Hv. Kher et al., The effect of push and pull lot splitting approaches on lot traceability and material handling costs in stochastic flow shop environments, INT J PROD, 38(1), 2000, pp. 141-160
This study evaluates how the procedures followed in splitting job lots on t
he shop floor influence both material handling and lot integrity in stochas
tic flow shop environments. Former work has shown that lot splitting improv
es flow time and customer service performance, but with an increased number
of transfers along with a corresponding increase in material handling cost
s. Physical lot integrity. which is important to lot tracing, has not been
considered in prior literature. In order to overcome these limitations and
address material handling concerns better, we define a new measure of perfo
rmance called the lot integrity loss exposure (LILE). We use this and other
measures to show that the traditional 'push' approach that has been follow
ed in modelling lot splitting complicates lot traceability in the shop and
leads to an excessive number of transfers. As an alternative. we propose a
'pull' approach in which an order is split between any successive pair of m
achines only on an as-needed basis. The push and pull approaches for lot sp
litting are compared under a range of conditions characterized by factors s
uch as machine utilization levels within the shop, setup-to-processing time
ratios, and number of splits created in job lots. Our results indicate tha
t relative to the push approach, pull lot splitting helps significantly in
reducing the number of transfers incurred and in maintaining a greater degr
ee of physical lot integrity. At the same time, there is no significant dif
ference in the two approaches with respect to improvements in flow time and
customer service measures. Both the degree to which lot integrity is prese
rved, and the extent of savings in material handling that result from using
the pull approach, are shown to be most pronounced under conditions charac
terized by high machine utilizations rates and setup-to-processing time rat
ios. Managerial implications of our study along with further research direc
tions in this area are also discussed.