Page 82 - Mechatronics for Safety, Security and Dependability in a New Era

Ch14-I044963.fm Page 66 Tuesday, August 1, 2006 12:50 PM
Ch14-I044963.fm
66 66 Page 66 Tuesday, August 1,2006 12:50 PM

3.4 Implementation

This proposed workplace tasks design support system is developed based on Jack in this study.

4. CASE STUDY

4.1 Test case
Figure 4 shows a test case. A worker sets a main part on a pallet, and then assembles a part A on it
with a screw B, and a part C. After assembling, the worker flicks the switch in order to move the pallet
to the next process. The initial plan of that process is shown in the left picture in figure 4. The
improved plan has five differences including the positions of the box for main parts, the box for
screws B, the box for parts C, the screwdrivers, and the switch. Also the sequence of assembling a part
A is changed to after a part C. The right picture in figure 4 shows this improved plan.

Initial plan Improved plan
m
• Screwdriver!

i part|-
(Cycle Time 15.3 sec.) (Cycle Time 12.1sec.)

Figure 4: Test result

4.2 Test result
By building simulation models of the initial plan and the improved plan, it becomes clear that the
improved plan shortens worker's operation time by 3.2 seconds. Through this case, time taken for
remodeling the initial plan into the improved plan is compared between the cases using the original
Jack and the developed system. The result is that the original Jack took 8.0 hours, and the developed
system took 0.4 hours. The developed system can remodel the simulation plan more than 10 times as
fast as the original Jack.

5. CONCLUSION

This study shows that remodeling time, which consists of the time to teach 3-D computer mannequins
and the time to move 3-D objects, can be reduced dramatically by reusing the recorded status-
generating procedure. The proposed workplace tasks design support system provides easier and
quicker remodeling for planning manual operation processes than conventional simulation systems.

6. REFERENCES
Maynard H. B., et al. (1948), Methods-time measurement, New York, McGraw-Hill Book Co., USA.