How Many Blanks Fit Across Your Coil?
Pick a blank shape and how many parts the die cuts each stroke. Staggering circles, honeycombing hexagons and flipping trapezoids are how multi-cavity dies get more blanks, and less skeleton scrap, out of every foot of coil.
How It's Calculated
- Web
- 0.187 in under 0.125 in gauge; 1.5 × gauge from 0.125 in up
- Coil width
- the narrowest coil that fits the parts per stroke, with a web at each edge; 72 in at most
- Circles, staggered
- cavities zigzag across the strip, (diameter + web) × 0.86603 apart: coil width = (diameter + web) × 0.86603 × (parts − 1) + diameter + 2 × web, progression = diameter + web
- Straight
- parts side by side across the strip: coil width = parts × (size across + web) + web, progression = size along + web
- Hexagons, honeycomb
- two rows a stroke, the second shifted half a part, (across the flats + web) × √3 ÷ 2 apart
- Trapezoids, flipped
- one part every (long side + short side) ÷ 2 + web ÷ cos(side slope)
- Steel used
- blank area × blanks per inch ÷ coil width
- Coil per blank
- coil width × gauge × 0.2836 ÷ blanks per inch
- Net steel cost
- (coil per blank × steel price − scrap per blank × scrap credit) ÷ 100
Related: How a Coil Becomes Blanks · Wheels · Water Heaters
Questions About Nesting
What does "steel used" mean?
It is the share of the coil that ends up as blanks. The rest is scrap: the skeleton left between blanks and the strip left along each edge. Material is usually the largest cost in a blank, so a few points of steel used can matter more than press speed.
What are parts per stroke?
A multi-cavity die cuts several blanks each time the press strokes. The parts per stroke set how wide the coil has to be: each layout uses the narrowest coil that fits them, up to the 72 in maximum. More parts per stroke means more blanks per foot and usually less scrap.
How are staggered circles laid out?
The cavities zigzag across the strip, each one sitting in the gap beside the last, so the same parts per stroke fit on a narrower coil than straight across. The coil feeds one diameter plus the web each stroke.
Why flip trapezoid blanks?
Turning every other trapezoid upside down lets neighbors share a sloped edge, so the wedge of steel that would sit between two upright parts becomes the next part instead. For a trapezoid whose sides differ a lot, flipping can save a fifth of the steel or more.
What is the web between blanks?
The web is the narrow bridge of steel left between neighboring blanks and at the coil edges. It keeps the skeleton strong enough to feed through the die. Here it is 0.187 in for steel under 0.125 in thick and one and a half times the gauge for thicker steel; your die sets the real number.
What is the scrap credit?
Skeleton scrap is sold back to a scrap buyer, usually for well under the price of new steel. Entering that price takes it off the cost of the coil, so the cost per blank reflects what the steel really costs you.