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print-export

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3MF/STL/STEP file export, slicer compatibility (BambuStudio/OrcaSlicer rejects 3MF, wrong/missing AMS colors, paint_color, project_settings.config), print-bed fitting and printBedSize, print-list bin splitting, baseplate split planner tongue budget, whole-layout ZIP export. Load when touching threemfExporter.ts, stlExporter.ts, splitPlanner.ts, src/features/print-export/, or src/shell/layoutExport/, or when an exported file misbehaves in a slicer.

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Print & Export

When to use

  • An exported 3MF/STL/STEP is rejected, mis-colored, off-center, or non-manifold in a slicer.
  • Changing print-bed fitting, print-list split counts, or baseplate plate tiling.
  • Adding/renaming files in the whole-layout ZIP export.
  • For defects in the generated geometry itself (walls, sockets, booleans), see the geometry-generation and geometry-debugging skills.

Map: five systems that do NOT share code

SystemLocation
Print LIST planning (piece counts, filament estimates — produces no 3D files)src/features/print-export/ (utils/split.ts, hooks/usePrintList.ts)
File writers (3MF/STL) + mesh validationsrc/features/generation/export/
Worker export handlers (STL/STEP only)src/features/generation/worker/handlers/exportHandler.ts
Whole-layout ZIP orchestrationsrc/shell/layoutExport/
Baseplate plate tilingsrc/features/baseplate/utils/splitPlanner.ts

Bed-capacity math (calcMaxGridUnits, getEffectivePrintBedDepth) lives in src/core/constants.ts. Main-thread packaging (STL→3MF, zone colors) is src/features/bin-designer/utils/binDownloadHelpers.ts. Shared helpers (ZIP, download, STL parse, winding repair) are in src/shared/generation/. splitBinSize only predicts counts — the geometric split is a separate worker system (splitBinBuilder.ts).

Mental model

  • The worker emits only STL and STEP (ExportFormat in src/features/generation/bridge/types.ts). 3MF is always produced on the main thread by parsing the worker's STL and re-encoding via export3MF / export3MFMultiObject. A new format wires into useLayoutExport.ts's workerFormat mapping and the packaging helpers, not the worker.
  • Other features must import the writers via the barrel src/shared/generation/export.ts, or pnpm run check:boundaries fails.
  • The 3MF exporter never moves vertices — it centers via the build <item> transform (row-major 3x4; translation is the LAST three numbers), placing the bbox centroid at PLATE_CENTER_MM (128,128) and bbox min-z at 0. STL keeps raw coordinates. See centeringTranslation / renderBuildItems in threemfExporter.ts.
  • 3MF slicer compat is THREE coupled mechanisms that must change together: (1) explicit paint_color on every triangle, slot N → FILAMENT_PAINT_CODES[N+1]; (2) Metadata/project_settings.config + Metadata/model_settings.config sidecars; (3) BAMBU_COMPAT_APPLICATION = 'BambuStudio-02.00.00.00' — Bambu gates sidecar loading on the BambuStudio- prefix, and that exact version is the only one both BambuStudio 2.6.0 and Orca 2.3.1 CLIs accept (failure table in the JSDoc above the constant).
  • printBedSize is per-layout, stored in mm, never below CONSTRAINTS.PRINT_BED_MM_MIN (42) — the migration in src/core/storage/LayoutService.ts (search maxPrintSize) reinterprets any stored value < 42 as legacy grid units. printBedDepth undefined means square bed: resolve via getEffectivePrintBedDepth() or calcMaxGridUnits(), never read it directly.
  • Unit split: print-export/utils/split.ts works in grid units (pre-converted via calcMaxGridUnits); splitPlanner.ts works in mm. Passing mm into splitBinSize yields absurd "fits" results with no error. calcMaxGridUnits floors to 0.5 increments — integer Math.floor regresses half-bin mode.
  • ZIP packaging is fflate (JSZip needs unsafe-eval, blocked by the production CSP). packageFilesAsZip keys a plain object: duplicate paths silently drop the earlier file — route names through dedupeFileNames (src/shell/layoutExport/).

Recipes

Change 3MF output (metadata, colors, sidecars, positioning)

  1. Read src/features/generation/README.md § "3MF Multi-color Compatibility" first.
  2. Read the saga: git log --oneline -- src/features/generation/export/threemfExporter.ts. Most "obvious" fixes were tried and reverted — e.g. the identity claim was dropped (git show aaef540ae) then reintroduced at the one safe version. Fix one slicer, re-verify the other.
  3. Edit threemfExporter.ts, keeping the coupled mechanisms above intact.
  4. Update threemfExporter.test.ts (tests unzip the buffer and assert on model XML and sidecars).
  5. Run pnpm run test:run src/features/generation/export, then verify against real slicer CLIs (BambuStudio 2.6.0 / OrcaSlicer 2.3.1) — the constraints are undocumented C++ validators; unit tests cannot catch them.
  6. Sanity-check the artifact: unzip -l file.3mf must show [Content_Types].xml, _rels/.rels, 3D/3dmodel.model, and (multi-color) both Metadata/*.config sidecars.

