A/P Lee Kim Seng

A/P Lee Kim Seng

1. Purpose of Material Handling2. Criteria to Fulfil during Material Handling3. Areas of Application4. Types of Material Handling Equipment5. Types of Material Handling System6. Analysis of Material Handling System7. Analysis Techniques:

- From-to-chart (Tabular technique)- Flow diagram (Graphical technique)

A/P Lee Kim Seng

Common Types:Conveyor systemAGVS

A/P Lee Kim Seng

Types of conveyor:Roller conveyorSkate-wheel conveyorBelt conveyorChain conveyorSlat conveyorOverhead trolley conveyorIn-floor towline conveyorCart-on-track conveyoretc

Analysis of conveyor system:Single directionContinuous loopRe-circulating conveyor

A/P Lee Kim Seng

AGVS:

Types of AGVS:Driverless trainAGV pallet truckAGV unit load carrier

Application of AGVS

Quantitative Analysis of AGV

A/P Lee Kim Seng

A/P Lee Kim Seng

Criteria to Fulfil during Material Handling

1. Must be performed safely

2. Must be performed efficiently (at low cost)

3. Must be performed in a timely manner

4. Must be performed accurately (right materials in right quantities to the right location)

5. Must be performed without damage to the materials

A/P Lee Kim Seng

• Manufacturing

• Warehousing

• Distribution

• Retailing

• Inventory

• Postal services

• Airport baggage handling etc.A/P Lee Kim Seng

A/P Lee Kim Seng

Table 14.1 Types of Material Handling Equipment

• Hand trucks – platforms with wheels for manual movement of items, unit loads, and bulk materials

• Powered trucks – powered vehicle with platform for mechanized movement of items, unit loads, and bulk materials. Driven by human beings, powered by battery, gasoline, or propane gas

• Cranes, monorails, and hoists – handling devices, usually manually operated, designed for lifting, lowering, and transporting heavy objects

• Conveyors – large family of handling devices, often mechanized, sometimes automated, designed to move materials between specific locations over a fixed path, generally in large quantities or volumes

• Automated guided vehicle systems (AGVS) – battery operated, automatically steered vehicles designed to follow defined pathways. Some are capable of automatically loading and unloading unit loads. Usually interfaced, with other automated systems to achieve full benefits of integrated automation

• Other handling equipment – miscellaneous category to cover the many other kinds of hardware that are used for material handling

Types of Material Handling Equipment (Con’t)

A/P Lee Kim Seng

Types of Material Handling Equipment (Con’t)

A/P Lee Kim Seng

Table 14.2 Attributes and Characteristics by Which to Classify Material Handling Equipment and Systems

• Manual (vs.) Mechanized (vs.) Automated and computer-controlled

• Mobile (vs.) Fixed-in-position

• Floor mounted (vs.) Overhead

• Fixed route (vs.) Programmable routing

• One-directional flow (vs.) Flow in multiple directions

• Discrete items or loads (vs.) Continuous

• Multiple items per carrier (vs.) Single item per carrier

• Delivery-only (vs.) Delivery-and-storage systems

• Single pickup station and single drop-off station (vs.) Multiple pickup stations and multiple drop-off stations

• Pickup and drop-off at the same station (vs.) Pickup and drop-off stations separate

• Equal rates of loading and unloading (vs.) Unequal rates of loading and unloading

• Placement of items on the handling system Continuous placement (vs.) Uniformly spaced discrete placement (vs.) Randomly spaced discrete placement

Types of Material Handling Equipment (Con’t)

A/P Lee Kim Seng

• Usually assembled into system which must be specified and configured for the particular application

• Design of system depends on:

1. Parts, materials, or products to be handled

2. Quantities to be moved

3. Distances of the moves

4. Type of production system that handling equipment will serve

5. Available budgetA/P Lee Kim Seng

1. Transfer mechanisms in automated flow lines

2. Conveyors used in auto/manual assembly lines

3. Parts feeding devices in automated assembly

4. Pallet shuttles in NC machining centres

5. Industrial robots used for material handling

6. Automated guided vehicles

A/P Lee Kim Seng

• One must begin with an analysis of the materials to be moved when planning for a Material Handling System

