one after another.
A campaign cycle is a sequence of campaigns during which all the important products are produced up to a certain capacity and in the quantity required by demand.
The sequence of campaigns is used to reduce setup costs. As soon as the optimum batch size from the materials management viewpoint consists of several batches, it is then combined to form a campaign. Under certain circumstances, it is then advisable to produce a batch of a different product immediately afterward, if this will avoid the need for a cleaning process, for example. The formation of campaigns in this way is a characteristic feature of processor-oriented resource management. This means that the entire campaign must be considered, rather than just the individual batches, when scheduling capacity. A campaign can, of course, be split back into its constituent batches if necessary.
Campaign planning aims to create optimum campaign cycles.
Campaign planning is one type of sequencing, or the combination of optimum sequences. Optimization can target various areas: production costs, manufacturing time, or product quality. Figure 8.3.1.1 shows the example introduced in Figure 8.1.1.2, with the addition of a packaging process. The example is taken from [TaBo00], p. 18 ff.
Fig. 8.3.1.1 Example of a process chain in chemical production (see Figure 8.1.1.2).
The grades A, B, and C produced at a plant are packed into two drum sizes (4 liters and 20 liters) in the subsequent packaging process. The demand is for the 6 end products (3 grades times 2 packaging sizes). To simplify the example, the minimum batch is assumed to be one day’s production. The demand for an end product is specified in relation to the overall demand: A4, 30%; B4, 20%; C4, 10%; A20, 20%; B20, 10%; and C20, 10%. Bill-of-material explosion results in the proportionate demand for the intermediate products obtained from the reactor: 50% A, 30% B, and 20% C.
Assuming that the long time required to set up the packaging process arises when the packaging size is changed and that the reactor setup costs can be minimized by the sequence A, B, and C, as well as the specification of a minimum campaign of one day’s production, the campaign cycles shown in Figure 8.3.1.2 result.
Fig. 8.3.1.2 Campaign cycles for the example in Figure 8.3.1.1 (see Figure 6.2.1.2) and a minimum campaign of one day’s production.
The reactor rhythm is determined by the minimum proportion of the demand, 20% for C. The campaign cycle thus lasts 5 days. The packaging rhythm is determined by the minimum proportion of the demand of 10% for C4 or C20. This campaign cycle thus lasts 10 days.
The ideas behind processor-oriented resource management thus correspond in some respects to those of the lean / just-in-time concept (see Section 6.2), in which the optimum sequence of operations is important with a view to reduce the setup times (see also Figure 6.2.1.3). The reduced setup times should result in small lots and, therefore, continuous demand. Only then will it be possible to totally separate the processes that make up the various production structure levels, which will allow the use of the Kanban technique in the process industry.
If continuous demand cannot be achieved, then quasi-deterministic techniques will still be required. In this case, the response to a net demand will be to schedule at least one campaign for production, rather than just a batch. A batch also results in by-products. Both of these contradict the simple pull logistics of the Kanban technique, since production is determined by the technical process and savings in terms of setup time, rather than in response to consumption. The dominating factor is capacity management.
The conventional MRP II / ERP concept of resource management does not incorporate the processor-oriented techniques, such as manufacture of by-products and campaigns, making them less suitable for the process industry. Campaign planning enables demand to be synchronized in terms of quantities with the goods to be produced at all production structure levels, particularly with respect to end products. Where synchronization is not possible, buffers must be kept to absorb any shortfall. The aim of campaign planning is thus to minimize the inventories that have to be kept in the intermediate stores by synchronizing the various (process) stages as accurately as possible. Figure 8.3.1.3 shows how the two (process) stages (or production structure levels) could be synchronized for the above example.
Fig. 8.3.1.3 Campaign planning: how the (process) stages could be synchronized.
The diagram shows the start and end of the overall campaign for each product, but not the individual batches. It can be used to calculate the resulting stock curves for the end and intermediate product stores for given quantities. The inventory curves are of the type discussed in detail in Chapter 11 for determining the available stock. They are used as the basis for troubleshooting, particularly for determining the buffers that will be needed.
The campaign planning technique described here is modified finite capacity planning (see also Section 14.3) that requires continuous intervention by the scheduler. The planning diagrams are similar to the Gantt charts or planning boards used in finite capacity planning (see the illustrations in Sections 14.3 and 15.2.2). The only difference is that they include — as well as individual batches — entire campaigns or even campaign cycles.
Exercise: Campaign cycle planning
Try to plan the campaign cycle of a two-step production (reactor and packaging) for four different products, each with two packaging options. You are the production manager. Before beginning with the planning task, take note of the constraints and hints offered.
Course section 8.3: Subsections and their intended learning outcomes
8.3 Processor-Oriented Resource Management
Intended learning outcomes: Explain campaign planning. Differentiate between processor-dominated Scheduling and material-dominated scheduling. Describe a nonlinear usage quantity and a product structure with loops.
8.3.1 Campaign Planning
Intended learning outcomes: Explain campaign planning using an example of a process chain in chemical production. Identify campaign cycles for the example and a minimum campaign of one day’s production. Describe how the process stages could be synchronized.
8.3.2 Processor-Dominated Scheduling versus Material-Dominated Scheduling
Intended learning outcomes: Differentiate between processor-dominated scheduling and material-dominated scheduling. Produce an overview on the use of the MRP II / ERP concept or of the lean / just-in-time concept compared to the processor-oriented concept.
8.3.3 Consideration of a Nonlinear Usage Quantity and of a Product Structure with Loops
Intended learning outcomes: Present the quantity of a manufactured product P as a nonlinear function of the usage quantity of a resource R. Identify possible solutions of issues entailed by a nonlinear usage quantity.
