A decision model for selecting parts feeding policies in assembly lines
| DOI | https://doi.org/10.1108/IMDS-02-2015-0054 |
| Pages | 974-1003 |
| Published date | 13 July 2015 |
| Date | 13 July 2015 |
| Author | Antonio C. Caputo,Pacifico M. Pelagagge,Paolo Salini |
| Subject Matter | Information & knowledge management,Information systems,Data management systems |
A decision model for selecting
parts feeding policies
in assembly lines
Antonio C. Caputo
Department of Engineering, University of Roma Tre,
Rome, Italy, and
Pacifico M. Pelagagge and Paolo Salini
Department of Industrial Engineering, Information and Economics,
University of L’Aquila, L’Aquila, Italy
Abstract
Purpose –The purpose of this paper is to develop an optimization model allowing the choice of parts
feeding policy to assembly lines in order to minimize total cost.
Design/methodology/approach –An integer linear programming mathematical model is developed
to assign the optimal material feeding policy to each part type. The model allows choice between
kitting, line stocking and just in time delivery policies.
Findings –The choice of assembly lines feeding policy is not trivial and requires a thorough economic
comparison of alternatives. It is found that a proper mix of parts feeding policies may be better that
adopting a single material delivery policy for all parts.
Research limitations/implications –The model is aimed at single-model assembly lines operating
in a deterministic environment, but can be extended to the multi-model line case. While relevant
quantitative cost drivers are included, some context-related qualitative factors are not included yet.
The model assumes that information about product structure and part requirements are known and
that a preliminary design of the assembly system has been carried out.
Practical implications –Production managers are given a quantitative-decision tool to determine
the optimal mix of material supply policies at an early decision stage.
Originality/value –Respect previous simplified literature models, this approach allows to quantify a
number of additional factors which are critical for successful implementation of cost-effective parts
feeding systems, allowing comparison of alternative policies on a consistent basis.
Keywords Cost estimation, Kitting, Assembly lines parts feeding, Just in time, Line storage,
Linear programming optimization
Paper type Research paper
Nomenclature
a
k
container base dimension, first
direction (m);
b
k
container base dimension, second
direction (m);
c
k
container vertical dimension (m);
C
c
container equivalent daily unit
cost (€/day);
C
E
equipments equivalent capital
cost (€/day);
C
FS
floor space unit cost (€/m
2
day);
C
M
personnel daily cost (€/day);
C
op
daily cost of a worker (€/day);
C
S
space occupation cost (€/day);
C
SRU
equivalent daily cost of storage
rack per unit volume (€/m
3
day);
C
std i
daily unit holding cost of ith
component (€/piece day);
C
V
daily equivalent vehicle unit cost
(€/vehicle day);
C
VMR
daily equivalent unit cost of
tugger train performing milk runs
(€/vehicle day);
Industrial Management & Data
Systems
Vol. 115 No. 6, 2015
pp. 974-1003
©Emerald Group Publishing Limited
0263-5577
DOI 10.1108/IMDS-02-2015-0054
Received 2 March 2015
Revised 28 April 2015
Accepted 7 May 2015
The current issue and full text archive of this journal is available on Emerald Insight at:
www.emeraldinsight.com/0263-5577.htm
974
IMDS
115,6
C
VRS
daily equivalent unit cost of
vehicle replenishing the
supermarket (€/vehicle day);
C
WIP
holding cost of the work in
process (€/day);
Ddaily demand for finished
products (units/day);
hdaily shift working hours (h/day);
knumber of operators to move a kit
or to transport a load to the line;
Llength of one-way transport route
from kitting department to line
start (m);
L
BWS
operator walking distance at the
workstation in case of line storage (m);
L
MR
average length of the milk run (m);
L
WH
average distance between
warehouse and supermarket (m);
L
WS
averagedistance of the workstation
from the warehouse (m);
L
WSK
operator walking distance at the
workstation in case of kitted
parts (m);
LT containers lead time in kanban
policy (h);
Mnumber of workstations;
Nnumber of different components
in a finished product;
n
cont kit,i
number of equivalent containers
in a kit required to hold
components of type i;
n
i
multiplicity of ith components
in a finished product;
n
ij
number of items iutilized at
station jper each unit of
finished product;
n
sl
number of stackable containers
on the shop floor;
Nop
Av
maximum available operators
number;
NS
i
number of workstations
utilizing part i;
p
i
weight of the ith component (kg);
p
max
maximum allowed weight of a
container (kg);
Qnumber of parts simultaneously
picked from a storage location in
the warehouse;
S
j, av
floor space available at
workstation j(m
2
);
S
KS
floor space available at first
workstation for kits storage (m
2
);
t
fr
time to fraction bulk component
cartons in warehouse (s/carton);
t
pb
time to pick a piece from bulk
container (s/piece);
t
pick
picking time for a single kitted
item (s/piece);
t
r/s
time to locate and reach
components in the warehouse
(s/part type);
v
i
volume of the ith component;
V
c
volume of a components container
(a
c
×b
c
×c
c
, being a
c
,b
c
,c
c
the
container dimensions) (m
3
);
V
k
volume of a kit container
(a
k
×b
k
×c
k
, being a
k
,b
k
,c
k
the
dimensions of the container) (m
3
);
V
O
operator walking speed (m/s);
V
V
transport vehicle velocity (m/s);
X
i,p
decision variable;
Z
i
equivalent number of parts that
can fit into a container;
α
ij
integer numer of containers of part
iat workstation j;
η
op
average workers efficiency;
ωnumber of containers transported
simultaneously; and
ω
WH
number of container
simultaneously moved from
warehouse to supermarket.
Indexes
icomponent index (1 to n);
jstation index (1 to M); and
ppolicy identifier.
1. Introduction
Design and managementof assembly lines requires decisionsabout the way components
and subassemblies are delivered to assembly stations. This issue attractedinterest from
academic researchers in recent times as reviewed by Kilic and Durmusoglu (2015) and
975
Parts feeding
policies in
assembly lines
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