TOTAL QUALITY MANAGEMENT (Continuous Quality Improvement)

QUALITY PLANNINGWho is customer?

What do they need?

QUALITY CONTROLEvaluate, compare, act

QUALITYIMPROVEMENT

Establish infrastructure

Who is customer?What Level of Quality do they need?Are they purchasing to Some Quality Specification?Any Safety Considerations?Future Litigation?Ethical Issues?

QUALITY PLANNINGWho is customer?

What do they need?

QUALITY CONTROLEvaluate, compare, act

QUALITYIMPROVEMENT

Establish infrastructure

QUALITY CONTROL Inspection        Destructive        Non-destructive        Sampling Process Control        Monitoring Process (relates to inspection)        Feedback Control        Statistical Process Control (knowing when the process is out of control) Correction        Knowing what to correct when process is out of control 

Cost of Quality Before & After Improvement

0 10 20 30 40 50 60 70 80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time Series1

Tools for Quality Control

Check Sheets

Pareto Charts

Why-Why Diagrams

Cause & Effect Diagrams

Flowcharts

Histograms

Scatter Diagram

Control Charts

Problem Solving Steps

PlanDo StudyAct

Link these Two in Quality Circle

CHECK SHEETSUsed to keep a record of the number and type of discontinuities over a specified period of time or within a certain batch of product.

PARETO CHARTA graphical representation ranking discontinuities from the most to least significant. Used to help brainstorm what discontinuities, if worked upon first, would be the most likely to produce the greatest improvement in quality.

  Class ExampleOur manufacturing procedure is composed of several steps. Several of these

procedures have lead to discontinuities noticed upon inspection. The steps causing defectives are as follows:        Caulking 198 defectives        Fitting 25 defectives        Connections 103 defectives        Torque 18 defectives        Gapping 72 defective  A Pareto Diagram will be developed.

WHY-WHY DIAGRAMSA systematic representation of causes of why some occurrence happens. Used to guide brainstorming sessions.

FLOW CHARTSFlow charts are graphical representations of the steps involved in a process. Constructing a flow chart helps give a better understanding of the systems involved.

Process

DecisionData

Process

Process

Terminator

Yes

No

Controltransfer

CAUSE AND EFFECT DIAGRAMS (Fishbone Diagram)Used in brainstorming session to help identify the causes of quality losses. This diagram is particularly useful after the flow chart and the Pareto diagrams have been developed.

QUALITY(Effect)Cause

Step 1:Decide on the quality characteristic {e.g. Reduction of wobble during machine rotation}Step 2:Set up the fish bone backboneStep 3:Identify main factors causing effect {e.g. Workers, Materials, Inspection, Tools}Step 4: Add Cause to each branch

Benefits of Cause and Effect Diagram         Making diagram is educational in itself         Outline relationship         Note what samples need to be taken         Guide for discussion         Causes are actively sought and results written on diagram         Appropriate data collected - no time wasted         Shows level of technology

Problem Solving Steps

PlanDo StudyAct

Link these Two in Quality Circle

CONTROL CHARTS        Used to test if the process is in control        Used to see if significant changes have occurred in the process over time

“Indiscreet” or “Continuous Data Chart” or “X-R Chart”Measurement at time intervals Measurements compared - control over time. Examples:

Length (mm) Volume (cc)Weight (gm) Power (kwh)Time (sec) Pressure (psi)Voltage (v)

“Discrete Data Charts” or “pn-p charts”Inspection on lot or batch Note # good/defective

# of parts inspected in the lot = nFraction of defective in lot = pNumber of defectives = pn

- R CHART CONSTRUCTION X

In the manufacturing process for this example parts are being machined with a nominal diameter of 13 mm. Samples are taken at the following times of day: 6:00, 10:00, 14:00, 18:00 and 22:00, for 25 consecutive days. The diameter measurements from these samples are presented on the table in the next slide.

Class Example

S t e p 1 : C o l l e c t D a t a

S t e p 2 : S o r t d a t a i n t o s u b g r o u p s ( i . e . l o t s , o r d e r # , d a y s , e t c . )

n = s i z e o f t h e s u b g r o u p { i n t h i s e x a m p l e 5 t i m e s p e r d a y )

k = n u m b e r o f s u b g r o u p s { i n t h i s e x a m p l e 2 5 d a y s }

S t e p 3 : F i n d t h e m e a n f o r e a c h s u b g r o u p ( X )

X = X X X X

n

n1 2 3 . . . . .

S t e p 4 : F i n d R a n g e f o r e a c h s u b g r o u p ( R )

R = X l a r g e s t v a l u e - X s m a l l e s t v a l u e

Step 5: Find Overall Mean ( X )

X = X X X X

kk1 2 3 ...

Step 6: Find average value of range ( R ) R = R R R R

kk1 2 3 ...

Step 7: Complete control limits using attached table

For X Control Chart

Central Line - CL = X

Upper Control Limit - UCL = X +A2R

Lower Control Limit - LCR = X- A2R

For R Control Chart

Central Line - CL = R

Upper Control Limit - UCL = D4R

Lower Control Limit - LCR = D3R

Step 8:Plot Chart

P CONTROL CHART CONSTRUCTION

An inspector at the end of the manufacturing line for the production of car wheel rims, at the end of each shift, inspects the lot of wheel rims made during that shift. On good days when the welder is running properly, over 400 wheels are made per batch. On poor days, as low as 50 to 60 wheels are made per batch. The inspector marks on his/her “check sheet” for each batch the total number of wheels inspected and the number of defects returned for rework in each lot.

Class Example

Step 1: Collect Data

Step 2: Divide data into subgroups (usually days or lot). Subgroup size should be

greater than 50 units. n = number in each subgroup

pn = number of defects in each subgroup

Step 3: Compute fraction of defectives (for %, multiply by 100)

p = pn/n

Step 4: Find the Average Fraction of Defectives ( p )

p = ( )

( )

total defectives

total inspected =

pn

n

Step 5: Compute the Control Limits for each Lot

Central Line CL = p

Upper Control Limit UCL = p + 3p p

n

( )1

Lower Control Limit LCR = p - 3p p

n

( )1

Step 6:Draw P Control Chart

PN CONTROL CHART CONSTRUCTION Class Example

On an assembly line of windshield wiper motors, the inspector selects randomly 100 motors per hour to examine. The inspector notes on the “check sheet” the number of defective motors in each 100 selected.

Step 1: Collect Data (lot size set constant)

Step 2: Calculate Values p =

n

pn

CL = p n

UCL = p n + 3 pn p( )1

LCL = p n - 3 pn p( )1

Step 3: Plot Chart

QUALITY PLANNINGWho is customer?

What do they need?

QUALITY CONTROLEvaluate, compare, act

QUALITYIMPROVEMENT

Establish infrastructure

ISO9000