Activity 1: the spindle housing’s record
Chapter 6, session 1. Work in pairs. 14 minutes.
Names: ______________________________________________
The item. The spindle housing (H) from the mower deck structure. Its lead time is 2 periods. There are 45 on hand at the start of period 1, and a scheduled receipt of 40 is due in period 2. The planner holds a safety stock of 10. Order lot-for-lot.
Conventions. Projected on hand is an end-of-period figure. A net requirement is never negative. A release sits in the period its receipt is due, less the lead time. A release that would fall before period 1 is past due: write its receipt in the planned order receipts row and count it in projected on hand as if it arrives, but leave the release out of the release row and report it below the record.
Notation. For period \(t\): \(G_t\) is the gross requirement, \(SR_t\) the scheduled receipt, \(I_t\) the projected on hand at the end of the period (\(I_0\) is the opening stock, 45 here), \(NR_t\) the net requirement, \(POR_t\) the planned order receipt and \(Rel_t\) the planned order release. \(SS\) is the safety stock and \(L\) the lead time, in periods.
\[ I_t = I_{t-1} + SR_t + POR_t - G_t, \qquad NR_t = \max(G_t + SS - SR_t - I_{t-1},\ 0), \qquad Rel_{t-L} = POR_t \]
Part A. Complete the record
| Period | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|---|
| Gross requirements | 20 | 35 | 0 | 50 | 30 | 0 | 60 | 25 | |
| Scheduled receipts | 0 | 40 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Projected on hand | 45 | ||||||||
| Net requirements | |||||||||
| Planned order receipts | |||||||||
| Planned order releases |
Check: opening stock + scheduled receipts + planned receipts = total gross requirements + ending on hand. Does yours balance? ______
Part B. The receipt is late
The supplier calls: the 40 housings will arrive in period 4, not period 2. Complete the record again.
| Period | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|---|
| Gross requirements | 20 | 35 | 0 | 50 | 30 | 0 | 60 | 25 | |
| Scheduled receipts | 0 | 0 | 0 | 40 | 0 | 0 | 0 | 0 | |
| Projected on hand | 45 | ||||||||
| Net requirements | |||||||||
| Planned order receipts | |||||||||
| Planned order releases |
How many units are past due, and in which period are they needed? How many of them are an outright shortage, and how many only restore the safety stock? What should the planner do about it?
Part C, if you have time. A fixed order quantity
Back to Part A’s data. Now every planned receipt is 80, or the net requirement if that is larger. (The scheduled receipt of 40 is unchanged.) Complete the record.
| Period | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|---|
| Gross requirements | 20 | 35 | 0 | 50 | 30 | 0 | 60 | 25 | |
| Scheduled receipts | 0 | 40 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Projected on hand | 45 | ||||||||
| Net requirements | |||||||||
| Planned order receipts | |||||||||
| Planned order releases |
Compared with Part A: how many orders, and what is the sum of the projected on-hand row?
Part D, if you have time. Without the safety stock
Without doing the whole record again: which rows of Part A change if the safety stock is removed, and by how much?
Exit ticket (tear off and hand in)
Name: ____________________
- In one sentence: what does the \(\max\) in the net requirement stop from happening?
- Next time we plan the housing’s parent first. Which of the parent’s rows do you think becomes the housing’s gross requirements?