Transcript New Design Control Req'mts - IQSoft Software Consultants

Material Handling Systems
Design
Applied Basics of Queuing
1
MATERIAL HANDLING
Twenty principles of material handling
 Selecting material handling methods
 Simplifying/eliminating material handling
 Simple analysis techniques

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Material Handling

Material handling adds COST, but not
VALUE.





as much as 60% of total production cost
20%-30% of direct labor costs
50%-70% of indirect labor costs
What’s the best way to handle materials?
DON’T!!
Goal: MINIMIZE COSTS OF MATERIAL
HANDLING
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Muther’s Material Handling
Equation
Yes
WHY
?
WHAT
WHERE
MAT’L
No
+
WHEN
MOVE
HOW
+
WHO
METHOD
B
A
Q
D
etc.
E
P
C
Type,
Qty,
Characteristics
Sink, Source Flow;
Direction Flow, Volume
Type of Move, etc.
Unit
Manpower
Equipment
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Muther’s Material Handling
Equation

Use to analyze flow within and between:
Receiving
 Storage
 Production
 Warehousing
 Shipping

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The Twenty Principles of Material
Handling
1. Orientation Principle: Study the system relationships
thoroughly prior to preliminary planning in order to
identify existing methods and problems, physical and
economic constraints, and to establish future
requirements and goals.
2. Planning Principle: Establish a plan to include basic
requirements, desirable options, and the consideration
of contingencies for all material handling and storage
activities.
3. Systems Principle: Integrate those handling and
storage activities which are economically viable into a
coordinated system of operation including receiving,
inspection, storage, production, assembly, packaging,
warehousing, shipping and transportation.
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The Twenty Principles of Material
Handling
4. Unit Load Principle: Handle product in as large a unit
load as practical.
5. Space Utilization Principle: Make effective utilization
of all cubic space.
6. Standardization Principle: Standardize handling
methods and equipment wherever possible.
7. Ergonomic Principle: Recognize human capabilities
and limitations by designing MH equipment and
procedures for effective interaction with the people
using the system.
8. Energy Principle: Include energy consumption of the
MH systems and material handling procedures when
making comparisons or preparing economic
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The Twenty Principles of Material
Handling
9. Ecology Principle: Minimize adverse affects on the
environment when selecting MH equipment and
procedures.
10. Mechanization Principle: Mechanize the handling
process where feasible to increase efficiency and
economy in the handling of materials.
11. Flexibility Principle: Use methods and equipment
which can perform a variety of tasks under a variety
of operating conditions.
12. Simplification Principle: Simplify handling by
eliminating, reducing, or combining unnecessary
movements and/or equipment.
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The Twenty Principles of Material
Handling
13. Gravity Principle: Utilize gravity to move material
wherever possible, while respecting limitations
concerning safety, product damage and loss.
14. Safety Principle: Provide safe MH equipment and
methods which follow existing safety codes and
regulations in addition to accrued experience.
15. Computerization Principle: Consider
computerization in MH&S systems, when
circumstances warrant, for improved material and
information control.
16. System Flow Principle: Integrate data flow with the
physical material flow in handling and storage.
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The Twenty Principles of Material
Handling
17. Layout Principle: Prepare an operational sequence
and equipment layout for all viable system solutions,
then select the alternative system which best
integrates efficiency and effectiveness.
18. Cost Principle: Compare the economic justification
of alternate solutions in equipment and methods on
the basis of economic effectiveness as measured by
expense per unit handled.
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The Twenty Principles of Material
Handling
19. Maintenance Principle: Prepare a plan for PM and
scheduled repairs on all material handling
equipment.
20. Obsolescence Principle: Prepare a long range and
economically sound policy for replacement of
obsolete equipment and methods with special
consideration to after-tax life cycle costs.
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Unit Load Principle

Follows traditional thinking
$/unit
Quantity
The greater the amount moved per trip,
the less the cost per unit moved
Maximize Unit Load
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Unit Load Principle

But:
Creates more inventory
 Requires expensive, heavy-duty material
handling equipment
 Increases lag time between operations
poor process communication, slower
reaction to quality problems
 Requires more floor space

WASTE!
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Selecting Material Handling
Methods
Systematic Approach
1. Define the problem
Preliminary Survey Check sheet (see
Appendix at end of section)
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Selecting Material Handling
Methods
2. Analyze the problem
Observe
activities
Obtain layouts, flow patters, schedules, etc.
Obtain information on existing material handling
equipment
Analyze situation by material handling equation,
Twenty Principles of Material Handling, and/or
forms such as Basic Data Form (see insert)
Can activities be combined, simplified,
eliminated???
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Selecting Material Handling
Methods
3. Identify possible solutions
Organize meeting with:
material handlers
machine operators
supervisors
support engineers
4. Evaluate alternatives
Meet again to rate alternatives using Factor
Analysis
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Improvement of MH
Systems

Cellular Manufacturing
Eliminate Handling
 Eliminate Storage
 Eliminate Inventory
 Eliminate waste due to poor quality

