hospital in Semarang to get an optimal lot size for the
drugs categorized as a deathstroke-return. Another
study also conducted by Ludmila et.al (Dawidowicz
and Postan, 2016) with the problems of perishable
products subject to deterioration during warehousing.
Analyzation and controlling a perishable product to
maintain size of inventory to minimizing the total
cost. The same study also conducted by Dalfard and
Nosratian (Dalfard and Nosratian, 2014) described a
pricing constrained single-product and inventory-
production model in perishable food with
deterioration rate to maximizing the total profit.
However, studies on perishable inventory issues
has been done before did not consider the total cost
incurred by the producer in optimizing the delivery
and this study aims to optimize the number of
delivery with the consideration of total cost producer
and expired products become reduced.
2 METHODOLOGY
The research was conducted on one of the industries
producing perishable products in the form of cakes
with various types. The object in this study is the total
of expired products produced on SMEs. The research
begins by making observations directly to SMEs to
see the conditions existing in the SMEs. By making
observations, will be obtained problems occurs in
SMEs and will be determined Formulation of the
problem according to the real condition.
Based on the formulation of the problem,
determined the purpose of research as a solution in
analyzing and handling these condition. Next stage,
problem solving using supporting data as an input in
problem solving. The data used in handling the
problem of products number expired and high cost of
returns in the form of the request numbers per
product, product capacity, delivery frequency,
product purchasing price, ordering costs, delivery
costs, storage costs, and expired costs.
Based on these data, calculates the optimal
number of delivery by considering the total cost
producer and the number of expired products to be
reduced. The calculation of the optimal number of
delivery is done by several stages. The first stage is to
calculate the aggregate demand. The aggregate
demand is obtained by determining the conversion
factor first. The conversion factor is determined by
looking at the minimum raw material requirements in
producing at each product.
After obtaining the number of demand in
aggregate units, the next step is to determine the total
delivery. Total delivery can be obtained by
determining the time interval and the size of the
finished pr/duct delivery lot first. The time interval is
obtained from the ratio between the planning cycle
(T) and the delivery frequency (n). The time interval
calculation can be done using the formula (Rau, etc,
2004):
Time Interval (t) =
T
n
(1)
And the calculation of lot size in finished product
delivery is done by using formula:
Delivery Lot Size(q
B
) =
D
θB
[e
θBt
-1]
(1)
D is a product demand for a month while "θB"
represents the rate of damage to the finished product
to the consumer. Based on these two formulas, we
will get the total delivery at each delivery frequency
by multiplying the delivery time interval which is
obtained by the size of the finished product delivery
lot.
The next step is to calculate the producer’s total
cost. This calculation is done to determine the total
cost expenses due to many expire products and done
immediately. Calculation of total cost of producer is
done by using the formula:
Total Cost Producer = Setup Cost +
Delivery Finished Product Cost + Storage
Finished Product Cost + Expired Cost of
Produce
(1)
Setup cost is the cost expenses when an order is
filed with the formula. Delivery cost is the cost
expenses when the finished product is delivered to the
consumer. Storage costs represent expenses for
maintenance purposes, rental of premises, or
insurance cost on products / raw materials available.
And expired cost is the cost expenses because the
products passed the life already (Limansyah and
Lesmono, 2011). Based on the value at each cost, the
total cost will be obtained for the producer and the
total optimal product delivery determined by
considering the minimum total cost of producer.
3 RESULT AND DISCUSSION
3.1 Aggregate Demand
Calculation of aggregate demand is done by
determining the convection factor first. Based on the
raw materials needed to produce each product, it is
found that brownies products have the minimum
requirement of raw material among other products