Cellular Manufacturing Systems an Introduction - DR Upload

7/25/2019 Cellular Manufacturing Systems an Introduction - DR Upload

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CELLULAR

MANUFACTURING

SYSTEMSManufacturing Operations Management


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Progress so far

CostTime

Lot sizing

principles

EOQ-based

Lot sizing

principles

Material resource planning

Flow of variability, throughput measure

Station

Line Linking machines/ stations to form cells

Controlling material flow between cells

Simulate a manufacturing company and

apply principles


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PROCESS

UNDERSTANDING


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Drilling Machine


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Lathe/ Milling Machine

Lathe is mainly used to machine cylindrical jobs and operation like

turning, grooving, facing, knurling and treading whereas milling is

used to produce slots, flat surface, boring and gear cutting also.


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Casting


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Forging


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LAYOUT

UNDERSTANDING


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Process Layout/ Functional Layout/ Job Shop

TM

TM TM

TM

DM

DM

DM

VMM VMM BM BM

What are the nice features?What are the issues?


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Group technology/ Cellular layout

TM

TM

TM

TM

DM

DM

DM

VMM

VMM

BM

BM

Decreasing lot size, increasing part variety, diverse material choices,


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TRANSFERLINE

SPECIAL

SYSTEM

MANUFACTURING

Cells

STD. AND GEN.

MACHINERY

VOLUM

E

HIGH

VARIETY

LOW HIGH

FLEXIBLE

MANUFACTURING

SYSTEM


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Product Family

Similar design

attributes (shape),

dissimilar

manufacturingattributes

Similar

manufacturing

routings, dissimilardesigns

Also dishes in restaurants.


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The missing link?

Drawings

Material

selection

Design

LinkingProcess? Machine

Routings

etc

Manufacturing

Process

Planning

Lack of a database leads to redesigning the wheel

Database to drive automated process planning


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Group Technology

Examining Opitz Code:


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1st Digit

part class

ositions

ith a

igit

2nd Digit

main shape

3rd Digit

rotational

machining

4th Digit

plane surface

matching

5th Digit

additional

holes teeth &

forming

FORM CODE

Opitz coding and classification system.

(H. Opitz,AClassification System to Describe Workpieces, Pergamon Press.)

Special

Non-rotational

Special

Rotational

9

8

7

6

5

4

3

2

1

0

Internalshape

element

Rotational

machining

Main bore& rotational

machining

Other holes

and teeth

Other holes

teeth and

forming

Other holesteeth and

forming

Machiningof plane

surfaces

Machiningof plane

surfaces

Machining

of plane

surfaces

Externalshape

element

Main shape

Main shape

Main shape

Main shape

Supplim-

entary

code

Digit

6 7 8 9

Dim

ensions

Material

Orig

inalshapeofra

w

materials

Acc

uracy


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Examining Opitz Code:

This Form

code is the

Opitz Code

Solution on this

shaft- like part


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Group technology/ Cellular layout

TM

TM

TM

TM

DM

DM

DM

VMM

VMM

BM

BM

Decreasing lot size, increasing part variety, diverse material choices,

Can we explore the existing part design and manufacturing processes?


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Product families

Part familyagroup of

machines

People,

Incentives,Justification


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Benefits of GT and CMS (Companies Reporting):

52% Report reduction in new part design

10% Report reduction in # of new drawings thrustandardization

30% Report reduction in new shop drawings

20% Report reduction in floor space

45% Report reduced scrap

80% Report reduced production and quality costs

69% Report reduced set-up time (cost)

Note: Reported by companies in a survey of adopters of GT


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Benefits of GT and CMS (Companies Reporting):

70% Report reduced throughput time (even more report

better predictability of delivery)

82% Report reduced numbers of overdue orders

42% Report reduced raw-materials inventory

62% Report reduced WIP

60% Report reduced finished goods inventory

33% Report increased employee output/time unit

(productivity improvement)


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FORMING PART

FAMILIES


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Create part families:

i. Many times the company has a naturalclassification of families, e.g. for sales, forforecasting, for routing, etc.

ii.If not use part routings to create thedistinction (if necessary adding additionalobvious characteristics to differentiate thefamilies e.g. size, options, etc.)

iii. In many cases start with a nucleusFTMS(Risk of losing business completely vs. bigopportunity if improvements could bedemonstrated)


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Estimate Aggregate Measures

Annual DemandBatch sizeRun timeSetup time

Part 1 - 10,000 100 5 60

Part 212,000 200 10 45

Aggregate batch size?

Aggregate run time?

Aggregate setup time?


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The Central Idea in Cell Development

We cluster parts to build part families

Part Families visit cells

Part Families share set-up ideas and equipment (Family Fixtures)

Part Families follow the same (or similar) process routing

These are the ideas and activities that offer reported benefits


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FORMING CELLSAssigning part families to machines


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Clustering Techniques We cluster Machines to build cells:

Cells lead to Flow Mathematics

Cells contain all equipment needed to produce a part family

Cells allow development of Multi-functional workers

Cells hold work teams responsible for production and quality TheyEmpower the workers

Empowered to set internal schedules

Empowered to assign tasks

Empowered to train and rotate jobs

Etc, etc, etc


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Building the CMS Facility

BeforeClustering

AfterClustering


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Rank order Clustering

This method automates the cluster study by computing Binary

weights from a machinepart matrix

It orders parts and machine cells automatically by structuring and

computing the matrix with binary weights

It implies a computer algorithm for solving the clustering problem It may not solve if machines are needed by more than one family

forces intelligence in application and hand scanning after several

ordering iterations


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Example

Part Number

M

achineID

X 1 2 3 4 5 6

A 1 1

B 1 1

C 1 1

D 1 1 1

E 1 1 1


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Step 1:

Part Numbers D. Equiv Rank

MachineID

1 2 3 4 5 6

B. Wt: 25 24 23 22 21 20

A 1 1 23+21 = 10 5

B 1 1 24+23= 24 4

C 1 1 25+22=36 2

D 1 1 124+23+21

= 263

E 1 1 125+22+20=

371

Step 2: Must Reorder!


