Sistem Produksi 03 Material Handling
The 10 Principles of Material Handling
a) Wooden pallet b) Pallet box c)
Tote box
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The 10 Principles of Material Handling
Planning Principle
Planning Principle All material handling should be the result of a deliberate Standardization Principle
plan where the needs, performance objectives and Work Principle
functional specification of the proposed methods are Ergonomic Principle
completely defined at the outset
Unit Load Principle Definition: A plan is a prescribed course of action that is defined in advance of implementation. In its simplest
Space Utilization Principle form a material handing plan defines the material (what) System Principle
and the moves (when and where); together they define Automation Principle
the method (how and who).
Environmental Principle Life Cycle Cost Principle
The plan should be developed in consultation between the
planner(s) and all who will use and benefit from the equipment Material handling methods, equipment, controls and
to be employed. software should be standardized within the limits of Success in planning large scale material handling projects
achieving overall performance objectives and without generally requires a team approach involving suppliers,
sacrificing needed flexibility , modularity and throughput consultants when appropriate, and end user specialists from
management, engineering, computer and information systems, finance and operations.
The plan should promote concurrent engineering of product, process design, process layout, and material handling methods, as opposed to independent and sequential design practices.
The material handling plan should reflect the strategic objectives of the organization as well as the more immediate needs.
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Standardization Principle : Key Points
Work Principle
Standardization means less variety and customization in Material handling work should be minimized without the methods and equipment employed
sacrificing productivity or the level of service required of Standardization applies to sizes of containers and other
the operation
load forming components as well as operating procedures and equipment
The planner should select methods and equipment that can perform a variety of tasks under a variety of operating conditions and in anticipation of changing future requirements
Standardization, flexibility and modularity must not be incompatible
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34 Production System
Work Principle : Key Points
Work Principle : Key Points
The measure of material handling work is flow rate Where possible, gravity should be used to move materials (volume, weight or count per unit of time) multiplied by
or to assist in their movement while respecting the distance moved
consideration of safety and the potential for product Consider each pickup and set-down, or placing material in
damage
and out of storage, as distinct moves and components of The work principle applies universally, from mechanized the distance moved
material handling in a factory to over-the-road trucking Simplifying processes by reducing, combining, shortening
The work principle is implemented best by appropriate or eliminating unnecessary moves will reduce work
layout planning: locating the production equipment into a physical arrangement corresponding to the flow of work. This arrangement tends to minimize the distances that must be traveled by the materials being processed
Human capabilities and limitations must be recognized Ergonomics is the science that seeks to adapt work or and respected in the design of material handling tasks and
working conditions to suit the abilities of the worker equipment to ensure safe and effective operations
The material handling workplace and the equipment employed to assist in that work must be designed so they are safe for people
The ergonomic principle embraces both physical and
mental tasks Equipment should be selected that eliminates repetitive
and strenuous manual labour and which effectively interacts with human operators and users
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Unit Load Principle Unit Load Principle : Key Points
Unit loads shall be appropriately sized and configured in a
A unit load is one that can be stored or moved as a single way which achieves the material flow and inventory
entity at one time, such as a pallet, container or tote, objectives at each stage in the supply chain
regardless of the number of individual items that make up the load
Less effort and work is required to collect and move many individual items as a single load than to move many items one at a time
Large unit loads are common both pre and post manufacturing in the form of raw materials and finished goods
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Unit Load Principle : Key Points
Space Utilization Principle
Load size and composition may change as material and Effective and efficient use must be made of all available product moves through stages of manufacturing and the
space
resulting distribution channels. Smaller unit loads are consistent with manufacturing strategies that embrace operating objectives such as flexibility, continuous flow and just-in-time delivery. Smaller unit loads (as few as one item) yield less in- process inventory and shorter item throughput times.
Space in material handling is three dimensional and Material movement and storage activities should be fully therefore is counted as cubic space
integrated to form a coordinated, operational system In storage areas, the objective of maximizing storage
which spans receiving, inspection, storage, production, density must be balanced against accessibility and
assembly, packaging, unitizing, order selection, shipping, selectivity.
transportation and the handling of returns When transporting loads within a facility the use of
Definition: A system is a collection of interacting and/or overhead space should be considered as an option. Use of
interdependent entities that form a unified whole overhead material handling systems serves valuable floor space for productive purposes.
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System Principle : Key Points
Automation Principle
Systems integration should encompass the entire supply chain Material handling operations should be mechanized including reverse logistics. It should include suppliers,
and/or automated where feasible to improve operational manufacturers, distributors and customers.
efficiency, increase responsiveness, improve consistency Inventory levels should be minimized at all stages of
and predictability, decrease operating costs and to production and distribution while respecting considerations of
eliminate repetitive or potentially unsafe manual labor process variability and customer service.
