Architectural Flashing Supply
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Production throughput and material yield · Lesson 3 of 4

Production throughput and material yield: methods and worked application

AFS's takeoff method step by step, first fit decreasing in plain words, a worked job with and without a cut allowance, and worked throughput examples for lead time and the constraint.

You will be able to: Run AFS's takeoff method by hand on a small job, show the effect of a cut allowance, estimate lead time with Little's Law and find the constraint, recording every assumption and unit.

10 min · 11 slides · 7 questions

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Slide 1 of 11

The AFS takeoff method

List each line: material, thickness, blank width, length, quantity. Check the limits: blank at most 48 in, piece at most 126 in.

Set aside coil pieces. Pool pieces by material, thickness and width; pack them into 10 ft strips; pack strips across 48 in sheets.

Report sheets, utilization and weights. No prices.

AFS's takeoff method, step by stepA flow chart: order lines, then a limits check (blank at most 48 inches, piece at most 126 inches), then a decision. Pieces longer than 10 feet go to coil pieces, listed apart. The rest are pooled by metal, thickness and width, packed into 10 foot strips by first fit decreasing with n minus 1 cuts, then strips are packed across 48 inch sheets. The report gives sheets as an upper estimate, utilization and weights, with no prices. An inset lists first fit decreasing in three moves.Order linesmaterial, thickness, width, length, qtyCheck the limitsblank ≤ 48 in; piece ≤ 126 inLonger than10 ft?yesCoil pieces,listed apartnoPoolmetal, thickness, widthPieces into 10 ft stripsfirst fit decreasing; n − 1 cutsStrips across 48 in sheetsfirst fit decreasing on widthReportsheets (upper estimate), utilization, weightsNo pricesFirst fit decreasing, in three moves› sort the pieces, largest first› put each in the first strip with room› open a new strip only if none has room

Order lines, a limits check, a split that sets pieces longer than 10 ft aside as coil pieces, pooling by metal, thickness and width, pieces packed into 10 ft strips, strips packed across 48 in sheets, and a report of sheets, utilization and weights with no prices.

The method AFS's public material takeoff runs. First fit decreasing is a heuristic, so the sheet count is an upper estimate.

Sources

Videos for this lesson

What this video shows: Jim Womack of the Lean Enterprise Institute on the purpose and value of value-stream mapping; its chapter list includes how to create a value-stream map (from the video's own description).

Video: Introduction to Value Stream Mapping by Lean Enterprise Institute, on YouTube. AFS checked its description against this lesson.

Glossary

First fit decreasing
A bin-packing method: sort the items largest first, then put each into the first bin where it fits. AFS's takeoff uses it for pieces in strips and strips across sheets.
Bin packing
The problem of putting the most objects in the fewest fixed-size bins (NIST Dictionary of Algorithms and Data Structures).
Cut allowance
Material lost per cut between pieces in one strip. In AFS's takeoff it is entered by the user, and n pieces in a strip take n - 1 allowances.
Value-stream mapping
Diagramming every step in the material and information flows needed to take a product from order to delivery (Lean Lexicon).