3D printing and parametric enclosures

Printed parts fail in a few repeatable ways. A fit face is scarred by supports. A load peels the layers apart. A hole prints small and a screw will not start. A clip cracks because the plastic is filled and brittle. A screw boss cracks off the wall. A temperature sensor reads the regulator instead of the room. A USB plug cannot reach its socket because the wall is too thick. A Wi-Fi module loses 10 dB because an insert sits next to the antenna. A pull on a cable rips its solder joint. Every rule here exists to close one of those failure modes. Fix them in the process choice and the geometry; a slicer setting is the second move, and only after the shape is printable. Follow the rules by default and say so when a brief forces an exception.

Numbers in the references are starting points from printer vendors (Prusa, Bambu, Formlabs) and from desktop FDM practice. A fit coupon printed on the actual machine overrides every one of them.

Scope

One skill, two job families that share the same profile, FDM rules, and verification. Process jobs: which machine, which material, which way up, what the slicer must do, and whether the shape can survive that — new parts, design reviews, print plans for a mesh, failed prints, material questions. Enclosure jobs: parametric electronics enclosures — PCB fit, connectors, closures, vents, sensors, wiring, and their export as printable parts. A wiring or power question with no box is still an enclosure-family job (the wiring reference is the whole deliverable).

Match the length of the reply to the question. A material comparison does not need a print plan. The full contracts below are for a part you are designing or clearing to print.

Preserve the project format

Use the existing CAD language and parameter names. For .rhai projects read references/rhai-design-and-export.md; do not replace them with OpenSCAD or use OpenSCAD-only syntax. For an existing .FCStd project, or whenever the user asks for FreeCAD, STEP, the FreeCAD MCP connection, or mechanical-CAD interchange, read references/freecad-design-and-export.md and preserve that project the same way. New standalone enclosure designs default to OpenSCAD when the user states no engine preference. The Customizer, SCAD library and SCAD export contract apply to OpenSCAD only; the Rhai and FreeCAD references give the equivalent deliverables for their engines. Process rules (fits, structural columns, ventilation, sensor compartments, closures, safety) apply to all three. If the user already has a mesh, review it against the chosen process; do not rebuild it in another CAD tool unless they ask.

Read only what the job needs

This file holds the workflow and the rules that apply to every part. Detail lives in references/ and is loaded when the task touches it:

Assets and tools (copy, don't re-derive):

• assets/fit-coupon.scad — one print (~84 × 57 mm) that sets hole_comp, tol, and the insert bore for a printer-material pair. Edit its parameters for another nozzle or insert; do not redraw it.
• assets/enclosure_lib.scad — reusable modules: chamfered rounded boxes, gusseted filleted columns, standoffs, tongue-and-groove and the rim band, face-frame cutters, vent patterns, teardrops, keyholes, nut traps, snap hooks, labels, zip-tie anchors, cable channels and chamfered cable exits. Reusing it keeps geometry consistent across the user's product line.
• assets/template.scad — complete base + lid enclosure on the default profile. Give it the board in its own coordinates (outline, holes, antenna, heat sources) and each connector by board edge; it lays out the box from that: board against every connector wall, corner columns elsewhere, zones stretched to clear the antenna keepout, lid split above the tallest cutout, vents on free faces, plus plug recesses, roofed openings, rails, an optional sensor chamber, wiring bays, feet/ears/keyholes, asserts, a fastener BOM echo, and part views (assembly, exploded, base, lid, section, check). Start every new design from it; most briefs are parameter edits.
• assets/selftest.scad — renders every library module; run after any library change.
• assets/enclosure_lib.py — the same module set ported to FreeCAD's Part/Draft API for the live MCP connection (real OCCT chamfers and B-rep fillets). Load it once per FreeCAD session with execute_code; execute_code_headless does not share that session and must re-load it.
• assets/enclosure_template.py — the FreeCAD equivalent of template.scad: parameters in a top-level PARAMS dict, named Part::Feature objects per part, and a set_view(doc, mode) helper. There is no CLI -D; parameters are edited in the script text.
• assets/selftest.py — exercises every enclosure_lib.py function once; same discipline as selftest.scad.
• scripts/check_stl.py — standard-library STL topology/envelope/bed checker.
• scripts/check_scad.py — static SCAD check that runs without OpenSCAD.
• scripts/export_parts.sh — renders parts, the interference check and PNG previews.

