Page 231 - Mechatronics for Safety, Security and Dependability in a New Era

Ch44-I044963.fm Page 215 Tuesday, August 1, 2006 4:00 PM
Tuesday, August
1, 2006
Page 215
4:00 PM
Ch44-I044963.fm
215
215
4. ABC BASED APPROACH
As a first algorithm of cost based scheduling, we propose an ABC based approach. We tend to the
practicality and global improvement of cost structure rather than the optimality.
We focus on three types of simple dispatching rules, named EDD (Earliest Due Date), SPT (Shortest
Processing Time) and HC (Highest Commonality). HC is our original rule. Under this rule,
materials which have higher commonality for the products are granted higher priority. Simulation
for term ti is performed three times applying each rule (shown as Step 1 in Figure 3). Then,
product costs are estimated for each trial with ABC and the rule which produces with the minimum
cost is selected as the scheduling rule for term ti (shown as Step 2 and 3 in Figure 3). Those
procedures are iterated for all over the scheduling term.
Step! Step 3
Simulation Applying Each Rule Analysis with ABC Rule Selectio
(a)S123,456
M (b)S124,879
HDD (c) $134,586
SPT
(c)
HC
Figure 3 Concept of Proposed Method

Table 1 List of Objective Costs
Cost Name Cost Driver 1 Cost Driver 2 Charge Rate
Depreciation Cost A Utilization Time 100,000(Yen/Month)
Depreciation Cost B Utilization Time 150,000(Yen/Month)
Depreciation Cost C Utilization Time 500,000(Yen/Month)
Stock Cost A 3,000(Yen/Month)
Stock Cost B 8,000(Yen/Month)
Indirect Energy Cost Utilization Time Processing Time 100,000(Yen/Month)
Indirect Labor Cost Processing Time Processing Time 750,000(Yen/Month)
Material Cost 100(Yen/Each)
Penalty for Tardiness 10( Yen/Minute)
Direct Energy Processing Time 10( Yen/Minute)
Setup Cost 50(Yen/Each)

4.1. Experiments 1
We have simple experiments with the DVF to investigate the effectiveness of the proposed method
and the effectiveness of dispatching rules for product cost. The proposed method is implemented in
processing A and B. Experiments conditions are following.
1. Total scheduling period is 6 days.
2. Term of rule selection (shown as tl in Figure 3) is 2 days.
3. Order amount for day 1 and 2 makes utilizations of facilities about 85%.
4. Order amount for day 3 and 4 is 10% higher than that of day 1 and 2.
5. Order amount for day 5 and 6 is 10% lower than that of day 1 and 2.
4.2. Results of Experiments I
Product cost at 4 areas, such as, Processing A, B, Assembly Line and Storages, for day 1 and 2 are
shown in Table 2. At first, we decided HC as the dispatching rule for day 1 and 2, since HC
produces in the lowest cost. However, HC is the best rule only for Processing B and it is also the