7. layout and safety issues_ts_l7
DESCRIPTION
industrial automationTRANSCRIPT
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What is Facility Layout? Location or arrangement of everything within & around
buildings Pay attention to following to decide layout design
Customer satisfaction Level of capital investment Utilization of space, equipment, & people Ease of equipment maintenance Amount of flexibility needed Efficient flow material and worker Employee safety
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Types of Layouts Product - Product layout involves locating the machines
and equipment so that each product follows a pre-arranged route through a series of processes. The products flow along a line of processes, which is clear, predictable and relatively easy to control.
Process - In process layout, similar manufacturing processes (cutting, drilling, wiring, etc.) are located together to improve utilisation. Different products may require different processes so material flow patterns can be complex.
Group Technology / Cellular (HYBRID) – product families Fixed-position - large bulky projects such as ships and
buildings
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Process Layout
Lathe Drill
Grind
Lathe Weld
Assembly
Drill
MillWar
ehou
se Lathe PaintLathe
Weld
Paint
Mill
Mill
Mill Grind
Assembly
War
ehou
se
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Product Layout - Advantages Reduces materials handling.
Accommodates small amounts of work in process.
Reduces transit times.
Simplifies production planning and control systems.
Simplifies tasks, enabling unskilled workers to learn task quickly.
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Product Layout - Limitations Disadvantages of product layout
Lack of process flexibility. Lack of flexibility in timing: the product can not flow
through the line faster than the slowest task can be accomplished unless that task is performed at several stations.
Large investments: special-purpose equipment and duplication is required to offset lack of flexibility in timing.
Dependence of the whole on each part: a breakdown of one machine or absence of enough operators to staff all work stations may stop the entire line.
Worker fatigue: workers may become bored by the endless repetition of simple tasks.
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Product Requirements Standardized product High production volume Stable production quantities
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Product-Oriented Layout Types
Assembly Line • Assembles fabricated parts • Uses workstation • Repetitive process • Paced by tasks
Fabrication Line • Builds components • Uses series of machines • Repetitive process • Machine paced
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Process-Oriented Layout Department areas having similar processes located in close
proximity
Design places departments with large flows of material or people together
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Process Layout - Advantages Better utilization of machines Fewer machines required High degree of flexibility relative to equipment or
manpower allocation for specific tasks Comparatively low investment in machines is
required The diversity of the task offers a more interesting
and satisfying occupation for the operator Specialized supervision is possible
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Process Layout - Limitations Since longer flow lines usually result, material
handling is more expensive Production planning and control systems are more
involved Comparatively large amounts of in-process
inventory results Space and capital are tied up by work-in-process Because of the diversity of the jobs in specialized
departments, higher grades of skill are required Total production time is usually longer
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Comparison Of Product And Process Layouts PRODUCT LAYOUT PROCESS LAYOUT1. Description Sequential arrangement Functional grouping
of machines of machines
2. Type of Process Continuous, mass Intermittent, job shopproduction, mainly batch production,
assembly mainly fabrication
3. Product Standardized Varied,made to stock made to order
4. Demand Stable Fluctuating5. Volume High Low6. Equipment Special purpose General purpose7. Workers Limited skills Varied skills
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Comparison Of Product And Process Layouts PRODUCT LAYOUT PROCESS LAYOUT 8. Inventory Low in-process, High in-process, high finished goods low finished goods 9. Storage space Small Large10. Material Fixed path Variable path handling (conveyor) (forklift)11. Aisles Narrow Wide
12. Layout decision Line balancing Machine location13. Goal Equalize work at Minimize material each station handling cost14. Advantage Efficiency Flexibility
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Line balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.
Design Product Layouts: Line Balancing
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Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.
Cycle Time
Maximum cycle time is given by the summation of the task times.
Minimum cycle time is given by the longest of the task times.
6-17D
OT = timecycle = CT
rateoutput desired = D
dayper timeoperating OT
CTOT = rateOutput
Determine Maximum Output
Steps in Product LayoutStep 1: Develop the precedence diagram showing the sequence and performance times for each task.
Step 2: Calculate cycle time to meet the output requirement. Take the demand per day and divide it into the productive time available per day (in minutes or seconds).
productive time Demand per day or production rate per day
Step 3: Determine the theoretical minimum number of workstations. This is the sum of all task times divided by the cycle time. Fractions are rounded to the next higher whole number.
time for task i
Cycle timeStep 4: Perform the line balance by assign specific assembly tasks to each workstation. An efficient balance is one that will complete the required assembly, follow the specified sequence, and keep the idle time at each workstation to a minimum.