Definition: Automation is a technology concerned with Information flow and physical material flow should be
integrated and treated as concurrent activities. the application of electro-mechanical devices, electronics
Methods should be provided for easily identifying materials and computer-based systems to operate and control
and products, for determining their location and status within production and service activities. It suggests the linking
facilities and within the supply chain and for controlling their of multiple mechanical operations to create a system movement.
that can be controlled by programmed instructions
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Automation Principle : Key Points Automation Principle : Key Points
In any project in which automation is being considered, Interface issues are critical to successful automation, pre-existing processes and methods should be simplified
including equipment to equipment, equipment to load, and/or re-engineered before any efforts at installing
equipment to operator, and in-control communications. mechanized or automated systems. Such analysis may lead
Computerized material handling systems should be to elimination of unnecessary steps in the method. If the
considered where appropriate for effective integration of method can be sufficiently simplified, it may not be
material flow and information management. necessary to automate the process.
Items that are expected to be handled automatically must have standard shapes and/or features that permit mechanized and/or automated handling.
Environmental impact and energy consumption should be Environmental consciousness stems from a desire not to considered as criteria when designing or selecting
waste natural resources and to predict and eliminate the alternative equipment and material handling systems
possible negative effects of our daily actions on the environment
Containers, pallets and other products used to form and protect unit loads should be designed for reusability when possible and/or biodegradability after disposal
Materials specified as hazardous have special needs with regard to spill protection, combustibility and other risks.
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Life Cycle Cost Principle Life Cycle Cost Principle : Key Points
A thorough economic analysis should account for the Life cycle costs include all cash flows that will occur entire life cycle of all material handling equipment and
between the time the first dollar is spent to plan or resulting systems
procure a new piece of equipment, or to put in place a new method, until that method and/or equipment is totally replaced.
Life cycle costs include capital investment, installation, setup and equipment programming, training, system testing and acceptance, operating (labor, utilities, etc.), maintenance and repair, reuse value, and ultimate disposal.
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The 10 Principles of Material Handling: Life Cycle Cost Principle : Key Points
Benefit
A plan for preventive and predictive maintenance should
Safer Operating Conditions
be prepared for the equipment, and the estimated cost of maintenance and spare parts should be included in the
Lower Costs
economic analysis. Better utilization and performance of material handling
A long-range plan for replacement of the equipment
systems
when it becomes obsolete should be prepared. Although measurable cost is a primary factor, it is certainly not the only factor in selecting among
alternatives. Other factors of a strategic nature to the organization and which form the basis for competition in the market place should be considered and quantified whenever possible.
One of the most important of the principles is the unit Included in the definition of unit load is the container that load principle
holds or supports the materials to be moved In general, the unit load should be as large as practical for
These containers are standardized in size and the material handling system that will move and store it
configuration to be compatible with the material handling
A unit load is the mass that is to be moved or otherwise
system
handled at one time Pallets are probably the most widely used, owing to their Reasons for using unit loads in material handling:
versatility, low cost, and compatibility with various types Multiple items handled simultaneously
of material handling equipment
Required number of trips is reduced Loading/unloading times are reduced Product damage is decreased
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The 10 Principles of Material Handling: The Most Important
Depth =
Width =
x Dimension
y Dimension
800 mm (32 in)
1000 mm (40 in)
Material Transport Systems 1000 mm (40 in)
900 mm (36 in)
1200 mm (48 in)
1200 mm (48 in)
1060 mm (42 in)
1060 mm (42 in)
1200 mm (48 in)
1200 mm (48 in)
Standard Pallet Sizes Commonly Used in Factories and Warehouses
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Material Handling Equipment Material Handling Equipment
Material Handling Features
Industrial truck, Low cost
Moving light loads in
manual Low rate of
a factory
deliveries/hour Industrial truck,
Medium cost
Movement of pallet
powered
loads and palletized containers in a factory or warehouse
Material Handling Features
Automated Guided High cost
Moving pallet loads
Vehicles Systems Battery-powered
in factory or
vehicles
warehouse
Flexible routing
Moving work in-
Non-obstructive
progress along
pathways
variables routes in low and medium production
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Material Handling Equipment Material Handling Equipment
Material Handling Features
Monorails and other High cost
Moving single
rail guided vehicles Flexible routing
assemblies, products,
On the floor or
or pallet loads along
overhead types
variable routers in factory or warehouse
Moving large quantities of items over fixed routes in
a factory or warehouse
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Material Handling Equipment Material Handling Equipment
Material Handling Features
Typical
Wheel Conveyor
Roller Conveyor
Equipment
Application
Conveyors, powered Great variety of
Moving product along
equipment
a manual assembly
In-floor, on-the-floor,
line
or overhead
Sortation of items in a
Mechanical power to
distribution center
move loads resides in pathway
Chain
Slat Conveyor
Cranes and hoists Lift capacities ranging Moving large, heavy
Conveyor
up to more than 100
items in factories,
tons
mills, warehouses, etc.
