By trade · Machining, mechanical engineering and finishing
Lean Six Sigma in precision machining
This is where statistical process control was born, and where it keeps the most meaning: measurable dimensions, written tolerances, slow drift from wear. The question there is almost never "is the process conforming" but "is it stable", and confusing the two is very expensive.
The other permanent subject is the measurement system itself. On tight tolerances, the spread of the instrument and the operator uses up a large share of the available interval — something no production record shows, and which silently invalidates the analyses built on top of it.
The tools illustrated by a case from this sector
9 entries reviewed in English — 9 entries in all on the French page.
DMAIC
DMAIC is the five-phase problem-solving approach — Define, Measure, Analyze, Improve, Control — that structures every Six Sigma project.
Method · case: Watchmaking
5S
5S organises the workstation in five steps — sort, set in order, shine, standardize, sustain — so that an anomaly is visible at once.
Lean tools · case: Precision machining
Process capability
Capability indices compare the spread of a process with the tolerance interval: Cp measures what the process would be capable of if it were centred, Cpk what it is capable of as it stands.
Statistics · case: Machining
Ishikawa / fishbone diagram
The Ishikawa diagram lays out in a fishbone all the possible causes of a problem, grouped by family, so as not to stop at the first plausible hypothesis.
Problem solving · case: Mechanical engineering
Regression analysis
Regression models the link between a quantity one wants to explain and one or more quantities that influence it. It quantifies what the scatter plot lets one guess.
Statistics · case: Surface treatment
MSA — measurement system analysis
Measurement system analysis checks that the instrument and the method are reliable enough for the data to be used to decide. Without it, every analysis rests on figures whose quality is unknown.
Measurement and indicators · case: Precision engineering
ANOVA (analysis of variance)
Analysis of variance compares the means of several groups at once, judging whether the gap between the groups is large compared with the spread observed within each of them.
Statistics · case: Surface treatment
Histogram
The histogram shows the distribution of a measured quantity by grouping the values into classes. Its shape tells you about the process well before the calculation of a mean does.
Statistics · case: Precision machining
Control plan
The control plan writes down what is monitored on a process, how, how often, by whom, and what is done when the measurement leaves the expected range.
Method · case: Foundry
Practise
The training corpus is not split by sector: the questions are about the tools, which are the same everywhere, and the certifications do not split their exams by sector either. To find your level, the shortest way is a fifteen-question quiz, no account needed:
The other trades: Lean Six Sigma by sector.