Workflow

1. Classify the job. Enclosure design or revision; new non-enclosure part; design review of an existing model; print plan for a mesh; failed print; material question; wiring question. Failed prints start in references/slicer-and-troubleshooting.md and come back here only if the fix is geometry. A mesh starts with the units, envelope, and manifold checks in references/mesh-and-export.md. An enclosure that is "too low", will not close, or does not fit after wiring is a geometry/measurement failure, not a slicer problem: rebuild the vertical stack from the assembled board (soldered pins below the devkit, standoff, PCB, seated Dupont housing, relaxed wire bend, closure margin), never scale Z or force the lid.
2. Pick the process. Desktop FDM on the house profile unless the part cannot succeed there or the user names another process. See the table below.
3. Load the profile from references/manufacturing-profiles.md. Use it without asking. A named printer or material replaces it; write the override down and recompute anything that came from extrusion width.
4. For an enclosure: fill the brief (below) and read the references it touches — every sensor in sensors.md; a known board in pcb-and-components.md; outdoor/battery/child contexts in environment-and-safety.md; more than one module, a battery, a switched load or a cable out in electronics-and-wiring.md. Then write the .scad from assets/template.scad using assets/enclosure_lib.scad (or the engine the project already uses).
5. For any part: decide orientation before shape. The bed face, the weak axis, and which face may be sacrificed determine the geometry. Infer the load from how the part is used and tag that inference as an assumption. Change the geometry so the part prints without supports on a working face, so the load does not peel layers, and so the part is one solid with no island in the air. A warning in the reply is not a fix.
6. Verify and export. Run scripts/check_scad.py on SCAD sources; render with scripts/export_parts.sh when OpenSCAD is available. One STL per part, bed face on z = 0. Run scripts/check_stl.py with the selected envelope, layer height and --require-bed on every STL. Fix measured errors; resolve sampled warnings in the slicer. An ok result covers only the checks listed in the report; it does not certify printability.
7. Deliver the contract that matches the job, then run the self-check.

Process choice

The house machine is an open-frame FDM printer. Recommend another process only when FDM cannot do the job, and say what the user must own or order.

Rules that apply to every FDM part

The profile overrides the numbers. The reasons live in references/fdm-design-rules.md.

• Choose walls and ribs around whole extrusion widths, and floors around whole layer heights. Use this as a house design target; confirm actual perimeter coverage in the slicer, which may vary line width and overlap. Minimum feature 0.8 mm; minimum free-standing pin Ø 2 mm.
• Supports are a defect, not an option. Every part prints on a flat face with nothing under it. Overhangs stay at or under the profile limit, measured from vertical; steeper needs a chamfer, a teardrop, or a different orientation. Supports on a fit, seal, or sliding face are a design failure.
• Horizontal holes print oval. Above the profile's teardrop threshold, use a teardrop or a flat bridged top, or plan to drill. Downward-facing screw recesses get a 45° cone.
• Vertical holes print small. Add the profile's hole compensation on functional diameters only.
• Bridges stay under the profile's limit. Wider openings get a 45° roof (template cutout_roof); if you turn it off, say which tops will sag.
• Chamfer every edge that runs parallel to the bed, including the bed contact and the underside of a lip — a fillet there starts as a flat overhang — unless the chamfer would eat a one-extrusion land (the lid's groove side); there, rely on the slicer's elephant-foot compensation and say so in the build notes. Fillet vertical edges, and fillet a loaded internal corner without thinning the wall. On filled or brittle plastic the inside radius is at least 1 mm.
• Nothing solid thicker than about 4 mm. Hollow it and rib it. Thick lumps warp and do not get stronger in proportion.
• The part is weakest between layers. Tension and bending stay in the XY plane of the print. A screw that pulls a flange apart along Z is peeling the stack.
• Every part fits the profile envelope, or it is split and joined with fasteners and dowels. Do not specify cyanoacrylate on PETG or PETG-CF; it does not hold.
• One named clearance drives each fit. "Make it tight" is not a dimension.
• Each exported part is one solid. Fuse intended features with a deliberate overlap and check the exported topology. Keep a structural neck wide enough for its load; two extrusion widths is only a geometric starting minimum.
• Nothing starts in mid-air. In the print orientation every region has plastic under it, down to the bed, or it is a bridge within the profile limit whose ends land on walls. An island is a modeling error, including one that rejoins the body only higher up.
• The STL topology is checked before it reaches the slicer. Every edge has two faces, windings agree, and there are no collapsed triangles. Clicking Repair is not a step in the plan; repair can change intended holes or thin walls, so inspect the result instead of assuming equivalence. Details and the checker are in references/mesh-and-export.md.