Industrial Trucks
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Non-powered Industrial Trucks
Industrial Trucks
(Hand Trucks)
Two basic categories: Non-powered
Human workers push or pull loads Powered Self-propelled, guided or driven by human
Common example: forklift truck
a)
Two-wheel hand truck
b)
Four-wheel dolly
c)
Hand-operated low-lift pallet truck
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Powered Trucks: Walkie Truck Powered Trucks: Walkie Truck
Wheeled forks insert into
pallet openings No provision for riding;
truck is steered by worker using control handle at front of vehicle
The forward speed of
walkie truck is limeted to around 3 mil/hr (5 km/hr)
Widely used in factories and warehouses because pallet loads are so common
Capacities from 450 kg (1000 lb) up to 4500 kg (10,000 lb)
Power sources include on- board batteries and internal combustion motors
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Powered Trucks: Towing Tractor Powered Trucks: Towing Tractor
Designed to pull one or
more trailing carts in factories and warehouses, as well as for airport baggage handling
Powered by on-board
batteries or IC engines
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Automated Guided Vehicles Systems An Automated Guided Vehicle System (AGVS) is a
material handling system that uses independently operated, self-propelled vehicles guided along defined pathways in the facility floor
Automated Guided Vehicles
The vehicles are by on-board batteries that allow many
Systems hours of operation (8-16 hr is typical) between
recharging
A distinguishing feature of an AVGS is that the pathways are unobtrusive
Appropriate where different materials are moved from
Driverless Vehicle
various load points to various unload points suitable
Electric motors, battery powered
for automating material handling in batch production and mixed model production Programming capabilities
Destination
Highly flexible, intelligent and versatile material-handling systems Path selection
Positioning
A very flexible solution for the problem of integrating a
Collision avoidance
new automated transportation line into an existing
System Discipline
transportation environment by using automatic guided vehicle
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Automated Guided Vehicles Systems: Advantages
Driverless Automated Guided Train
Clear floor space
First type of AGVS to be
No floor deck construction
introduced around 1954
Simple installation
Common application is
High availability/reliability
moving heavy payloads
Flexible performance increments
over long distances in warehouses and factories
Short installation times
without intermediate
Simple expansion
stops along the route
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AGV Pallet Truck
AGV Pallet Truck
Used to move palletized loads along predetermined routes
Vehicle is backed into loaded pallet by worker; pallet is then elevated from floor
Worker drives pallet truck to AGV guide path and programs destination
Used to move unit loads from station to station Often equipped for automatic loading/unloading of pallets and tote pans using roller conveyors, moving belts, or mechanized lift platforms
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AGVs Applications Vehicle Guidance Technology
Driverless train operations - movement of large Method by which AGVS pathways are defined and vehicles quantities of material over long distances
are controlled to follow the pathways
Storage and distribution - movement of pallet loads
Three main technologies:
between shipping/receiving docks and storage racks Imbedded guide wires - guide wires in the floor emit Assembly line operations - movement of car bodies and
electromagnetic signal that the vehicles follow major subassemblies (motors) through the assembly
Paint strips - optical sensors on-board vehicles track the white stations
paint strips
Flexible manufacturing systems - movement of work parts Self-guided vehicles - vehicles use a combination of between machine tools Dead reckoning - vehicle counts wheel turns in given direction to
move without guidance
Miscellaneous - mail delivery and hospital supplies
Beacons located throughout facility - vehicle uses triangulation to compute locations
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Vehicle Guidance Using Guide Wire
Vehicle Management Traffic control - to minimize interference between
vehicles and prevent collisions Forward (on-board vehicle) sensing Zone control
Vehicle dispatching On-board control panel Remote call stations Central computer control
Zone control to implement blocking system. Zones A, B, Travel velocity of AGV is slower than typical walking and D are blocked. Zone C is free. Vehicle 2 is blocked
speed of human worker
from entering Zone A by vehicle 1. Vehicle 3 is free to Automatic stopping of vehicle if it strays from guide path enter Zone C.
