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Int J Adv Manuf Technol (2005) 25: 551–559
DOI 10.1007/s00170-003-1843-3
ORIGINAL ARTICLE
S.H. Masood · B. Abbas · E. Shayan · A. Kara
An investigation into design and manufacturing of mechanical conveyors systems
for food processing
Received: 29 March 2003 / Accepted: 21 June 2003 / Published online: 23 June 2004
? Springer-Verlag London Limited 2004
Abstract This paper presents the results of a research investi-
gation undertaken to develop methodologies and techniques that
will reduce the cost and time of the design, manufacturing and
assembly of mechanical conveyor systems used in the food and
beverage industry. The improved methodology for design and
production of conveyor components is based on the minimisa-
tion of materials, parts and costs, using the rules of design for
manufacture and design for assembly. Results obtained on a test
conveyor system verify the bene?ts of using the improved tech-
niques. The overall material cost was reduced by 19% and the
overall assembly cost was reduced by 20% compared to conven-
tional methods.
Keywords Assembly · Cost reduction · Design · DFA · DFM ·
Mechanical conveyor
1 Introduction
Conveyor systems used in the food and beverage industry are
highly automated custom made structures consisting of a large
number of parts and designed to carry products such as food
cartons, drink bottles and cans in fast production and assembly
lines. Most of the processing and packaging of food and drink in-
volve continuous operations where cartons, bottles or cans are re-
quired to move at a controlled speed for ?lling or assembly oper-
ations. Their operations require highly ef?cient and reliable me-
chanical conveyors, which range from overhead types to ?oor-
mounted types of chain, roller or belt driven conveyor systems.
In recent years, immense pressure from clients for low cost
but ef?cient mechanical conveyor systems has pushed con-
veyor manufacturers to review their current design and assembly
methods and look at an alternative means to manufacture more
economical and reliable conveyors for their clients. At present,
S.H. Masood (u) · B. Abbas · E. Shayan · A. Kara
Industrial Research Institute Swinburne,
Swinburne University of Technology,
Hawthorn, Melbourne 3122, Australia
E-mail: smasood@swin.edu.au
most material handling devices, both hardware and software, are
highly specialised, in?exible and costly to con?gure, install and
maintain [1]. Conveyors are ?xed in terms of their locations and
the conveyor belts according to their synchronised speeds, mak-
ing any changeover of the conveyor system very dif?cult and ex-
pensive. In today’s radically changing industrial markets, there is
a need to implement a new manufacturing strategy, a new system
operational concept and a new system control software and hard-
ware development concept, that can be applied to the design of
a new generation of open, ?exible material handling systems [2].
Ho and Ranky [3] proposed a new modular and recon?gurable
2D and 3D conveyor system, which encompasses an open re-
con?gurable software architecture based on the CIM-OSA (open
system architecture) model. It is noted that the research in the
area of improvement of conveyor systems used in beverage in-
dustry is very limited. Most of the published research is directed
towards improving the operations of conveyor systems and inte-
gration of system to highly sophisticated software and hardware.
This paper presents a research investigation aimed at im-
proving the current techniques and practices used in the de-
sign, manufacturing and assembly of ?oor mounted type chain
driven mechanical conveyors in order to reduce the manufactur-
ing lead time and cost for such conveyors. Applying the con-
cept of concurrent engineering and the principles of design for
manufacturing and design for assembly [4, 5], several critical
conveyor parts were investigated for their functionality, material
suitability, strength criterion, cost and ease of assembly in the
overall conveyor system. The critical parts were modi?ed and
redesigned with new shape and geometry, and some with new
materials. The improved design methods and the functionality of
new conveyor parts were veri?ed and tested on a new test con-
veyor system designed, manufactured and assembled using the
new improved parts.
2 Design for manufacturing and assembly (DFMA)
In recent years, research in the area of design for manufacturing
and assembly has become very useful for industries that are con-
552
sidering improving their facilities and manufacturing methodol-
ogy. However, there has not been enough work done in the area
of design for conveyor components, especially related to the is-
sue of increasing numbers of drawing data and re-engineering
of the process of conveyor design based on traditional methods.
