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1. Stores and Warehouse
Organisation
1.1
The Purposes of the Stores / Warehouse
The stores is self-evidently a major company service department.
Service is provided on behalf of the following functions:
Service to Purchasing
& Quality:
The stores receives raw materials and bought-out parts
on behalf of Purchasing. The receipts must therefore be counted accurately
and the material checked or sampled as to quality. Information about receipts
must be promptly notified to the central database.
Service to Production:
The stores must marshal and issue all works orders on behalf
of production, and perhaps any tools and fittings needed. The stores also
accepts material from production, whether completed work or scrap. The nature
of production is such that emergency issues of material are always likely
to be required. It would follow from this for a factory stores that the
facility should provide a service during all times that production takes
place ... including second and third shifts.
Service to Production
Planning:
The planning of production and the correct maintenance
of stocks are essential services as the company progresses manufacture,
but these tasks simply cannot sensibly proceed unless the stores/warehouse
correctly maintain stock records at a very high level of accuracy.
Service to Distribution
(Logistics):
The stores or warehouse must prepare goods for despatch
to external customers within a turnaround time that has been agreed between
its manager, the distribution manager and transport supervision. The function
of despatch includes packaging and, perhaps, making ready all documentation.
Service to Field
Service or Engineering:
There may be a requirement to hold and dispense spares
for machines both within the factory or installed at customers' premises
on a 24-hour basis. The stores' role in providing this service entails call-outs
... not merely leaving a key with security.
Service to Finance
(and Senior Management):
Stock is regarded for financial
purposes as a current asset of the company - ie an asset of the same
nature as cash and debtors - so that consequently Stores' maintenance of
accurate records is a vital contribution to company management. The accuracy
of the records is not merely an issue at year end when the balance sheet
is being struck. On going accuracy is needed continually for integrated
financial accounting purposes.
Other important functions of the stores relate simply to
the internal good management of the facility. Obvious examples are the safe
and economical handling of material; and security from fire and theft. As
well, there is a requirement to maintain stock in good condition. (It is rarely
accepted, however, that the stores or warehouse is responsible for the ordering,
forecasting or replenishment of stock itself, except perhaps inexpensive consumable
items or fuel in the course of operating a simple "2-bin replenishment" system
. We must return to the question of purpose and function in the final Section
of this on-line course, when the matter is discussed as to how well the stores
has performed and the need for its continuous improvement.
1.2
Stores & Warehouse Construction
1.2.1
The Building
A single storey building is almost always to be preferred
- it is cheaper to construct and it is cheaper to fit out with ancillary
services. Above all, a single storey is more suitable for fork lift trucks
which, in a multi-level facility, would otherwise need sometimes to go
from level to level via lifts. Although single storey buildings are nowadays
the norm, there are two ways in which some of the advantages of a two
storey building can be obtained. The first is by the construction within
the warehouse of a mezzanine floor for offices and limited specialised
sub-stores. The second is to have multi-tiered binning. This consists
of stacking one run of shelving, say 3m high, on another that is also
3m high. A floor is then provided for storesmen at the higher 3m level.
It should be noted, however, that a disadvantage with both mezzanines
and multi-tiering is the exclusion of natural light at the lower levels.
This forces up operating costs due to the need for artificial lighting,
and may lead to accidents. (Inadequate lighting is a major cause of accidents
generally.) Of course, if the new stores needs to be in the centre of
a major city, land prices may force the company to develop a multi-storey
facility.
Multi-storey warehouses can be successful if care is
taken to 'zone' the stored material carefully. Typical zoning schemes
are: (i) high and low pick densities (see later); and (ii) bulk stock
/ back-up stock / picking stock. A financial reason for single-storey
is given in the relationship between the cost of the construction, worked
out in £ per cubic metre of space obtained, and the (single storey) height
to the eaves. This can be illustrated by a graph showing how the relative
cost per cubic metre of space created falls exponentially as the overall
height of a building rises. As a rough estimate, a 12 metre high building
would cost only 15% more than a 6 metre building. However, a 12 metre
(tall) warehouse would show major cost savings over a 6 metre (more extensive)
warehouse of the same racking capacity, with savings in land costs, rates,
heating etc.. Perhaps as important as this is the resale value of the
warehouse, as more and more companies are looking for new premises and
focus on buildings well over 6 m high.
1.2.2
Large Scale Equipment
A two-stage approach can be used to work out the best
system of materials handling. First, the best or most likely range of
units loads of incoming materials is determined: size, weight, frequency
etc.. This will enable the equipment to be decided that is necessary to
handle them, and the design of the receiving docks. Secondly, the unit
loads required by the company's own customers are considered, so that
the equipment needed at this end of the materials handling system can
be determined. (For example, consider the requirements to fit out a supermarket
... receiving docks and fork lift trucks are necessary to deal with incoming
cartons brought in from the retailer's depot, and wire trolleys and trolley
parks are needed to deal with the carrying away of customers' weekly groceries
to their cars.)
1.2.3
Flooring and Floor Flatness
Floors are always of concrete, sometimes treated with
compounds to reduce slippage and to minimise dust and grit. Specialist
contractors must be employed to lay them, capable of constructing them
to the required high standards of flatness and delivering the required
degree of durability.
Flatness is especially important: if a floor is not flat,
fork lift trucks will slow down and may collide with racking. But what
is flat? To answer, consider an elevation difference of 10mm across a
1500mm aisle. Put a narrow aisle truck on the floor at this level and
raise its cab 15m. Now the 10mm difference has become a 100mm static lean.
At speed, that 100mm lean becomes a lean of 300mm. Floor flatness is specified
by BS8204 (Part 2). Floors should have an elevation difference of less
than 3mm. Flatness is measured by a prophilograph machine, which traces
the floor contours electronically. An uneven floor can be flattened by
a laser-guided grinding machine, or, alternatively, a new floor can be
laid as an apron on the old one.
1.2.4
The Loading Bay
Loading bays are positioned so that vehicles can have
direct, unhindered access to them without the need for complicated manoeuvring.
Among other things, easy access will speed the loading and unloading processes
and may even reduce the need for extra bays. A key decision is whether
to allow for side loading or end loading of vehicles. End loading
offers many advantages. Although it restricts access to only one part
of the load, the narrower width is such that than one can get two bays
in a space, compared to one with side loading. End loading also provides
better temperature control and greater safety. (Loading bays are a particularly
critical area for safety ... 25% of all industrial
accidents occur in this area). Note incidentally, that clockwise
circulation of traffic up to the loading bays is required to provide better
driver control of the reversing turn into the bay. The construction of
the loading bay must clearly allow for modern materials handling equipment
and practices. Doors should be 9 ft, or a little more for higher trailers.
