WIP Data for Operations with Continuous Input or Output
WIP Data for Operations with Continuous Input or Output
Use
In the Enhanced view of the evaluation
WIP list (network) the system also calculates WIP data for operations that produce or consume material at a constant rate (operations with continuous output or input).Features
Below you will find a description of how the system calculates WIP data for the simplest case, in which the total material quantity that an operation needs and continuously consumes, is continuously provided by exactly one operation.
The system uses the following data for the calculations:
The system uses these dates and the total quantity to determine the temporal development of the transferred material quantity; that is, of the total quantity that the operation produces as planned up to a specific point in time and has transferred to the consuming operation. Before the transfer starts, the transferred quantity is zero; the operation has not yet transferred a material. Between the start and end date, the transferred quantity increases uniformly to the total quantity. (The system assumes that the operation transfers the material continuously even in non-working times). At the end date, the operation has transferred the total quantity. As of this point in time, the entire quantity transferred is constantly the same as the total quantity.
The system uses these dates and the total quantity to determine the temporal development of the consumed material quantity; that is, of the total quantity that the operation has consumed as planned up to a specific point in time. Before the consumption starts, the consumed quantity is zero; the operation has not yet consumed a material. Between the start and end date, the consumed quantity increases uniformly to the total quantity. (The system assumes that the operation consumes the material continuously even in non-working times). At the end date, the operation has consumed the total quantity. As of this point in time, the entire quantity consumed is constantly the same as the total quantity.
The system determines the WIP curve from the temporal curves of the transferred and consumed quantity. The WIP curve displays the difference between the entire transferred quantity and the entire quantity consumed for each point in time. The curve depends on
The curve values can be positive and negative. Positive values indicate that the material was completed but has not yet been processed further. Negative values indicate missing material. This case occurs, for example, if the consuming operation needs material earlier or consumes it faster than it was provided by the producing operation. Negative values are also a sign of inconsistent planning.
The system shows the following data in the WIP evaluation:
The WIP area is the area under the WIP curve.
The WIP time is the quotient from the WIP area and the total quantity.
Similarly, the system carries out the calculation of the WIP data in the general case, if several operations, which are continually producing or consuming, are involved in the material flow. The system breaks down the WIP data here, corresponding to the partial quantities that flow between a producing and a consuming operation respectively. You differentiate between the following cases:
The system assumes that the operation that is continuously producing firstly delivers the consuming operation, which has the earliest start date for material consumption. When this operation has received the total quantity required, the producing operation delivers the material to the next consuming operation, and so on.
The system assumes that the consuming operation firstly consumes the material of the operation, which has the earliest start date for material transfer. If this material is consumed, the consuming operation consumes the material that is provided by the next producing operation, and so on.
In the WIP evaluation, the WIP data refers in these cases to the partial quantity of the material that is transferred from a producing operation to a consuming operation. The WIP times are determined by the partial quantities and by their availability dates or requirement dates.