Where the waste comes from
- The offcut on each bar. A 6 m bar takes four 1,480 mm pieces and leaves a 71 mm offcut, practically no waste. With 1,200 mm pieces it still takes four, but 1,191 mm are left: almost a whole piece left on the bar.
- The blade. Every cut uses up the thickness of the blade, usually between 1.5 and 4 mm, depending on the saw. Over 100 cuts, that is between 15 and 40 cm of material.
- Angled cuts. On a 40×40 mm tube cut at 45° at both ends, each end leaves behind a triangle with a 40 mm side. If neighbouring pieces are nested into each other, the angled cut becomes shared and that triangle is no longer lost.
Six ways to reduce waste
- Plan all the pieces at once. With a longer list to work from, there are more combinations that fill the bar. A plan made on small orders, one at a time, leaves more offcut.
- Use stock offcuts first. A 1.8 m offcut taken from the shelf costs less than a new bar. Put a code on offcuts longer than 1 m, so you can find them.
- Compare the available bar lengths. The same list of pieces can leave less offcut on 12 m bars than on 6 m bars, or the other way round. Check before you order.
- Nest pieces with angled cuts. Flip every second piece, so the angled cut is shared. In detail, in the guide to cutting at an angle.
- Take the blade into account, not just the lengths of the pieces. A plan made without it looks right on paper, but does not work out in the workshop.
- Check the plan before you cut: how many bars, what offcut is left on each, and which pieces go on each bar.
A worked example
The values below are calculated with the formulas of the e-utilio Steel Cut Pro program, for a 40×40 mm tube with 45° cuts at both ends, 6 m bars, a 3 mm blade and 100 pieces of the same length.
| Piece length | Pieces per bar, one after another | Pieces per bar, nested | Bars for 100 pieces, one after another | Bars for 100 pieces, nested |
|---|---|---|---|---|
| 700 mm | 8 | 8 | 13 | 13 |
| 900 mm | 6 | 6 | 17 | 17 |
| 1,200 mm | 4 | 5 | 25 | 20 |
| 1,500 mm | 4 | 4 | 25 | 25 |
There is no simple rule. At 700, 900 and 1,500 mm nesting does not add a single piece per bar, while at 1,200 mm it goes from 4 to 5 pieces per bar and saves 5 bars out of 25. That is why it is worth calculating on your own list of pieces, not estimating.
How to do this without a spreadsheet
A spreadsheet handles straight-cut bars well, but gets hard to maintain once you have angles, coded offcuts and several materials. e-utilio Steel Cut Pro imports the cut list from Excel, uses the stock offcuts, nests the pieces with angles and gives you operator sheets. You can start with the free demo, without an account.
If you also need the weight of the material you order, use the metal weight calculator.
Try the cutting program
Import your cut list and see the cutting plan and the number of bars. Free demo, 3 days of full trial for new accounts.
Frequently asked questions
What does cutting optimization mean?
Arranging the pieces on the bars of material so that as little offcut as possible is left and the stock offcuts are used first.
How big is the cutting waste?
It depends on the length of the pieces, the blade and the angles. In the example above, the offcut on a bar ranges from a few tens of millimetres to over a metre, depending on the length of the piece.
Does optimization also work for sheet metal?
This guide is about bars (tubes, profiles, angles, flat bars, rebar), where pieces are cut along a single dimension. For sheet metal, cutting is done in a plane, along two dimensions, and uses other methods.