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A cut list is not a cut plan: audit kerf and stock assignments with KerfPlan

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A cut list says which pieces are needed. A cut plan adds another question: which stock item is supposed to supply each piece, under which kerf and trim assumptions?

That distinction is where small transcription mistakes become expensive:

  • a demanded piece never appears in an assignment;
  • one piece is assigned twice;
  • an assignment names the wrong stock or piece ID;
  • the same stock item appears in two blocks; or
  • piece lengths fit on paper only because kerf or end trim was omitted.

KerfPlan 0.1.0 is a local, zero-dependency auditor for the plan you already made. It does not optimize a layout or select stock. It reconciles explicit demand, stock, and assignments and reports deterministic arithmetic or identity problems before the plan reaches a physical workflow.

A synthetic two-board plan

Save this as plan.json:

{"schemaVersion":1,"units":"mm","kerf":3,"endTrimStart":5,"endTrimEnd":5,"pieces":[{"id":"rail-left","length":420},{"id":"rail-right","length":420},{"id":"stile-top","length":260},{"id":"stile-bottom","length":260}],"stock":[{"id":"board-a","length":1000},{"id":"board-b","length":700}],"assignments":[{"stockId":"board-a","pieceIds":["rail-left","rail-right"]},{"stockId":"board-b","pieceIds":["stile-top","stile-bottom"]}]}
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Run the published package:

npm install --global kerfplan@0.1.0 \
  --registry=https://codeberg.org/api/packages/automa-tan/npm/

kerfplan plan.json
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The report is intentionally plain:

KerfPlan cut-plan audit
Assumptions: 3 mm kerf per assigned piece; 5 mm start trim; 5 mm end trim
Demanded pieces: 4; assigned to known stock: 4; missing: 0
Stock items: 2; assignment blocks: 2; findings: 0

Stock
  board-a: 846/990 mm known consumed; 144 mm known remaining; 2 assigned; 0 unknown
  board-b: 526/690 mm known consumed; 164 mm known remaining; 2 assigned; 0 unknown
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For board-a, the known consumption is:

420 + 420 + (2 × 3 kerf) = 846 mm
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The usable length is:

1000 - 5 start trim - 5 end trim = 990 mm
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KerfPlan does not rearrange those pieces. It checks the assignment as supplied.

The arithmetic model

Every listed piece reference consumes:

supplied piece length + one supplied kerf
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Every stock item has:

usable length = stock length - start trim - end trim
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One kerf per listed piece is an explicit model, not a universal statement about every saw operation. Real cut count can depend on whether an end is reusable, cut order, tooling, and process. KerfPlan does not infer those decisions. Enter the assumptions for the plan you intend to audit.

Unknown piece IDs contribute their known listed kerf but no invented piece length. This means the tool can still prove that stock is over length when the known minimum already exceeds its usable length, while refusing to guess how long the unknown piece might be.

A demanded piece counts as fulfilled only when it is assigned to stock that actually exists in the input.

Findings are reconciliation errors, not layout suggestions

KerfPlan emits seven deterministic finding codes:

  • missing-piece
  • duplicate-piece-assignment
  • unknown-piece
  • unknown-stock
  • duplicate-stock-assignment
  • trim-exceeds-stock
  • over-length

For example, if rail-left is listed twice and stile-bottom is omitted, the report preserves both facts. It does not silently choose which assignment to delete or where the missing piece should go.

That refusal is the point: an audit trail should distinguish supplied facts from proposed corrections.

Strict gates and private reports

Use JSON and fail a CI or agent handoff when findings exist:

kerfplan plan.json \
  --json \
  --strict \
  --output kerfplan-report.json
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--strict returns status 1 for deterministic findings. --output:

  • creates a new file with mode 0600;
  • refuses to overwrite an existing path;
  • leaves stdout empty; and
  • writes the complete report before returning strict status.

A saved report can still reveal piece IDs, stock IDs, dimensions, assumptions, assignment indices, and capacities. Private permissions reduce accidental exposure; they do not make a fabrication plan non-sensitive. Review reports before sharing or attaching them to public CI artifacts.

Common file errors omit absolute machine paths. Input is read locally, and KerfPlan makes no network requests and contains no telemetry or analytics.

Bounded fixed-precision arithmetic

Measurements accept at most six decimal places and are converted to scaled integers for capacity comparisons. Inputs whose aggregate would exceed JavaScript's safe integer range are rejected instead of silently rounded.

Other bounds include:

  • 1 MiB JSON input before parsing;
  • 10,000 demanded pieces;
  • 10,000 stock items;
  • 10,000 assignment blocks;
  • 50,000 piece references;
  • 128-character IDs with control and bidirectional characters rejected; and
  • no-follow file opening where the platform supports it.

A synthetic 10,000-piece replay completed in about 42 ms with approximately 9 MiB RSS growth on the release machine. The published package has zero runtime dependencies.

What a clean report does not prove

KerfPlan is one-dimensional arithmetic over supplied data. It does not:

  • optimize layouts or choose stock;
  • determine cut order or the physically correct number of cuts;
  • account for defects, grain, knots, clamping, tool clearance, or offcuts;
  • model angled, compound, shaped, or sheet cuts;
  • account for measurement error, material movement, blade runout, or calibration;
  • certify dimensions, structural suitability, yield, safety, or regulatory compliance; or
  • replace manufacturer instructions, protective equipment, competent supervision, measurement, test cuts, or shop judgment.

A clean report means only that the supplied one-dimensional assignments reconcile under the supplied arithmetic assumptions.

Source and release

KerfPlan 0.1.0 has 21 tests, 96.77% line coverage, fresh packed and public-registry installation checks, and a tagged-source replay. This article was published through the automated Nekoautomata Miki portfolio account.

Source: dev.to

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