A firm s game plans for saleable products provide the primary driver of production activities. The primary coordination tools for a manufacturing environment consist of a planning worksheet and production orders, plus work center load analysis and schedules when routing data has been defined.
A planning worksheet identifies suggested action messages about production orders as well as purchase orders and transfer orders. Many manufacturing firms use just a planning worksheet, while others prefer to separate coordination of manufactured and purchased items with two types of worksheets ”a planning worksheet and a requisition worksheet. The suggested action messages can be analyzed , changed, and automatically implemented. The planning worksheet also provides the starting point for execution of planning calculations.
The planning worksheet can have multiple versions identified by a userdefined template name , just like the requisition worksheet. The use of different template names provides the ability to segment messages, as discussed below.
Execution of Planning Calculations The user initiates execution of planning calculations from the planning worksheet. The planning calculations can be performed on a regeneration or net-change basis; they calculate material and capacity requirements. They require a specified planning horizon and an order date (typically today s date). They are typically executed for all items, but they can be executed for a subset of items based on item number, location, or other filter.
 The system uses three types of worksheets ”a planning worksheet, a requisition worksheet, and a subcontracting worksheet ”for coordinating supply chain activities.
Some firms prefer a two-phased approach to planning calculations. The first phase focuses on items (termed MPS items ) with independent demands such as sales orders or forecast; the second phase focuses on all other items (termed MRP items ). The system determines whether an item is designated as an MPS or MRP item based on the presence of independent demand. With a two-phase approach, realistic schedules can be firmed up for MPS items before calculations are performed for MRP items. Most firms use the simpler one-phase approach.
In some situations, items may require immediate notification of suggested action messages without executing the planning calculations. These items have changes to their supplies or demands, such as changes to a sales order that must be communicated immediately. A user-initiated function gets and displays these action messages on the planning worksheet.
Suggested Action Messages Suggested action messages are displayed on the version (or template name) of the planning worksheet that acted as the starting point for executing the planning calculations. The displayed messages reflect the entire planning horizon, all types of orders (purchase orders, production orders, and transfer orders), and five types of messages (new order, cancel order, reschedule order, change quantity, and reschedule and change quantity).
Segmenting Messages on the Planning Worksheet Action messages may be segmented into subsets to support more effective coordination efforts. For example, a version (template name) of the planning worksheet can display a subset of action messages generated by planning calculations. Planning calculations must be initiated from the desired template name using a filter for the calculations such as a location. Using the location as a filter, planning calculations generate the location s suggested action messages on the template name.
 A master production schedule (MPS) typically represents the highest possible stocking level within a product structure and the level for defining forecasted demand to drive replenishment.
There are other examples of segmenting messages. Suggested action messages for purchase orders can be copied to the requisition worksheet (for a specified template name) or to another template name for the planning worksheet. In addition, situations requiring immediate attention (after a changed supply or demand) may be displayed on a separate template name that serves as the starting point for getting the action messages.
Filtering and Analyzing Messages Messages can be filtered by planner responsibility with additional filters to focus attention on the subset of critical actions. For example, a filter regarding planner responsibility can be based on the Product Group Code or General Product Posting Group . Additional filters for identifying critical messages include the following examples.
Messages for new production orders can be filtered and sorted based on order start date to focus attention on near- term actions. Special attention is required for suggested production with an order start date or due date before today s date.
Messages for existing production orders can be filtered by starting or ending date, with special attention required when the due date is before today s date.
Messages for purchase orders can be filtered by vendor and date information, such as identifying needed action for new purchases based on order start date. Grouping messages by vendor provides a convenient basis for communicating with each vendor.
Suggested action messages for production orders often require analysis to understand the rationale behind the suggestion or to assess the situation in more detail. For example, the user may need to review information about the item s supply/demand schedule, order-dependent bill and routing, or planning data. Analysis of a message concerning a production order can lead to one or more actions that can be implemented from the planning worksheet. Examples of taking action include:
Changing and refreshing a production order. Changes to order quantity and due date, or assigning a different version of the master or routing, require a refresh process for the production order.
