ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Fundamentals of Equipment Selection:
Conveyors used where:
> Flow of material is continuous or very close to being continuous
> Path of material movement is fixed
Trucks used where:
> Delivery in batches is adequate
> Flexibility is important
Cranes are used:
>Mainly to lift very heavy pieces
Methods of Equipment Selection:
Major factors that can impact equipment selection:
 Material
(type, weight, volume, shape, size)
 Movement
(path, freq., loading/unloading mechanism, aisle space)
 Storage
(area, volume, obstacles, shape of storage facility, columns, spacing, policies)
 Costs
(operating expenses, investment, interest rate, depreciation, useful life of equipment)
 Flexibility
(Multiple Tasks, Different Products, Use Obsolete Equipment)
Material-Handling Equipment Evaluation:
> Cost per unit distance evaluation
Example: Forklift cost $20,000 with 5 years expected life
Fuel cost = $10 per 8 hours
Maintenance = $1.50 / hour
Average truck travel per day = 10,000 feet
(Assume 360 days operation / year with operator earning $10/hour)
Calculate cost per foot.
Solution:
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ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Equipment Selection Example:
A warehouse receives daily loads of A, B, and C from the plant. Shipments are made once a week. Material
characteristics are listed in the following table:
Warehouse:
Volume (in.)
Distance (ft)
Distance (ft)
Units
Units
Item
(LxWxH)
from receiving
from shipping
received / day shipped /wk
A
12x6x6
525
125
118
590
B
48x36x24
225
375
165
825
C
24x24x24
400
200
121
605
The company is considering purchasing a tractor that pulls four trucks, a forklift truck, or a hand-truck for
use in transporting. Pertinent sizes and costs for these are listed in the following table:
Equipment
Tractor truck
Forklift truck (pallet)
Hand-truck
Maximum
Volume (in3)
4(60x27x72)
48x48x48
60x27x72
Loading/Unloading
Cost ($)
1.20/trip
0.05/trip
0.40/trip
Cost/
Foot ($)
0.010
0.007
0.005
The loading and unloading cost includes the cost for loading and unloading for one trip and the cost for
making the return trip to pick up another load.
Determine the least expensive method for transporting the mfg items for the options given:
Solution:
The number of units that can be moved per trip is the equipment capacity (in volume) / unit (in volume).
> For Item A & using tractor truck: the volume of truck / volume of the item:
> For Item A & Forklift:
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Using this information and table information, find transportation cost for Item A using each piece of
equipment.
Equipment Selection
Item
A
B
C
Volume(in.)
Distance (ft)
(LxWxH)
12x6x6
48x36x24
24x24x24
from Receiving
525
225
400
Distance (ft)
from
shipping
125
375
200
Units
Units
Received/day
118
165
121
Shipped/wk
590
825
605
Max.
Load/Unload
Cost per
Equipment
Volume (in3)
Cost ($)
Foot ($)
Tractor Truck
4(60x27x72)
1.200
0.010
Forklift
48x48x48
0.050
0.007
Hand-truck
60x27x72
0.400
0.005
Trips for Item A
Equipment
R
S
R
S
Tractor Truck
1
1
118/960
590/960
Forklift
1
3
118/256
590/256
Hand-truck
1
3
118/240
590/240
Trips for Item B
Equipment
R
S
R
S
Tractor Truck
21
104
165/8
825/8
Forklift
83
413
165/2
825/2
Hand-truck
83
413
165/2
825/2
Trips for Item C
Equipment
R
S
R
S
Tractor Truck
6
26
121/24
605/24
Forklift
16
76
121/8
605/8
Hand-truck
21
101
121/6
605/6
Receiving Costs = Loading & Unloading cost per week + Travel Cost per Week
RC = (Loading/Unloading costs/trip)(trips/day)(5 days) + (cost/ft)(number trips)(ft/trip)(5
days)
Shipping Costs = Loading & Unloading cost per order + Travel Cost per Order
SC = (Loading/Unloading cost/trip)(number trips) + (cost/ft)(number trips)(ft/trip)
Total Costs = RC+SC
eg. RC (A_TT) = (1.20 per trip)(1 trip/day)(5 days) + (.01/ft)(1trip)(525feet)(5days) = $32.25
SC(A_TT) = (1.20 per trip)(1 trip) + (.01/ft)((125ft)(1trip) = $2.45
TC = $32.25 + $2.45 = $34.70
(Total Costs)
Equipment
Tractor Truck
Forklift
Hand-truck
Item
A
34.70
21.40
19.23
B
583.05
1779.16
Too Heavy
3
C
239.20
338.20
203.60
TC
856.95
2138.77
NA
LC
ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Equipment Selection Notes:
Receiving cost = loading & unloading cost per week + travel cost per week
RC = (Loading & unloading cost per trip)(trips per day)(5 days) +
(cost per foot)(number of trips)(feet per trip)(5 days)
Shipping cost = loading & unloading cost per order + travel cost per order
SC = (Loading & unloading cost per trip)(number of trips) +
(cost per foot)(number of trips)(feet per trip)
Total Cost (Item) = Receiving Cost + Shipping Cost
Calculations for Equipment Selection Problem:
Items
Equipment
A
B
C
Tractor truck
$34.70
$583.05
$239.20
Forklift truck
$21.40
$1779.16
$338.20
Hand truck
$19.23
Not feasible*
$203.60
* Item B is too heavy for Hand Truck
The Tractor truck has the least total cost and is therefore selected.
Total Cost
$ 856.95
$2138.77
Not feasible
Work Volume Analysis:
Tabular method (See Table 9.4) for finding the number of material handling units (forklift trucks) needed
to perform a material moving task. It consists of measuring the volume, characteristics, and handling
requirements of work that must be moved from one work center to another. The measurements may be
divided on the basis of the type of work such as receiving, shipping, storage, and in-process movement.
Table 9.4 is an analysis of receiving docks for a plant that is supplied by both rail cars and trucks.
Note:
Column 1 identifies the location where the analysis is performed.
Columns 2 & 3 identify the commodity and mode of transportation used.
Columns 4,5,6 estimate the loads per day of the transportation unit that will need services.
Column 6 is taken as the design parameter.
Column 7 indicates where the unloaded material should be stored.
Column 8 indicates the load quantity per unit of the transportation (one truck, etc).
Column 9 identifies the MH unit used to unload & its capacity per operation.
Column 10 calculates how many complete operations of the handling unit are required to unload #8. 10 =8/9
Column 11 is an estimate of the time to perform one stroke of the handling unit.
Column 12 is the time (hrs) needed to unload one transportation unit. Col 12 = (Col 11) x (Col 10)/60
Column 13 modifies the time in Col 12 by including allowances.
Column 14 states the working hours of the plant (one shift = 8 hours, two = 16).
Column 15 is the dock spot capacity. Col 15 = Col 14 / Col 13
Column 16 is the number of docks needed. Col 16 = Col 6 / Col 15
Column 17 is the actual number of dock spots required. Must be integer greater than or equal to Col 16.
Column 18 calculates the handling loads per day. Col 18 = Col 6 * Col 10
Column 19 indicates the expected number of hours a forklift will work. Col 19 = Col 18 / ( 20)
Column 20 calculates the number of trucks required. Col 20 = Col 19 / Col 14
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ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Material Handling Robots:
Robots are used in material handling when it is profitable.
Technical Factors: Weight & quantity of parts
Rate at which items must be moved
Orientation of the parts
Ease of handling parts
Working conditions
Production Rate:
Find cycle time: How long it takes to process an item through the existing machines & robot.
Operational time available per day divided by the cycle time in the same units equals production rate.
Example of Robot Loading / Unloading Operation:
Operation time of the sequential activities associated with using a robot to load & unload work pieces
from (1) machine.
Time
Machine operation time
25.0 (seconds/part)
Robot Unload Machine
1.2 (2)
Move to finished part conveyor
1.7
Release unit
0.2
Move arm to Finished Input Conveyor
2.6
Pick up a unit
0.3
Move to the machine
1.9
Load the machine
2.1 (2)
Two grippers give the robot the ability to hold the unfinished part as the other hand unloads the finished part
from the machine. The unfinished part is then loaded into the machine before the finished part is transported
to the final destination. All others operations can be performed by the robot during machining operation as
long as the time for each individual gripper is less than the machining operation which is usually the case.
