Glass · Cutting · Worked examples
Three glass cutting jobs worked out: a shower screen, a building’s windows and a shop
A shower screen: 4 panes on 1 DLF sheet, 77.5 % yield, 1.8 % scrap. The windows of a small job: 14 panes on 2 DLF sheets, 74.2 % yield, 2.5 % scrap. A shop fit-out: 20 panes on 3 DLF sheets, 69.8 % yield, 5.2 % scrap. Every figure below is what the cutting optimiser computes for that order, and each order opens in it with one click.
These are example orders, not jobs of a real customer: the first two are the ones the optimiser offers under «Start from an example», the third is the order of the example job. The figures are worked out by the optimiser’s own code with its defaults and an empty offcut rack, as on a first visit; with offcuts on your rack it cuts from them first. Glass on the table counts whole sheets, because that is what you buy.
In the drawings, each sheet is to scale: a filled rectangle is a pane with its code and size, a dashed outline is an offcut that goes back on the rack, and a blank space with no outline is scrap.
1. Shower screen: 4 panes on 1 sheet of 3210 × 2250
The order is the optimiser’s own «shower screen» example: stock sheets of 3210 × 2250 mm, 10 mm edge trim per side, 4 mm breakout between cuts, panes may be turned.
| Size, mm | Qty |
|---|---|
| 900 × 2000 | 1 |
| 800 × 2000 | 2 |
| 300 × 2000 | 1 |
| What the optimiser answers | Figure |
|---|---|
| Sheets to buy | 1 |
| Glass on the table | 7.22 m² |
| Finished panes | 5.60 m² |
| Yield | 77.5 % |
| Offcuts back on the rack (2) | 1.49 m² |
| Scrap | 0.13 m² (1.8 %) |
Of the 1.62 m² that does not become a pane, 1.49 m² goes back on the rack as 2 offcuts of at least 150 mm a side (378 × 2000, 3190 × 230) and 0.13 m² is scrap. That is why a yield of 77.5 % is not the same as 22.5 % thrown away.
Open this order in the optimiser →
2. The windows of a small building job: 14 panes on 2 sheets of 3210 × 2250
The order is the optimiser’s own «windows» example: stock sheets of 3210 × 2250 mm, 10 mm edge trim per side, 4 mm breakout between cuts, panes may be turned.
| Size, mm | Qty |
|---|---|
| 1000 × 1200 | 4 |
| 600 × 1200 | 6 |
| 800 × 500 | 4 |
| What the optimiser answers | Figure |
|---|---|
| Sheets to buy | 2 |
| Glass on the table | 14.45 m² |
| Finished panes | 10.72 m² |
| Yield | 74.2 % |
| Offcuts back on the rack (7) | 3.36 m² |
| Scrap | 0.37 m² (2.5 %) |
Of the 3.72 m² that does not become a pane, 3.36 m² goes back on the rack as 7 offcuts of at least 150 mm a side (182 × 1200, 282 × 1000, 1200 × 400, 500 × 200, 174 × 1200, 782 × 500, 3190 × 526) and 0.37 m² is scrap. That is why a yield of 74.2 % is not the same as 25.8 % thrown away.
Open this order in the optimiser →
3. A shop: window, partitions, cabinet doors and shelves: 20 panes on 3 sheets of 3210 × 2250
The order is the order of the example job, invented for that page: stock sheets of 3210 × 2250 mm, 10 mm edge trim per side, 4 mm breakout between cuts, panes may be turned.
| Size, mm | Qty | Reference |
|---|---|---|
| 1200 × 1800 | 2 | Shop window, left and right |
| 900 × 1500 | 4 | Office partitions |
| 600 × 900 | 6 | Cabinet doors |
| 450 × 600 | 8 | Shelves |
| What the optimiser answers | Figure |
|---|---|
| Sheets to buy | 3 |
| Glass on the table | 21.67 m² |
| Finished panes | 15.12 m² |
| Yield | 69.8 % |
| Offcuts back on the rack (7) | 5.41 m² |
| Scrap | 1.13 m² (5.2 %) |
Of the 6.55 m² that does not become a pane, 5.41 m² goes back on the rack as 7 offcuts of at least 150 mm a side (182 × 1800, 600 × 296, 3190 × 430, 450 × 296, 628 × 1500, 450 × 296, 3190 × 730) and 1.13 m² is scrap. That is why a yield of 69.8 % is not the same as 30.2 % thrown away.
Open this order in the optimiser →
What the three have in common
Every layout is built in strips, because glass is scored and snapped and every cut runs from edge to edge: how to cut glass walks through the order of the cuts. The cutting plan prints each sheet with that sequence and the measurement of every cut, and the offcut inventory keeps the offcuts so the next order is cut from them first. For the stock sizes and what one sheet gives, see the glass sheet sizes.
Questions people ask
- How many DLF sheets does a glass shower screen take?
- The optimiser’s shower screen example, 1 × 900 × 2000, 2 × 800 × 2000, 1 × 300 × 2000 mm, fits on 1 DLF sheet of 3210 × 2250 with 10 mm edge trim and 4 mm breakout: 77.5 % yield and 0.13 m² of scrap; the rest comes back as offcuts.
- What yield should a glass cutting job get?
- It depends on the order against the sheet. Here the optimiser gets 77.5 %, 74.2 % and 69.8 %, and yet the scrap is only 1.8 %, 2.5 % and 5.2 %: most of what is not a pane goes back on the rack as offcuts. Judge a layout on its scrap, not on its yield alone.