Agility perspective

The agility perspective deals with the rapid adaption of the process to changes in customer demand and the business environment. This means that the production schedule must be flexible in order to create value even when variation in customer demand occurs. The production schedule must let work flow through the process in accordance to a pull system that provides value when it is required by the customer.

Phase 1: Continuous flow

Continuous flow, also called one-piece flow, is the rapid and uninterrupted step-by-step movement of material or information through a system with minimal delays and the shortest travel distance. Continuous flow aims to increase value added activities and production throughput, but it also forces problems to the surface in order to improve the process and develop the people. Although flow is not always practical because of variation in the process and demand, it provides many opportunities for improvement.

There are several advantages to continuous flow. First, defects are easier detected and fixed in smaller batches. Second, processes are more flexible because of shorter lead times. Third, operations are pushed together to improve floor space utilisation and encourage waste elimination. Fourth, employee morale increases because of transparent operations and visible improvement. Fifth, standard procedures and an organised environment reduce the likelihood and severity of hazardous occurrences.

Phase 2: Load levelling

Level the workload over a period of time, rather than to produce output in relation to the actual fluctuation of customer demand. This is important because customers do not submit orders for specific batch sizes, even though batch production is the norm, and variation of customer demand causes overburden and unevenness. Overburden is the assignment of unreasonable stress or effort to a person, piece of equipment, or machine. Unevenness is the presence of variation that leads to unbalanced situations.

Production of smaller batches that are aligned with actual customer consumption must be considered when one-piece flow is not practical. This approach should focus on a levelled production volume and mix in order to level out the total demand on people, equipment, and suppliers. The three inputs to considered for a levelled schedule are built-to-stock, built-to-order, and the amount of buffer stock required to maintain the constraint. Note that single minute exchange of die is crucial for this to be successful.

Chapter 6 The theory of perspective Industrial Engineering Page 163 Phase 3: Drum-buffer-rope method

The drum-buffer-rope method has two functions. First, work flow is regulated through the constraint in order to produce what is needed, when it is needed; understand that this pull system is contrast to the push system, which releases work into the process as demand is predicted or as work becomes available. Second, non-constraints are subordinated to the constraint in order to create value, even when variation is present.

The drum is the capacity constraint of the process, which provides a beat (cycle time) to which other operations can be subordinated. Subordination is important to ensure that the constraint always operate at or near full capacity, because an hour lost at the constraint is an hour lost for the total system. The drum also provides the opportunity for a visual control point that can be used to focus improvement activities and also to maintain a levelled production schedule in order to ensure consistent process output.

The buffer is used to compensate for process variation. This buffer is measured in units of time, which schedule material release; material is released into the system at fixed time intervals in order to arrive at the constraint some period of time prior to its scheduled start. A second buffer is also used between shipment and the constraint in order to create a control point for a levelled work schedule. Furthermore, when the process is unstable a protective buffer (Kanban) can be placed in front of the constraint.

The rope is a signal that is generated, when there is a pull from the customer, in order to communicate and schedule the release of work into the process at a certain time as dictated by the buffer; the kanban pull system is analogous to a series of short “ropes”. A larger buffer can therefore be used to release work into the process earlier than required in order to compensate for variation between operations. This subordinated schedule ensures flow, without the accumulation of excess inventory.

The drum-buffer-rope method is used to release material into the process, at fixed time intervals, with the amount of work that the customer requested. This creates an unbalanced production line, which allows non-constraints to ensure smooth operation of the constraint even in a system with high variation and product mixes. This method is opposite to the inventory based kanban pull system, but the kanban system is still useful when the process is unstable. However, a large kanban is considered a waste.

Chapter 6 The theory of perspective Industrial Engineering Page 164