Fabrication labor and machine time estimating · Lesson 4 of 4

Fabrication labor and machine time estimating: defects, verification and case study

Six ways an estimate goes wrong, two counting mistakes, setup charged per piece, a wage used as a loaded cost, verification against actuals, a case study of a miscounted 63 ft run, and a twelve-point check before release.

You will be able to: Spot and correct the common defects in a time estimate, separate a wage from a loaded cost, verify an estimate against recorded actuals, and work a miscounted run from discovery to a documented fix.

9 min · 9 slides · 6 questions

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Slide 1 of 9

Six ways an estimate goes wrong

Six common ways an estimate goes wrong: an operation left out, setup charged on every piece, a piece or girth over the limit assumed makeable, a thickness rule ignored, a wage used as a loaded cost, and a learning curve applied to a one-off.

Each is found by checking the estimate against the drawing and the registers, not by feel.

Sources

GAO Cost Estimating and Assessment Guide: Best Practices for Developing and Managing Program Costs (GAO-20-195G, 12 March 2020) - U.S. Government Accountability Office
AFS fabrication limits - materials, thicknesses, bend rules and sizes the shop can make - Architectural Flashing Supply

Glossary

Fixed cost: GAO's idea that some costs do not change with quantity, so unit cost rises when fewer items share them. Setup is the shop version for a batch.
Shop review: AFS's status for a profile the shop must confirm before fabrication; the customer sentence is "AFS confirms this profile before fabrication."
Elapsed time: The calendar span between two events, such as AFS recording when a job first goes in progress and when it is marked complete; it includes waiting.
Time study: A way of collecting data on production by observing work, which BLS lists among the ways industrial engineers collect data on processes.