• Factors include:

1. The quantities of materials to be moved

2. The rate of flow required

3. The scheduling of the moves

4. The route by which the materials are to be moved

5. Miscellaneous factorsmoving of materials between floors,number of loading & unloading stations etc.

A/P Lee Kim Seng

A/P Lee Kim Seng

Table 14.3 Characteristics of Materials

Consideration of material and movement conditions (Con’t)

HotWetDirtySticky

Condition

ExplosiveToxicCorrosive

Safety risk

FragileBrittleSturdy

Risk of damage

Long and FlatRoundSquare

Shape

Weight per pieceWeight per unit volume

Weight

Length, width, and heightVolume

Size

SolidLiquidGas

Physical form

Measures or descriptorsCategory

A/P Lee Kim Seng

• Several approaches that can be used –Tabular, graphical techniques and quantitative approach

• 2 common types of techniques:

1. From-to chart (Tabular technique)

2. Flow diagram (Graphical technique)

A/P Lee Kim Seng

Table 14.4 From-to Chart Showing Number of Deliveries Required between Different Stations in a Layout

00000580000432000390000206590154321From:

To:

A/P Lee Kim Seng

Table 14.5 From-to Chart Showing Distances between Different Stations in a Layout a

0NANANA10053000NANANA46003000NANA3300NANA0NA2NA7004002000154321From:

To:

a Distances shown in feet. “NA” indicates that the distances are not applicable to this layout

A/P Lee Kim Seng

Flow diagram showing material flow between different loading and unloading stations. Nodes represent load or unload station; arrows with numbers indicate material flow rates.

1

2

3

4583

9

9

5

26

A/P Lee Kim Seng

Assuming Flow rate = Rf

Length of delivery = Ld

According to Muther and Haganas, the

Transport work = RfLd

Total Transport Work (TTW) = ΣΣΣΣRfLd

Due to time and inefficiency in the operation, material handlingsystem must be designed for higher capacity than that given by TTW

Let handling time for loading & unloading activities = Th

Distance of empty move = Le

Velocity of carrier = Vc

Inefficiency sometimes defined by term Traffic factor (Ft)

A/P Lee Kim Seng

Where Eh is the overall efficiency of the handling system

Efficiency for a material handling system:Ld/Vc

Eh = FtLd/Vc + Th + Le/Vc

If, the number of individual parts or items in the unit load = np

TTWThus, in planning, the required system capacity =

Eh

TTWThen, the required handling system capacity =

npEh

A/P Lee Kim Seng

• Reasons for losses and inefficiency during operation of the system include:

1. Loading and unloading time

2. Return trip with no loads

3. System downtime for maintenance & repair

4. Traffic congestion

5. Schedule problems etc.A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

Attributes:• Generally mechanized, and sometimes automated

• Fixed-in-position to establish the path

• Either floor mounted or overhead

• Almost always limited to one-directional flow of materials

• Generally move discrete loads, but some types can be used to move bulk or continuous loads

• Either delivery-only or delivery-plus-storage of items

A/P Lee Kim Seng

1. Roller conveyors – The pathway consists of a series of tubes (rollers) that are ⊥⊥⊥⊥ to the direction of travel

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

2. Skate-wheel conveyors – Similar to roller conveyors. Instead of rollers, skate wheels rotating on shafts connected to the frame are used. Loads must be lighter since the contacts between the loads and the conveyor are much more concentrated

A/P Lee Kim Seng

A/P Lee Kim Seng

3. Belt conveyors –

a) Flat belts for pallet, parts, or even certain types of bulk materials;

b) Troughed belts for bulk materials

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

4. Chain conveyors – Made of loops of endless chain in an over-and-under configuration around a powered sprockets at the ends of the pathway

