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eBook: Production-Activity-Control — $3.00
PRODUCTION ACTIVITY CONTROL (Sample of Full-Text)
OverviewPAC, Production Activity Control, is concerned with converting plans into action, reporting the results achieved, and revising plans and actions as required achieving desired results. Thus, PAC converts plans into action by providing the required direction. This requires the appropriate prior master planning of orders, work force personnel, materials, and capacity requirements.
While there are better methods available via JIT and other strategies, PAC is an essential system for managing in relation to specific orders that must be properly launched, when material and labor resources, and equipment are properly timed to be delivered or allocated for the completion of those orders. There is no such thing as a “late or past due” order. There is only correct planning and poor planning. The date of an order that cannot be completed simply has the wrong completion date. At this level, errors are due more to improper long-range and mid-range planning. The availability of resources in the short-range is only possible via proper management of the tasks prior to starting the job.
Order release, dispatching, and progress reporting are the three primary functions of PAC. Dispatching is the activation of orders per original plans. Dispatching decisions are affected by queue management, I/O control, and priority control principles and techniques that are intertwined and mutually supportive. They are useful in the management of lead-time, queue length, work center idle time, and scheduled order completion. Reports on the status of orders, materials, queues, tooling, and work center utilization are essential for control. Many report types with various information are possible. Examining a given situation will reveal which reports and information are required.
The time arrives when plans must be executed, when material requirements planning and capacity requirements planning have been completed and the detail purchasing and production schedules must be determined and released for execution. The function of production activity control (PAC)--often called shop floor control (SFC)---is to have activities performed as planned, to report on operating results, and to revise plans as required to achieve desired results. Figure 1 shows the sequence of the various planning and control activities.
The PAC system also closes the control loop, as illustrated in Figure 6, by measuring actual output and comparing it to the plan Thus, PAC is an essential component of closed-loop MRP. Although all PAC Systems perform the same basic functions, individual systems differ because each manufacturing environment is unique. Each has a specific number of products, production processes, facility layouts, and relationships of available capacity of personnel and equipment to the required capacity.
SCHEDULING IN MANUFACTURING ENVIRONMENTS
The Master Scheduling Section described different types of production environments: continuous and repetitive flow lines, batch flow lines, manufacturing cells, job shop, and project (fixed site) processes. Each environment is distinctive. Scheduling continuous and repetitive flow lines is discussed in the Section on JIT: Just-In-Time & TQC: Total Quality Control.
Scheduling for Batch Flow Lines
Batch flow lines exist in beverage companies, ice cream manufacturers, soap powder packaging facilities, and pharmaceutical plants. Typically, a group of similar items is manufactured on the batch line. A family of items may be produced in batch quantities on the same line with some changes in the setup, a cleaning of the equipment, and changes in incoming materials. (If no time is required for switching from one item in the family to another, then the different items can be mixed in the same run and a mixed model line exists.) Thus, a primary production management objective is to reduce and eventually eliminate the time required for changing between items in a group. The smaller the changeover time, the greater the scheduling flexibility and the smaller will be the scheduling problem.
The quantity of an item produced depends on that item's production rate and the length of time it is run. Deciding the item to be run next and the quantity to be run depends on the following factors:
A. The on-hand (available) quantity of each item
B. The demand rate of each item
C. The times required to change between different items
D. The production rate of each item
F. The sequence, if any, in which items should be run
When the setup (changeover) times are relatively small and independent of the sequence in which the items arc produced, the decision is relatively simple: the item with the smallest runout time is run first.
Runout time is the period existing inventory will last given forecast usage. For example, if a company uses (or sells) 20 printed circuits (Part No. 101) each day and has 80 of them in stock, the runout time of Part. No.101 is four days. Runout time (R) is calculated as follows:
R = Units in Inventory
Demand (Usage) RateIf the setup times for the items in a group are relatively short and the production lot quantities are small due to relatively low demand rates and low setup costs, there is no problem. Sufficient time usually will exist to manufacture all items on schedule.
Let's look at another example. Assume we have a table of run out times for three machined parts made on the same machine, a traditional machine tool with a larger setup time and corresponding larger production quantities.
The company has a problem. Items A, B, and C should be run immediately. Some of these items should have been manufactured last week. The purpose of this example is to point out that:
A. Manufacturing engineering should reduce the setup times and, thus, improve the production run quantities and time. A computer numerically controlled, (CNC), machine that can shift from one part to another with little or no setup time may be appropriate.
B. Proper timing of order releases is as important as the quantity decision,
In addition, the appropriateness of a model depends on the situation. Order quantity and order release decisions are more complicated when more than one group is run on the same equipment, when capacity is limited, or when items in a group must be run in a particular sequence to achieve minimum changeover times (for example first Item A, then B, C, and so on).
When sufficient inventory is available, personnel may be used for preventive maintenance, methods analysis, and setup time reduction to reduce lead time and improve quality rather than to produce unneeded parts. (These topics are discussed further in Section on JIT: Just-In-Time & TQC: Total Quality Control as part of Just-in-Time concepts.)... (there's much more!)
eBook: Production-Activity-Control — $3.00