Acquisition distance
Obstacle detection system in forward direction
Use of ultrasonic sensors common
Emergency bumper - brakes vehicle when contact is
made with forward object Warning lights (blinking or rotating red lights) Warning sounds of approaching vehicles
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Monorails and Other Rail Guided Vehicles Self-propelled vehicles that ride on a fixed-rail system
Vehicles operate independently and are driven by electric motors that pick up power from an electrified rail Fixed rail system
Monorails and Other Rail Guided
Overhead monorail - suspended overhead from the ceiling
Vehicles
On-floor - parallel fixed rails, tracks generally protrude up from
the floor
Routing variations are possible: switches, turntables, and
other special track sections
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Overhead Monorail
Conveyors
Large family of material transport equipment designed to
Pathway consists of a
move materials over fixed paths, usually in large quantities
series of rollers that are
or volumes
perpendicular to direction of travel
Non-powered
Loads must possess a flat
Materials moved by human workers or by gravity
bottom to span several
Powered
rollers
Power mechanism for transporting materials is contained in
Powered rollers rotate to
the fixed path, using chains, belts, rollers or other mechanical
drive the loads forward
devices
Un-powered roller
conveyors also available
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Skate-Wheel Conveyor
Belt Conveyor
Similar in operation to
Continuous loop with
roller conveyor but use
forward path to move
skate wheels instead of
loads
rollers
Belt is made of reinforced
Lighter weight and
elastomer
unpowered
Support slider or rollers
used to support forward
Sometimes built as
loop
portable units that can be
Two common forms:
used for loading and
Flat belt (shown)
unloading truck trailers in
V-shaped for bulk materials
shipping and receiving
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Conveyors Driven by Chains and Cables
Chain Conveyor
Driven by a powered chain or cable that forms an endless
Consist of chain loops in
loop
an over-and-under
In some case, the loop forms a straight line, with a pulley at each end usually in an over-and-under configuration
configuration around
In other conveyors, the loop has a more-complex path, with
powered sprockets at the
more than two pulleys needed to define the shape of the path
ends of the pathway
Variations:
The chains travel along
Chain
channels in the floor that
Slat
provide support for the
In-floor towline
flexible chain sections
Overhead trolley Power-and-free overhead trolley
Uses individual platforms,
Four-wheel carts powered
called slats, connected to a
by moving chains or cables
continuously moving chain
in trenches in the floor Carts use steel pins (or
grippers) to project below floor level and engage the chain (or pulley) for towing
This allows the carts to be disengaged from towline for loading and unloading
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Overhead Trolley Conveyor
Cart-On-Track Conveyor
A trolley is a wheeled carriage running on an overhead track
Carts ride on a track
from which loads can be suspended
above floor level
Trolleys are connected and moved
Carts are driven by a
by a chain or cable that forms a complete loop
spinning tube
assemblies between major Often used to move parts and
Forward motion of cart is
production areas
controlled by a drive
conveyor is similar to the A power-and-free overhead trolley
wheel whose angle can be changed from zero (idle)
that the trolleys are capable of overhead trolley conveyor, except being disconnected from the drive
to 45 degrees (forward)
an asynchronous capability chain, providing this conveyor with
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Powered Conveyor Operations and Features Powered Conveyor Operations and Features Types of motions:
Another classification of conveyors:
Continuous - conveyor moves at constant velocity
Single direction
Asynchronous - conveyor moves with stop-and-go
Continuous loop
motion
Recirculating
They stop at stations, move between stations
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Cranes and Hoists Handling devices for lifting, lowering and transporting
materials, often as heavy loads Cranes Used for horizontal movement of materials
Cranes and Hoists
Hoists
Used for vertical lifting of materials
Cranes usually include hoists so that the crane-and-hoist
combination provides Horizontal transport Vertical lifting and lowering
Production System
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Hoist
Types of Cranes
Hoist with mechanical
Bridge Crane
advantage of four:
Gantry Crane
a)
sketch of the hoist
Jib Crane
b)
diagram to illustrate mechanical advantage
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Production System
Jib Crane
Recommended Hand signals
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Analysis of Material Transport Systems
Analysis of vehicle-based systems From-to charts and network diagrams Types of systems: industrial trucks, AGVS, rail-guided vehicles,
and asynchronous conveyor operations
Analysis of
Conveyor analysis
Material Transport Systems Single-direction conveyors
Closed loop conveyors Recirculating conveyor systems
The chart is organized for possible material flows in both
To
1 2 3 4 5 Represent various parameters of the material flow
direction between the load/unload stations in the layout
2 0 0 0 0 9/80 Number of deliveries
3 0 0 0 2/85 3/170 Flow rates between locations in the layout
From
4 0 0 0 0 8/85 Travel distances between from-to locations
From-To Chart Showing Flow Rates, loads/hr (Value Before the Slash Mark) and Travel Distances, m (Value After the Slash Mark) Between Stations in a Layout
Production System
Production System
Network Diagram Showing Deliveries between Load/Unload Stations
Analysis of Vehicle-Based Systems Mathematical equations can be developed to describe the
operation of vehicle-based material transport systems We assume that the vehicle operates at a constant velocity throughout its operation and ignore effects of acceleration, deceleration, and other speed differences that might depend on whether the vehicle is travelling loaded or empty or other reasons
moved or load and unload stations in a facility) points are represented by nodes Origination and destination (production departments between which parts are
Material flows are depicted by arrows between the points 123
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Analysis of Vehicle-Based Systems Analysis of Vehicle-Based Systems
The time for a typical delivery cycle in the operation of a
THE TOTAL CYCLE TIME PER DELIVERY PER VEHICLE
vehicle-based transport system consists of : Loading at the pickup station
T c = delivery cycle time (min/del)
T L = time to load at load station (min)
Travel time to the drop-off station
L between load and unload station (m, d = distance the vehicle travels
Unloading at the drop-off station
ft)
Empty travel time of the vehicle between deliveries
v c = carrier velocity (m/min, ft/min)
(min) T U = time to unload at unload station
LL
until the start of the next delivery L e cycle (m, ft) = distance the vehicle travels empty
ft/min) v e = empty vehicle velocity (m/min,
T c (slide 126) must be considered an ideal value, because The delivery cycle time can be used to determine certain it ignores any time losses due to reliability problems,
parameters of interest in the vehicle-based transport traffic congestion, and other factors that may slow down
system.
a delivery. In addition, not all delivery cycles are the same.