The height of the loading bay platform must accommodate any number of
vehicle types and make allowance for the fact that vehicle heights rise
and fall during the loading and unloading processes. The usual (very cost
effective) solution nowadays is to build permanent docks levellers.
As for location, two common practices are diametrically opposed to each
other. One is to locate both the receiving and despatch bays next to each
other. The other is to put them as far apart as possible! However, with
modern communications and materials handling, it may be more effective
to place bays at several points around the building to allow direct pick-up
and easy despatch by factory departments. If this is done, of course,
all such bays must be centrally controlled and berth activity supervised.
The question of how many loading/unloading bays should be provided in
the construction of the stores or warehouse can be decided best through
the use of a simulation model as described below.
1.2.5
Other Important Areas
Further vital topics which must be dealt with include
those in the list below. Perhaps the most important point, however, is
that the stores should be designed, at least in rough, by stores staff
themselves - it will be realised that an inadequately planned facility
can have massive, permanent on-going effects on operational costs. For
example, failure to obtain the know-how and inside knowledge of staff
may result later in queues; excessive waiting times for drivers or shop
floor operators; double handling; and delays in clearing materials for
use.
(a) Doors
For the sakes of security and to minimise heating costs,
instal only those doors which are essential. Aspects of doors to consider
are from (1) to (5) as follows - or perhaps a combinations of them is
required ... (1) their speed (speed is clearly important for doors to
cold areas); (2) whether automatic control is desirable; (3) security;
(4) thermal efficiency: (5) whether specialist factors apply, such as
use as fire shutters, extra high security or heavy duty. How much traffic
will use the door and what types of traffic will it be? Alternative door
types are (i) sectional insulated overhead doors ('up and over' doors,
or Thermadoors), which may be standard, or normal, lift, high lift or
low lift, (ii) Rapid Roll doors. An essential accompaniment to internal
doors is either a traffic light or one-way system. (Warning klaxons are
an additional safeguard.) Door control activators should also be given
attention - it is grossly inefficient if drivers of FLTs need to dismount
to open/close the door. The necessity for high speed, insulated doors
is dealt with under Cold Stores.
(b) Lighting
Ensure that the fullest possible advantage is taken of
natural light, especially in gangways and passages, so make sure shelves
and racks when they are installed will not obscure windows. (Windows of
continuous glazing with wired glass.) Inadequate lighting can make it
difficult to read documents, labels and screens. Anto-glare filters should
also be considered. (On the matter of clarity of documents, ensure that
bold, clear fonts are used and that the pitch of letters and numbers is
sufficiently large.)
(c) Picking Areas
Dealt with below.
(d) Special Storage Areas.
Heavy goods, bins, safes and others may be zoned into
special stores areas to be laid out in conjunction with the main pallet
racking.
(e) Ancillary Services Areas.
These are: the boiler house; electricity sub-station;
garage; fuel pumps; canteens; toilets; car parks; first aid stations,
etc..
1.2.6
Gathering Data
(A) Calculating Pallet Space
The following simple six step procedure can be used to
find the average palletised area that will be occupied by a case or package.
i. If the cases are to be stacked on a pallet, find
the number of cases per tier on each pallet and the number of tiers
per pallet. For example, 5 cases per tier and 4 tiers per pallet =
20 cases per pallet.
ii. Decide the maximum number of pallets per stack.
For example, with 3 pallets per stack, the number of cases is 20 ×
3 = 60.
iii. Each stack occupies the area of one pallet,
plus, say, 1.5 cms overhang on each side. The area is thus 1030 mm
× 1230 mm, = 103 cm × 123 cm = 12,670 sq cm, or 1.267 sq metres per
stack.
iv. The gross area in iii. is reduced to 60% net
after allowing for aisles, staging areas and offices. Thus net area
is 1.267 / .6 = 2.11 sq metres per stack.
v. We must now allow 20% wasted space for honeycombing,
so that the actual space per stack is 2.11 / .8 = 2.64 square metres.
vi. The area per case for planning purposes is therefore
2.64 / 60 square metres per case, = 0.044 square metres per case.
(For example, if stacking 2,000 cases, allow 2000 × 0.044 square metres
= 88 square metres.)
(B) Calculating Pick Popularity
(P)
Analyse existing data such as the stock records transaction
trail and record the total number of picks plus putaways per item per
month. If the file holding this data is sorted into descending order of
the number of picks + putaways, it will be found that the top 20% of the
items account for 80% of the total number of picks + putaways ... the
familiar ABC effect.
(C) Calculating Volume Movement
(V).
From the data in (B), apply the volume of each item V.
This is defined as V = T × C, where T = the average total number of units
of the item put away and withdrawn per month and C = physical volume of
each unit - ie the space occupied by one item, measured in cubic centimetres
(or cubic feet). That is, volume movement is the volume of each item stored
and picked per month. Analysis of items in descending order of volume
movement will show typically that 15% of items account for some 80% of
the total volume movement. Of equal interest to the stores planner is
the fact that 50% of the items account for less than 0.5% of the total
volume movement.
(D) Calculating Pick Density (D)
If P = the average number of putaways and withdrawals
per month for an item, and V is its volume movement, then each item's
pick density D = P / V. Pick density is needed in determining storage
location, as explained further below.
Hint: In order to find the volume of a small item, institute a "measuring
cup" of fixed volume ( say 100 cc) and determine how many units will fit
in a cup. For large items, imagine them being in a box, and apply a tape
measure to the imaginary box.
1.2.7
Changes in Modern Stores Design
The stores designer today must be very conscious of the
rapidity of change taking place in the tempo of modern manufacturing.
With Just-in-Time supplier receipts, kanban and JIT deliveries, the quantities
of stock ordered from suppliers, manufacturing lot sizes and the delivery
quantities demanded by customers are becoming progressively smaller and
their frequency of movement correspondingly greater. So while in the past
the emphasis in design was on economy of storage density, todays emphasis
is on speed and flexibility. Issues today are traffic jams and the quick
attention to incoming goods and shop floor receipts.
1.3
Storage Options
Storage options here means the stores or warehouse 'furniture'
- the physical containers, shelving and the rest used to contain the items
being stored. Note that the term stores furniture seems to imply that
the fixtures and fittings are static and the goods within them are at rest.
