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Sheet Metal Production Runs by the Numbers
From a customer's requirement to a costed, inspected batch of sheet metal products: capacity, blanks, nesting, routing, batch size and learning
Plan a sheet metal production run with numbers: capacity and fill lines, flared blanks and corners, nesting yield, routing times, setups, batch size, learning, unit cost and first-article inspection.
Start readingAbout this book
A sheet metal shop that makes one-off parts thinks in jobs; one that makes products thinks in runs. A run of five hundred identical trays, brackets or enclosures is a different problem from a single fabrication. The product must be specified so that it meets the customer’s need with the fewest operations. Its blank must nest well, because material is now the largest cost. Its routing must be planned and timed, because every minute is multiplied by the batch. Its setups must be spread over a sensible batch size, its labour falls as the operators learn, and its first part must be right before the other four hundred and ninety-nine are made.
This book works through those numbers for one product, from the customer’s requirement to the run record. It starts with capacity and specification, develops the product’s blank and its corners, nests the blank, builds a routing, works out setups, batch size and learning, costs the run, and ends with first-article inspection and the records that make the next run easier.
It is for production engineers, shop supervisors, estimators and product designers in sheet metal manufacturing. It assumes school algebra, a little geometry and a working knowledge of laser cutting and press brake folding. The Library’s Sheet Metal Parts by the Numbers covers bend allowances, springback and press brake force in more depth; this book uses them where a production run needs them. Setting prices and writing quotations are separate subjects, and this book stops at cost.
The running case
Every chapter follows one fictional product. This is an illustration. An equipment distributor has asked a sheet metal shop for 500 steel tote trays for parts storage in its warehouse. The trays must fit the distributor’s shelving, which takes a 600 × 400 mm footprint, hold at least 36 litres to a fill line 20 mm below the rim, carry 25 kg of parts, nest twenty high in no more than 700 mm when empty, and be powder coated.
The shop’s design is a flared tray of 1.2 mm cold-rolled steel, 600 × 400 mm at the top and 205 mm deep, with walls flaring at 11.31° from vertical, a hemmed rim, riveted corners, handle slots in the short walls and pressed denesting lugs. It cuts blanks on a fibre laser from 2,400 × 1,200 mm sheet, folds on a press brake, rivets on a bench jig and sends the trays out for powder coating.
The distributor, the shop, the dimensions, the times, the rates, the prices and the mistakes are invented. None describes KEVOS® work or a real business. Money is in Australian dollars, and each figure states whether GST is included.
How to use the book
Read Chapters 1 and 2 first: they turn the requirement into the tray’s dimensions, which every later chapter uses. Chapters 3 to 6 deal with the product’s geometry and material, Chapters 7 to 9 with time and cost, and Chapter 10 with inspection and records. Each chapter calculates with the running case, includes a plausible mistake and how it was found, and ends with an exercise and its worked answer.
Source limits and professional responsibility
The geometry is exact, and every calculation was checked by running it. Operation times, machine rates, material prices and coating costs are illustrations: real values come from the shop’s own records and suppliers, and the book shows how to measure them. The learning curve and economic batch quantity are long-established models that describe tendencies and give estimates, not guarantees.
A storage tray carries loads and is handled by people. Its load rating, handling features and any claims made about it are the manufacturer’s responsibility, under Australian consumer and work health and safety law. This book teaches planning and calculation. It is not a design or a rating for any product.
Who this book is for
Production engineers, sheet metal shop supervisors, estimators and product designers who turn a sheet metal product into a planned, costed production run of hundreds of identical parts.
What you will learn
- Turn a customer's capacity, stacking and load requirements into a product specification with checked dimensions.
- Develop a flared sheet metal container's blank, corners and rim, and nest it for the best material yield.
- Build a routing with operation times, and work out setups, economic batch size and the learning curve.
- Calculate a unit cost for the run from material, machine, labour, finishing and setup, with GST stated.
- Plan first-article inspection, in-process checks and the run record so the batch is right from the first part.
