MOACUTSpacing and yield guide
How Kerf Affects Sheet Nesting
Kerf is small compared with most parts, but it appears between neighboring rectangles. Across repeated rows and columns, that spacing can change which parts fit on a sheet. MOACUT treats the entered kerf as layout clearance—not as a CAM toolpath command.
Last updated: August 31, 2026Kerf in a nesting plan
Physical cutting removes a band of material rather than an infinitely thin line. That removed width is commonly called kerf. For layout planning, the important question is how much separation is required between two finished rectangular parts so the intended cutting process can produce both without violating their dimensions or process clearance.
The correct planning value is not universal. It can change with the tool or beam, material, thickness, focus, feed, tool wear, compensation strategy, and whether two neighboring parts are allowed to share a cut. Use a value established for the actual machine and process; this guide does not prescribe a generic CNC, saw, or laser number.
How MOACUT applies the kerf field
Inside the current calculator, the kerf input is the inter-part spacing value. When MOACUT creates a candidate beside an existing rectangle, it starts at the existing edge plus that spacing. The overlap test also rejects candidates that would leave less than the entered spacing between rectangles.
Vertical neighbor start = existing y + existing height + entered kerf
A kerf value of 0 allows rectangle edges to touch in the layout. A positive value reserves that amount between adjacent rectangles. The value does not enlarge the part's reported width or height, and MOACUT's Used Area remains the sum of the original rectangle areas.
MOACUT does not generate offset toolpaths or decide which side of a part outline a tool should follow. Apply cutter compensation and process-specific geometry later in appropriate CAM or machine software.
Kerf and edge margin solve different constraints
| Setting | Reserved location | Current MOACUT calculation |
|---|---|---|
| Kerf | Between neighboring parts | Used as rectangle-to-rectangle spacing during placement and overlap checks. |
| Edge margin | Around all four outer sheet edges | Usable width = sheet width − 2 × margin; usable height = sheet height − 2 × margin. |
Margin can represent a damaged stock edge, clamping zone, vacuum boundary, or any other perimeter area the operator chooses not to use. Kerf does not replace margin, and margin does not create separation between parts. Enter both when the job requires both.
Why a few millimetres can change sheet count
If n equal-width parts form one row, there are n − 1 gaps between them. Their required row width is:
A row that exactly matches usable width at zero spacing stops fitting as soon as positive spacing is added. Rotation may create another arrangement, but it cannot guarantee that the original sheet count will remain possible. Mixed part lists are less predictable because a gap may have sufficient area but insufficient width or height for the next rectangle.
Kerf can therefore change positions, rotation choices, the number of parts on the last sheet, and total required sheets. If the sheet count stays the same, MOACUT's overall utilization percentage also stays the same because its numerator is pure part area and its denominator is full nominal sheet area. The drawing will still show different gaps.
Worked comparison: 0 mm versus 3 mm
Compared input → kerf 0 mm and kerf 3 mm.
The margin leaves 1200 × 2420 mm usable. The part-area total is 2,880,000 mm², while one full sheet is 2,976,800 mm². Area alone suggests that one sheet might be possible.
| Kerf | Width of two 600 mm parts | MOACUT placement result | Utilization / scrap |
|---|---|---|---|
| 0 mm | 600 + 600 = 1200 mm | 12 parts on 1 sheet | 96.7% / 3.3% |
| 3 mm | 600 + 3 + 600 = 1203 mm | 10 parts on sheet 1, 2 on sheet 2 | 48.4% / 51.6% |
These results were produced by reproducing the current MOACUT calculation path: quantity expansion, descending-area sort, bottom-left candidates, optional 90° rotation, margin-reduced bounds, and spacing-aware overlap checks. The example is deliberately tied to that input; it is not a claim that 3 mm is appropriate for any particular machine.
How to choose and verify the input
- Identify the actual cutting process and whether adjacent parts will use independent cuts or an approved common-line strategy.
- Measure or obtain a validated process allowance for the specific machine, material, thickness, and setup.
- Enter that required part-to-part clearance in MOACUT's kerf field.
- Enter perimeter clearance separately as Edge Margin.
- Run the layout and inspect narrow gaps and the last occupied sheet.
- Transfer the layout only after the CAM or production plan applies the required compensation, holding, and safety rules.
What the kerf setting does not calculate
MOACUT does not measure a machine's kerf, model beam heat, select a tool, set feeds or speeds, generate lead-ins, add tabs, determine cut order, or validate common-line cutting. It calculates spacing for rectangular nesting from the value supplied by the user. Those production decisions remain separate.