Lesson 3 Stabilize the Process
Objectives You will be able to understand: Key activities for process stability Difference between special and common cause variation Responsibilities for taking action on variation Difference between specifications and control limits
Lesson 3: Stabilize the Process Activity 3.1 Determine process measures Activity 3.2 Examine the process by using control charts Activity 3.3 Act on special causes Activity 3.4 Check for capability
Activity 3.1 Determine Process Measures Process measures must: - be objective and representative of the process - measure appropriate quality characteristics Flow charts are useful tools for determining process measures
Determine Process Measures Products & Services CVN Processes Air Wing Suppliers Inputs Processes Outputs Outcomes Quality of supplies Time to deliver Condition of materials Accuracy of information etc. Ordnance assembly Moving ordnance Staging ordnance etc. Launch / recover Berthing / messing Training time etc. Timely launch / recovery Safe launch / recovery Effective launch / recovery Satisfaction with service etc.
Run Chart Line graph showing variation plotted over time 55 50 45 Elapsed Time (minutes) 40 Average 35 30 Sequence Line graph showing variation plotted over time
Activity 3.2 Examine the Process by using Control Charts Upper Control Limit Average Measurement Lower Control Limit Time or Sequence Line graph that shows process variation Limits calculated from process data
Common Causes Data appear randomly UCL Average Measurement LCL Time or sequence Data appear randomly Control limits provide predictable range
Special Causes Appear as nonrandom variation Are not predictable UCL Average Measurement LCL Time or sequence Appear as nonrandom variation Are not predictable
Activity 3.3 Act on Special Causes Common Causes: - Inherent in the process - Affect everyone in the process - Affect all outcomes of the process Special Causes: - Are not in the process all the time - Do not affect everyone in the process - Arise because of specific circumstances
Responsibility for Reducing Variation Special cause - people working in the process Common cause - command’s leaders & managers
Avoid Tampering and Underadjusting Taking action when no action is needed Failing to act when action is required
Specifications vs Control Limits UCL Measurement Specifications LCL Time or sequence
Activity 3.4 Check for Capability Unstable - Measures fall outside control limits, or - Measures show non-random pattern Stable - Measures fall randomly within control limits Capable - Stable process that also meets customer or mission requirements
Stability and Capability UCL USL LSL LCL Situation 1
Stability and Capability USL UCL LCL LSL Situation 2
Stability and Capability UCL USL LCL LSL Situation 3
Stability and Capability USL UCL LCL LSL Situation 4
Lesson Summary Stabilize the Process Activity 3.1 Determine process measures Activity 3.2 Examine the process by using control charts Activity 3.3 Act on special causes Activity 3.4 Check for capability