4QA3 F12 Week 10 Lecture Notes

Gandomi 21 item clipboard lot size l4l llc 0 period lt

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Unformatted text preview: andomi 20 Master Production Schedule 1 3 4 5 85 Clipboard 2 95 120 100 100 Item Master File Clipboard On hand On order Rivets 25 175 (Period 1) 150 0 0 L4L 1 1 Multiple of 100 1 (scheduled receipt) LLC Lot size Lead time 4QA3 F12 A. Gandomi 21 Item: Clipboard Lot Size: L4L LLC: 0 Period LT: 1 1 2 3 4 5 95 120 100 100 Gross Requirements 85 Scheduled Receipts On- Hand inventory 25 175 115 Net Requirements Time- phased net req. Planned Order Releases 4QA3 F12 A. Gandomi 20 100 100 100 100 100 100 100 100 100 22 Item: Clipboard LOT SIZE: L4L LLC: 0 LT: 1 1 Planned Order Releases 2 Period 3 4 100 100 100 2 Period 3 4 200 200 200 50 50 150 200 50 150 150 200 50 50 150 5 x2 Item: Rivets Lot Size: Mult 100 Gross Requirements Scheduled Receipts On- hand inventory Net Requirements Time- phased net req. Planned Order Releases 4QA3 F12 LLC: 1 LT: 1 150 1 150 50 100 A. Gandomi 5 23 Item Clipboard Rivets 4QA3 F12 Period 1 2 3 4 5 100 100 100 100 200 200 A. Gandomi 24 ●  The simplest lot sizing scheme for MRP systems is lot- for- lot. This means that the number of units scheduled for production in each period is the same as the time- phased net requirements for that period. ●  However, more cost effective lot sizing plans are possible. These would require knowledge of the cost of setting up for production and the cost of holding each item. 4QA3 F12 A. Gandomi 25 ●  Assume there is a known set of requirements (r1, r2, . . . rn) over an n- period planning horizon. Both the set up cost, K, and the holding cost, h, are given. ●  The objective is to determine production quantities(y1, y2, . . ., yn) to meet the requirements at minimum cost. ●  The feasibility condition to assure there are no stockouts in any j j period is: ∑ yi ≥ ∑ ri for 1 ≤ j ≤ n i =1 ●  i =1 Property of the optimal solution: every optimal solution orders exact requirements, that is, y1 = r1 4QA3 F12 or y1 = r1 + r2 A. Gandomi or y1 = r1 + r2 + ... + rn 26 ●  The lot sizing problem can be represented as a network, where each node i represents a period. An arc from node i to node j represents the fact that we order (or produce) in period i to cover requirements in periods i, i+1, …, j−1. 1 6 2 5 3 4QA3 F12 4 A. Gandomi 27 1 6 5 2 3 4 •  Interpretation: Order (or produce) in periods 1, 3, and 4, so y1 = r1 + r2 ; y2 = 0; y3 = r3; y4 = r4 + r5 ; and y5 = 0. 4QA3 F12 A. Gandomi 28 ●  The cost cij of reaching node j from i is the cost of ordering in i but not in i+1, i+2, …, j−1: cij = K + h ( ri+1 + 2 ri+2 + 3ri+3 + ... + ( j − 1 − i)rj−1 ) ●  Finding the minimum cost solution is equivalent to 8inding the least costly path (short...
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This document was uploaded on 04/01/2014.

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