It is possible, however to install what is termed 'live' storage facilities.
With live storage, either the goods themselves move, or the equipment moves,
or both. An example of live storage where the goods alone move is a chute.
1.3.1
Shelves and Bins
Open shelving is suitable for items within strong packages,
such as small boxes of components. A working ledge at the front is typically
provided for counting out items being picked. Closed shelving usually
means closed at the back and is more common. It is suitable for non-packaged
goods and can be fitted with shelf trays. Lockable fronts may be provided.
A shelving bay means a single multi-shelf construction ... ie one
unit of shelving from the equipment supplier. By bolting several bays
together side-by-side, we form a 'run'. A very strong, stable structure
is formed when two runs are bolted together back to back, and, as indicated
above, runs can also be stacked in tiers. Guidelines on shelving are contained
in BS826, specifying preferred dimensions.
1.3.2
Racking (Non-Pallet)
The term "racking" is applied to any storage fixture
that is not shelving or binning. Racking is used for the storage of an
enormous variety of goods - pallets themselves, tyres, cables, bars, tubes,
drums ... The layout of racking must be given the greatest attention at
the design stage, since the decisions made will have a considerable effect
on the utilisation of floor space (and volume) and on the speed and efficiency
of storing and picking.
A common requirement in industrial stores is for racking
for bars and tubes. The basic options are to hold the stock either horizontally
or vertically. The preference is usually for horizontal racking. This
may be either pigeon hole or antler ('horn'). Pigeon
hole racking consists of angle irons in which the bars are stored together.
A disadvantage of it is that mechanical handling is difficult. With the
antler method, the racking consists of a framework of angle irons, so
that each bar is stored in an individual slot like bottles in a wine rack,
making mechanical handling easy. Horizontal racking clearly demands corresponding
horizontal working space, and if this is limited compared to height, vertical
racking may be preferred. Two problems with this are (1) that the bar
or tubing may become distorted due to the pressure of its own weight;
and (2) the greater safety hazard it presents.
Note that warehouse racking is regulated under the Construction
(Design and Management) Regulations ('CDM'), part of the Health &
Safety at Work Act. The CDM regulations were amended and re-issued in
April 2007. Although racking in a warehouse may seem a long way from a
building site, the Health & Safety Executive classifies the installation
of racking as a construction project. To comply with the CDM regulations,
companies must ensure that a health and safety plan has been developed
before any construction work begins. A health and safety file that
is available for inspection at any given time must also be produced. The
preparation of the plan is the responsibility of the warehouse manager.
It will usually begin with a description of the 'project' and a general
statement of health and safety principles and objectives of the work.
It will include arrangements for managing and organising the project,
and include the identity of those responsible for the actual erection.
1.3.3
Pallet Racking
There are a great many standard storage arrangements
for pallet racking. The Stores planner can decide on the configuration
suitable for a specific need simply by contemplating a standard layout,
the type of material to be stored and the picking/putting away rates to
be achieved. Seven standard arrangements are given below, with very brief
comments on each. Their pro's and con's are summarised below.
(i) Block Stacking
Unit loads are stacked on top of each other, and stored
on the floor in storage lanes ("blocks"), two to ten deep. Block stacking
is suitable only for a very limited number of different items, where product
quantities are large and/or where products themselves are bulky and turnover
is high. Very high storage density is achieved though ease of access is
not good. Also note that block stacking is strictly LIFO (see below),
so that if FIFO is necessary, block stacking is not a feasible option.
(ii) Single and Double Deep Pallet Racking
Single deep racking is a simple system that is associated
with pallet racking for picking faces (see Two-Step Picking later). It
allows immediate access to every load stored. A major disadvantage, however,
is the loss of some 60% of floor space to aisles. Double deep pallet racking
is merely an extension of single with less loss of space to aisles (but
with more honeycombing).
(iii) Drive In and Drive Thru Racking
The racking consists of upright columns with horizontal
rails to support pallets. Storage lanes of the chosen depth reduce space
lost to aisles even more. High density, but suitable only for low/ medium
thruput items. LIFO only. Drive thru merely means access from two sides.
(iv) Pallet Flow Racking
This superior though expensive system is similar to Drive
In Racking, except that loads are moved on skate wheel conveyors. As a
load is removed from the front of the storage lane, the next lane advances
to the picking face. Pallet flow racking gives high throughput and good
space utilisation, and permits FIFO. It is used for high density, high
thruput storage, but costs some £200 per storage position.
(v) Push-Back Racks
As a load is placed in storage, its weight and the force
of the FLT (fork lift truck) pushes back the other loads in the lane.
As a load is removed, the rear loads push forward. Expensive and LIFO.
(vi) Mobile Pallet Racks
Whole rows of rack are moved forward together, eliminating
aisles.
Safety is a most important concern
with all racking. Training must be given by the equipment manufacturer
and the greatest care exercised to ensure loads are evenly distributed
and that they never exceed the manufacturer's limits. Operating conditions
must also be satisfactory, such as lighting and working space, and the
racking installation must be rigorously inspected on a regular basis,
not simply when someone 'notices something is wrong'... For Racking Safety
Trainining, visit SESS.
1.4
Allocating Storage to Stock
The first task is to obtain and analyse the volume movement
of all items so that the correct storage capacity can duly be assigned to
the items to be stored. The four principles which the planner will typically
follow are:
1. Low volume movement; high popularity:
These items should be assigned to very productive, low
volume storage media - for example, carousels (see below).
2. Low volume movement; low popularity:
Expensive storage media cannot be justified for these
items. The media selected for them will be storage drawers and bin shelving.
3. High volume movement; high popularity:
These items must be stored in pallet racking systems
that lend themselves to frequent picking and restocking, such as flow
racks and single deep racking.
4. High volume movement; low popularity:
Other, less expensive styles of racking will typically
be chosen.
Consideration should be given to the relative merits of the
seven types of pallet racking described in the previous sub-session. The characteristics
and appropriateness of the seven systems are summarised in the following table.
Characteristics
and Appropriateness of Racking Systems
....................................Cost
.Storage Density .Load Access .Thruput Capacity .FIFO? Variabl Load Sizes?
