How to quote a sheet metal part

What goes into a sheet metal quote?

1. Material. The flat blank's weight, plus the share of the sheet that ends up as skeleton, at your price per pound.
2. Cutting. Laser or waterjet time from the cut length, the number of pierces and the thickness, plus the machine's setup.
3. Forming. Press brake setup (tooling, backgauge, first piece) and a short run time per bend.
4. Deburr and handling. Bench time per part, more with more holes.
5. Outside services. Powder coat, plating, galvanizing and hardware at the vendor's lot charge, piece price and fees, plus their lead time.
6. Markup and minimums. Your margin on the total cost, never below a minimum line charge.

How do you calculate sheet metal material cost?

Start from the flat pattern, not the formed part. Add a little for the kerf and the gap to the next part, then divide by how much of a sheet a nest really uses. QuotedPart adds 5 mm (0.2 in) to the flat length and to the width, and assumes 80% of the sheet becomes parts:

blank weight = (flat length + 0.2 in) × (flat width + 0.2 in) × thickness × density ÷ 0.8

For the bracket: a 6.00 × 4.00 in flat becomes a 6.20 × 4.20 in blank in 0.075 in cold-rolled steel (7.85 g/cm³). That's 0.31 kg (0.69 lb) at $0.95/lb, so $0.66 of steel a part.

If a job uses whole sheets, or a part is too big to nest well, price the sheets you'll actually buy. Remnants you'd scrap anyway can go in at a lower price.

How do you estimate laser cutting time?

Cut length is the outside perimeter plus every hole and cutout. Each closed contour needs a pierce. Speed falls as the sheet gets thicker. QuotedPart's default laser formula, in minutes per part:

part.cut_length_in / (137.8 * material.machinability / max(1, part.sheet_thickness_in * 12.7)) + part.pierces * 0.03 + 0.3

It reads as 137.8 in/min in mild steel up to 14 ga, slower in proportion above that, 0.03 min per pierce and 0.3 min to load and unload. Machinability scales the speed for other materials. The bracket's 23.53 in of cut and 5 pierces (the outline and four holes) take 0.62 min. On a $175/h laser that's about 2.1¢ per inch of cut and 8.8¢ per pierce.

Waterjet

Abrasive waterjet is much slower in thick plate, and each pierce takes longer the thicker it gets. The default waterjet formula:

part.cut_length_in / min(60, 2.2 * material.machinability / max(0.04, part.sheet_thickness_in) ^ 1.15) + part.pierces * (0.1 + part.sheet_thickness_in * 0.25) + 1

How do you price press brake bending?

Bending is mostly setup: choosing and loading the punch and die, setting the backgauge and bending a first piece to check the angle. Then each bend takes seconds. The default press brake formulas:

setup min = wc.setup_min + part.bends * 3
run min = part.bends * 0.2

With the brake's 20 min setup, one bend gives 23 min of setup and 0.2 min per part. Add a setup when bends need different tooling. Large parts that need two people at the brake need a higher rate or longer run time.

How do you quote hardware, powder coat and plating?

As outside services, the way the vendor bills you: a lot charge (their minimum), a price per part, sometimes a minimum per piece and an invoice fee, and their lead time on top of yours. A few from QuotedPart's US starting catalog:

For the bracket's powder coat: $7.00 × 100 parts = $700.00, which beats the $200 lot charge, plus the 12% fee: $784.00. Small parts pay less per piece: QuotedPart scales the per-part price down for parts under about 46 in² of surface. This bracket is just over that, so it pays the full price.

Hardware such as PEM nuts and studs is a per-piece cost plus insertion time per piece. Add the vendor's price and a few seconds a piece at the press, and check whether the customer wants it installed before or after finishing.