Cycle time =
Minimum number of workstations =
1. Longest operating task time
Choose the available task with the longest task time
2. Greatest number of following tasks
Choose the available task with the largest number of following tasks
3. Ranked positional weight Choose the available task for which the sum of following task times is the longest
4. Shortest operating task time
Choose the available task with the shortest task time
5. Least number of following tasks
Choose the available task with the least number of following tasks
Line-Balancing Heuristics (Rules of Thumb)
Rule Meaning
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Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements
A Simple Precedence Diagrama b
c d e
0.1 min.
0.7 min.
1.0 min.
0.5 min. 0.2 min.
Figure 6.11Precedence Diagram
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task timeof sum = t
CT t)(
=N
Determine the Minimum Number of Workstations Required
What is the minimum number of workstations for the previous precedence diagram? (assume minimum cycle time)
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• Arrange tasks shown in Figure 6.11 into three workstations.– Use a cycle time of 1.0 minute– Assign tasks in order of the most number of
followers
– There is another rule called the order of greatest positional weight
Example 1: Assembly Line Balancing
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Workstation
TimeRemaining Eligible
AssignTask
RevisedTime Remaining
StationIdle Time
1 1.00.90.2
a, ccnone
ac–
0.90.2
0.22 1.0 b b 0.0 0.03 1.0
0.50.3
de–
de–
0.50.3 0.3
Example 1 Solution
Total idle time = 0.5
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%100*(N)(CT)cycleper timeIdle
= timeidle %
Efficiency = 100% – Percent idle time
Calculate Percent Idle Time
What’s the % idle time and efficiency for the above example?
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• Assign tasks in order of most following tasks.
– Count the number of tasks that follow
• Assign tasks in order of greatest positional weight.
– Positional weight is the sum of each task’s time and the times of all following tasks.
Some Heuristic (intuitive) Rules:
Line Balancing Rules
Example
A manager wants to assign workstations in such a manner that hourly output is 4 units. Working time is 56 minutes per hour. What is the cycle time?
Cycle time = operating time/output rate= 14 mins.
What is the positional weight for each task?A= 3+2+4+9+5 = 23 E = 4+9+5 = 18B= 2+4+9+5 = 20 F = 5+6+4+9+5 = 29C= 9+5 + 4 =18 G= 6 + 4 + 9 + 5 = 24D= 7+4+9+5 = 25 H = 14
Example
Numbers above the circles indicate task times
Assign the tasks above to workstations in the order of greatest positional weight.
Steps:1)Arrange the task in the decreasing order of positional weights.2) Find out the number of workstations
# of workstations = sum of task times/cycle time = 45/14 = 3.2 =4
Task - Task time F = 5 D = 7 G = 6 A = 3 B = 2 C = 4 E = 4 H = 9 I = 5
Task - Task time F = 5 D = 7 G = 6 A = 3 B = 2 C = 4 E = 4 H = 9 I = 5
%64.19%100*(4)(14)
11 = timeidlePercent
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1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.
Bottleneck
Bottleneck Workstation
Theoretically, the line should be able to produce at 60 units per hour.
But the 3rd station has a task time of 2 mins, therefore limiting the output to 30 units per hour.