Let us make use of T c to determine two parameters: (1) Originations and destinations may be different from one
rate of deliveries per vehicle and (2) number of vehicles
required to satisfy a specified total delivery requirement. in preceding equation.
delivery to the next, which will affect the L d and L e terms
We will base our analysis on hourly rates and Accordingly, these terms are considered to be average
requirements; however, the equations can readily be values for the population of loaded and empty distances
adapted for other periods.
travelled by the vehicle during the course of a shift or other period of analysis.
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Analysis of Vehicle-Based Systems Analysis of Vehicle-Based Systems
The hourly rate of deliveries per vehicle is 60 min divided
To deal with time losses due to traffic congestion, let us define the traffic
factor T f by the delivery cycle time T as a parameter for estimating the effect of these losses on system
c , adjusting for any time losses
performance.
during the hour.
intersections, blocking of vehicles (as in an AVGs), and waiting in a queue at Sources of inefficiency accounted for by the traffic factor include waiting at
The possible time losses include: (1) availability, (2) traffic
load/unload stations.
congestion, and (3) efficiency of manual drivers in the case If there is no blocking of vehicles, then T
decreases. f value of T = 1.0. As blocking increases, the
of manually operated trucks. f Blocking, waiting at intersections, and vehicles waiting in line at load/unload stations are affected by the number of vehicles in the system relative to the Availability (symbolized A) is a reliability factor defined as
size of the layout.
the proportion of total shift time that the vehicle is
If there is only one vehicle in the system, little or no blocking should occur,
operational and not broken down or being repaired
and the traffic factor will be very close to 1.0.
For systems with many vehicles, there will be more instances of blocking and congestion, and the traffic factor will take a lower value.
Typical values of traffic factor for an AGVs range between 0.85 and 1.0
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Analysis of Vehicle-Based Systems Analysis of Vehicle-Based Systems
For system based on industrial trucks, including both hand
THE AVAILABLE
trucks and powered trucks that are operated by human
TIME PER HOUR PER
workers, traffic congestion is probably not the main cause
VEHICLE as 60 min
of the low operating performance sometimes observed in
adjusted by A, T f , and E
these systems. Their performance is very dependent on the work
AT = available time
AT 60 AT f E
efficiency of the operators who drive the trucks.
(min/hr per vehicle)
Let us define efficiency here as the actual work rate of
A = availability
the human operator relative to work rate expected
under standard or normal performance. T f = traffic factor
Let E symbolize the worker efficiency.
E = worker efficiency
The parameters A, T f , and E do not take into account
THE RATE OF
poor vehicle routing, poor guidepath layout, or poor
DELIVERIES PER
management of the vehicles in the system
VEHICLE
These factors should be minimized, but if present they are
accounted for in the values of L d and L e .
R dv = hourly delivery rate
AT
We now can write equations for the two performance
per vehicle (del/hr per vehicle)
R dv
parameters of interest.
T c = delivery cycle time
(slide 126) AT = the available time in
1 hr with adjustments for
time losses (min/hr)
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Analysis of Vehicle-Based Systems Analysis of Vehicle-Based Systems
The total number of vehicles (trucks, AGVs, trolleys, carts,
WORKLOAD
etc.) needed to satisfy a specified total delivery schedule R f in the system can be estimated by first calculating the
WL = workload (min/hr)
total workload required and then dividing by the available time per vehicle.
R f = specified flow rate of
Workload is defined as the total amount of work,
total deliveries per hour
WL R T
expressed in terms of time, that must be accomplished by
for the system (del/hr)
the material transport system in 1 hr.
T c = delivery cycle time
(min/del)
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Production System
Analysis of Vehicle-Based Systems Analysis of Vehicle-Based Systems
THE NUMBER OF
THE NUMBER OF
WL
n c = number of carriers
n c = number of carriers
required
required
WL = workload (min/hr)
R f = total delivery
AT = available time per
c requirements in the
AT
R dv
vehicle (min/hr per
system (del/hr)
vehicle)
R dv = delivery rate per
vehicle (del/hr per vehicle)
Although the traffic factor accounts for delays experienced by Given the AGVs layout shown in Slide 141. Vehicles travel the vehicles, it does not include delays encountered by a
couterclockwise around the loop to deliver loads from load/unload station that must wait for the arrival of a vehicle.
the load station to the unload station. Loading time at the Because of the random nature of the load/unload demands,
load station = 0.75 min, and unloading time at the unload workstations are likely to experience waiting time while
station = 0.50 min. It is desired to determine how many vehicles are busy with other deliveries.
vehicles are required to satisfy demand for this layout if the preceding equations do not consider this idle time or its
total of 40 del/hr must be completed by the AGVs. The impact on operating cost
following performance parameters are given: vehicle If station idle time is to be minimized, then more vehicles may
velocity = 50 m/min, availability = 0.95, traffic factor =
0.90, and operator efficiency does not apply, so E = 1.0. and (slide 138)
be needed than the number indicated by equation (slide 137)
Determine (a) travel distances loaded and empty, (b) ideal Mathematical models based on queuing theory are appropriate
delivery cycle time, and (c) number of vehicles required to analyze this more-complex stochastic situation
to satisfy the delivery demand.