·
·
·
·
·
Emphasise standardisation
Use the simplest possible operations
Use operations of known capability
Minimise setups and interventions
Undertake engineering changes in batches
A vast amount of papers have been published that have investi-
gated issues related to DFMA and applied to various methodolo-
gies to achieve results that proved economical, ef?cient and cost
effective for the companies under investigation.
The main classi?cations of DFMA knowledge can be iden-
ti?ed as (1) General guidelines, (2) Company-speci?c best prac-
tice or (3) Process and or resource-speci?c constraints. General
guidelines refer to generally applicable rules-of-thumb, relat-
ing to a manufacturing domain of which the designer should
be aware. The following list has been compiled for DFM
guidelines [6].
These design guidelines should be thought of as “optimal
suggestions”. They typically will result in a high-quality, low-
cost, and manufacturable design. Occasionally compromises
must be made, of course. In these cases, if a guideline goes
against a marketing or performance requirement, the next best
alternative should be selected [7].
Company-speci?c best practice refers to the in-house design
rules a company develops, usually over a long period of time, and
which the designer is expected to adhere to. These design rules
are identi?ed by the company as contributing to improved quality
and ef?ciency by recognising the overall relationships between
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Design for a minimum number of parts
Develop a modular design
Minimise part variations
Design parts to be multifunctional
Design parts for multiuse
Design parts for ease of fabrication
Avoid separate fasteners
Maximise compliance: design for ease of assembly
Minimise handling: design for handling presentation
Evaluate assembly methods
Eliminate adjustments
Avoid ?exible components: they are dif?cult to handle
Use parts of known capability
Allow for maximum intolerance of parts
Use known and proven vendors and suppliers
Use parts at derated values with no marginal overstress
Minimise subassemblies
particular processes and design decisions. Companies use such
guidelines as part of the training given to designers of products
requiring signi?cant amounts of manual assembly or mainte-
nance. Note that most of the methodologies are good at either
being quick and easy to start or being more formal and quanti-
tative. For example, guidelines by Boothroyd and Dewhurst [8]
on DFA are considered as being quantitative and systematic.
Whereas the DFM guidelines, which are merely rules of thumb
derived from experienced professionals, are more qualitative and
less formal [9].
3 Conventional conveyor system design
Design and manufacturing of conveyor systems is a very com-
plex and time-consuming process. As every conveyor system is
a custom-made product, each project varies from every other
project in terms of size, product and layout. The system design
Fig. 1. Layout of conveyor sys-
tem for labelling plasic bottles
553
is based on client requirements and product speci?cations. More-
over, the system layout has to ?t in the space provided by the
company. The process of designing a layout for a conveyor sys-
tem involve revisions and could take from days to months or in
some instances years. One with the minimum cost and maximum
client suitability is most likely to get approval.
Figure 1 shows a schematic layout of a typical conveyor
system installed in a production line used for labelling of
plastic bottles. Different sections of the conveyor system are
identi?ed by speci?c technical names, which are commonly
used in similar industrial application. The “singlizer” sec-
tion enables the product to form into one lane from multiple
lanes. The “slowdown table” reduces the speed of product
once it exits from ?ller, labeller, etc. The “mass ?ow” sec-
tion is used to keep up with high-speed process, e.g., ?ller,
labeller, etc. The “transfer table” transfers the direction of prod-
uct ?ow. The purpose of these different conveyor sections is
thus to control the product ?ow through different processing
machines.
A typical mechanical conveyor system used in food and bev-
erage applications consists of over two hundred mechanical and
electrical parts depending on the size of the system. Some of
the common but essential components that could be standard-
ised and accumulated into families of the conveyor system are
side frames, spacer bars, end plates, cover plates, inside bend
plates, outside bend plates, bend tracks and shafts (drive, tail and
slave). The size and quantity of these parts vary according to the
length of conveyor sections and number of tracks correspond-
ing to the width and types of chains required. The problems and
shortcomings in the current design, manufacturing and assembly
of mechanical conveyors are varied, but include:
4 Areas of improvement
In order to identify the areas of cost reduction in material and
labour, a cost analysis of all main conveyor parts was conducted
to estimate the percentage of cost of each part in relation to the
total cost of all such parts. The purpose of this analysis was to
identify the critical parts, which are mainly responsible for in-
creasing the cost of the conveyor and thereby investigate means
for reducing the cost of such parts.