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ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Example Robot Sequential Loading:
Loading of several machines with one robot (utilize more fully)
Fixed sequence of operations must be followed 1 > 2 > 3 >4 (assembly line type)
Conveyors supply & remove parts to system
Cycle time is the total time a unit spends in the system
Machine dominance: Robot ( R ) waits on one or more machines (eg. drilling, milling, etc.)
Processing time plus loading/unloading
Robot dominance, machines wait on Robot (Robot services in high demand)(Machine short/ R long)
> Adding times associated with all robot actions in a cycle
[When the machine B is over, the robot must unload the unit & transfer to D then travel back to machine A
and unload to machine B if operation is over].
Example Two Machines (2 &3): (1 & 4 are loading/unloading stations) N = 4
Loading & Unloading times are (0.1) minutes each
Moves times between two successive stations = (0.3) minutes
2 operation = (5) minutes; 3 operation = (3) minutes
Robot Forward i Actions
Time (mins)
Unload machine i
.1
Move to station i+1 .3
Load station i+1
.1
Robot Backward i Actions Time (mins)
Move to pick up i-1 .6 (move 2 stations)
Unload station i-1
.1
Move to i
.3
Load i
.1
F-action Total = .5
B-action Total = 1.1
Combined (F+B) = 1.6 minutes
Machine Dominance Time:
M(2) = 5 + 1.6 =
M(3) = 3 + 1.6 =
Robot Dominance Time:
= (F-Action times + B-Action times) + (N-2-1) x B-Action times + (N-2-1) x 1 Station Move Time
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ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
Types Of Automated Guided Vehicle (AGV)
Towing Vehicles: (earliest type) Moved bulk in/out of warehouse; large weight capacity.
Load Vehicles: Equipped with decks & integrated with conveyor and automated storage/retrieval.
Systems (warehouses fully automated)
Fork Truck: Forklift trucks with automatics pickup & drop off loads at various “heights”.
Light Load: Light loads to 500 lbs.; maneuver in tight areas.
Assembly Line Vehicles: Modifications of light load for subassemblies from station to station.
Example: Finding the Required Number of AGV’s:
Small parts from storage to four shops in plant:
Each vehicle can carry parts to & from only one shop at a time:
Travel speed is 200 feet/minute:
Shop Number
1
2
3
4
Distance from storage (ft)
300
500
600
800
Trips/hour
14
16
5
8
Unload or Load (minutes)
2
3
3
2
1) Find total time needed to travel from storage to each shop (round trip).
Add the time for loading and unloading to this total
Time per shop = (Round Trip x Freq) / (Travel Speed) + (Trips/hour x Unload/Load (minutes) x 2 )
Shop
1
2
3
4
Travel Time
Calculations
600 x 14 / (200) + 14 x 2 x 2
1000 x 16/(200) + 16 x 3 x 2
1200 x 5/(200) + 5 x 3 x 2
1600 x 8/(200) + 8 x 2 x 2
Minutes of AGV
Use per Hour
98
176
60
96
Total Vehicle Use Time
2) Find the total required vehicle time (minutes).
Total required vehicle time = Total Vehicle Use Time / Traffic Congestion Factor
3) Find the number of AGV’s required.
Number required = Total required vehicle time / 60
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ISE 312 Chapter 9 (Sule) Material Handling: Equipment Selection
Spring Semester
AGV Issues
What should be the configuration of the path?
How many should be in system & their capacity?
What control system rules should be used?
Random Vehicle (RV)
Nearest Vehicle (NV)
Longest Idle Vehicle (LIV)
Least Utilized (equalize work load on all)
If more than one station is demanding services, what priority rule should be followed in selecting the first
station to visit?
Random Work Center Rule
Shortest Travel Time or Distance
Max. Outgoing Queue Size
Min. Remaining Outgoing Queue Space
How large should the in-process storage banks be for incoming & outgoing units at each station?
Which route should be followed?
What rules follow at intersections to avoid collisions or blocking?
Random Selection; Full over empty, Critical station, Critical part
Efficiency Test with a Simulation
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Bridge Crane:
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