The Quality Control Tools Statistical Process Control

Objectives

Identify the 7 Basic QC Tools

Understand the application of the 7 Basic QC Tools

Determine appropriate tool for a specific problem solving process

Make use of the tools on real life problems for Continuous Quality Improvement

SPC STATISTICAL PROCESS CONTROL

A collection of problem solving tools used as improvement methodology whose ultimate goal is to reduce process variability

SPC can be applied to any process 1. Checksheet

2. Histogram or stem -and-leaf plot

3. Pareto chart

4. Defect Concentration diagram

5. Cause-and-effect diagram

6. Scatter diagram

7. Control charts

SPOT THE DIFFERENCE

Difference between two objects

No two items will be perfectly identical.

A fact of nature and of industrial life

Always present in a process

There is always a CAUSE to all variation.

VARIATION

Chance/ Random/ Common Causes

Combined influences of countless minor factors

Difficult to detect, sometimes uneconomical to correct

Things that affect all production output ( Deming)

e.g. vibration in machines, slight variation in raw materials, inadequate training, fatigue

TYPES OF VARIATION CAUSES

TYPES OF VARIATION CAUSES

Assignable/ Nonrandom/ Special Causes

Factors that unpredictably induce variation over and above the common causes

Large in magnitude, thus readily identifiable

e.g., operator blunder, faulty machine setup, batch of defective raw material, worn tool, human factors - carelessness, failure to follow correct procedures

State of Statistical Control Absence of assignable or special causes of variation Stable and predictable within some control limits

Out - of - Control State Presence of assignable or special causes of variation Unstable and unpredictable

CONTROL STATE

Problem Definition

Problem = Idea (Target) Fact (Reality)

Idea

(Target) Fact

(Reality)

Problem

Problem Solution

(fill up the gap) by

QC Techniques and Intrinsic Technology

Understanding Problem:

Different QC Tools and techniques have different

roles to play in improving quality. Some roles

include:

Assessing capability

Collecting Data

Discovering problems

Finding and correcting root

causes of the problem

Identifying relationships

Implementing actions

Measuring performance

Monitoring and

maintaining control

Planning

Presenting Data

Selecting Problems

Structuring Ideas

Summarizing Data

Understanding a problem

Tool Selector Chart

Working with

Numbers Counting Measures

Check Sheet

Control Chart

Histogram

Pareto Diagram

Process Capability

Run Chart

Scatter Diagram

#

Brainstorming Creating bigger and better ideas

Why Use It?

To establish a common method for a team to creatively and efficiently generate a high volume of ideas on any topic by creating a process that is free of criticism and judgment

Brainstorming

What does it do? Encourages open thinking when a team is

Gets all team members involved and

dominate the whole group

Allows team members to build on each

their joint mission

Check Sheet Counting and Accumulating Data

Why Use It?

To allow the team to systematically record and compile data from the historical sources, or observations as they happen, so that patterns and trends can be clearly detected and shown

Check Sheet

What does it do? Creates easy-to -understand data that come from a simple, efficient process that can be applied to any key performance areas

Builds with each observations, clearer picture of the facts

Forces agreement on the definition of each condition or event

Makes patterns in the data become more obvious quickly

Constructing the Check Sheet

Step 1 Agree on Definitions

Step 2 Plan the Data Collection

Step 3 Design the Check Sheet

Step 4 Collect the Data

Check Sheet 1

Check Sheet Essentials

Key Success Behaviors

data will not result in blame or poor performance reviews

Train the data collectors

form

Check Sheet 2

Step -by-Step Construction

Step 3 Design the Form

Check Sheet 4

DateTotal

3/10 3/11 3/12 3/13 3/14 3/15 3/16

Lab delays 9 4 6 6 3 12 12 52

No bedsavailable 2 7 2 4 5 8 3 31

Incompletepatient

information7 3 1 2 2 4 5 24

Total 33 28 36 30 25 47 38 237

Project: Admission Delays

Location: Emergency Room

Name: (if applicable)

Dates: 3/10 to 3/16

Shift: All

Reason:

cd

h j

e

g

a

b

f iName of project

Location of data collection

Name of person recording data, if it applies

Date(s)

Other important identifiers

Column with defect/event name

Columns with collection days/dates

Totals for each column

Totals for each row

Grand total for both columns and rows

Source Information (a-e)

Content Information (f -j)

a

b

c

d

e

f

g

h

i

j

Check Sheet Example Keyboard Errors in Class Assignment

Information provided courtesy of Millcreek Township School District,

Millcreek Township, Pennsylvania

Check Sheet 5

Centering

Spelling

Punctuation Missed paragraph

Wrong numbers

Wrong page numbers

Tables

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Mistakes March

1 2 3

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|

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Total

8

23

40 4

10

4

13

34 35 33 Total 102

Check Sheet 6

Check Sheet Example

Types of

defects in

finished pies

Data collected by: Carl

Location: Heavenly, Maine plant

Dates: June 20-26

Lot size: 200

Defect June 20 June 21 June 22 June 23 June 24 June 25 June 26 Total

Too much cream

Too little cream

Too crumbly

Too big

Too small

Has a bite in it

24

9

21

13

14

9

Not chocolaty enough

6

1

Not sweet enough

Project:

A customer response group use a Check Sheet to track the time band during the day when each customer calls. They then ensure that there are enough people available to cope with the heavy load periods . This reduces fatigue and increases customer satisfaction .

A drinks retailer has a Check Sheet to log the types of purchase made, and changes her stock and displays to expand the range in the more popular types of wine. The result is a measurable increase in turnover .

A garage uses a Checklist to ensure all service points are completed . The engineer then signs it and gives a copy to the customer as an assurance. This significantly reduces service omission errors .

Check Sheet Examples

Defect Concentration Diagram

A schematic diagram which shows the various sides of a unit of production, with the positions where nonconformities occur pinpointed

This would be analyzed to determine if the locations

of the nonconformities in the unit convey any useful information about the potential causes of the nonconformities

Defect Concentration Diagram When to use it

During data collection phase of problem identification

Collecting data to monitor the post solution situation

Analyzing a part or assembly for defects to guide improvement efforts

Investigating a part being produced with numerous defects

Identifying positional patterns of problems/defects

Defect Concentration Diagram