Table 1 shows the cost analysis of a 50-section conveyor sys-
tem. The analysis reveals that 12 out of 15 parts constitute 79%
of the total material cost of the conveyor system, where further
improvements in design to reduce the cost is possible. Out of
these, seven parts were identi?ed as critical parts (shown by an
asterisk in Table 1) constituting maximum number of compo-
nents in quantity and comprising over 71% of overall material
cost. Among these, three components (leg set, side frame and
support channel) were found to account for 50% of the total
conveyor material cost. A detailed analysis of each of these 12
parts was carried out considering the principles of concurrent en-
gineering, design for manufacture and design for assembly, and
a new improved design was developed for each case [10]. De-
tails of design improvement of some selected major component
are presented below.
5 Redesign of leg set assembly
In a conveyor system, the legs are mounted on the side frame to
keep the entire conveyor system off the ?oor. The existing design
of conveyor legs work, but they are costly to manufacture, they
·
·
·
·
Over design of some parts
High cost of some components
Long hours involved in assembly/maintenance
Use of non-standard parts
have stability problems, and cause delays in deliveries. The delay
is usually caused by some of the parts not arriving from over-
seas suppliers on time. The most critical speci?cations required
for the conveyor legs are:
Table 1. Conveyor critical parts based on parts cost analysis
Product description
Leg set?
Side frame?
Support channel?
Bend tracks
Rt. roller shaft?
Tail shaft
Spacer bar?
Support wear strip?
Support side wear strip?
End plate
Cover plate
Bend plates
Torque arm bracket
Slot cover
Inside bend plate
Qty
68
80
400
8
139
39
135
400
132
39
39
8
18
97
8
Material used
Plastic leg + SS tube
2.5 mm SS
C channel SS
Plastic
20 dia. SS shaft
35 dia. Stainless steel
50X50X6 SS
40 × 10 mm plastic
Plastic
2.5 mm/SS
1.6 mm S/S
2.5 mm/SS
6 mm S/S plate
Stainless steel
2.5 mm/SS
Cost (%)
20.22
16.07
15.00
14.36
6.70
6.27
5.43
5.36
3.01
1.88
1.57
1.29
1.21
0.97
0.66
Improvement possible (Yes/No)
Yes
Yes
Yes
No
Yes
No
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Total
?Critical
parts
100.00
554
·
·
·
·
Strength to carry conveyor load
Stability
Ease of assembly
Ease of ?exibility (for adjusting height)
1 and part 3 in Fig. 2) was not rigid enough. The connections
for these parts are only a single 6 mm bolt. At times, when the
conveyor system was carrying full product loads, it was observed
that the conveyor legs were unstable and caused mechanical vi-
bration. One of the main reasons for this was due to a single bolt
Figure 2 indicates all the parts for the existing design of
the conveyor leg. The indicated numbers are the part numbers
described in Table 2, which also shows a breakdown of cost an-
alysis complete with the labour time required to assemble a com-
plete set of legs. The existing leg setup consists of plastic leg
brackets ordered from overseas, stainless steel leg tubes, which
are cut into speci?ed sizes, leg tube plastic adjustments, which
are clipped onto the leg tube at the bottom as shown in Fig. 2.
Lugs, which are cut in square sizes, drilled and welded to the leg
tube to bolt the angle cross bracing and backing plate to support
leg brackets bolts. The # of parts in Table 2 signi?es the number
of components in each part number and the quantity is the con-
sumption of each part in the leg design. Companies have used
this design for many years but one of the common complaints
reported by the clients was of the instability of legs.
From an initial investigation, it became clear that the connec-
tion between the stainless steel tube and plastic legs bracket (part
Fig. 2. Existing leg design assembly with part
names shown in Table 1
Table 2. Cost analysis for old leg design assembly
connection at each end of the lugs in part 3 and part 7. The sta-
bility of the conveyor is considered critical matter and requires
recti?cation immediately to satisfy customer expectations.
Considering the problems of the existing conveyor leg de-
sign and the client’s preferences, a new design for the conveyor
leg was developed. Generally the stability and the strength of
the legs were considered as the primary criteria for improve-
ment in the new design proposal but other considerations were
the simplicity of design, minimisation of overseas parts and ease
of assembly at the point of commissioning. Figure 3 shows, the
new design of the conveyor’s leg assembly, and Table 3 gives a
description and the cost of each part.
