Quality & Statistics · Capability
Cp and Cpk: spread versus centering
A weld-collapse example shows why a narrow spread can still sit too close to a specification limit.
Articles, updates and engineering notes
A place for the thinking around the work.
The Mechatrovich blog connects engineering methods to working tools, explains product decisions, shares practical knowledge, and documents observations worth keeping.
01 / Quality & Statistics
12 POSTS
Measurement systems, process stability, and capability
Quality & Statistics · Capability
Pp and Ppk: the overall performance view
Calculate the overall standard deviation and both performance indices from 100 weld measurements.
Quality & Statistics · Capability
Why Cpk and Ppk can disagree
Follow the time sequence to see why local variation and overall variation tell different stories.
Quality & Statistics · Capability
Capability results: from numbers to engineering action
Use the graphs, study conditions and requirements to decide what the capability results support.
Quality Engineering · SPC
Is the adhesive dose staying consistent?
Follow the measurements through subgroup sampling, both control charts, investigation and verification.
Quality & Statistics · MSA
Gage R&R NDC Below 5: What It Means and What to Check First
Why %GRR can look acceptable while the measurement system still cannot separate enough distinct part categories.
Quality & Statistics · MSA
Gage R&R Acceptable But Cpk Still Low? Why That's Not a Contradiction
Why a trustworthy measurement system can correctly report a process that is off-center or too variable for specification.
Quality & Statistics · SPC
X-bar R Chart In Control But Cpk Still Low: What Stability Doesn't Tell You
Why statistical stability describes consistent behavior—not whether the process distribution fits specification.
Quality & Statistics · Process Capability
Capability report
Cp vs Cpk: what the difference actually tells you
Understand potential capability, process centering, and why a stable process should come before the final capability conclusion.
Quality & Statistics · MSA
Gage R&R example: calculation and interpretation
Follow 20 measurements through repeatability, reproducibility, Total GRR, part variation, %Study Variation, and ndc—then reproduce the result in the calculator.
Quality & Statistics · MSA
Gage R&R basics
A practical introduction to repeatability, reproducibility, %GRR, variance components, and number of distinct categories.
Quality & Statistics · SPC
X̄–R charts and rational subgrouping
Why subgroup logic, data order, and enough subgroups matter before interpreting calculated control limits.
02 / Control & Automation
1 POST
Motors, drives, control methods, and the equations behind system behavior
Control & Automation · Electric Drives
DC Motor Speed Control: Constant Speed, Armature Voltage & Field Methods
How armature voltage, field flux, load torque, and PWM affect DC motor speed—and what each control method trades away.
03 / Data & Automation
1 POST
Turning engineering data into reviewable working information
Measurement Data & Automation
From machine-export CSV to a reviewable table
Header detection, numeric-column mapping, specification checks, and row traceability in a practical inspection workflow.
04 / CAD & Product Design
1 POST
Hands-on modeling practice and product-development workflows
CAD & Product Design · Siemens NX
Siemens NX Practice Exercise 01: Sketch-to-Part Modeling
Model a real part from a dimensioned drawing, with progressive hints, a recommended feature sequence, and a downloadable exercise sheet.
05 / Updates & Field Notes
OPEN CATEGORY
Shorter observations from engineering work and product development
No dated field-note posts have been published here yet. This category is reserved for concise project observations, engineering lessons, and product-development updates that do not need a full technical guide.