Change bed fitting or split behavior

  1. Pick the system: print-list prediction = split.ts; bed capacity = calcMaxGridUnits; baseplate tiling = splitPlanner.ts.
  2. Preserve: the 0.5-increment floor and width/depth asymmetry in calcMaxGridUnits; splitHalf's dual rounding (integer for whole dims, 0.5-aware for fractional) in split.ts; the TONGUE_PROTRUSION bed budget in makeAxisConfig/axisChunkMm in splitPlanner.ts.
  3. Under preferIdenticalPieces the canonical piece is reused 180°-rotated — every positionally-indexed field must rotate with it in pieceToBaseplateParams (splitPlanner.ts): padding L↔R/F↔B, fractionalEdge start↔end, cornerRadii tl↔br/tr↔bl. A forgotten field silently puts dovetails/corners on the wrong world side of the printed piece; no test or type catches it.
  4. Update sibling tests, then pnpm run test:run src/features/print-export && pnpm run typecheck.

Add or rename files in the layout ZIP

  1. Planning/naming: planLayoutBinExport.ts (pure). Orchestration: useLayoutExport.ts. Manifest text: buildLayoutManifest.ts.
  2. Dedupe every new path family via dedupeFileNames before packageFilesAsZip; add a collision case to dedupeFileNames.test.ts.
  3. The deep import of binDownloadHelpers bypassing the bin-designer barrel is deliberate (lazy chunk) — see the comment at the import in useLayoutExport.ts.
  4. Run pnpm run test:run src/shell/layoutExport && pnpm run check:boundaries.

Debug "slicer says the exported file is broken"

  1. Winding/non-manifold on baseplates: pnpm exec vitest run --config vitest.profile.config.ts __kernel-tests__/diagnoseBaseplateWinding (real WASM kernel; excluded from normal runs).
  2. If validateMeshData (src/features/generation/export/validation.ts) wouldn't have caught it, the defect is upstream in worker tessellation — geometry-debugging skill.
  3. 3MF broken but the same mesh's STL is fine: suspect deduplicateVertices precision (toFixed(6) key in threemfExporter.ts — loosen it and distinct vertices weld; tighten it and shared vertices fragment into open edges) or the STL→3MF round-trip (parseSTLBinary).

Verification

CommandWhen
pnpm run test:run src/features/generation/exportAny writer/validation change
pnpm run test:run src/features/print-exportSplit/estimate changes
pnpm run test:run src/shell/layoutExportZIP planning/packaging changes
pnpm run check:boundariesNew imports across print-export/generation/bin-designer/baseplate/shell
Real slicer CLI load (Bambu + Orca)Any 3MF change — non-negotiable

Traps

SymptomCause → fix
Multi-color 3MF shows fewer colors than designedpaint_color slot mapping broken: the N+1 offset lost, or slot-0 triangles emitted without an explicit code so body collapses onto the default extruder. Every triangle gets FILAMENT_PAINT_CODES[slot + 1] in buildObjectXml. See git show cd841c9fc.
Orca CLI rejects 3MF (exit -24) or "file is newer than cli"BAMBU_COMPAT_APPLICATION version outside the empirically safe window. Never bump casually; if forced, re-run both slicer CLIs.
Lid/secondary object renders body-colored despite paint_colorMetadata/model_settings.config per-object extruder (dominantSlot + 1) removed — it, not paint_color, colors a uniform object. Keep both sidecars.
Exported bin sits off-bed on small printers (A1 mini)Claiming Bambu identity disables auto-arrange, so the file self-positions at (128,128). Adjust the build-item transform in renderBuildItems — never the vertices.
Split baseplate piece ~1.5mm too wide for the bedMale dovetail tongue extends the bbox past grid math; budget lives in makeAxisConfig/axisChunkMm. Known unbudgeted exception: the detached-margin seam tongue (NOTE comment in splitPlanner.ts). Any new protruding connector must be budgeted there.
File silently missing from layout ZIPDuplicate path overwrote it in fflate's plain-object keying → route through dedupeFileNames.
Saved layout shows a tiny bed (e.g. 4mm) or absurd split countsprintBedSize written in grid units. Always write mm clamped to PRINT_BED_MM_MIN/MAX (canonical clamp in src/core/store/layout/coreActions.ts); the load-time migration only rescues values < 42.
"Cannot export empty mesh (0 triangles)"Correct behavior — validateMeshData refuses spec-invalid files. Fix the generator (geometry-generation skill).
stack option silently does nothingVertical stacking is honored by single-object export3MF only; export3MFMultiObject ignores it by design.
Layout ZIP ignores custom name for inner files / baseplate errors vanishBoth deliberate: inner files force descriptive style (one custom name would collide), and baseplate failure degrades to a bins-only archive with a toast (.catch(() => null) in useLayoutExport.ts). Don't "fix" either.

Other by-design facts that look like bugs: binary STL headers must not start with solid (writeHeader in stlExporter.ts prepends a space); repairMeshWinding is wired into baseplate STL only and is currently a no-op safety net (wire the same pass into bins if they show winding symptoms — don't write a new repair); in the STEP combined export, divider/lid solids are freed in finally but binSolid belongs to shapeCache and must NOT be freed (exportHandler.ts); print estimates use the calibrated shell-volume model in src/shared/printSettings/standardBinVolume.ts — don't re-derive its constants from first principles.