Figure 3 shows that the new design consists of only ?ve main
parts for the conveyor’s leg compared to eight main parts in the
old design. In the old design, the plastic leg bracket, the leg
tube plastic adjustment and the leg tube were the most expensive
items accounting for 72% of the cost of leg assembly. In the new
Part no.
1
5, 6
4
7
2
3
8
Part description
Plastic leg bracket
Leg tube plastic adjustment
Lug
Angle cross bracing
Backing plate
Leg tube
Bolts
# of parts
2
4
2
1
2
2
6
Qty
2
2
2
1
2
2
6
Cost
$ 30.00
$ 28.00
$ 4.00
$ 5.00
$ 4.00
$ 25.00
$ 3.00
Source
Overseas
Overseas
In-house
In-house
In-house
In-house
In-house
Total assembly cost (welding)
$ 15.00
In-house
Total
19
17
$ 114.00
555
Fig. 3. New design for leg assembly with part
names in Table 3
Table 3. Cost analysis for new design leg assembly
Part no.
1
3
4
5
2
Part description
Stainless steel angle (50 × 50 × 3 mm)
Leg plastic adjustment
Cross brassing
Bolts
Backing plate
# of parts
2
2
1
8
2
Qty
2
2
1
4
2
Cost
$ 24.00
$ 10.00
$ 7.00
$ 4.00
$ 4.00
Source
In-house
Overseas
In-house
In-house
In-house
Total assembly cost
$ 10.00
In-house
Total
design, those parts have been replaced by a stainless steel angle
and a new plastic leg adjustment reducing the cost of leg assem-
bly by almost 50%. Thus the total numbers of parts in the leg
have been reduced from 19 to 15 and the total cost per leg setup
15
·
·
·
·
11
Size of side frame (depth)
Strength of the material
Ease for assembly
Ease for manufacturing
$ 59.00
has been reduced by $ 55 in the new design.
The new conveyor leg design, when tested, was found to be
more secure and stable than the old design. The elimination of
part number 1 and 5 from old conveyor design has made the new
design more stable and rigid. In addition, the width of the cross
bracing has also been increased with two bolts mount instead of
one in old design. This has provided the entire conveyor leg setup
an additional strength.
6 Redesign of the side frames
The side frame is the primary support of a conveyor system
that provides physical strength to conveyors and almost all the
parts are mounted on it. The side frame is also expected to have
a rigid strength to provide support to all the loads carried on
the conveyor. It also accommodates all the associated conveyor
components for the assembly. The critical considerations of side
frame design are:
Figure 4 shows the side frame dimension and parameters.
The side frame used in existing design appears to be of rea-
sonable depth in size (dimension H in Fig. 4). From the initial
investigation, it was found that the distance between spacer bar
holes and return shaft (dimensions G and F in Fig. 4) could be
reduced, as there was some unnecessary gap between those two
components. The important point to check before rede?ning the
design parameters was to make sure that after bringing those two
closer, the return chains would not catch the spacer bar while the
conveyor is running. The model of the new side frame design was
drawn on CAD to ensure all the speci?cations are sound and the
parts are placed in the position to check the clearances and the
?ts. Using the principle of design for manufacturing the new side
frame design was made symmetrical so that it applies to all types
of side frames. This change is expected to reduce the size of side
frame signi?cantly for all sizes of chains.
Table 4 shows a comparison of dimensions in the old design
and the new design of side frames for the same chain type. It
556
Fig. 4. Side frame dimensions
Table 4. New and old side frame dimension parameters
Old design
Chain type
3.25 LF/SS
STR/LBP/MAG
A
31
B
92
C
71
D
196
E
65
F
105
G
211
H
241
I
136
J
58
K
85
L
196
TAB
22
83
62
187
56
96
202
232
127
New design
Chain type
3.25 LF/SS
STR/LBP/MAG/TAB
A
31
B
100
C
73
D
173
E
67
F
107
G
167
H
199
I
92
J
58
K
85
L
152
is noted that the overall size (depth) of the conveyor has been
reduced from 241 mm to 199 mm (dimension H), which gives
a saving of 42 mm of stainless steel on every side frame manu-
factured. Thus, from a stainless steel sheet 1500 × 3000 mm, the
old design parameter