Block Storage ........................n/a..............v.good............................poor
............................average...................y.............................good
Stacking Frames....................low..............good...............................poor.................................poor.....................n.............................poor
Sing/Dou Deep ......................low..............good..........................good/OK.........................good/OK................poor......................average
Drive In/Thru ........................ low...............good.............................good...............................average..............difficult......................poor
Flow Racks..............................high..............good............................good.................................v.good..................yes............................poor
Push Bk...................................high...............good.............................v.good...........................average..............difficult...................average
Mobile.......................................high..............v.good............................poor................................v.poor...................no.........................average
As we see from the table, both relative volume movement
and relative picking popularity are taken into account in working out required
storage volume and determining the specific storage media to be installed.
Relative volume movement and relative popularity are consequently taken into
account in determining where "regions" of stock and storage media are to be
located. In short, where both volume movement and popularity are high, flow
racking might be best. Where volume movement is low, then we might turn to
(1) storage draws (low popularity); (2) bins and shelves (medium popularity);
and (3) carousels (high popularity).
1.5
Allocating Stock to Storage (Pick Density and 'Golden Zone')
For a very small number of special items, the decision as
to which locations they are to be assigned for storage will be made on an
individual basis. For example, precious metals will be located in safes and
material likely to give off fumes will be located in well ventilated areas.
The decisions for the great majority of items within a general storage region,
however, will be made after first considering how easy (quick) it is to put
away into, or pick from, those locations. In stores jargon, the locations
where these activities may most easily be accomplished are referred to as
"the golden zone" - locations which are between
waist and shoulder high, and are close to a central point in the stores. Next
come locations in the "the silver zone". Finally, the slowest and most distant
locations make up "the bronze zone". Nominating locations and zones is the
first task in deciding what to put where.
At first thought, it seems intuitive that the criterion for
deciding which items are to be assigned to the golden zone should be on the
basis of their popularity. However, popularity alone ignores the fact that
the stores planner is trying to optimise the use of the golden zone, and that
consequently he should also take into account how much space is taken up by
items. What he wishes to do is to maximise the degree of picking that takes
place there. Consequently, the notion of pick density,
previously defined, must be examined further.
As previously stated, if P = the average number of putaways
and withdrawals per month for an item (ie popularity) , and V is its volume
movement, then each item's pick density D = P / V.
The planner must calculate the pick density of each item
within a stores region and allocate the group of items with the highest pick
densities to the golden zone, the group with next highest pick densities to
the silver zone and those with the lowest densities to the bronze zone.
To illustrate the optimisation of golden zone space, consider
a simple example of a golden zone of just 10 cubic meters of space. Now consider
three items A, B and C, with the attributes shown in the table below.
...............................Item ....................Popularity
P ................Volume-Movement V (T × C) ..........Pick Density D (P /
V)
................................A .....................200
per month ......................10 m3 per month .................................20
requests/m3
................................B .....................150
per month .......................6 m3 per month ..................................25
request/m3
................................C ......................120
per month .......................4 m3 per month .................................30
requests/m3
Suppose now that we decide to store one months supply of
material in the golden zone. If we were to allocate Item A to the zone on
the basis of highest popularity, this will exhaust the capacity of the zone
and the number of visits we will get to it will be 200. If , however, we use
the basis of pick density, the items assigned to the golden zone will be C
and then B. Together, these will exhaust the zone's capacity of 10 m3 (ie
6 + 4 = 10) and the number of visits we will get will be 270 (150 + 120).
The use of pick density instead of popularity in allocating items will make
a significant difference to the stores' utilisation of prime space.
1.6
Material Flow Planning (Layout)
The dominant scheme for the layout of the facility is as
a U-shaped flow. The advantages of a U-flow are as follows:
* There is very good utilisation of dock resources (doors,
dock levellers, space, goods in/out staff), since receiving and despatch
operations can share docks;
* U-flow makes cross docking easier, and also facilitates
the immediate onward movement of incoming Just-in-Time supplies to the
factory floor;
* U-flow gives excellent FLT utilisation, since putaway
and picking trips can be combined;
* There is good security;
* U-flow design is inherently more flexible - it is easier
to expand the various facility areas as operations change.
Other layout schemes are "Straight Through" (for distribution
depots) and "Modular Spine".
THE
USE OF SIMULATION IN MATERIALS FLOW PLANNING
Simulation is an immensely powerful tool
in warehouse design and warehouse development for providing
answers to such questions as "how many FLTs should be deployed?", "How many
cranes?", "What would be the effect of a conveyor system covering these locations?"
Simulation is particularly useful in warehousing since it incorporates the
mathematics of queuing theory in order to test the effect of likely activity.
For example, "How long will vehicles wait to unload by mid-morning, and how
many extra docks should be provided to reduce these queuing times by 75% ?"
Virtually every company planning and building a new warehouse will have used
simulation in order to do so. Recent past users of simulation have included
Boots, in building a complete distribution/logistics system, and Littlewoods
Home Shopping, for a £40m distribution centre eventually incorporating 18
cranes and 350, 000 locations. The main benefits reported were:
The ability to test and compare the performance of alternative
scenarios put forward at the 'ideas stage' of the projects;
An ability to monitor/assess the effects of changing
requirements by What-If?;
Accurate comparison of alternatives, with all supporting
data ;
Problem solving through the ability to test alternative
solutions.
The use of simulation requires the building of a computer
model of the proposed facility or proposed change - vehicles, traffic, routes,
times, loads etc.. Nowadays, easy-to-use systems which incorporate interactive
animation can easily to built by anyone. The completed models incorporate
animation and realism, with the advantages that people at all levels are quickly
able to grasp what is being proposed, and (through interaction) are able to
input their own ideas or get detailed information about what is being shown
on the VDU. For example, by clicking on a fork lift truck in the picture,
statistics can be obtained about its percentage use, distance travelled etc,
in operating the warehouse over, say, a specified hour. The training needed
to use an animated simulation package sufficiently well to obtain good results
is just a few days. In reality, users must spend most of the time fact finding,
discussing alternatives with colleagues and deciding objectives. (As a hint,
if the student of this course engages the service of a simulation consultancy,
perhaps paying fees in accordance with the time spent, it is essential to
find out beforehand precisely what data needs to be provided, and to have
such data readily to hand.) The foremost interactive animated simulation package
in the UK principally aimed at warehousing is Automod, and its sister module
Autostat, from Brooks Software, Reading. Visit http://www.automod.com
or phone 0118-921-5600.
1.7
The Installation of Automation
Automation is costly and the more flexible and extensive
in design it needs to be, the more costly it gets. Consequently, there are
four important requirements to consider before embarking on it, as follows.
There must be .....
1. sustained, high levels of steady production throughput;
2. a low, stable product range;
3. a high labour content;
4. large individual customer offtake quantities.
