SPC Training

Statistical Process Control Training Rev: 1, Dd:1/4/03
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Why we need SPC?
Prevention versus Detection
Detection – Waste time & materials Prevention – Avoid waste, more effective
Change in process setting Out of calibrated equipment
Statistical Process Control Training Rev: 1, Dd:1/4/03
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Local Action & Actions on the System
Local Actions Are usually required to eliminate special causes of variation. Can usually be taken by people close to the process. Can correct typically about 15% of process problems.
Statistical Process Control Training Rev: 1, Dd:1/4/03
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Key Factors in Control Chart
Must update real time Must highlight when out of control Must take appropriate actions timely and records maintained Determine cause factors of process variation
NOTES:
AND/OR MEASUREMENT
spec limits
EVALUATION AND/OR COMPARISON
• Characterized by traditional quality control • Product control cycle is oriented with the observing, comparing, diagnosing and correcting actions in a feed-forward loop. The feed-forward product control cycle result in a filtered output
Statistical Process Control Training Rev: 1, Dd:1/4/03
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Causes of Process Variation
Common Cause (Random)
Stable over time, predictable over time Process output “in control” Examples
Statistical Process Control TrainingRev: 1, Dd:1 Nhomakorabea4/03
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What is SPC?
SPC = Statistical Process Control – Use of statistical techniques such as control charts to analyze a process or its outputs in order to take appropriate actions to achieve and maintain a state of statistical control and to improve process capability. To assist in determining trends and patterns for decision making. Example: Preventive Action. To capture and monitoring Voice of Process (VOP) Assist in the Continuous Improvement Process.
Measurement method, material, machine, environmental control Measurement system must remain unchanged during analyzing cause factors
Statistical Process Control Training Rev: 1, Dd:1/4/03
Slight change in ionic concentration in plating bath Slight voltage fluctuation from power supply
Statistical Process Control Training
Rev: 1, Dd:1/4/03
Statistical Process Control Training Rev: 1, Dd:1/4/03
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Product Control
inputs PROCESS
FILTERED
outputs
OUTPUTS
OBSERVATION
MANIPULATION AND/OR CORRECTION DIAGNOSIS AND/OR DECISION
control
limits
EVALUATION AND/OR COMPARISON
NOTES: • Process control cycle is oriented with the observing, comparing, diagnosing and correcting actions in a feedback loop • Process control focuses on process improvement and nurtures a prevention philosophy
Statistical Process Control Training Rev: 1, Dd:1/4/03
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Product Variation
No two things are exactly the same Must be within acceptable control limit Use control charts to determine whether a process is under statistical control Process Variation Factors :People (experience, skill) Machine (calibration, damaged parts) Materials (Change of material quality) Methods of Measurements Environment (temperature, humidity, lighting)
Statistical Process Control Training
Rev: 1, Dd:1/4/03
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What is Control Chart ?
A fundamental tool to determine if a process is in control A graphic presentation of Quality Provide traceability to process history, plotted on a time axis Verify improvement or deterioration of a process Provide easily noticeable trend of machine or process performance Detect “special” cause variation and act upon it Quantify and Reduce “common” cause variation
Actions on the System Are usually required to reduce the variation due to common causes. Almost always require management action for correction. Are needed to correct typically about 85% of process problems.
Rev: 1, Dd:1/4/03
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Before Implement SPC…
Few points to be discussed:discussed:1) Gathering data and using statistical method to interpret them are not ends in themselves. The overall aim should be increased understanding of the processes. 2) Statistic can be applied to any area, not only limited to shop floor. 3) SPC stands for Statistical Process Control. Application of SPC to control output (product) should be only the first step. Until the process which generate the output become the focus, the full power of SPC cannot be realized. 4) Measurement system are critical to proper data analysis. When such system lack statistical control or their variation accounts for a substantial portion of the total variation in process data, inappropriate decision may be made.