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Step 3:

Part Number

B. WT. 1 2 3 4 5 6

Ma

chineID

E 24 1 1 1

C 23 1 1

D 22 1 1 1

B 21 1 1

A 20 1 1

D. Equiv24+23

= 24

22+21=

6

22+21+

20

=7

24+23=

24

22+20=

5

24=16

Rank 1 5 4 2 6 3

Step 4: Must Reorder


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Back at Step 1:

Part Number D. Eqv Rank

1 4 6 3 2 5

B Wt: 25 24 23 22 21 20

MachineID

E 1 1 125+24+

23=561

C 1 125+24=

482

D 1 1 1 22+21+

20= 73

B 1 1 22+21=6 4

A 1 1 22+20=5 5

Order stays the same: STOP!

Great

Cluster

Result!


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Rank Order Clustering Method:

1. For each row of the machine/part matrix (M/P/M) read the patternof cell entries as a binary word. Rank the rows by decreasingbinary value. Equal values stay in same order.

2. Ask if newly ranked rows in the matrix are the same as previousorder?Yes (STOP) No (continue)

3. Re-form the M/P/M with rows in new descending order. Now rankthe columns by decreasing binary word weight. Columns of equalweight are left where they are

4. Are current column weights the same as current column order?Yes (STOP), No (continue)

5. Re-form the matrix column order per rank order (highest to left)and return to #1.


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Try Rank Ordering

M a c h i n e

M1 M2 M3 M4 M5 M6 M7

P1 1 1 1

P P2 1 1 1

[aij] = a P3 1 1

r P4 1 1

t P5 1 1

P6 1 1 1


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Issues in Clustering:

R/O clustering oscillationsindicating need of machinereplication (happens often!)

Presence of Outliers and/or Voids in the finishedclusters

Outliers indicate the need of machine replication Voids indicate skipped machines in a cell

Generally speaking, these clustering algorithms aredesigned to convert existing routes for facility re-organization

They require a previous engineering study to be performed to developa series of routers on a core sample of parts that represent most ofthe production in the shop

Minimize inter-cell movements


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Implementation

of cellsBegin with a market opportunity or threat

Find a product family for which lead timereduction will create a splash

Ensure that the product family is self-

contained within the cell

Dedicate in one area all resources needed

to complete all operations in this family

Rethink processes, equipment choices, and

even design, to enable the family to be self-contained and resources to be dedicated

Determine lot sizes, m/c capacity

Create cell workforce through volunteers


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Performance Measures

Cost Based

Time Based

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MANUFACTURING CRITICAL-PATH TIME (MCT):

THE ENTERPRISEWIDE METRIC TO

SUPPORT ORDER FULFILLMENT ANDDRIVE CONTINUOUS IMPROVEMENT

Quality

On-timeDelivery

Price

MCT

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Current Metric for Supply Management :

Replenishment Lead TimeThe typical amount of calendar time from when

a manufacturing order is created until the order

is received by the customer.

oDoes not address how the order is fulfilled

oOrder fulfillment likely based on prebuilt stocksoForecast errors negatively impact the prebuilt stocks

Replenishment Lead Time is not a sufficient metric to

measure supplier flexibility

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Need for new metrics for measuring

supplier responsiveness

Manufacturing Critical-path Time (MCT)

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Manufacturing Critical-path Time

The typical amount of calendar time from when

a manufacturing order is created through the

critical path until the first piece of that order is

delivered to the customer.

MCT = MCTRaw+ MCTOperations+ MCTLogistics

MCT is the right metric to measure supplier flexibility and

responsiveness

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MCT Analysis Approach

Identify suppliers to pilot the MCT metric Supplier pre-visit survey and analysis

Visit supplier facility to:o Map the current MCT

o Identify simple ways for reducing MCT

o Develop long-term recommendations tosupport Build-To-Demand (BTD)


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Consider an Example

Operation 1: 15 days

Intermediate WIP: 100 units (consumption 5 per day)

Operation 2: 25 days

FGI: 500 units (dispatch 10 per day)

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Data Collection

Historical dataoPurchase orders

oPart usage rates

oPart receipts

Supplier pre-visit questionnaireoResponse capacity

oOperations chart

o

FGI quantitiesoComponents of replenishment lead time

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Data Analysis and

Develop Recommendations Map the process from order entry

through productionoQuoting process

oRaw material procurement

oOrder scheduling and production Littles law for converting inventory into time units

Adopt Quick Response Manufacturing principlesoLead time analysis using Rapid Modeling Tool (MPX)

C C


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Current and Future state MCT Map

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Cellular Manufacturing Systems an Introduction - DR Upload

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