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Analysis of Vehicle- Based Systems:
Analysis of Vehicle-Based Systems:
Example 1
Example 1
AGVs loop layout for Example 1
a)
travel distances loaded and empty
Unld = unload
b)
ideal delivery cycle time
Man = manual operation
a)
T c = 5.05 min
Dimensions in meters (m)
c)
number of vehicles required to satisfy the delivery demand
a)
AT = 51.3 min/hr per vehicle
b)
WL = 202 min/hr
c)
R dv = 10.158 del/hr
d)
n c = 3.94 = 4 vehicles
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Analysis of Vehicle-Based Systems: Analysis of Vehicle-Based Systems: Example 2
Example 2
Suatu sistem AGV akan digunakan untuk memenuhi aliran
Ke
1 2 3 4 menunjukkan pengiriman per jam antara stasiun (sebelum
material dalam Diagram Dari-Ke pada tabel berikut, yang
4L/110 garis miring) dan jarak dalam meter di antara stasiun 6L/75 (setelah garis miring). Gerakan dengan indikasi “L” adalah
10L/80
0/NA 3L/70 perjalanan kereta dengan beban (Loaded), sementara “E”
0/0 0/NA menandakan pergerakan kereta saat kosong (Empty).
3 4E/110
0/NA
0/NA 0/0 Faktor lalu-lintas diasumsikan bernilai 0.9. Asumsikan
4 9E/80
0/NA
ketersediaan A = 0.95. Kecepatan AGV = 0.8 m/detik. Apabila waktu penanganan beban tiap penyerahan = 1.5 menit, tentukan berapa jumlah kereta yang diperlukan untuk memenuhi pengiriman seperti yang ditunjukkan dalam tabel per jam?
Three basic types of conveyor operations: Consider the case of a single direction powered conveyor with one load station at the upstream end and one
Single direction conveyors unload station at the downstream end as in (Slide 147). Continuous loop conveyors
Materials are loaded at one end and unloaded at the
other.
Recirculating conveyors The materials may be parts, cartons, pallet loads, or other
unit loads.
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Conveyor Analysis: Single Direction Single-Direction Conveyor
Conveyors
THE TIME REQUIRED TO MOVE MATERIALS FROM LOAD STATION TO UNLOAD STATION
(assuming the conveyor operates at a constant speed)
T = delivery time (min)
d = length of conveyor
between load and unload
stations (m, ft) v = conveyor velocity
(m/min, ft/min) c
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Conveyor Analysis: Single Direction Conveyor Analysis: Single Direction Conveyors
Conveyors
The flow rate of materials on the conveyor is determined
THE FLOW RATE OF
by the rate of loading at the load station.
MATERIALS
The loading rate is limited by the reciprocal of the time required to load the materials.
R f = material flow rate
Given the conveyor speed, the loading rate establishes
(parts/min)
the spacing of materials on the conveyor.
R L = loading rate
(parts/min)
c = center-to-center
spacing of materials on the
conveyor (m/part, ft/part) T L = loading time (min/part)
One might be tempted to think that the loading rate R L is
An additional requirement for
the reciprocal of the loading time T . However, R is set by
loading and unloading is that
the flow rate requirement R the time required to unload
f , while T L is determined by
the conveyor must be equal to
ergonomic factors.
or less than the loading time
The worker who loads the conveyor may be capable of performing the loading task at a rate that is faster than
T U = unloading time (min/part)
the required flow rate.
On the other hand, the flow rate requirement cannot be
If unloading requires more time
than loading, then unremoved
set faster than it is humanly possible to perform the
loads may accumulate or be
loading task.
