The repeated measurements are called trials. Calculations are then made to determine the level of variation between the appraisers, parts and across the trials. It is not necessary to go into the actual calculations here since there are numerous software programs and templates available to assist operators. Instead, let's focus on how to perform a valid study and how to interpret the results.
Selecting part samples is perhaps the most critical step in performing a successful study--and probably the most misunderstood. Part samples used for gauge studies should represent the true variation of the production process. A common mistake is trying to select production samples that are similar. Some instructions for gauge studies even state that samples must be from the same batch.
The truth is that using products that do not represent the variation of the process will cause the gauge study results to be worthless. If necessary, operators may even select samples over a period of days or weeks to get samples that truly represent the process. Always remember that it is the measurement system that is being evaluated here, not the products.
Now it is time to start measuring. Here are a few guidelines for the measuring process:
+ The operators should share one calibrated gauge or measurement system.
+ Five or more samples that represent the range of the process variation should be used. Do not use one part or parts that have little variation.
+ Samples should be measured in random order if possible.
+ There should be at least two trials or measurements taken from each operator.
This series of blogs will include:
- What does it measure?
- Evaluating the Gauge Study: The TV Report
- Evaluating the Gauge Study: The TT Report
- Evaluating the Gauge Study: The Average and Mean Report