Automated equipment consists of electromechanical devices,
communication systems and computers. Electromechanical devices and communications
systems include powered rollers, vehicles guided by wire contacts along floor
mounted tracks, automated stacker cranes and other apparatus with feedback
and sensing devices. For example, a common scheme is to install vertical pallet
racks of conventional design, but with a power / computer operated fork lift
truck on a track in the gangways, the truck capable of reaching all pallet
heights. The automation then consists of the truck moving along the tracks
and moving the forks up and down, in and out, under the control of a computer
program. Many early attempts to automate, however, were failures. There were
three reasons:
A. Technical Overambition.
It was not unknown for the design of early systems to
take two or three years to complete. The designers of the automated system
moreover then required that every movement should be as perfectly meshed
in the real world as on paper. Mechanical devices, however, break down.
The scale of early warehouse projects was greater than experience showed
to be practical.
B. Logical Overambition.
In order to automate the warehouse fully, it is necessary
for software designers and programmers to understand and describe its
operations fully. Computer programs must be written and database data
properly set up. But many of the activities in the manual warehouse are
simply too involved to describe, and must of necessity rely on human knowhow
and intuition, which cannot be programmed.
C. Commitment and Discipline.
Early automation attempts were looked on as technical
and engineering projects. Success however requires full, multi disciplined
team commitment and massive advance training and publicity. These requirements
were not recognised.
To achieve success and avoid the mistakes of the past, five
guidelines are put forward.
1. Islands of Automation.
The monolithic automated warehouse is a myth. Instead,
automation must be seen as a set of projects physically isolated from
each other. Each project can be put in alone and should generally be capable
of justification in its own right. Examples of islands of automation are
the automatic storage and retrieval of full pallets; and the installation
of automated guided vehicles using wire-to-the-floor, as described above.
2. Flexible Operational Interfaces.
It must be possible for the storeman or warehouseman
to take control of operations at suitable interfaces. For example, if
there is a breakdown or incident in the marshalling of (automated) retrieved
pallets, it must either be possible to divert the retievals to a temporary,
manually controlled area or to take over the system.
3. Supplier / Customer Liaison.
The obligations of the automated equipment supplier are
not confined merely to the customer's experience
with the technology. He must liaise closely with the customer as part
of a team in setting up training schemes and seeing to other matters (eg
in developing manuals). By the same token, the customer must realise that
he also has an obligation to cooperate fully with the supplier.
4. Dedication and Organisation.
The heart of success in automation is not technology.
It is the dedication of the company and its managers to achieving success,
including taking into account the fears and aspirations of all personnel.
Success comes from organisation, competence and hard work. (These lessons
have long been known in the field of big project development).
5. Partial Automation.
The stores or warehouse supervisor should contemplate
partial automation only ... the installation, say, of AGVs, carousels,
automatic weighing machines, labelling etc, each installed only as and
when its use seems to be individually justified on a strictly local basis.
1.8
Coding and the Stores' 'Vocabulary'
For identification, classification and computer purposes,
each unique item in the stores must be assigned a unique code. Together, the
codes and each code's associated information, such as the item's name and
other major features, are known as the stores' vocabulary. One obvious
property of a coding system is that the codes generated through it should
be consistent. In fact, codes are often made up using a "hierarchical approach",
based on the particular types of goods in store. An example is the assignment
of a 6 figure numeric code (ie NNNNNN), where the 1st digit is the type of
material (ie raw material, component, piece part ...), the 2nd is 'metal'
or 'non-metal', the 3rd is type of metal, the 4th the form ('rod', 'tube',
'ingot' ...), the 5th the shape and the 6th the size. (A well-established
methodology is the Brisch system, which is a means by which a company
can put together a coding set itself, geared to its own use.)
For the stores, there are two vital coding issues: memorability
and meaning.
Memorability means that the code can be copied down
or transcribed onto transactions easily and with consistent correctness. (Incorrect
recording is a major cause of error in stock records.) It has been shown that
to achieve memorability the maximum length of a code should be 7 digits (and
6 would be better - but very definitely not 8 or longer, unless a barcode
or RFID reading system is in place).
The question of incorporating meaning into the code
is more difficult. First, it should be said that there is very obvious merit
in keeping to the same coding as used by production and purchasing. However,
the general company scheme may not be best for the stores since it is desirable
in this environment for the storeman to be able to tell from the code that
the material he is about to pick or place has certain properties. For example,
suppose that a material which was subject to special quality procedures (QP)
had to be handled within the stores in a certain way. The fact that the material
is a "QP" can be stored on the database so that special instructions are displayed
as necessary by the computer system. But to be safe, it may be desirable to
include this on the code itself, so that storemen can recognise it on occasions
not involving the computer. A second example relates to packaging. It may
be logically correct to designate the 50kg Box Packet as 01, the 50kg Soft
Packet as 02, the 100kg Box Packet as 03 and 100kg Soft as 04. But it may
be safer to code them B50, S50, B100 and S100 to prevent errors during the
physical act of picking. All the attributes of a material qualified by its
package can be maintained on the database internally, available to the storesmen
through computer programs. But it may be necessary to incorporate a number
of these classifications in the visible code itself to help staff in the operational
side of their jobs. If so, the risk then arises, of course, of making the
code more unwieldy from the viewpoint of memorability!
1.9
Installing Technology
1.9.1
Batch v. On-Line
Batch.
'Batch' processing means that data events are progressively
recorded through some medium (whether paper forms or an electronic recording
collector) and the records then input to the computer all together. That
is, the original data are deliberately held back from being input to the
computer until a reasonable quantity of information has been collected,
so that input, although efficient, is made usually several hours after
the events being recorded. If a transaction is found to be in error when
finally submitted to the computer, there can be a delay of many days before
its investigation and final correction.
On-line.
In on-line processing, data relating to an event is notified
to the computer on an individual basis as soon after the event as possible.
(There is usually nevertheless a brief time delay between the event and
the transmission of the record. The delay may be minutes or, in a slacker
environment, one or two hours.) There are two advantages to on-line processing.
First, the central computer database is brought up to date far sooner,
and usually accurately reflects the current situation. Secondly, there
is immediate feedback after submitting the transaction and, if it is in
error, the opportunity exists for immediate error correction by the person
responsible for completing it in the first place.
1.9.2
Data Recording Equipment
Data recorders:
These are hand-held machines similar to electronic
personal organisers. When its capacity has been reached, or after an
appropriate period of time, the device is taken to a terminal and the
data that has been captured is transmitted, or 'down loaded', to the
computer.