dumped onto the floor at the downstream end of the conveyor
Production System
Production System
Conveyor Analysis: Single Direction Conveyor Analysis: Single Direction Conveyors
Conveyors
We are using parts as the material in (slide 150) and
THE FLOW RATE OF
(slide 152), but the relationships apply to other unit loads
MATERIALS
as well The advantages of the unit load principle can be
R f = flow rate (parts/min)
demonstrated by transporting n p parts in a carrier rather
n p = number of parts per
than a single part
carrier
s c = center-to-center
spacing of carriers on the
conveyor (m/carrier,
ft/carrier)
T L = loading time per carrier (min/carrier)
Production System
Production System
Conveyor Analysis: Single Direction Conveyor Analysis: Single Direction Conveyors
Conveyors: Example 3
The flow rate of parts transported by the conveyor is
A roller conveyor follows a pathway 35 m long between a potentially much greater in this case
parts production department and an assembly department. Velocity of the conveyor is 40 m/min. Parts are loaded into
However, loading time is still a limitation, and T L may large tote pans, which are placed onto the conveyor at the consist of not only the time to load the carrier onto the
load station in the production department. Two operators conveyor but also the time to load parts into the carrier
work the loading station. The first worker loads part into tote
The preceding equations must be interpreted and pans, which takes 25 sec. each tote pan holds 20 parts. Parts enter the loading station from production at a rate that is in perhaps adjusted for the given application
balance with this 25-sec cycle. The second worker loads tote pans onto the conveyor, which takes only 10 sec. Determine: (a) spacing between tote pans along the conveyor, (b) maximum possible flow rate in parts/min, and (c) the maximum time required to unload the tote pan in the assembly department balance with this 25-sec cycle. The second worker loads tote pans onto the conveyor, which takes only 10 sec. Determine: (a) spacing between tote pans along the conveyor, (b) maximum possible flow rate in parts/min, and (c) the maximum time required to unload the tote pan in the assembly department
spacing between tote pans along the conveyor Consider a continuous loop conveyor such as an
a) s c = 16.67 m overhead trolley in which the pathway is formed by an
maximum possible flow rate in parts/min endless chain moving in a track loop, and carriers are
b)
suspended from the track and pulled by the chain R f = 48 parts/min
a)
The conveyor moves parts in the carriers between a load
c)
the maximum time required to unload the tote pan in
station and an unload station
the assembly department The complete loop is divided into two sections: a delivery
a) T U ≤ 25 sec (forward) loop in which the carriers are loaded and a return loop in which the carriers travel empty (slide 159)
The length of the delivery loop is L d , and the length of the
return loop is L e
Total length of the conveyor is therefore L=L d +L e
Production System
Production System
Conveyor Analysis: Continuous Loop Conveyor Analysis: Continuous Loop Conveyors
Conveyors
THE TOTAL TIME REQUIRED TO TRAVEL THE COMPLETE LOOP
T c = total cycle time (min)
v c = speed of the conveyor chain (m/min,
ft/min)
Production System
Production System
Conveyor Analysis: Continuous Loop Conveyor Analysis: Continuous Loop Conveyors
Conveyors
THE TIME A LOAD
The total number of carriers in
SPENDS IN THE the loop (carriers are equally
spaced along the chain at a
FORWARD LOOP
distance s c apart) n c = number of carriers
T d = delivery time on the
L = total length of the
forward loop (min)
conveyor loop (m, ft)
between carriers (m/carrier, c = center-to-center distance
ft/carrier)
The values of n c must be
c integer, and so L and s consistent with that c must be
requirement
Each carrier is capable of
(as in the single direction
holding n p parts on the
conveyor) THE
delivery loop, and it holds
MAXIMUM FLOW
no parts on the return RATE BETWEEN LOAD
AND UNLOAD
trip.
Total Parts in System
STATION
Since only those carriers
on the forward loop
R f = parts per minute
contain parts, the
maximum number of parts
Again, this rate must be
in the system at any one
consistent with limitation on the time it takes to load and
time is given by:
unload the conveyor
Production System
Production System
Conveyor Analysis: Recirculating Conveyors Conveyor Analysis: Recirculating Conveyors
– Speed Rule
Recall “conveyor operations and features” and the two This principle states that the operating speed of the problems complicating the operation of a recirculating
conveyor must be within a certain range
conveyor system: (1) the possibility that no empty carriers are immediately available at the loading station
The lower limit of the range is determined by the when needed and (2) the possibility that no loaded
required loading and unloading rates at the respective carriers are immediately available at the unloading station
stations
when needed These rates are dictated by the external systems served There are three basic principles that must be obeyed in
by the conveyor
designing such a conveyor system ( Kwo’s principles):
Speed rule L and R U represent the required loading and
Let R
unloading rates at the two station, respectively Capacity constraint
Uniformity principle
Production System
Production System
Conveyor Analysis: Recirculating Conveyors Conveyor Analysis: Recirculating Conveyors – Speed Rule
– Speed Rule
The conveyor speed must The upper speed limit is determined by the physical satisfy the relationship
capabilities of the material handlers to perform the loading and unloading tasks
R L = required loading rate Their capabilities are defined by the time required to load (parts/min)
and unload the carriers
R U = the corresponding
max R L , R U
unloading rate
– Speed Rule
– Speed Rule
T L = time required to load In addition to (slide 167 and 169), another limitation is of
a carrier (min/carrier) course that the speed must not exceed the technological T U = time required to
limits of the mechanical conveyor itself
unload a carrier
v c 1 1 min ,
Production System
Production System
Conveyor Analysis: Recirculating Conveyors Conveyor Analysis: Recirculating Conveyors – Capacity Constraint
– Capacity Constraint
The flow rate capacity of the conveyor system must be at
In this case, R f must be
least equal to the flow rate requirement to accommodate
interpreted as a system
reserve stock and allow for the time elapsed between
specification required of
loading and unloading due to delivery distance
