Contents
Which is the lower specification limit or upper specification limit?
The Lower Specification Limit is 48 The Nominal, or Target Specification is 55 The Upper Specification Limit is 60 Therefore, the Tolerance is 60 – 48, or 12 As seen in the illustration, the 6-Sigma process spread is 9. Therefore, the Cp is 12/9 or 1.33.
Which is spatial control chart for the mean?
Spatial Control Charts For The Mean ( Journal of Quality Technology) The properties of this control chart for the means of a spatial process are explored with simulated data and the method is illustrated with an example using ultrasonic technology to obtain nondestructive measurements of bottle thickness.
How are the lines in a process control chart determined?
These lines are determined from historical data. By comparing current data to these lines, you can draw conclusions about whether the process variation is consistent (in control) or is unpredictable (out of control, affected by special causes of variation).
How to implement statistical process control ( SPC )?
Implementing Statistical Process Control 1. Determine Measurement Method 2. & 3. Qualify the Measurement System 4. & 5. Initiate Data Collection and SPC Charting 6. & 7. Develop and Document Reaction Plan 8. Add Chart to Control Plan 9. Calculate Control Limits After 20-25 Subgroups. 10. Assess Control. 11. & 12.
How are SPC charts used in statistical software?
Most statistical software will run a series of tests (if selected) to check for special cause condition (s) and provide the type of violation it is. A couple of common misconceptions for using SPC charts are that the data used on a control chart must be normally distributed and that the data must be in control in order to use a control chart.
When to use subgroups to estimate process variation?
For example, if appraisers are measuring parts every 30 minutes and they sample and measure 6 consecutive parts each 30 minute interval then the subgroup size is 6 and the range should be used to estimate the process variation. For subgroups >8, use the standard deviation to estimate variation: X-bar, S.
What should the process control limits be in SPC?
For the process to be in-control AND meeting the customer specifications, the process control limits should be within the customer specification limits (or a least the amount which customer wants acceptable parts). Several other non-Shewart based control charts exist and most statistical software programs have these options.