The problem: Pproduce 500 Model J Wagons per 8-hour day
Setup time and work breaks total 45 minutes Production time available = 480 – 45 = 435 minutes Assembly steps and times for the Model J Wagon are
given below:
Assembly Line Balancing Illustration
ABCDEFGHIJK
Position rear axle support and hand fasten 4 screws to nutsInsert rear axle
Tighten rear axle support screws to nutsPosition front axle assembly and hand fasten with 4 screws to nuts
Tighten front axle assembly screwsPosition rear wheel #1 and fasten hub capPosition rear wheel #2 and fasten hub capPosition front wheel #1 and fasten hub capPosition front wheel #2 and fasten hub cap
Position wagon handle shaft on front axle assembly and fasten bolt and nutTighten bolt and nut
Task Task Description4511950151212121289
195
AA,B
DA,B,CA,B,CD,ED,E
A,B,C,D,E,F,G,H,IJ
Tasks ThatMust Precede
Time
A
B C
F
G
D E H
I
J K
Step 1: Draw the precedence diagram
45
11 9
50 15
12
12
12
12
8 9
Assembly Line Balancing Illustration
Step 2: Calculate the cycle time
Cycle Time = time available / output required
= 435 minutes / 500 units = 0.87 minutes = 52.2 seconds
Step 3: Calculate the minimum number of workstations
Minimum number of work stations = total task time / cycle time
= 195 seconds / 52.2 seconds = 3.74 = 4 stations
Step 4: Balance the line using the following heuristics (rules of thumb):
1. According to Greatest-Number-of-Following-Tasks rule2. According to the Longest-Operating-Time rule
Assembly Line Balancing Illustration
Station 1
Station 2
Station 3
Station 4
Station 5
A
D
B/E/C/F
G/H/I/J
K
45
50
11/15/9/12
12/12/12/8
9
7.2
2.2
41.2/26.2/17.2/5.2
40.2/28.2/16.2/8.2
43.2
None
None
C,E/C,H,I/F,G,H,I/None
H,I/I/J/None
None
C,E/C/F,G,H,I
H,I
Workstation Task Task Time Idle TimeFeasible Remaining
TasksTasks With
Most Followers
Step 4: Balancing the line using the Greatest-Number-of-Following-Tasks rule:
Assembly Line Balancing Illustration
Station 1
Station 2
Station 3
Station 4
D
A
E/H/I/B
C/F/G/J/K
50
45
15/12/12/11
9/12/12/8/9
2.2
7.2
37.2/25.2/13.2/2.2
43.2/31.2/19.2/11.2/3.2
None
None
H,I,B/I,B/B/None
F,G/G/J/K
E/H/I/B
C/F/G/J/K
Workstation Task Task Time Idle TimeFeasible Remaining
TasksTasks With Longest
Operating Time
Efficiency of the line = total task time / (number of stations * cycle time):
Step 4: Balancing the line using the Longest-Operating-Time rule:
Efficiency of line balance using the greatest-number-of-following-tasks rule= 195 / (5 x 52.2) = .747 = 74.7%
Efficiency of the line using the longest -operating-time rule= 195 / (4 x 52.2) = .934 = 93.4%
Assembly Line Balancing Illustration
Facility Layout
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Designing Process LayoutsMain issue in the design of process layouts concerns the relative
positioning of the departments involved. Process layouts features:1. Some departments benefit from adjacent locations.2. Some departments must be kept separate.3. External factors such as the location of entrances, loading docks,
elevators, windows, and areas of reinforced flooring have to be considered.
4. Flow costs for material and personnel within the building are critical.
Facility Layout
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Steps for Process LayoutStep 1: Construct a “from-to-matrix showing the flow of parts or materials from
department to department.Step 2: Determine the space requirements for each department.Step 3: Develop an initial schematic diagram showing the sequence of
departments through which parts will have to move. Try to place departments with a heavy flow of materials or parts next to one another.
Step 4: Determine the cost of this layout by using the following equation: Minimize cost = XijCij
where: n = number of work centres or departments i,j = individual departments Xij = number of moves between department i and department j
Cij = cost of a move between department i and department j
Step 5: Try to improve this layout by trial and error or by use of a computer program.
Step 6: Prepare a detailed plan considering space or size requirements of each department.
Facility Layout
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1 2 3 4 5 6 7 8
175 25 0 30 200 20 25 0 100 75 90 80 90 17 88 125 99 180 20 5 0 25 0 180 187 374 103 7
Flows Between Departments
(number of moves)
12345678
12345678
Department
Shipping & receivingPlastic molding & stamping
Metal formingSewing departmentSmall toy assemblyLarge toy assembly
PaintingMechanism assembly
Activity
1
2
3 5 7
4 6 8
160 ‘
80 ‘
Step 1
Step 240’ 40’ 40’ 40’
40’ 40’ 40’ 40’
40’ 40’ 40’ 40’
40’ 40’ 40’ 40’
Process Layout Illustration - Minimizing Flow Costs for a Toy Company
Facility Layout
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1 2 3 4 5 6 7 8
175 25 0 60 400 60 75 0 100 150 180 240 270 17 88 125 198 360 20 5 0 50 0 180 187 374 103 7
12345678
Cost Matrix - First SolutionAssume flow cost = 1 for adjacent movesAssume flow cost = 2 for moves over 1 deptAssume flow cost = 3 for moves over 2 depts (Assume diagonal moves are possible)
Sample Calculations: 1 to 2 = 175 x 1 = 175 1 to 6 = 200 x 2 = 400 1 to 8 = 25 x 3 = 75, etc.
