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IENG 471 - Lecture 06

Flow: Quantitatively and Qualitatively Measured

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Space Considerations

Equipment footprint Utilities space Maintenance space Operating space

(Operator space is discussed AFTER Exam I) Material space

Tooling space Scrap space Work-In-Process (WIP) Receiving Space Shipping Space

Plus Material Transportation!

Depends on cell production rate and on production control policy for material flow

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Production Control of Flow

Push Production:TraditionalBuild To Schedule

Cell Efficiency Effects – OptimalOverall Efficiency Effects – Sub-Optimal

Pull Production:JITKanban

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 awkward/compactWeight mass per unitSize L x W x HValue wood / goldFragility delicate / sturdyCondition sticky / hot / wet / frozenEquipment fork truck / cart / craneDistance short / long / elevation change

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Flow Intensity

Four Basic Factors of All Moves (Phillips)

MaterialsMethods of handlingMoves (distance & elevations)Money cost of mfg. philosophy

cost of materials movementcost of handling equipment

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Flow – Quantitative

Equivalent Load UnitAccounts for volume and methodApproximates cost (macro-level)

ELUs become the unit of measure for flow between pairs of areas (dept.s)Flow is tracked on a square matrixSeek 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 verticallyTo department is listed horizontally

Establish Equivalent Load Unit measureDistance Qty Cost/Trip*

Record flow volume in chartAbove diagonal is forward flowBelow 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

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 Closeness Ratings

Accounts for info transfer & contact frequency and intangibles … Noise tolerance, control needs, aesthetics, security, dirt control, safety issues, etc.

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 FlowObtained from

InterviewsList departmentsConduct interviewsDefine criteriaEstablish 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 departmentsTypical 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 departmentsTypical Information to capture for Materials:

Receiving and In-bound storageWork In-ProcessOut-bound storage and ShippingWaste storage and ShippingStorage 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 departmentsTypical Information to capture for Operators:

Operator while workingOperator while restingOperator while handling materialOperator while entering (ingress) and leaving

(egress)

Remember Ergonomic considerations!

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Space – Production Floor

Personnel need space for:Operating equipment

Dependent on operationInterview operators, observe similar cells

Material HandlingDependent on material and sizes

See Tables 3.3 & 3.4 (see next slide) from Bozier, et. al.

Ingress & EgressDependent on safety, equipment footprint:

30 inches between static objects36 inches between static object & operating equipment42 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 departmentsAlso need to allow for space for moving materials moving

between departmentsTypically, 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) 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