ALT 1 - Are We Too Cool?

Process Dominance

Why are we interested in the concept of process dominance? This concept provides the link between the forms of variability and the appropriate control system for controlling that variability. Joseph Juran in Quality Planning and Analysis introduced the concepts of process dominance, when describing the primary forms of process variation, Setup, Machine, Operator, and Component. The Automotive Industry Action Group (AIAG) in the Advanced Product Quality Planning and Control Plan (APQP) Section 6.4 on Process Analysis expanded the list of four to include a total of eight forms of process dominance.

Juran provides examples of a variety of processes and their appropriate control system.

In the prerequisite to this course you studied two of the control systems - run charts and histograms. Additional techniques to be studied in this course include, Variable and Attribute Control Charts, Pre-Control, and revisiting capability. The other control systems will be covered in the Quality Assurance, Advanced Statistical Quality Control, and in the ISO/QS9000 courses.

Juran's Forms of Dominance

AIAG Forms of Dominance
Setup Dominant Equipment -Setup Dominant
Machine Dominant

Equipment:

*Machine or
*Fixture/Pallet or
*Tooling Dominant
Operator Dominant People: Operator Dominant
Component Dominant Material: Material or Component Dominant
  Methods:Preventive Maintenance Dominant
  Environment: Climate Dominant

 

Assignment and Assessment

Read "The First Session" in the Process Control Participant Journal and prepare to answer the questions as part of the Discussion Forum.

  1. To which processes in an organization does process control apply?
  2. Does this include order entry, sales, production, customer services - all processes? Why or Why not?
  3. Can process control be applied to a variety of organizations? Name some examples.
  4. List example processes that could require control.
  5. What happens when products or services do not meet their control requirements?
  6. What happens when products and services do not meet customer requirements?
  7. Develop a definition of an in-control process in terms of work, home, consumer products, statistics , etc.

Individual and Moving Range Variable Control Charts

Are We Too Cool ?

Scenario 1 uses an Individual and moving range control chart (Ind and movR) to measure the temperature variation within a room over two different time spans, and

Assignment and Assessment

  1. Read "Authentic Learning Task #1 Are We Too Cool?" in the Process Control Participant Guide pages 11- 23.
  2. Working with your digital thermometer complete the Scenario 1 activity.
    1. First find a room in an climate controlled environment - an office in an office building, a classroom at a school or some other location which utilizes a industrial heating or air conditioning area.
    2. Complete the Planning a Control Chart Data Sheet - see example answers below.
    3. The first scenario suggests measuring the temperature in the room, at the same point, every thirty seconds for a total of 25 data points and record the data on the provided data sheet in the Process Control Guide.
    4. Create an Individual and Moving Range Control Chart per the procedure as described in Section 4 pps. 74-78 of the AIAG Statistical Process Control (SPC) Manual and at Control Chart Link at Carillontech.com
    5. Determine the Control Limits and answer the question is the Process in Statistical Control?
    6. Repeat the previous four steps but this time make the measurement interval every 3 minutes for a total of 30 minutes or 10 data points.

Planning a Control Chart

Key for the selection and appropriate implementation of a control chart to measure and control process variation is the completion of a planning sheet.

A blank data sheet can be found in the Process Control Participant Guide. pp 14-15.

Example answers for measuring temperature variation in a room using a control chart.

  1. Objective of control chart - To determine the temperature variation in the room.
  2. Sampling, measuring, and subgrouping
    1. variables to be charted - temperature
    2. method of measurement - digital thermometer
    3. expected magnitude of measurement variation - +/- 3 degrees F
    4. point of sampling - center of room, 2 feet off the floor
    5. strategy for subgrouping - no subgrouping, using X-movR chart
    6. frequency of sampling - 30 seconds
  3. Most likely special causes - number of people in room, placement of ducts, door(s) open or closed, movement of people in and out of the room, problems with air distribution system.
  4. Reaction plan for special causes - Notify facilities management to correct
  5. Notes- blower on and doors opening and closing frequently
  6. Adminstration Tasks and Responsibility
take measurement - Jane Houston, reader
record data - Jake Harris, recorder
compute statistics - Mindy Higgins, statistician
plot stats - Mindy Higgins, statistician
extend/change control limits - Brenda Boss, supervisior
filing report - Jennifer Hadley, shift manager

Average and Range Variable Control Charts

3) The Average and Range Chart (X Bar and R) using either Are We Too Cool Scenario 2 Multiple Temperature Readings or Are Our Two Pasta Suppliers Different?

Assignment and Assessment

Read the cited materials and prepare to answer the questions.

An excellent additional web resource is the i six sigma site.

Complete Homework Problem Set M2 ALT1 XBarR

  • Read "Authentic Learning Task #1 Are We Too Cool?" in the Process Control Participant Journal pages 24- 30.
  • Unless you are working with at least three other participants you will unable to complete the assignment successfully as written in the Process Contol Participant Guide. Instead we will use XBar and R charts to compare the two different suppliers.
    1. If you have not already cooked the penne pasta secure the two boxes of pasta (one for each supplier).
    2. Complete the Planning a Control Chart Data Sheet
    3. Create a XBar (Average) and Range Control Chart per the procedure as described in Section 1 pps. 29-63 of the AIAG Statistical Process Control (SPC) Manual, and at Control Chart Link at Carillontech.com for pasta supplier one (subgroup size at least 4, with a minimum of 15 data sets)
    4. Determine the Control Limits - Is the Process in Statistical Contol?
    5. With the second pasta supplier plot points (same sub group size and at least 10 data sets on the control chart for the first supplier). Does the second supplier's data points indicate a process significantly different from the first supplier? (special causes)

Other Variable Control Charts and Precontrol and selection

X Bar and Standard Deviation Charts

Median and Range Charts

PreControl

Selecting the correct control techniques is a complex task.

In the section "The First Session" the concept of process dominance was introduced.

Three other factors can be considered, cost of nonconformance, capability of the process, and skill set of the inspector/operator.

You have practiced two types of variable control charts - Individual and mov R and the X Bar and R charts.

There are other possible variable charts to choose from, Median and Range charts, X Bar and s charts, and precontrol

Factors in addition to the process dominance requirements

(1) the cost impact of a nonconforming product - Higher Cost means selecting a more rigorous control method,
(2) the capability of the process - Larger Cpk means selecting a less rigorous methods, and
(3) the skill set of the operator - Lower SPC skill set means selecting a less rigorous control method.

 

Assignment and Assessment

Read in the AIAG Statistical Process Control Manual the sections on Median and Range and XBar and s (sigma) and then complete homework assignments using the problem set M2 ALT1XBarR problem #2 data set.

Read the web page on precontrol

  1. Read the AIAG Statistical Process Control Manual the sections on Median and Range and XBar and s charts pages 64-72.
  2. Visit the following web sites for further clarification and examples:
  1. Visit Control Chart Link at Carillontech.com download the free excel control chart software use it to generate a XBar and s (sigma) chart using the problem 2 data set used to create the median and range chart. Using the software generate the control limits for both the Xbar and s. Post your answers to the discussion board.
  2. Read the web page on how to use the precontrol technique.