Total cost = $3,449
Step 4
Step 31 3 5
2 4 6
25 88
200 20
100 5
175
Process Layout Illustration - Minimizing Flow Costs for a Toy Company
Facility Layout
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4 3 5 7
2 1 6 8
Revised LayoutExchange 1 & 4
Why 1 & 4? Youwant to bring 1 and6 next to each other,and this is one way
to do it!
Costs affected:1&5, 1&6, 1&7,1&8, 4&5, 4&6,
4&7, 4&8
1 2 3 4 5 6 7 8
175 50 0 30 200 40 50 0 100 150 180 240 270 17 88 125 198 360 40 10 0 75 0 180 187 374 103 7
12345678
Cost Matrix - Second SolutionCost reductions:
1&5 = 30, 1&6 = 2001&7 = 20, 1&8 = 25
Cost additions:4&5 = 20, 4&6 = 54&7 = 0, 4&8 = 25
Total cost = $3,234
Step 5
Process Layout Illustration - Minimizing Flow Costs for a Toy Company
Facility Layout
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Small ToyAssembly
5
MechanismAssembly
8
Shipping andReceiving
1
Large ToyAssembly
6
MetalForming
3
Plastic Mldg. / Assb.
2
Sewing
4
Painting
7
A final,feasiblesolution
after severaliterations
Step 6
Process Layout Illustration - Minimizing Flow Costs for a Toy Company
Facility Layout
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Process Layout Illustration - Systematic Layout PlanningEven though the approach of minimizing flow costs is widely used, it suffers from the limitation of being able to focus on only one objective, and many situations involve multiple criteria.A more general approach, systematic layout planning (SLP), allows for subjective input from analysts or managers to indicate the relative importance of each combination of department pairs.
The following is an example of SLP for the floor of a department store:
From
1. Credit dept
2. Toy dept.
3. Wine dept.
4. Camera dept.
5. Candy dept.
To 2 3 4 5 I U A U 6 --- 1,6 --- U I A --- 1 1,6 A E 2,3 1 X 1
Area (sq. ft.)
100
400
300
100
100
Letter
Number
Closeness Rating
Reason for Rating
Facility Layout
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Reason
Type of customer
Ease of supervision
Common personnel
Contact necessary
Share same space
Psychology
Code
1
2
3
4
5
6
5 2 4
13
Initial layout based upon relationship requirements
(ignoring space and building constraints)
2 4
3 15
20 ft.
50 ft.
Final layout adjustedby square footageand building size
Facility Layout
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Process Layout - Additional Illustration # 1
A small printing shop wishes to locate its seven departments in a one-floor building that is 40 unitswide and 50 units long. Department sizes are :
Department Length (units) Width (units)Layout 10 10Cutting 20 10Shipping 10 10Supply Storage 20 15Printing 25 20Binding 20 20Art 20 20
The average number of loads flowing between departments is expected to be:
From Dept Layout Cutting Shipping Supply Storage Painting Binding ArtLayout --- --- --- --- --- --- ---Cutting --- --- --- 100 --- 400 ---Shipping --- --- --- 500 --- --- ---Supply Storage --- 600 100 --- 400 100 ---Printing --- --- --- --- --- 1200 100Binding --- 100 1000 --- 200 --- ---Art --- 100 --- --- 100 --- ---
What is your layout recommendation?
Facility Layout
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Process Layout - Additional Illustration # 2
Eight work centres must be arranged in an L-shaped building. The location of centres A and E are designated as shown in the accompanying diagram. Assuming transportation costs are $2 per load per metre, develop a suitable layout that minimizes transportation costs using the information below.
From / To A B C D E F G H A -- 40 40 60 120 80 100 110 B -- 60 40 60 140 120 130 C -- 45 85 40 70 90 D -- 40 50 40 45 E -- 90 50 40 F -- 40 60 G -- 60 H --
A * B
C D E *
F G H
From / To A B C D E F G H A -- 10 5 90 365 135 125 0 B 0 -- 140 10 0 35 0 120 C 0 220 -- 110 10 0 0 200 D 0 110 240 -- 10 0 0 170 E 5 40 100 180 -- 10 40 10 F 0 80 40 70 0 -- 10 20 G 0 45 20 50 0 40 -- 20 H 0 0 0 20 0 0 0 --
Loads per day
* cannot be moved
Distances (metres)
Facility Layout
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Process Layout - Additional Illustration # 3
Hercules Manufacturing, a producer of corrugated cardboard boxes, is planning a 3600 square foot layout. The operations manager has obtained SLP ratings for locating departments next to each other.