Inside this book
Chapters
- 01From a requirement to a product specificationTurn a customer's needs for 500 tote trays into a specification: footprint, capacity to a fill line, flare for nesting, thickness for load, denesting lugs, and a 36 L requirement read as brim-full.
- 02Capacity of a flared trayCalculate a flared tray's capacity with the prismoidal formula, compare the shortcuts, size the depth from 200 to 205 mm for 36 L to the fill line, and catch a depth set by average areas.
- 03Developing the flared tray's blankDevelop the tray's one-piece blank: walls on their slant height, corner edges that check the pattern, 78.69° folds and their allowance, the corner notch, and walls cut to the vertical depth.
- 04Corners, rims and nestingClose the tray's corners with lap tabs at 92.2°, stiffen the rim with a hem, find why flared trays jam at a 6.1 mm pitch, set denesting lugs for a 25 mm pitch, and lugs pressed the wrong way.
- 05Nesting the blanks and material yieldNest 500 cross-shaped tray blanks: three per 2,400 × 1,200 sheet at 60% yield, why larger sheets do worse, the steel cost with GST, and a nest that ordered 83 sheets too many.
- 06Mass, finishing area and bought-in partsWork out the tray's mass, its powder coat area on both faces, the coater's charge and racking, rivets with an allowance, pallets and shipping mass, and a coating estimate made on one face.
- 07Routing and operation timesBuild the tray's routing, time each operation from its parts, find the press brake as the bottleneck at 35 hours, plan the days, and catch a laser time without the sheet handling.
- 08Batch size, setups and the learning curveSpread A$316.25 of setup over a batch, find an economic batch of about 300 trays, follow an 85% learning curve to standard by tray 19, and catch a run timed from its first three trays.
- 09Cost per tray across the runBuild the tray's unit cost from steel, machines, labour, coating, setup and learning: A$66.69 at 500 and A$73.25 at 50 excluding GST, with sensitivity, a die's payback and GST errors.
- 10First article, inspection and the run recordProve the first tray against every requirement, check every twentieth tray, estimate how often a tray falls below 36 L, keep the run record, and catch a capacity test filled to the brim.
Apply This in Practice
Use these KEVOS® tools to try the method from this reading with your own numbers.
Applies this method
Prismoidal Formula Volume
Gives the exact volume of a prismoidal shape from its three areas and height.
Used in Capacity of a flared tray
Applies this method
Sheet Nesting Yield Check (Parts per Sheet, Material Utilisation, Sheets and Cost per Part)
Works out blanks per sheet, yield and sheets for a batch; for shaped blanks like this chapter’s trays, enter the bounding rectangle.
References and source notes
The manuscript and worked examples are original KEVOS® writing. References inform particular concepts; their authors do not endorse this book. Web references were consulted on 26 October 2026.
- Ellsworth M. Longfield, McGraw-Hill Book Company, New York. Sheet Metal Drafting (first edition) (1921). Supplied source, read as a subject map: its pairing of each pattern with related mathematics, its flaring pans and its planning for quantity production of a sheet metal product. No text, figures, problems or answers are reproduced, and all numbers, cases and methods in this book are its own.
- T. P. Wright, Journal of the Aeronautical Sciences, vol. 3. Factors affecting the cost of airplanes (1936). Source of the learning curve relationship, in which unit labour falls by a constant fraction each time cumulative output doubles, used in Chapter 8.
- F. W. Harris, Factory, The Magazine of Management, vol. 10. How many parts to make at once (1913). Source of the economic order quantity relationship between setup cost, holding cost and demand, applied as an economic batch quantity in Chapter 8.
- Australian Taxation Office. GST (Goods and services tax) (2026). Reference for the 10% goods and services tax applied when the book states prices including GST.
- Standards Australia and Standards New Zealand. AS/NZS 4506 Metal finishing: Thermoset powder coatings for architectural applications (edition as called up). Named by number and scope as an Australian standard for powder coatings, to show where coating requirements come from. The running case's coating is an illustration and no values are quoted from the standard.