LSL and USL Subcommand (SPCHART command)

LSL and USL allow you to specify fixed lower and upper control limits. Fixed control limits are often used in manufacturing processes as designer-specified limits.

  • For chart types other than CPCHART, these limits are displayed on the chart, along with the calculated limits. If you do not specify LSL and USL, no fixed control limits are displayed. However, if you want only the specified control limits, you must edit the chart in a chart window to suppress the calculated series.
  • For a chart type of CPCHART (process capability chart), LSL and USL are required. The REFERENCE subcommand controls whether these limits are displayed on the process capability chart. By default, they are displayed.

Example

SPCHART /TEMPLATE='ctrl.sgt'
  /XS=SUBSIZE
  /USL=74.50 
  /LSL=73.50.
  • The USL and LSL subcommands specify the control limits according to the designing engineer. The center line is probably at 74.00.
  • The specified upper and lower limits are displayed together with the control limits that are calculated from the observed standard deviation and the sigma value.