From / To Storage Corrugator Folder/Gluer Taper/Bailer Inspection ShippingStorage --- AN U U I U Corrugator --- --- I U U XFolder/Gluer --- --- --- AN I UTaper/Bailer --- --- --- --- U IInspection --- --- --- --- --- AN Shipping --- --- --- --- --- ---
AN = Absolutely Necessary I = Important U = Unimportant X = Undesirable
Area(sq.ft.)1200400400400400800
What should be the layout used by Hercules Manufacturing?
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Before Group Technology
Drilling
D D
D D
Grinding
G G
G G
G G
Milling
M M
M M
M M
Assembly
A A
A A
Lathing
Receiving and shipping
L
L L
L L
L L
L
Jumbled flows in a job shop without GT cellsJumbled flows in a job shop without GT cells
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Group Technology / Cellular
Cell 3
L M G G
Cell 1
Cell 2
Assembly area
A A
L M DL
L MShipping
D
Receiving
G
G
Hybrid Layouts: Cellular layouts
Notice:The distancedistance that each part must travel before
completionthe irregularityirregularity of the part routingsAmount of “paperwork”“paperwork” needed to direct the flow of each
individual part and to confirm that the right operation has been performed
Original Process Layouts
Hybrid Layouts: Cellular layouts
In its current form, there is no apparent pattern to the routings.
PRODUCT FLOW ANALYSIS (PFA) reorders part routing matrices to identify families of parts with similar processing requirements.
If we reorder the matrix listing which parts have four machines in common, three...Part Routing Matrix
Hybrid Layouts: Cellular layouts
Part Routing Matrix Reordered to Highlight Cells
Revised Layout with Three Cells
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Group Technology / Cellular - Advantages Increased machine utilization
Compromise between product layout and process layout, with associated advantages
Shorter travel distances and smoother flow lines than for process layout
Reduced Material flow path
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Work Cell Advantages
Decreased: Inventory Floor space Direct labor costs
Increased: Equipment utilization Employee participation Quality
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Group Technology / Cellular - Limitations General supervision is required Higher skill levels required of employees than for product
layout Depends on balanced material flow through the cell;
otherwise, buffers and work-in-process storage are required Lower machine utilization than for process layout
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Fixed Position Layout
Lathe Grind
Drill
Press
War
ehou
se
Paint
War
ehou
se
Assembly
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Fixed-Position Layout Design is for stationary project Workers and equipment come to site Limited space at site Changing material needs
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Fixed-Position Layout - Advantages Material movement is reduced Continuity of operations and responsibility results from team High flexibility; can accommodate changes in product
design, product mix, and production volume Independent of production centers allows scheduling to
achieve minimum total production time
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Fixed-Position Layout - Limitations Increased movement of personnel and equipment Equipment duplication may occur Higher skill requirements for personnel General supervision required Cumbersome and costly positioning of material and
machinery Low equipment utilization
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Types of LayoutsHigh
Medium
Low
Low Medium High
Product Layout
Fixed LocationLayout
Group Technology / Cellular Layout
ProcessLayout
Volu
me
Variety
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WHY do we need safety precautions???
Accident must be avoided. An accident is an unexpected action that results in
injury to people or damage to property. Causes of accident:• Carelessness• Use of wrong tools• Unsafe work practices• Horseplay• Ignore safety rules• Inadequate maintanence
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WHY do we need safety precautions???
Sources of accident:• Machines with moving parts• Electrical equipments• Sharp equipments• Chemicals
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Safety Issues for Prevention of accidents
Safety features in machines; Limit switches, part detector, machine in operation signal, robot teach pendant normally open switch
Individual attitude towards safety: proper attire, safety shoes, Knowledge about Standard Operational Procedure, FIRST AID ect.
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Safety IssuesLockout/Tagout
Machine needs maintenance / Servicing must be locked out .
To minimize injuries. Machine cannot be used until tagout/lockout device
is removed. Only authorized service person can use. If the machine cannot be locked out then go for
tagout option.
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Lockout procedure
Notification Understanding about the machine. Stop the machine with proper procedure if in
operation. Deactivate energy isolating devices Lock energy isolating devices with dedicated locks. Stored energy should be dissipated (ie grounding of
Capacitors) Final checking Confirm locked out.
Homework
A shop wants an hourly output of 33.5 units per hour. The working time is 60 minutes per hour. Assign the tasks using the rules:
a)In the order of greatest positional weight.