Intended learning outcomes: Present an example of a rough-cut network plan with two rough-cut work centers. Explain the resource profile of both rough-cut work centers as well as the resource profile for the combination of the two rough-cut work centers.
The rough-cut process plan for a product is the rough-cut production structure along the time axis.
Section 1.2.5 introduced rough-cut bills of material and rough-cut routing sheets. These are either derived from the detailed structures of a product or determined and maintained “manually.” These rough-cut structures allow us to derive a rough-cut process plan with lead-time setoff for components or operations. As Section 13.3.3 also shows, a rough-cut process plan can easily form a directed network of operations.
Figure 14.4.1.1 shows a production order in a form similar to the familiar network plan. Rough-cut order structures are often represented in this way. In our example, we have combined the work centers into two rough-cut work centers.
Fig. 14.4.1.1 Rough-cut network plan with two rough-cut work centers.
A resource profile is essentially a load profile, that is, standard hours of load placed on a resource by time period, for rough-cut capacity planning.
Figures 14.4.1.2 and 14.4.1.3 show the resource profile derived from the rough-cut process plan or from the rough-cut network plan. Figure 14.4.1.4 shows how they are combined to form a single rough-cut work center.
Fig. 14.4.1.2 Resource profile of rough-cut work center 1 as shown in Fig. 14.4.1.1.
Fig. 14.4.1.3 Resource profile of rough-cut work center 2 as shown in Fig. 14.4.1.1.
Fig. 14.4.1.4 Resource profile for the combination of rough-cut work centers.
For the sake of simplicity, in rough-cut planning we can regard the load as a rectangular distribution over the duration of the process. Indeed, this interpretation is also common in detailed planning.
If we chose the technique shown in Section 1.2.5, using lead-time setoff as the data structure behind the resource profile, we lose the typical information concerning operations before and after each operation in the network. Keeping the information in the data model is conceivable, however, and it would make the load and adjustment algorithms more flexible. However, the algorithms would also be more difficult to implement, which could result in longer response times.
Rough-cut planning is extremely interactive, that is, it requires the planner to intervene and make decisions. It is not surprising, therefore, that rough-cut planning often works using the simplest data models, that is, ignoring the interdependencies among operations.
The problem of taking account of demand derived from bids, described in Section 5.2.1, also arises in rough-cut capacity planning. Regardless of whether we are planning for limited or infinite loading, the procedure to deal with this problem entails the following steps:
- The simplest method multiplies the product load profile by the probability of order success (“devalues” it) and thus loads only the resulting reduced load. Validation of the order success probability is a key factor here.
- Bids must be confirmed at an early stage or must be unloaded in order to make room for orders requiring definitive planning. The bid should therefore be assigned an expiration date. From that date on, we designate the bid as inactive or defer the promised delivery date by a sufficient number of periods.
- If a very large number of bids have already been planned, it will be difficult to assign a reliable delivery date to new bids. The completion date determined in planning is only a possible completion date. Additional information is required, such as a “maximum” completion date, for example, which is calculated assuming that all bids (or a significant proportion thereof) will be accepted. We do this by adding together the unloaded portions of the bids after calculating the probability, and dividing this figure by the capacity available per period. This gives the number of periods that must be added to the probable date in order to arrive at the “maximum” date.
Course section 14.4: Subsections and their intended learning outcomes
14.4 Rough-Cut Capacity Planning
Intended learning outcomes: Describe rough-cut network plans and load profiles. Explain rough-cut infinite loading and rough-cut finite loading.
14.4.1 Rough-Cut Network Plans and Load Profiles
Intended learning outcomes: Present an example of a rough-cut network plan with two rough-cut work centers. Explain the resource profile of both rough-cut work centers as well as the resource profile for the combination of the two rough-cut work centers.
14.4.2 Rough-Cut Infinite Loading
Intended learning outcomes: Present an example of a resource profile for one rough-cut work center. Describe the result of rough-cut capacity planning with deferred completion date.
14.4.2b Rough-Cut Infinite Loading — Example with two Rough-Cut Work Centers
Intended learning outcomes: Explain rough-cut capacity planning with two rough-cut work centers and the result after moving the completion date of one operation.
14.4.3 Rough-Cut Finite Loading
Intended learning outcomes: Present the cumulative resource profile of an order as well as cumulative load and capacity before loading the order. Explain rough-cut planning of the cumulative load and capacity after loading the order.