the recirculating conveyor
Production System
Production System
Conveyor Analysis: Recirculating Conveyors Conveyor Analysis: Recirculating Conveyors – Uniformity Principle
– Example 4
This principle states that parts (loads) should be
A recirculating conveyor has a total length of 300 m. Its uniformly distributed throughout the length of the
speed is 60 m/min, and the spacing of part carriers along conveyor, so that there will be no sections of the
its length is 12 m. Each carrier can hold two parts. The conveyor in which every carrier is full while other
task time required to load two parts into each carrier is sections are virtually empty
0.20 min and the unload time is the same. The required The reason for the uniformity principle is to avoid
loading and unloading rates are both defined by the unusually long waiting times at the load or unload stations
specified flow rate, which is 4 parts/min. Evaluate the for empty or full carriers (respectively) to arrive
conveyor system design with respect to Kwo’s three principles
Function – to store materials (e.g., parts, work-in-process, finished goods) for a period of time and permit retrieval when required
Used in factories, warehouses, distribution centres,
Storage System Performance And
wholesale dealerships, and retail stores
Location Strategies
Important supply chain component Automation available to improve efficiency
Production System
Production System
Types of Materials Typically Stored in Types of Materials Typically Stored in Factory (relate to the product)
Factory (relate to the process)
Type Description
Type
Description
Raw materials Raw stock to be processed (e.g., bar stock, sheet
Chips, swarf, oils, other waste products left over after metal, plastic moulding compound)
Refuse
processing; these materials must be disposed of, Purchased
Parts from vendors to be processed or assembled sometimes using special precautions parts
Cutting tools, jigs, fixtures, molds, dies, welding wire, Work-in-
(e.g., castings, purchased components)
Tooling
Partially completed parts between processing and other tooling used in manufacturing and assembly; process
operations or parts awaiting assembly supplies such as helmets, gloves, etc., are usually Finished
Completed product ready for shipment
included
product
Parts are needed for maintenance and repair of Rework and
Spare parts
Parts that are out of specification, either to be
factory equipment
scrap reworked or scrapped
Production System
Production System
Types of Materials Typically Stored in Factory (relate to overall support of factory operations)
Storage System Performance: Measures
Type Description
Storage capacity - two measures:
Office supplies Paper, paper forms, writing instruments, and other
Total volumetric space
items used in support of plant office
Total number of storage compartments (e.g., unit loads)
Plant records Records on product, equipment, and personnel Storage density - volumetric space available for storage relative
to total volumetric space in facility Accessibility - capability to access any item in storage
System throughput - hourly rate of storage/retrieval
transactions Utilization - the proportion of time that the system is actually being used for performing storage and retrieval operations compared with the time it is available
Availability ( reliability ) – the proportion of time that the system is capable of operating (not broken down) compared
with the normally scheduled shift hours
System throughput is limited by the time to perform a The sum of the element times is the transaction time that S/R transaction
determines throughput of the storage system Elements of storage transaction:
Throughput can sometimes be increased by combining Pick up load at input station
storage and retrieval transactions in one cycle, thus Travel to storage location
Place load into storage location reducing travel time; this is called a dual command cycle
Travel back to input station When either a storage and a retrieval transaction alone is Elements of retrieval transaction:
performed in the cycle, it is called a single command cycle Travel to storage location
Pick item from storage Travel to output station Unload at output station
Production System
Production System
Storage Location Strategies
Storage Location Strategies
Randomized storage –
Typical bases for deciding locations:
Incoming items are stored in any available location
Items stored in item number sequence
Usually means nearest available open location
Items stored according to activity level
Dedicated storage – Items stored according to activity-to-space ratios Incoming items are assigned to specific locations in the storage facility
Production System
Production System
Comparison of Storage Strategies Types of Storage Equipment and Methods Less total space is required in a storage system that uses
Storage type
Advantage/
Typical
a randomized storage strategy
Disadvantage
application
Dedicated storage requires space for maximum inventory level
•Storage of low of each item
Bulk storage
•Highest density is
turnover, large stock Higher throughput rates are achieved in a system that
possible
or large unit load uses dedicated storage strategy based on activity level
•Low accessibility
•Low possible
The most active items can be located near the input/output
cost/square foot
•Palletized loads in Compromise: Class-based dedicated storage
point
Rack systems
•Low cost
•Good storage
warehouses
Items divided into classes according to activity level
density
•Good accessibility
Random storage strategy used within each class
Storage type Advantage/
Typical Disadvantage
Typical
Storage type
Shelves and bins •Some stock items
•Work in progress not clearly visible
•Storage of
Automated storage
•High throughput
commodity items in
•Computerized
•Final product
warehousing and Drawer storage
shelve/bins
inventory control
•Contents of drawer •Small tools
distribution center easily visible
system
•Order picking •Good accessibility •Repair part
•Small stock items
•Highest cost
equipment
•Relatively high cost
•Automated material handling systems
Production System
Production System
Conventional storage methods and equipment
Bulk Storage
Bulk storage - storage in an open floor area
Bulk storage
Problem: achieving proper balance between storage density
arrangements:
and accessibility
(a) high-density bulk
Rack systems - structure with racks for pallet loads
storage provides low
Permits vertical stacking of materials
accessibility,
Shelving and bins - horizontal platforms in structural
(b) bulk storage with loads
frame
forming rows and blocks for improved