From Cut List to Sheet

Yield, and why it is money

Yield is the share of a sheet that ends up as parts. Cut ten square feet of usable parts out of a thirty-two square foot sheet and you are running low; pack it tight and most of the sheet leaves the shop as cabinet. Waste is just the flip side, the offcut you paid for and did not use.

How much does planning help? Cut-optimization software vendors commonly cite an unoptimized, cut-by-eye layout at around 60 to 70 percent yield, and a well-planned layout at 85 to 95 percent. Treat those exact numbers as vendor estimates rather than an audited industry figure, but the direction is not in doubt: a thought-out layout beats guessing, and on sheet goods that difference is real money over a kitchen.

The catch is that the last few percent are genuinely hard. Once the big, common parts are placed, what remains are odd small gaps that rarely match the parts still on your list. That is not a software weakness; it is a property of the problem itself. Packing rectangles into sheets is a known hard problem in mathematics, called two-dimensional bin packing, and it is provably difficult even at small sizes. Good tools get close to the best answer quickly; no tool gets a perfect one every time.

Kerf, the gap you must plan

Kerf is the width of material a cut removes: the channel the blade or bit leaves behind. It is small, but it is not nothing, and if a layout ignores it every part comes out undersized. Place two parts edge to edge on paper, then cut them for real, and the blade eats a strip out of the middle, so both parts finish narrower than you drew them.

The right kerf value depends on the tool. A standard table-saw or panel-saw blade removes about 1/8 in, roughly 3.2 mm; a thin-kerf blade closer to 3/32 in, about 2.4 mm. A CNC router does not have a blade, so its kerf is the diameter of the bit, commonly 1/4 in to 3/8 in, about 6 to 9.5 mm. The number matters more than it looks: set your layout to a saw's slim kerf and then cut it on a fat CNC bit, and every shared edge eats into the next part. Whatever nests your parts, tell it the true kerf for the tool that will actually cut.

Grain direction

On plywood, grain direction barely changes strength, but it changes looks a lot. A run of doors with the grain running different ways on each one reads as amateur work, and stain takes differently along the grain than across it, so mismatched parts show as uneven color. The shop convention is simple: door grain runs vertical, drawer-front grain runs horizontal, and in general the grain follows a panel's longest dimension.

Here is the tension with yield. When you lock a part's grain direction, you cut its placement options from four rotations down to two. The optimizer has less room to shuffle, so a grain-locked cut list often needs more material than a free one. One cut-optimization vendor's worked example put grain constraints at roughly 10 to 15 percent more material; read that as illustrative, not a law, but the mechanism is real.

The move that keeps both looks and yield is selective locking: fix the grain only on the parts a person will see, the doors, drawer fronts and finished ends, and leave the hidden parts, the backs, bottoms and internal supports, free to rotate. One more note worth money: melamine has a printed, non-directional face, so it usually carries no grain constraint at all and nests with more freedom than real-wood veneer. If your job is melamine boxes with veneer fronts, you can often let the boxes pack freely and only lock the fronts.

Guillotine vs free nesting

How your parts can be arranged depends on the machine that cuts them. A panel saw can only make a guillotine cut: a single straight cut, edge to edge, that splits the current piece into two rectangles. It cannot stop partway or step around a part. That forces the layout into clean rows and columns, which is easy to cut by hand or on a beam saw but leaves some yield on the table.

A CNC router is not bound by that rule. It can plunge and follow any contour anywhere on the sheet, so parts can be staggered and interlocked in ways a panel saw cannot reach. For many small or oddly sized parts, that free placement squeezes more onto each sheet. This is why the same cut list can want a different layout depending on whether it is heading to a beam saw or a nesting CNC, and why a good optimizer asks which one you are using.

Under the hood, both are versions of that hard packing problem, and optimizers lean on sensible rules of thumb rather than trying every arrangement. A common one is to sort the parts largest first and place each into the first spot it fits; sorting big-to-small alone measurably tightens the pack. You do not need the math to use it, but it explains why feeding the tool a complete, accurate parts list matters so much: it can only pack what you tell it about.

Edge banding

Edge banding is the thin strip that covers a raw plywood or melamine edge so it looks finished and resists chipping. Most iron-on PVC or ABS tape is about 0.4 to 1 mm thick, though thicker bands up to around 3 mm exist for counter edges and high-wear spots. At the thin end it is usually thin enough to ignore in the cut list.

The thicker the band, the more it matters. Any real-thickness edge, a heavy PVC band or a solid-wood lip, adds to the finished size, so the panel underneath has to be cut narrower by the band thickness to land on target. A worked example: to finish a shelf at 12 in with a 1/4 in solid-wood edge, cut the plywood to 11 3/4 in so the banded result measures 12 in. Cabinet software handles this by reducing the part in the model by the band thickness, so the size it sends to the saw already nets out correct. If you band by hand, do the same subtraction yourself.

From cut list to cut parts, step by step

Put the pieces together and the shop workflow is short and repeatable.

1. Build the cut list. List every part with its finished width, length, material and quantity, so the optimizer knows exactly what it is packing.
2. Set the stock and the real kerf. Choose the sheet size you will actually cut on and enter the true kerf for the tool: about 3 mm for a panel saw, or the bit diameter for a CNC.
3. Lock grain only where it shows. Fix the grain on visible parts, leave hidden parts free to rotate, and keep both the look and the yield.
4. Nest and read the yield. Let the optimizer place the parts and check the reported yield, then decide whether a small change to a size or the sheet count buys back a sheet.
5. Cut, label and save the offcuts. Cut the layout, label each part as it comes off the saw so nothing gets mixed up, and record usable offcuts back into inventory for the next job.

If you are starting further back, at the cabinets themselves, the 32mm system guide covers where all those part sizes come from. From there, the whole loop is what CabDesign's tools do together: the Designer and the cut list produce the parts, the Materials Library holds your real sheet sizes and thicknesses, and the optimizer nests it all with kerf, grain and banding handled.

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