Heads, samples, and positions

Heads

In some manufacturing processes, multiple samples can be produced on the same machine, at the same time. Each of these outputs is a 'head' and can be, for example, from a different output position on the machine or from different molds or cavities on the tooling.

Samples can be taken from each of the heads of the machine to track performance of each individual head over time.

It is also possible to name each head on each machine. For example, if a process produced two reels of material at the same time, one on a spool at the top of the machine and one on a spool at the bottom of the machine, then the heads can be named 'top' and 'bottom'.

Typically, the same number of samples are taken from each head for measurement.

Samples

A sample is the number of pieces on which to perform variable measurements.

For example, In a can factory, if five samples are required, then the person performing the inspection would take five cans from the production line.

Typically, it is enough to take samples from the line and perform the inspection, but it might be required to label the sample:

If the sample is taken from the line and taken to a quality laboratory, then there might be multiple samples in the laboratory. It is therefore important to label the sample, showing what it is and where it came from.

If the sample is measured more than once, such as the weight, then it must be measured before and after the filling process. The difference in weight before and after is the fill weight.

Positions

You might want to measure the same variable at a number of positions on a single piece. For example, measure the diameter of a can at various points on its body height, around its circumference, or the thickness of a piece at various positions along its length.

Understanding the within-piece variation of a variable can be as important as understanding the variation between samples produced on the same head or between samples from different heads.