Sheet yield: how many pieces, how many sheets.
The yield is the number of pieces you get out of one sheet. It decides how many sheets you buy, how much waste you throw away and, on short runs, a good part of the margin. The block count is quick; the one with the true shape is right.
The block count
Take the bounding rectangle of the flat layout, add the gap between pieces and divide it into the usable sheet, that is the sheet size minus the margins. Try it both ways round and keep the better one. It is the calculation the free tool on this site does.
What the block count misses
- The shape. A cross-shaped layout leaves four empty corners: interlock the crosses head to tail and you often fit one more piece per row.
- Grain direction. On paper and board the direction matters: if the grain has to be fixed, the piece cannot be turned through 90° and the yield changes.
- Machine margins. Gripper, side lay and trim eat into the sheet on one side only, not on all four.
- Base and lid together. Two different pieces on the same sheet can fit better than either on its own.
From yield to sheets
Sheets = pieces required ÷ yield, rounded up, plus make-ready and spoilage sheets. On 200 pieces those extra sheets count as much as the yield itself: it is one of the reasons the margin at 200 pieces is not what it seems.
How Cartis handles it
The sheet layout uses the true shape of the flat layout, for the paper and for the board, with the margins of your sheet size and the grain direction if fixed. If a piece does not fit, the summary flags it. In print layouts, three plans side by side, ‘Fewer sheets’, ‘Reduce layouts’ and ‘Minimum layouts’, gave 4 print layouts over 281 sheets instead of 10 over 280 in a real case.
Do the block count for a first idea, then look at the shape. If the layout has large empty corners, try interlocking; if the customer wants the grain one way, fix it before you promise the yield.
The guides are written by the box maker that built Cartis. If something in your practice is different, write to us: we will correct them.
The yield with your own shape.
In the demo we lay out one of your boxes on the sheet: in blocks and with the true shape, side by side.