Radio data terminals (RDTs):
These are hand-held devices which incorporate a small
VDU screen, plus a tiny keyboard (say, 3"). More importantly, they
are able to communicate directly, on-line, with the computer via a radio
signal - ie a cable is not required. Data recorders and RDTs can optionally
have bar code scanners attached and some models are suitable for rugged
or hostile environments.
1.9.3
Voice Directed Picking
Voice directed picking is a highly effective and increasingly
popular technology that has many advantages in both stores and warehouse
operations. With 'voice', workers wear a headset, earphones and a belt-attached
portable computer which enable them to hear instructions from the computer
and to speak words of confirmation as to action taken - below under Order
Picking.
1.9.4
Communications
Electronic Data Interchange (EDI): This medium
is perhaps being eclipsed by the Internet. The term EDI refers simply
to the creation of data by one computer, in computer readable form, and
its acceptance directly by a second computer. Usually, the transfer of
data is through a data network known as a Value Added Network (VAN).
The sending company transmits the data with the code of the intended recipient
company. The data is stored on the VAN operator's computer at the nearest
position to the receiver. The receiving company scans the VAN computer
at times convenient to itself for any messages addressed to it. Local
networks mean in-house networks communicating via coaxial cable laid
in the premises. Wideband networks are inter-site, and are capable
of carrying vastly greater volumes of data traffic. They are typically
provided by BT between specified major towns and cities. The Internet
is a communication medium based simply on ordinary, existing telephone
cabling, and has the consequent virtue of being cheap. Direct access between
a distribution depot and a central warehouse is via a local telephone
call using simple software. Both text and graphics can transmitted and
received.
1.9.5
Weighing and Measuring Devices
Computerised weighing machines. A sample scale
can be used to find the 'mean', or average, unit weight of a product,
and the average then stored on a computer. Large electronic scales are
subsequently employed to weigh the main stock entering the stores or warehouse,
with direct links to the computer database holding the unit weight. Care
must be taken to account correctly for the container weight, referred
to as the "tare", and to ensure the items' weight is not distorted
by oil, wetness etc. Other devices of value are simple weighbridges,
non-computer weighing scales, calipers and micrometers.
In the process industries, bulk liquids are measured by flowmeters
or even simple dip tapes and dip sticks. Many methods used
for measuring liquids are acknowledged as being problematical, with comparatively
wide tolerances arising inherent in the techniques themselves. Problems
may be compounded by the need to take the temperature of the liquid, and
the further need to assume the temperature is uniform throughout the material's
bulk.
Weigh Counting.
This method of counting items which are dispensed from a stores or
warehouse is used when items are small or light. It is normally done
on purpose-made weigh counting scales. (The first thing to
note is that a scale should be selected that has a sensitivity appropriate
to the weight of the items being counted - ie if the items are light,
the scale should be more sensitive). The procedure follows three steps:
(1) First, the "tare", or base weight, of the container
in which the parts are held should be determined most carefully by
separate weighing - say, weight T, which is entered into the memory
of the weighing scale; (2) Next, a sample of the items to be counted
should be taken and counted out most carefully, and the total
weight, including the container, determined. Say there were 12 items
in the sample, and the total weight was was W. This data is again
entered into the memory of the scale, which is then able to calculate
the unit weight of one item. In our example, this is (W - T)/12,
or X. Finally, (3) we weigh all the items which are to be counted.
Say, the weight is B, including the container. The number counted
is given directly by the counting scale, and here is (B - T)/X. Note
that ideally in order to be sure of the accuracy of the unit weight,
4 or 5 weighings should be taken and averaged. This is because the
differences in weight between the units being weighed is random and
the statistical distribution of these differences is Normal. The most
important factor is to obtain an accurate reading of the tare weight
of the container. Substantial errors can arise if the same unit weight
X is applied in weighings involving apparently identical, but
different, containers, each container therefore having a different
tare weight. Note that a variation of this method of weigh counting
is reverse sampling.
1.9.6
Bar Coding and RFID Tags
Bar
Codes
The familiar bar code is the representation of a numeric,
alphabetic or alphanumeric code by a pattern of dark and light stripes,
with 'start' and 'stop' characters at either end, and which can be interpreted,
or read, by a light scanning device called a bar code reader. Bar
code readers are either contact or non-contact. Contact
readers such as those used in retail shops are also called fixed beam
readers, since the device needs to be very close to the bar code. They
are comparatively inexpensive (£100 +). Non-contact scanners, or line
scan readers, work by repeatedly reading the code with a laser beam fired
by a gun, perhaps mounted on a truck, until the reading is error free.
They cost about £1000. There are a dozen or so different bar coding systems
for assigning a code to a material. One used extensively in the warehousing
of consumer goods, including the outside carton packaging of groceries,
is termed Interleaved 2 of 5. It is numeric only, and requires
the code to comprise an even number of digits. With Interleaved 2 of 5,
even numbers are represented by the white stripes and odd numbers by the
dark bars. Its advantage is its physical density. In industry generally,
however, there is a preference for the Code 39 system. This is
capable of encoding numbers and letters. Each character is represented
by a group of 5 bars and 4 spaces, and has an in-built check to eliminate
mistakes in the physical reading and interpretation of the code by the
bar code reader. Other bar code systems are EAN (European Numbering
System) and UPC (Universal Product System). UPC was devised
by IBM in 1973 and is the one used in groceries in supermarkets. Its advantage
is that the code does not need to be on a flat surface to be read by the
reader.
Bar coding in the stores or warehouse is not always successful
even when those attempting its implementation have carefully assessed
that it will be. There are three issues.
First, there is the matter of ergonomics.
Ergonomics is the science of man-machine interaction, and here means
how codes are to be assigned, how (literally) they are to be attached
to the objects and locations in question, how the codes are to be
read, and what equipment is to be used. It also encompasses the nature
of the computer system that will read the codes and how associated
data, such as quantities, are to be recorded.
The second issue relates to the physical nature of
the items actually to be bar coded and seems to be the most critical
of the three. If there is a wide variety of shapes and sizes, and
many items are irregular or have a unsuitable surfaces, it will be
difficult to devise satisfactory, consistent ergonomically sound procedures.
Thirdly, if it is intended that incoming raw materials
are to be bar coded by suppliers, their competence and willingness
to do so must be considered (or, at least, their willingness to apply
bar code labels and documents supplied by the company).
