Process specifications for Short Run

A process specification is very similar to a standard, but it defines the combination of process + characteristic instead of part number + characteristic.

You can set up Short Run process specifications in several places:

To enter a new process specification:

  1. Click New. Enter a name for the new process specification, and then click OK.

Best practice is to specify a combination of process name and characteristic being measured. For example: if multiple part numbers are modified by the CUTOFF process and are routinely sampled for length and weight, then you should create one process specification for CUTOFF LENGTH and a second process specification for CUTOFF WEIGHT.

  1. Specify all desired settings for the process specification, and then click OK.

Almost all of the settings on the Process Spec Information screen are identical to the settings for standards. The two settings that are different are found on the General tab:

Selecting this check box will add this item to the predefined list for this traceability field. This makes it easy to select the correct process specification during data entry or while setting up a planned session.

Select the method of Short Run calculations to use for this process. Your choices are:

      • Target/Nominal:  This subtracts the target or nominal dimension from the chart plot point. Target/Nominal assumes a constant subgroup size, and the variability of each process is not significantly different.

      • Range/Short Run:  Range/Short Run codes measurements by variability (range values). This subtracts the target value from the plot point, but also divides the coded value and R value by the variance factor (target R or s). This method requires uniform subgroup sizes across part numbers. The center line for the chart will be zero. The center line for the R chart will be one. The control limits for and R charts are plus/minus factors.

This is useful when the specification width from product to product is significant. The Range/Short Run method uses the range values from the Standard to factor out the difference from product to product.

      • Standardized:  Values are plotted as expressions of standard deviation. Standardized charts subtract a constant from the plot point and divide that value by the variance factor. The center line of the chart will always be zero, and the control limits will always be placed at plus or minus three standard deviations. Variance and sample size may vary.

The Standardized method uses the target range value from the Standard to factor out the difference from product to product.

      • Uncoded:  Functions as a conventional SPC program. The data is displayed as actual values. Dimension and variation must be identical or statistics will not be valid.

During data entry, almost all of the settings from the process specification will be used instead of the settings from the standard. The only settings that will be used from the standard are:

This means that for all data entered in Short Run mode:

If different part numbers will measure this characteristic with different numbers of decimal places, then you should configure this process specification with the largest number of decimal places that will be needed to display this characteristic.

Additionally: