Transcript IENG 471 Lecture 06: Quantifying Flow

IENG 471 - Lecture 06
Flow: Quantitatively and
Qualitatively Measured
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Space Considerations
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Equipment footprint
Utilities space
Maintenance space
Operating space
 (Operator space is discussed AFTER Exam I)
 Material space
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Tooling space
Scrap space
Work-In-Process (WIP)
Receiving Space
Shipping Space
 Plus Material Transportation!
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Depends on cell
production rate and on
production control policy
for material flow
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Production Control of Flow
 Push Production:
 Traditional
 Build To Schedule
 Cell Efficiency Effects – Optimal
 Overall Efficiency Effects – Sub-Optimal
 Pull Production:
 JIT
 Kanban
 Production Card (POK)
 Withdrawal Card (WLK)
 Minimizes WIP (and a host of other problems!)
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Flow Factors
 What makes moving a thing difficult?
 Shape
 Weight
 Size
 Value
 Fragility
 Condition
 Equipment
 Distance
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awkward/compact
mass per unit
LxWxH
wood / gold
delicate / sturdy
sticky / hot / wet / frozen
fork truck / cart / crane
short / long / elevation change
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Flow Intensity
 Four Basic Factors of All Moves
 Materials
 Methods
 Moves
 Money
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(Phillips)
of handling
(distance & elevations)
cost of mfg. philosophy
cost of materials movement
cost of handling equipment
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Flow – Quantitative
 Equivalent Load Unit
 Accounts for volume and method
 Approximates cost (macro-level)
 ELUs become the unit of measure for flow
between pairs of areas (dept.s)
 Flow is tracked on a square matrix
 Seek to minimize the sum of the flow volume and
distance product for each pair of areas
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From – To Chart
 Similar to Map Mileage Charts:
 Matrix of Departments (Mfg. Cells)
 Cell entries quantify flow AND direction of flow between
departments
 Steps to Create:
 List departments in OPC sequence
 From department is listed vertically
 To department is listed horizontally
 Establish Equivalent Load Unit measure
 Distance
Qty
Cost/Trip*
 Record flow volume in chart
 Above diagonal is forward flow
 Below diagonal is back-track flow
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Data Collection: From – To Chart

Set up a
spreadsheet with
extra wide / tall
cells
 Define ELU units
between
departments
 Could be
different in
each cell!
 Use tally marks
to track trips
 Could scale
for high trip
counts
 Final tally is
ELU trips per
unit time
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From – To Chart: Flow Qty
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Order according
to OPC flow
 Above diagonal
is forward flow:
 From Dept. is
on Left
 To Dept. is
on top
 ELU volume
(number of
trips) is
entered in
the cell
 Below diagonal
is back flow:
 Often rework /
scrap
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Flow – Qualitative
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Closeness Ratings
 Accounts for info transfer & contact frequency and intangibles …
 Noise tolerance, control needs, aesthetics, security, dirt control, safety issues, etc.
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 Rating Scale for closeness:
 A – absolutely necessary
 E – especially important
 I – important
 O – ordinary closeness OK
 U – unimportant to be close
 X – closeness is not desirable
Examples:
 Machining Center for magnesium parts and:
 First aid station
 Raw materials supply for the center
 Fire suppression station
 Packaging (cardboard) storage
 Next workstation on Operations Process Chart if next operation is
 Assembly
 Inspection
 Liquid paint
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Relationship Chart
 Qualitative Flow
 Obtained from
Interviews
 List departments
 Conduct interviews
 Define criteria
 Establish relationship
value & reason for all
pairs
 Review chart with ALL
involved parties for
evaluation &
discussion
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Relationship Chart - Example
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Evaluating Flow Information
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Estimating Dept. Space
 Space must be allowed for the activities
carried out in the departments
 Typical Information to capture for Equipment:
 Machine Data (manufacturer, type, model, s/n)
 Location of safety stops (big red buttons, …)
 Floor loading (weight of machine)
 Height, width, depth (static – non-operating)
 Maximum operating travel (up, left, right, back, fwd)
 Maintenance space and location (remove & repair)
 Plant service spaces and locations (utilities)
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Estimating Dept. Space
 Space must be allowed for the activities
carried out in the departments
 Typical Information to capture for Materials:
 Receiving and In-bound storage
 Work In-Process
 Out-bound storage and Shipping
 Waste storage and Shipping
 Storage for unused tools, fixtures, jigs, …
 Storage for maintenance equipment
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Estimating Dept. Space
 Space must be allowed for the activities
carried out in the departments
 Typical Information to capture for Operators:
 Operator while working
 Operator while resting
 Operator while handling material
 Operator while entering (ingress) and leaving
(egress)
 Remember Ergonomic considerations!
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Space – Production Floor
 Personnel need space for:
 Operating equipment
 Dependent on operation
 Interview operators, observe similar cells
 Material Handling
 Dependent on material and sizes
 See Tables 3.3 & 3.4 (see next slide) from Bozier, et. al.
 Ingress & Egress
 Dependent on safety, equipment footprint:
 30 inches between static objects
 36 inches between static object & operating equipment
 42 inches between two operating pieces of equipment
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Estimating Aisle Space
 Flow Analysis allows us to estimate space required
for the materials going through the departments
 Also need to allow for space for moving materials moving
between departments
 Typically, this is based on the size of the From department
(footprint), the size (of load) and the method of movement
(equipment size)
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Aisle Space Example
 Assume a reaction-injection molding (RIM) cell handling
car bumpers:
 Cell dimension is 50 ft x 15 ft = 750 ft2
 Bumper size is 6 ft x 1 ft = 6 ft2
 Aisle is desired between two operating cells (lengthwise):
 Using Table 3.3:
(15%)(750 ft2) = 2.25 ft = 27 inches
50 ft
 But, subject to OSHA, use the 42 inch width between
operating equipment!
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Aisle Space Example – Cont.
 Assume a RIM cell handling car bumpers – and a pallet of
bumpers at the end of the cell that is moved by a pallet-jack
(manual platform truck)
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Using Table 3.4:
Aisle width is 5 ft = 60 inches
OSHA Requirement:
42 inches (worst case) – met!
Bumper size is 6 ft x 1 ft:
so increase to 6 ft = 72 inches
But, the aisle is blocked while loading pallet, must allow for two-way
flow of bumper pallets:
so increase to 2 x 6 ft = 144 inches
 And then add some space for clearance!
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Questions & Issues
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