Eighteen kitchen carcasses from melamine
A two van kitchen firm cutting a whole kitchen in one go. One hundred and eight parts, all of them rectangles, all of them from the same 18 mm board. The job was never hard. It was just being cut in the wrong order.
The job
Eighteen base carcasses for a kitchen and a utility room in the same house, every one of them the same box: 600 wide, 720 high, 570 deep, in 18 mm melamine faced chipboard on 2440 by 1220 sheets. The firm standardised on that box years ago and builds everything from it, which is exactly why the sheet count matters to them.
Stripped of the joinery, the cutting list is four part types repeated:
- 36 side panels at 720 by 570
- 18 bases at 564 by 570
- 18 shelves at 560 by 555
- 36 rails at 564 by 100
That is 108 parts and 28.2 square metres of board. Backs are 6 mm hardboard and get cut separately, so they are not in this list. A sheet is 2.977 square metres, so in a world with no saw blade and no square edges you would need nine and a half sheets. Nobody lives in that world, but it is worth knowing the floor before you argue about the ceiling.
How they were cutting it before
Unit by unit. A sheet goes on the saw, the parts for one carcass come off it, the offcut gets stood against the wall, and the next sheet goes on. It is a completely reasonable way to work. You always know what you are holding, the parts stay together, and nothing gets mixed up between units.
It also means every carcass pays for its own edge waste. A carcass is about 1.57 square metres of parts against a 2.98 square metre sheet, so you finish each unit holding an awkward remnant that is not quite big enough for the next set of sides. Those remnants went against the wall and mostly stayed there.
They ordered 13 sheets for this kitchen and used all of them, one of which was cut wrong and became the offcut pile. Measured against the parts that ended up in the kitchen, that is 27.2 per cent waste.
What changed
The parts list got typed in once, as four rows with quantities rather than 108 separate lines, and saved as a template. The settings took another minute: a kerf of 3.2 mm for the blade on their panel saw, and a 10 mm trim on all four sheet edges because melamine sheets arrive with knocked corners more often than not. Melamine faced chipboard has no grain to respect, so parts were left free to turn.
Then the layout ran, and it came back with 11 sheets.
Job sheet
- Material18 mm MFC
- Sheet size2440 x 1220
- Sheet area2.977 m2
- Parts108
- Part area28.2 m2
- Kerf3.2 mm
- Edge trim10 mm
- GrainNot applicable
- Sheets before13
- Sheets after11
The layout
Eleven sheets came back. Eight of them are the same pattern, because eighteen carcasses means a lot of identical sides. The interesting sheets are the first and the last.
If the diagrams look unfamiliar, the guide on reading a cutting diagram walks through what every line on them means.
The result
11 sheets instead of 13. Waste down from 27.2 per cent to 13.9 per cent. Two sheets saved, which is 6.0 square metres of board, and at the roughly 38 dollars a sheet they were paying for that board, about 76 dollars on one kitchen.
Seventy six dollars is not a headline. Do it on forty kitchens a year and it is three thousand, which is real, and it arrives without anyone working faster or harder.
The part we cannot fix
There is still 13.9 per cent waste in this job and most of it is not going anywhere. The sides are 570 deep. Two rows of 570 plus the blade is 1143, and after a 10 mm trim top and bottom you only have 1200 to play with, so a strip about 57 mm deep runs along the foot of nearly every sheet. The narrowest part in this kitchen is a 100 mm rail, so nothing fits in that strip and no layout can rescue it.
That is worth saying plainly, because the honest saving on a job like this comes from packing the small parts into the ends of sheets that were being thrown away, not from some magic that beats geometry. If the firm ever changes to a 560 deep carcass, the same list drops again, and they would see that the moment they changed the number and re-ran it.
How long it took
Typing the parts list the first time took about twenty six minutes, most of which was the owner deciding whether the rails were 100 or 95. Running the layout took under a second. Checking it on screen and printing took another four minutes.
Since it is saved as a template, the next kitchen is a matter of changing quantities and a couple of widths. That is four or five minutes from opening the file to a printed diagram on the saw. The sheet count for the quote now comes out of the same file, before the job is won rather than after.
What it did not do
It did not tell them what order to cut in. That is still a decision made at the saw, and the guide on cutting order covers how they now sequence a sheet so the long rips come first.
The one offcut worth keeping
Sheets 1 to 10 leave thin strips and nothing else. Sheet 11 leaves a clear piece 1598 by 645, which went into the offcut library and came back out on a bathroom job three weeks later. That feature is in the pro licence and it arrived in version 3.0.
The other five examples
Every job here is written up the same way, with the sheet count before, the sheet count after and the time it took.
- Acrylic letters nested for a sign shopSignmaking. 41 letters and roundels onto a single sheet.
- A sideboard cut with the grain running one wayFurniture making. 14 grain locked parts, 4 sheets down to 3.
- A term of plywood for a school workshopEducation. 216 parts for 36 pupils, 6 sheets down to 4.
- Marine ply for a small launchBoatbuilding. Scarfed hull pieces, 10 sheets down to 6.
- Engineered oak floor cut from lengthsFlooring. 81 pieces from 2200 mm boards, 64 down to 58.
Read on
The settings behind this job, and how to price the next one.