A/P Lee Kim Seng

A/P Lee Kim Seng

5. Slat conveyors – Uses individual platforms, call slats, that are connected to a continuously moving chain

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

6. Overhead trolley conveyors – A wheeled carriage running on an overhead rail from which loads can be suspended

A/P Lee Kim Seng

Examples of Overhead trolley Conveyors

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Examples of Overhead trolley Conveyors

A/P Lee Kim Seng

7. In-floor towline conveyors – Make use of wheeled carts powered by means of moving chains or cables located in trenches in the floor

A/P Lee Kim Seng

Examples of In-floor towline Conveyors

A/P Lee Kim Seng

8. Cart-on-track conveyors – Use individual carts riding on a 2-railed track contained in a frame that places the track a metre or so above floor level. Carts driven by means of a rotating tube that runs between the 2 rails. A drive wheel, attached to bottom of cart and set at an angle to the rotating tube, rests against it and drives cart forward

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

9. Other types include chutes, ramps, tubes, screw conveyors, vibrating system and vertical lift conveyors

A/P Lee Kim Seng

Screw conveyor

A/P Lee Kim Seng

A/P Lee Kim Seng

Let Rf to be the rate of flow of parts (parts/hr) moving along the pathway

Let sc be the spacing between carriers

The time required to unload the conveyor = Tu

A/P Lee Kim Seng

Then flow rate

Vc 1≤≤≤≤ I.e (Tu ≤≤≤≤ TL)

Sc TL

The time required to unload the conveyor, Tu , must be less or equal to the loading time, TL

Assuming each carrier can hold np parts, the flow rate of parts on the conveyor system will be

npVc npRf = ≤≤≤≤

Sc TL sc is the spacing between carriers

A/P Lee Kim Seng

Consider a continuous closed-loop conveyor (e.g. an overhead trolley conveyor). The complete loop is divided into 2 portions: the delivery (forward) loop and the return loop.

Assumption:

The parts are transported in carriers or containers that are equally spaced at a separation of sc and fixed to the conveyor.

(Ld + Le)Time required to travel the complete loop =

Vc A/P Lee Kim Seng

If nc represent the number of carriers in the system, then

(Ld + Le)nc =

sc

Since only those carriers on the forward loop contain parts, thetotal number of parts in the system at any one time is

npLd npncLdTotal parts in system at any one time = =

sc Ld + Le

The parts feed rate of the system is again given by

npVcRf =

scA/P Lee Kim Seng

•Provides for storage and delivery of parts

•Used to accumulate parts to smooth out effects of changes in rates of loading and unloading the conveyor (Storage function)

•Problems in operating :

1.No empty carriers may be immediately available at the loading station when needed;

2.No loaded carriers may be immediately available at the unloading station when needed

A/P Lee Kim Seng

A re-circulating conveyor has a total length of 500 ft. Its speed is 100 ft/min and the spacing of part carriers along its length is 25 ft. Each carrier can hold two parts. Robots are used to load and unload the conveyor at its load and unload stations. The time required to load a part is 0.20 min and the unload time is the same. The required loading and unloading rates are both 1.0 part/min.

(a) What is the maximum possible flow rate of parts on the conveyor system?

(b) How many parts could be contained on the conveyor system if every carrier were filled to capacity?

(c) How much time is required for the conveyor to make one complete loop?

A/P Lee Kim Seng

(c) At the given speed, it takes (500 ft) / (100 ft/min) = 5.0 min for the conveyor to make a complete loop.

(b) The total number of carriers (Ld + Le)nc =

scnc = (500 ft) / (25 ft/carrier)

= 20 carriers

The total number of parts, at 2 parts/carrier = 40 parts = nc np

(a) The maximum possible flow rate occurs when every carrier on the conveyor system is filled. This flow rate is given by

npVc npRf = ≤≤≤≤

Sc TL

Rf = (2 parts/carrier) (100 ft/min) / (25 ft/carrier)

= 8 parts/min

A/P Lee Kim Seng

• Uses independently operated, self-propelledvehicles that are guided along defined pathways in the floor

• Generally applied in automation of low and medium-volume handling situation, where routing of materials is more individualized

• Used where different materials must be moved from various load points to various unload points

A/P Lee Kim Seng

1. Driverless train – This type consists of a towing vehicle (AGV) that pulls one or more trailers to form a train. Most suitable where heavy payloads must be moved over long distance in the warehouse or factories with intermediate pickup and drop-off points along the route.

