Exploring Repetitive Manufacturing

Repetitive manufacturing is mainly used for production scenarios with high product stability, high repetition rates, and low product complexity.

In our business example, repetitive manufacturing is used to initiate and control the production of the wheels in our bicycle company. Repetitive manufacturing includes the following information:

• Which types of wheels are to be produced?
• How many wheels are to be produced in what periods of time?
• Which and how many material components are required in which time periods?
• Which operations are to be carried out at which work centers?

Integration of Repetitive Manufacturing

The complex process chain from the creation of requirements to the goods receipts of the finished products is modeled in a lean version in repetitive manufacturing.

The in-house production process starts with the definition of a demand program. There are two basic planning strategies: make-to-stock production and make-to-order production. In the case of make-to-stock production, planned independent requirements are created based on forecasts; in the case of make-to-order production, sales orders are created in Sales. In our bicycle company, both planning strategies are used in repetitive manufacturing. Wheels for standard bicycles with a relatively constant, predictable sales volume are produced in make-to-stock production, while wheels for more expensive special bicycles that require a more complex production process are produced in make-to-order production.

The stock and requirements situation for the materials is checked regularly in material requirements planning (MRP). In case of shortage situations, planned orders are created to cover the planned independent requirements and sales orders. In our bicycle company, an MRP run is usually carried out once a day.

In repetitive manufacturing, the planned orders are assigned to production lines, synonymous with production versions. The planned orders are not converted to production or process orders. They have the order type Run Schedule Quantity (PE). The planned orders serve as carriers of the quantity and date information.

Production execution in repetitive manufacturing includes the regular staging of the required material components and the regular confirmation of the produced quantities of the finished product with simultaneous backflushing of the components.

In order to be able to use repetitive manufacturing (REM), various master data must have been created beforehand. The main master data required are:

• Materials
• Bills of material (BOM)
• Routings
• Work centers
• Production versions

Material master records must be created for the materials that are produced and procured in a company. As already outlined in the previous unit on production order processing, in our bicycle company, material master records were created for the finished bicycles, for the required assemblies that are produced in-house, such as frames or wheels, and for raw materials to be procured via purchasing, such as rims or tyres.

As already described in the unit on production order processing, the production of the bicycles is controlled by production orders in our bicycle company. However, since the same wheels are needed for different types of bicycles and the wheel production should be quantity and period-oriented, it was decided to use repetitive manufacturing for the wheel production. In the material master of a product (finished product or semi-finished material) that is to be manufactured in repetitive manufacturing, the Repetitive manufacturing indicator must be set and a Repetitive manufacturing profile must be assigned. As illustrated in the figure, the material master record for the wheel was configured accordingly.

The material components required for products are to be defined via bills of materials (BOMs). The bill of material for a wheel manufactured in our bicycle company consists of the material components tyre and rim.

Routings in repetitive manufacturing often have only one operation. You assign a work center representing the production line to this operation. Our bicycle company has two production lines for the production of the wheels. Therefore, as shown in the figure, two routings, Routing 1 and Routing 2, with the respective work centers, Assembly line 1 and Assembly line 2, have been created. The total production rate of a production line is specified in the respective operation. It defines how many products per time unit can be produced on this production line. The production dates, quantities and capacity requirements of the planned orders are scheduled and calculated according to the production rate using formulas in the work center.  

A planned order in repetitive manufacturing is created with reference to a production version of the corresponding product. A production version defines which routing in combination with which bill of material is to be used for the planned order. If a planned order is to be used in repetitive manufacturing, the corresponding production version must be allowed for repetitive manufacturing and the work center of the routing must be assigned as production line in the production version. As already mentioned, our bicycle company has two production lines for the production of the wheels. Therefore, as shown in the figure, two production versions 0001 and 0002 with the assignment of respective routings and the respective work centers as productions lines have been created. Both production versions are allowed for repetitive manufacturing. A suitable production version is automatically selected when the order is created according to criteria such as production quantity and production time. If several production versions are suitable, another production version can subsequently be assigned manually, e.g. in the planning table of repetitive manufacturing.