An Application of Shewhart Charts in Woodworking

In order to cope with a situation in which the setup capability is less than the machine capability and the runs per setup are short, a control system based on desired tolerances is proposed. For example, if a ?1/32 inch tolerance is desired, a control chart would be prepared with x at 0 which is the specified dimension. At ? “setup lines” are placed. Upper and lower control limits are set. Tolerance lines at ? could also be included. In use, the machine is set up at the specified dimension, a part machined and measured. Measurement is plotted in terms of specified dimension. If two successive points fall within the setup lines, the machine is allowed to run. If not, the machine is reset until two successive points fall within setup lines. Floor inspectors would periodically measure groups of five from single setup and plot average dimension on control chart. A range chart is used to monitor within-setup dispersion.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member