Material supply in industrial production
The aim when planning the supply of materials was and still is to optimise material management. However, the methods used to achieve this have changed dramatically. In the past, the flow of materials was usually managed in line with a central production plan. Today, however, materials can be supplied according to requirements on the production line.
Material supply and management
There are basically two principles in physical material supply operations – pull and push. In the push system, logistics personnel feed material from the stores to the production cells. In the pull system, production personnel have to manage the supply of material for their production unit themselves. When it comes to management, a distinction is made between demand and consumption-driven material supply, whereby the main determining factor is the direction in which information flows.
Consumption-driven material supply (pull)
In consumption-driven material supply, the usage of materials triggers the flow of materials, often irrespective of a specific order. This system is intended to create a security of supply conducive to setting up material stores that are of adequate size and ideally dimensioned. The Kanban system developed by Toyota can be used for this purpose (see just-in-time, Kanban, push and pull principle). Production processes are initiated in a slightly different way to normal. The final stage in production – when the end-product is manufactured – reports its requirements to the next production stage upstream, which reports its needs to the next stage upstream and so on, right back to the supply of raw materials. After a certain delay, once the first stage has been reached, the material flow is finally initiated and starts to head back toward the final production stage.
Demand-driven material supply (push)
Demand-driven material supply is fundamentally different from consumption-driven material supply. In this case, material planning is conducted by means of a production planning and control system. Material requirements planning (MRP) is used to plan each process. Secondary requirements and all additional parameters are calculated during the course of quantity planning. Calculations are based on information from the storage facility, knowledge about process times and detailed expertise relating to the company’s product structure. Scheduling specifies all the start and end times of every process. Once the system has been launched, planned and actual capacities need to be compared and amended. Everything is controlled centrally. However, that is exactly what lean principles aim to avoid. The lean concept moves away from the idea of fixed production processes. It demands that a dedicated process is initiated for each product and can be customised to cater for all eventualities and can minimise waste. It can be argued that demand-driven material supply places greater emphasis on planning than on management. The opposite is true of consumption-driven material supply.