At MtlWrx, we use statistical process control charts to ensure we ship and maintain part accuracy.
Each part is setup to have the machine operator record what the machine produced along the steps that were involved.
This measurement process will notify the operator of an unacceptable part and will produce a graph used to study how a process changes over time.
We check both incoming and outgoing products to ensure part accuracy.
Our control chart has a central line for the desired measurement, an upper line for the upper control limit and a lower line for the lower control limit.
These lines are determined from customer print requirements. As the part is measured a new line will be plotted showing where the measurement is running. (See examples below)
By analyzing these charts, we can draw conclusions about whether the process variation is consistent (in control), is unpredictable (out of control, affected by special causes of variation) or is running near the upper/lower control limits (requiring an adjustment before bad parts are produced)
Here are some screen shots of our statistical process control.