Manually scheduling an existing production order. A production order can be manually scheduled when an operation in the order-dependent routing has been flagged as manually scheduled.
Reserving component material.
Inflexibility to make change. An existing production order line item can be flagged as having no planning flexibility, thereby suppressing further suggested action messages.
The ability to suppress unnecessary action messages makes the planning worksheet a better communication tool. For example, messages about rescheduling slightly later or changing quantity to slightly less can be suppressed using manufacturing setup policies about message dampeners.
Implementing Suggested Action Messages Messages can be automatically implemented based on the accept action message flag and the user-initiated process to carry out action messages. In many cases, suggested messages further out in the planning horizon should be deleted or not accepted to avoid inadvertent implementation. For example, creating production orders and purchase orders prematurely can lead to unnecessary rescheduling messages.
Implementation of suggested messages can be performed for all types of orders or just a selected type such as production orders. Implementation also supports copying the suggestions for purchase orders and transfer orders to the requisition worksheet (for a specified template name). The suggested action messages for new production orders are typically accepted and carried out to create planned orders so that capacity requirements can be generated. The next planning calculation run deletes the planned orders.
Some manufacturing environments involve purchases of outside operations. The subcontracting worksheet displays suggestions for new purchases of outside operations for released production orders. It also provides the only method to create a purchase order for an outside operation. Chapter 6 described use of the subcontracting worksheet.
The production order routing data provides the basis for analyzing work center loads to identify overloaded periods. Period size can be monthly, weekly, or daily, representing the range of aggregate to detailed analysis. The load analysis provides drill-down to the production order operations, so that load adjustment decisions can be made. Aggregate load analysis can also be viewed for a work center group.
The load analysis for a capacity-constrained work center can also identify overloaded periods and production orders that will be completed late as a result of the finite scheduling viewpoint.
The production order routing data provides the basis for creating a production schedule by work center. The production schedule identifies each production order s routing operations performed in the work center. It consists of the same information as the load analysis drill-down but is presented in a format more appropriate for communicating the needed action. Production schedules can be displayed in different formats, such as tabular, Gantt chart, and schedule board.
A production schedule in tabular format identifies work center operations in a priority sequence with the hottest operations listed first. The simplest sequencing rule is based on operation start (or end) date and time. Operation information includes the remaining units and time and the units completed. It may include other information that proves useful to the planner or production personnel, such as the prior and next operation, the expected operation scrap percentage, and the operation description. Much of the information may be identified on a production order traveler , thereby minimizing the need for including it in the production schedule. Changes in the production schedule must be reflected in updated information about the affected production orders and their order-dependent routings, but this becomes cumbersome. Other production schedule formats make it easier to update this information.
There are several variations of a Gantt chart format for a production schedule. A simplistic format displays time along the horizontal axis and rows corresponding to production orders. It displays each production order as a bar, where bar length reflects the order s starting and ending date/time. A drag-and-drop feature performs the equivalent of manual scheduling of a production order (without changing bar length). A graphic load analysis may be displayed along the horizontal axis (e.g., for a bottleneck work center) to highlight overloaded periods and the impact of manual scheduling. Information about the affected production order(s) can be automatically updated.
Another format displays each operation within a production order as a bar, where bar length reflects each operation s starting and ending date/time. The drag-and-drop feature performs the equivalent of manual scheduling for an operation, with corresponding impacts on preceding and succeeding operations in the order-dependent routing. The rows in the Gantt chart display work centers so that an operation can be placed on a different work center. Information about the affected production order(s) and operations can be automatically updated.
The logic and capabilities underlying a Gantt chart production schedule can become very complex. For example, additional complexities include handling overlapping operations, concurrent operations, split operations, sequence-dependent setup times, and other advanced scheduling considerations. As a result of lean manufacturing practices the scheduling issues should become simpler, and a production schedule can be modeled as a simple schedule board.