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Tier 4 · Advanced Fabrication and Manufacturing

Precision forming and statistical inspection

Why a folded angle differs from the programmed one and how a shop measures and corrects it, then how control charts, run rules and capability indices separate a real process change from noise and from a measurement problem.

4 lessons · about 50 min · 7 diagrams · 5 videos

Version 1.0.0

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Lessons

0 of 4 complete

  1. Lesson 1 · 12 min · 10 slides · 10 questions

    Precision forming and statistical inspection: principles and terminology

    Why a folded angle never lands exactly on the programmed value, what AFS sends its folder, and the words statistical inspection uses: specification versus control limits, chance versus assignable causes, SPC versus SQC.

    You will be able to: Define springback, nominal, specification limits and control limits, chance and assignable variation, and SPC and SQC, and state the safety boundary for measuring formed parts.

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  2. Lesson 2 · 12 min · 9 slides · 10 questions

    Precision forming and statistical inspection: materials, standards and design constraints

    How material and thickness move a folded angle, AFS's own fabrication limits, why the order and the specification set the tolerance, oil canning, the standards for statistical methods, and how to tell whether a reading can be trusted.

    You will be able to: Explain how metal, thickness and machine type move a formed angle, which documents set the acceptance limit, and what makes a measurement trustworthy.

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  3. Lesson 3 · 14 min · 10 slides · 11 questions

    Precision forming and statistical inspection: methods and worked application

    The first-piece loop, what to measure on a Fascia Cover, how an angle error becomes a position error, and worked control charts and capability indices on hypothetical readings, with the assumptions each one needs.

    You will be able to: Run a first-piece check, build an individuals and moving-range chart for a short run, compute X-bar and R limits and Cp and Cpk with their assumptions, and choose between 100% and sampled inspection.

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  4. Lesson 4 · 12 min · 9 slides · 10 questions

    Precision forming and statistical inspection: defects, verification and case study

    A defect map for formed angles and legs, a coil-change case worked through the control chart and its action plan, what to do when a stable process is not capable, how to rule out the gauge, and the record a reviewer needs.

    You will be able to: Diagnose a forming-precision defect from measurements, separate a real process change from noise and from a measurement problem, and document the correction for review.

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Practical task

Run a first-piece check and a short individuals chart on one formed profile (a real order, or the Fascia Cover from this module), and produce a record a reviewer can check against its sources.

Hand in

  • An order summary: material, gauge, each leg to the mold line, each bend angle and its direction, and where the acceptance limits come from (order, specification or assumed for the exercise)
  • A first-piece sheet: every angle and leg measured off the machine, the tool and its resolution, the correction made and the approved reading
  • An individuals and moving-range chart of one bend over at least 20 pieces, with the center line, control limits and moving-range limit worked out and shown
  • A run-rule review: which WECO rules, if any, fired, at which piece, and the action taken under an out-of-control action plan
  • A capability note: Cp and Cpk against the stated limits, with the sample size, the normality and stability assumptions, and whether the data are enough to claim capability

Rubric

CriterionMeets the standard when
Acceptance limitsEvery limit used is traced to the order or the specification, or clearly labelled as assumed; none is taken from memory.
First pieceEvery angle and leg is measured off the machine with a named tool, to the mold line where the drawing is mold-line, and the correction is recorded.
Chart arithmeticThe average, moving ranges, 1.128 divisor and 3.267 moving-range factor are applied correctly and the limits come from the process, not the specification.
Signals and actionRun rules are applied correctly, and any signal leads to the material, gauge and first-piece checks before the machine is touched.
Capability honestyCp and Cpk are computed with s, and the note states that a large sample (generally thought to be about 50 independent values), normal data and a stable process are needed before claiming capability.
SafetyThe record notes that pieces were measured off the machine, that no adjustment bypassed the employer's energy control procedure, and the hand protection used.

Module quiz

10 questions drawn from a bank of 41; a new set each attempt. Pass mark 80%.

1. Under 29 CFR 1910.212(a)(3)(ii), what shall be guarded?
2. What is the published thickness band for 24 ga galvanized?
3. How does FlashDraft send each bend to AFS's Thalmann folder?
4. What does NIST call the main purpose of acceptance sampling?
5. Which activities does 29 CFR 1910.147 count as servicing?
6. Which materials does NIST say show larger and less predictable springback?
7. What does "in control" mean, according to NIST?
8. What numeric fabrication tolerance does the public 07 62 00 specification in this lesson state?
9. What does a 1992 Amada patent say about predicting the amount of elastic return?
10. What does NIST warn about the digits an instrument displays?