If bar coding works well and easily, without a continual
struggle to keep it going, there are two advantages to its use. First,
self-evidently, material and location codes are read correctly and more
easily. Secondly, the reading process ensures that each transaction relating
to an activity is indeed raised, and is not forgotten, and that it is
then input to the computer system in a timely manner. (Missing transactions
are a major source of error in attempting to achieve high stock records
accuracy.)
RFID
Tags (Radio Frequency Identification Tags)
By 'identification' is meant the attachment of a small
"tag" bearing the code and much other data of what is to be identified,
and the subsequent reading of the tag code and data at some later stage
by a tag reader. The physical tag attached to the object may commonly
be a label, in a flat, thin, flexible ticket or may take other forms depending
on the application to hand. Important attributes of tags are that they
are robust and capable of functioning in extremely harsh environments
and that they are reusable and can last for many years. The code and other
data associated with the tag is read by a special tag interrogator, a
primary function of the interrogator, or reader, being to excite a component
within the tag termed its antenna. Although the technology associated
with RFID tags and interrogators is changing rapidly, as at the date of
this on-line course (2006), the microchip incorporated in the tag 'structure'
is likely to be a silicon microprocessor and the antenna formed from conductive
carbon ink. The silicon chip will be attached to carbon - ink electrodes
at the back of the paper label. (Labels are referred to as smart labels.)
Note particularly in RFID tags that a battery may
be incorporated into the tag - that is, a tag may have a small lithium
battery to boost power. Tags with batteries are referred to as active
tags and without as passive tags. Power
is transmitted to the tag in the first place from an electric field created
by the tag interrogator. Data is transferred from the tag to
the interrogator through the modulation by the tag of the interrogator
signal. With their extra power, active tags are able to communicate with
an interrogator over considerably greater distances than passive tags
(many thousands of feet rather than only tens of feet). Active tags are
also capable of carrying and conveying greater amounts of data (thousands
of bits rather than tens). Not surprisingly, however, active tags are
more expensive. Cost is currently a major issue in RFID technology, especially
as it concerns its widespread adoption in retail.
A critical milestone in the practicality and acceptability
of RFID technology has been the adoption in late 2005 of the GEN2 data
technology standard and the ALE standard. GEN2 governs the
basic tag reading technology essential to the production of tags themselves
and tag readers. ALE deals with the collection, management and routing
of data; it addresses the problem of huge amounts of raw data generated
by RFID readers - readers can make multiple readings of the same tag in
a fraction of second, so that this "dirty data" must be filtered. In summary
the key benefits of GEN2 and ALE are the ability to read RFID tags quickly
and simultaneously.
Finally, and most importantly, we see from the technical
nature of the interaction between the RFID interrogator and the RFID tag,
that two major advantages lie with the technology and distinguish it from
bar coding.
First, that in order to read a tag,
it is unnecessary to have a direct view of it.
Communication is by electrical waves and antennas, and line of sight
is no more required than it is required of a radio in order to broadcast
to it a programme from a transmitter.
Secondly, it is possible easily to
read tags which have been attached to a succession of irregularly
shaped items which would be unsuitable to bar
code reading. Examples in everyday life typical of the application
of RFID tags are: car tagging for toll booths; hospital patients;
criminals on licence; airline luggage; library books; the tagging
of wild and domestic animals; and marathon runners.
For the
stores or warehouse, however, one critical application of tags is in making
use of the ability to read simultaneously the identities of all the tagged
components of an incoming* or outgoing load merely by scanning it from
a distance with the tag interrogator . * Provided
the supplier has tagged all materials, of course.
A second
is the ability quickly and easily to verify and count stored stock, as
in cycle counting or in the conduct of an annual stock take.
Yet a third
example, recently announced by Intermec and Cascade Products, is to mount
RFID readers in the tines of fork lift trucks and verify the correctness
of warehouse floor picks via a computer display in the truck cab.
As well,
RFID tags have been attached to stillages to help track and control the
(remarkable!) losses of these devices. A final example of use relates
to a national company distributing wines and spirits, which wished to
double check assembled loads for correctness on its vehicles before despatching
them to customers, and to a major retailer receiving loads of garments
hanging on rails at its major stores from its distribution warehouse.
Besides these, there are an ever increasing number of other applications
involving the simultaneous, mass reading of palletised loads at the point
of despatch and the verification of loads at their destinations.
In order to commence a move to RFID, the stores supervisor
might first attend a one-day course on the subject held at the DTI's RFID
Research Centre in Bracknell, Berks.. Further details are obtainable at
the Research Centre's website at http://www.rfidc.com.
In addition, it is possible to see RFID in action at an RFID demonstration
site run by Unipart Logistics and others at Oxford. Two consultancies
expert in RFID are Manhattan
Associates and Davies
& Robson.
1.10
Special Situations
1.10.1
Stockyards
Construction
The stockyard must be sited with immediate access to
adequate roads capable of taking heavy lorries. If it is to be accessed
by rail, railway lines should be sunk to ground level. And if so, if possible,
a single line to a deadend in the yard should be avoided because of subsequent
queuing problems. Beyond this, stockyards are cheap to construct, amounting
merely to expenditure on barbed wire or other fencing, plus the required
surfacing. Surfacing will depend on the loads to be stored. In order of
rising cost, they are: Gravel or Ashes - this will not support
heavy loads and heavy traffic in bad weather; Tarmac - popular,
though liable to damage and 3 times more expensive than gravel; and Concrete
- 5 times more expensive than gravel, but suitable for all loads in all
weathers. The most important additional feature is adequate drainage to
disperse rain water - even long life building materials are damaged by
constant contact with standing water.
Repairs and Maintenance
The need for a proper programme of repair and maintenance
of a stockyard is a matter of greater concern than points about the original
construction. Stockyard maintenance, especially in Winter, is a constant
activity. Areas to watch out for include: fencing (to ensure that
it is fully maintained); waterlogging (drains must be cleared so
that standing water is dispersed ... and Autumn leaves cleared up!); surface
holes (holes must be repaired); and lighting (ensuring floodlighting
is periodically checked).
