Every company has to compete each others to
survive in their business world. One of the ways is to
reducing the expense cost. A good scheduling can
minimize it, because production time equals with
production cost. If production takes long time to be
done, the production cost needed will be higher. So
the scheduling which can minimize makespan is needed.
Finding the effect of lot size and product structure
on makespan minimization in multilevel product
scheduling becomes the main theme of this research
that is included in the long term research project of
The Production System Laboratory of Universitas Atma
Jaya Yogyakarta.
There are some data used in this research, those
are product structure (BOM), lot size, setup time, and
run time. Product structure used is 4 level of product
structure with maximum number of parts are 4 in each
level where the combinations of product structure forms
are generated to fulfill that consideration. Number of
item produced is 45 and lot size evaluated are 5, 9,
15, and 45. Setup time is randomly generated by random
number that is varied from 5 to 10 minutes/lot, and run
time is varied from 1 to 5 minutes/unit. Optimum lot
size is lot size decision giving the minimum makespan.
Gantt chart is simulated to obtain the makespan each
product structure, lot size and replication. Optimum
lot size will be evaluated using ANOVA single factor.
Based on Gantt chart simulation, there is minimum
makespan for each lot size, product structure and
replication. Optimum lot size resulted is lot size 9
and 15. Based on ANOVA single factor result, the
conclusion is product structure complexity does not
significantly affect the optimum lot size.