KEYS:
 Efficient layout, scheduling, problem
prevention
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Conveyor Systems
• Reduce handling costs
• Better coordination of product thru processes
• Design WIP level into material handling system
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Simple Analysis Techniques
Queuing Analysis

Mathematical analysis of queues
(waiting lines which occur whenever the
current demand for service exceeds the
current capacity to provide that service).
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Simple Analysis Techniques
Queuing Analysis
 Suitable for “quick and dirty” evaluations when a high
degree of detail is not necessary.
System
Server (s)
Arrivals
l
Arrival Rate
m
Service Rate
Departure
Simple Systems
FIFO (FCFS)
 Single Server, Single Queue - M/M/1
System
 Poisson Arrivals
 Exponential Service Times

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Simple Systems
LIMITED:
Mathematical complexity becomes
insurmountable if the above is not
true
SIMULATION
Objective
Wait $
Service $
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Material Handling Applications
Highway Trailers: Ship/Receiving
 Parts on Conveyor
 Pallets/Mc. Waiting for Fork Trucks
 Orders Waiting at AS/RS
 Many More

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QUEUING PHENOMENON
Example
arrive every
40 min on avg.
l = 1.5/hr.
LOADING
DOCK
30 min avg. time to unload
m = 2.0/hr.
If m > l, why Queues?
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QUEUEING PHENOMENON
EVENT
Time (min)
Truck 1 Arrive
Truck 2 Arrive
Truck 1 Leave
Truck 3 Arrive
Truck 4 Arrive
Truck 2 Leave
Truck 3 Leave
Truck 4 Leave
156 min
4 arrivals
30
50
62
63
80
90
125
156
= 39 min. avg.
Truck Being
Serviced
Truck in
Queue
Truck Wait
Time
1
1
2
2
2
3
4
--
-2
-3
3,4
4
---
--32
--40
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FORMULAS for M/M/1 Model
l
=
avg. arrival rate
m
=
U
=
W
=
avg. service rate
l
utilization =
m
avg. wait time in system =
Wq
=
Lq
=
L
=
Pn
=
Pn
=
P0
=
1
l-m
l
avg. wait time in queue =
m(m-l)
l2
avg. length of queue =
m(m-l)
avg. number of “customers” in system =
l
m-l
probability that there are n customers in the system
n
l l
1m m
l
1m
M/M/1 EXAMPLE
LOADING
DOCK
arrive every
40 min on avg.
30 min avg. time to unload
l = 1.5/hr.
m = 2.0/hr.
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M/M/1 EXAMPLE
Lq
=
l2
m(m-l)
L
=
l
m-l
= 2.25 trucks in line
= 3 trucks in line & being served
also (L = Lq + l/m)
Lq
=
Lq/l = 2.25/1.5 = 1.5 hrs/truck
Lq
=
L/l = 3.0/1.5 = 2.0 hrs/truck
Lq
=
1-
1.5
l
=1= .25  25%
2.0
m
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Cost Function
E[TC] = E[WC] + E[SC]
E[SC]
E[TC]
Cost
E[WC]
No. of servers
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WAITING COST
Type I. Internal Customers
Example: Forklift truck drivers
Cost: Lost productivity of drivers
Type II. External customers
Example: People waiting for cabs
Cost: ??
E[WC] = CW[E(n)]
SERVICE COSTS
Total Cost: S(server cost) = S(CS)
THUS
TC = CW[E(n)] + S(CS)
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Example #1
Tool Crib Storage
Service Time
Inter-arrival time
60 sec/arr.
found by
sampling!
50 sec/service
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Example #1
l = 1/60 = 1 arrivals/min.
m = 1/50 = 1.2 services/min.
Idle Time of Server = P0 = 1 - l/m = 1-1/1.2  16.7%
Assume:1. Service Attendant Paid $12.00/hour
2.
Customers (machine oper) paid
$16.00/hour
Cost of Servers
E[SC] = 8 hrs/day  $12.00/hour = $96.00/day
Cost of Machine Operators Waiting for Service plus
Service)
L = l/(m-l) = 1/(1.2-1) = 5
E[WC] = $16.00/hr (5 people) (8 hrs/day) =
$640.00/day
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Example #1
640
E[SC]
$
96
E[WC]
1 Number of Servers
Conclusions? _________
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MH Cost Justification of
Cellular Manufacturing
Compare:
I. Functional Layout
--Fork truck
Maint. Labor: $10,000/yr
Parts:
$1,000/yr
Driver:
$30,000/yr
Truck Cost: $4,000/yr ($20,000/5 yrs)
$45,000/yr
*1 yr = 2000 hrs
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MH Cost Justification of
Cellular Manufacturing
Compare:
II. Cellular Layout
--Fork truck
--Cart/Basket
Cart Cost:
$40/yr ($200/5 yr)
4 Baskets Cost: $24/yr ($120/5 yrs)
$64/yr
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Questions
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