Layout and Organisation
The gatehouse is the nerve centre for all documentation
including the overall company stock records system. A very minimum requirement
is connection to the central office by phone and fax. Better, even for
small stockyards, is a proper telecommunication link, perhaps involving
RDTs. Points to watch in respect of organisation are:
(a) the establishment of a proper location system, with
ground areas coded by alley ways and local areas, perhaps being marked
out by posts;
(b) If dangerous or flammable material is stored, the
provision of emergency equipment and the establishment of full procedures;
(c) measures to prevent trespassers, especially children,
from entering the area - the company is liable if
children manage to gain access and subsequently come to harm;
(d) stockyards are very frequently seen as a nuisance
to residential neighbours - traffic, noise, lighting etc, so that if possible
they should be sited well away from houses or land where house planning
permission may be granted;
(e) setting up an efficient one-way system for traffic,
with good signposting;
(f) ensuring that there is supervision during all opening
hours, including meal breaks;
(g) neatness and tidyness must prevail to minimise the
risk of accidents;
(h) the stock must be cycle counted on a regular basis.
Note that it is not unknown in poorly managed stockyards for corners of
stock to become isolated and forgotten.
(i) Remember the effect of weather on signs and, especially,
labels. Even plastic labels can become unreadable after a time, and routine
label replacement may be necessary.
1.10.2
Cold Stores
The cost of building a cold stores is about 3 times that
of an ambient store. A second considerable cost is the cost of running
the store (and the colder, the more costly): this must be balanced by
the cost that would otherwise be suffered from the deterioration of the
product. As well, temperature controlled vehicles are expensive. The temperatures
needed for the degree of cold clearly depends on what is to be stored.
Thus:
......Frozen Stores ................-30C to - 10C .............................meat,
fish
......Chilled Stores ................- 5 C to 0C ..................................fresh
meat, fish, poultry
......Cool Stores ................... -1C to + 5C ..................................dairy
produce
......Cold Stores ................... +5 C to +15C
below ambient .... citrus produce
The critical factor in the operation of a cold store
is the activity taking place at the door. If warm air is allowed to enter
the building, ice will form and will be costly to remove. Solutions to
the problem are the installation of a conveyor tunnels; air locks; and
fast acting insulated doors. (A well-known vendor of high speed, insulated
doors is Hormann,
in Leicester; Hormann have developed the DOBO docking system,
whereby docking takes place before opening.) A related problem in cold
stores is condensation. Excessive condensation can form on the product
and damage it. To avoid this, loads are best removed in small quantities,
with immediate protection using moisture-proof covers. Note that it is
common practice that storemen in cold stores take a 15 minute break per
hour. The most careful watch must be kept on racking, fixtures and fork
lift trucks continually exposed to the cold. Steel can become brittle
and dangerous. (FLTs bought new and destined to work in cold stores are
in fact modified by manufacturers). Repairs to racking are also a problem
- oxyacetylene welding is not undertaken, since welds become eutectic
and break. Instead, bolted racking is used. Repairs to a floor also present
difficulties, since there is usually a need to raise its temperature to
effect them. Care must also be taken in product stacking - it is essential
that air should be allowed to circulate the product stored.
1.10.3
Tools Stores
In general, tool control is best accomplished in conjunction
with the planning of materials and jobs, in the normal management of the
shop floor. The ability to associate particular tools with particular
jobs by augmenting the database with the relevant data is not especially
difficult. What makes tools different, however, is (1) that tools are
reusable, and (2) that tools have a limited working life, after which
they must be replaced or repaired.
Storage
and Retrieval
Although many factories maintain separate tool stores,
there are considerable advantages in incorporating actual physical
tool storage within the standard materials store. The chief of these
is that the strict procedures which govern the stores itself are then
applied also to the management of tools. That is, (a) access is restricted
to storemen only; (b) there is meticulous booking in & out of material;
(c) there is, or should be, availability of service at all times that
production takes place.
The Issue
of Tools
The requirement for tools to be issued to the shop
floor can be coordinated from the job release planning data. From
this, tool picking data is prepared each evening and the tools distributed
to the work centres each morning. There will also be direct requests
of more or less urgency from shopfloor personnel each day. And finally,
there may also be 'reverse issues' - system-generated tool
recalls based on tool life calculations on the database.
Planning
Requirements for Tools
(a). Consumable Tools: These tools are generally
worn away over a matter of a few hours in operation, and are then
discarded and replaced by new ones. They include (say) small grinding
wheels, drills etc.. Assuming the annual usage of them is sufficiently
high, a satisfactory method of planning their stock and replenishment
is to employ the conventional 2-bin system; (b). Medium Life Tools:
Many tools such as milling cutters can be used a number of times -
say, for so-many dozen hours - after which time and after due inspection
they must be discarded or repaired. A consequence of this in planning
future replenishment schedules is the difficulty of accounting for
the stock of tools on hand; (c) Long Life Tools: Tools with
a comparatively long life such as milling fixtures and drilling or
assembly jigs are often associated with a specific component. If so,
the requirement for the tool can be monitored by associating it with
that component's bill of materials. Three well-spoken of software
packages in this area are Tyco, Autotask (from Sandvik) and Super
Capes.
Tool History
Database
Where tools are individually specified, with a tool-type
id and an individual serial number, a tool history should be maintained
by recording from other shop floor support systems the actual hours
each tool is in use, along with basic backup data such as expected
life, acquisition leadtime, operations / components used with etc...
Software packages in this area include the three packages above (ie
Tyco, Autotask and Super Capes).
2. Materials &
Materials Handling
2.1
Knowledge and Protection of Materials (including FIFO)
Having a knowledge of the materials that are handled and
stored are core requirements of the storeman or warehouseman. "Knowledge"
means knowledge of the materials' sources and suppliers; any special circumstances
in their manufacture; their technical characteristics; methods of measurement;
how their quality is assessed; and the uses to which the materials are put.
The simplest and most reliable scheme that the stores supervisor
can adopt for protecting the material in the store's care is surely adoption
of a policy of FIFO (First in - First out). FIFO
ensures that the oldest stock is used first so that it has less chance of
deterioration due to the passage of time. Identification of the oldest material,
however, may not always be easy when the storeman comes to make a withdrawal,
especially in a fixed location store. Three methods for doing so are:
(a) Since the stock recording system tracks the dates
stock was put away, picking instructions might be issued taking account
of the age of stock to be removed;
(b) When stock is originally stored, its putaway date
or batch sequence number should be clearly marked;
(c) If material is particularly sensitive to deterioration
due to time, the medium chosen for its storage should be geared to enable
FIFO to be accomplished readily. For example, stored objects may be placed
at one end of a long bin, and removed by access to the far end of the
bin, the material in the bin being pulled along on rollers (ie live storage).
For any storage medium, staff must be trained to put material away supermarket
style - ie the newest to the back.
For legal, tra