Industrial Statistics with Minitab

12.4 Arrow

An arrow shaped plastic pieces are made with two injection moulding machines: A and B. Each machine has its own mould with 4 cavities, as shown in the following figure:

Data is available on ARROW.MTW file:

Column	Content
C1 C2 C3 C4 C5	Defects found in the parts produced by machine A As C1, but for machine B Tensile strength of parts made in 15 injections with machine A (15×4 = 60 data) As C3 for machine B Cavity to which data from columns C3 and C4 belong.

The questions we pose are:

1. Looking at the distribution of defects in each machine, should the improvement measures be equally prioritized for both machines?

2. As for the tensile strength, is there a difference between machines? And between cavities?

1. Let's see what is the distribution of defects in each machine by: Stat > Quality Tools > Pareto Chart Doing the same for the machine B: Assuming that the data are representative of both machines, it would be appropriate to focus on the problem of deformation in machine A and scratches in machine B.

2. First of all, a graphical analysis ...