A/P Lee Kim Seng

A/P Lee Kim Seng

2. AGVS pallet trucks – Automated guided pallet trucks are used to move palletized loads along pre-determined routes. A more recent addition is the forklift AGV.

A/P Lee Kim Seng

A/P Lee Kim Seng

3. AGVS unit load carrier – This type of AGVS is used to move unit loads from one station to another station.

- Often equipped for automatic loading and unloading by means of powered rollers, moving belts, mechanized lift platforms, or other devices

- light load AGV – up to 250 kg

- assembly line AGV – design to carry partially completed sub-assembly through a sequence of assembly workstations to build the product

A/P Lee Kim Seng

A/P Lee Kim Seng

1. Driverless train operation

2. Storage/distribution systems

3. Assembly-line operation

4. Flexible Manufacturing System

5. Miscellaneous Applications – Mail delivery and Hospital material handling operation

A/P Lee Kim Seng

Let the velocity of the cart (vehicle) in the AGVS = Vc

Load handling time = Th

LdTravel time to the drop off =

Vc

LeEmpty travel time between deliveries =

Vc

Ignoring any effect of traffic congestion, the total time per delivery per vehicle is given by

Ld Le

Tv = + Th +Vc Vc

A/P Lee Kim Seng

60Number of deliveries per vehicle / hr =

Tv

Typical values of the traffic factor (Ft) for an AGVS range between 0.85 and 1.0

60 FtNumber of deliveries / hr / vehicle =

Tv

Alternatively, using the handling system efficiency Eh,

Delivery time (Ld / Vc)Eh = Traffic factor = Ft

Total time Tv

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The total number of vehicles required in the system is given by

Number of deliveries required / hrNumber of AGVs=

Number of deliveries / hr / vehicle

60 Ft 60 EhNumber of deliveries / hr / vehicle = =

Tv Ld / Vc

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It is desired to determine how many vehicles will be required to satisfy demand for a particular AGVS. The system must be capable of making 40 deliveries/hr. The following specifies the performance characteristics of the system:

Vehicle velocity = 150 ft/minAverage distance traveled per delivery = 450 ftPick-up time = 45 s (0.75 min)Drop-off time = 45 s (0.75 min)Average distance traveling empty = 300 ftTraffic factor = 0.90

Determine the number of vehicles required to satisfy the delivery demand. Also determine the handling system efficiency.

Vc Ld

LeFt

Th

A/P Lee Kim Seng

The total time per delivery per vehicle is given by

Ld Le

Tv = + Th +Vc Vc

450 300Tv = + 0.75 + 0.75 +

150 150= 3.0 + 1.5 + 2.0= 6.5 min

The number of deliveries per hour per vehicle is60 (0.90) / 6.5 = 8.3077 deliveries / hr/ vehicle

60 FtNumber of deliveries / hr / vehicle =

Tv

A/P Lee Kim Seng

Therefore, the number of vehicles required is

40 / 8.3077 = 4.81 vehicles

This value should be rounded up to 5 vehicles.

The total number of vehicles required in the system is given by

Number of deliveries required / hrNumber of AGVs=

Number of deliveries / hr / vehicle

Note: If value works out to be 4.1 vehicles, it is also rounded to 5 vehicles and NOT 4 vehicles so as to be able to meet the requirements

A/P Lee Kim Seng

Using the handling system efficiency Eh,

Delivery time (Ld / Vc)Eh = Traffic factor = Ft

Total time Tv

3.0 (0.90)Eh =

6.5= 0.4154

60 Ft 60 EhNumber of deliveries / hr / vehicle = =

Tv Ld / Vc

Using this value to check with the equation below

The number of deliveries per hour per vehicle is 60 (0.4154) / 3.0 = 8.31 deliveries / hr / vehicle

A/P Lee Kim Seng

A/P Lee Kim Seng