Body and lid must fit

The two halves are one assembly. A lid that copies the body's outer rectangle and rests on the rim does not fit: nothing stops it sliding, and a zero gap in the model binds or rattles once printed. Reject that shape the same way you reject a boss with no gusset. Give the pair a continuous register — tongue-and-groove (default), an internal lip, or a stepped lap; a butt joint does not count — with one slip clearance, from the profile, on each mating face. Fix the tongue and open only the groove. Outline, tongue, and screw holes on both parts come from the same parameters. Assembled, intersection() of body and lid is empty (part = "check"), a section shows the gap, and the lid cannot shift in XY without the register stopping it. The dimensions, the groove-land rule and the lip_groove_cut semantics are in references/fits-and-fasteners.md §3.

Fasteners in one pass

Read references/fits-and-fasteners.md before drawing a boss. Short version, so a casual answer does not invent a hole:

• Repeated assembly: heat-set insert. Select bore shape and dimensions from the actual manufacturer and validate the final CAD bore on a coupon. House M3 starts at 9.5 mm boss OD and at least 2.5 mm radial plastic; grow the OD for larger bores.
• A few assemblies, then never again: self-tapping or thread-forming screw. Pilot about 0.8 × major diameter, engagement at least 2 × diameter, boss wall ≥ 2 mm.
• Mating part: clearance hole (3.4 mm for M3, + hole_comp) plus counterbore/countersink.
• Printed threads are for coarse, lightly loaded closures. Below about M5, use an insert.
• Snaps and living hinges follow the strain limit in the fasteners reference, and only in a material that can flex. On house PETG-CF, offer screws or a switch to unfilled PETG. If the user insists on a PETG-CF clip, apply the limits in references/manufacturing-profiles.md and put the fatigue risk in Watch-out.

Enclosure design

The brief

Don't interrogate the user — extract what the conversation already gives, pick defensible defaults for the rest, and tag each one // ASSUMPTION: in the code and in the ASSUMPTIONS section of the reply. Defaults in brackets.

PCB — outline X × Y × thickness [1.6 mm], mounting hole Ø and coordinates from the board's bottom-left corner, tallest component on top and bottom, keepouts (antenna, HV, moving parts). Known dev boards: use the footprint table. Measure the board as assembled, including soldered header pins above and below the PCB. Record which board edge each header occupies and which side of the PCB carries the plastic spacer, solder joint, exposed pin and Dupont housing. Never assume the two header rows or four board edges are symmetric.

Interfaces — connectors (board edge, position along it, height above the board, overhang past the edge), display, buttons, LEDs, switches, cable exits.

Sensors — type and what each must sense (airflow, field of view, acoustic port, light path).

Power and wiring — supply (USB, adapter, battery, mains), every module and load with its peak current, how they connect, and each cable that leaves the box [USB 5 V, one board, no cables out]. Record whether devkits have soldered pins and whether Dupont leads enter from above or from the side. The power budget sets heat_w, the supply and the wiring bay.

Thermal — heat sources and rough dissipation, from the power budget [assume < 0.3 W if nothing is said].

Context — indoor/outdoor, dust, moisture, and whether children or animals can reach it. This changes the vent and battery rules, so raise it rather than silently assuming.

Mounting — desk feet, wall, DIN rail, handheld [desk feet].

Fasteners — M3 heat-set inserts [default] or self-tapping screws.

Limits — maximum outer dimensions, aesthetics.

If the PCB dimensions are missing and it isn't a known board, that is the one thing worth asking for. Everything else can be assumed and corrected later.

Parametrisation and frames

Millimetres throughout. Every input lives in one Customizer block at the top of the file, grouped with /* [Group] */; below /* [Hidden] */ there are only derived values — no magic numbers. That is what makes a design reusable at a different PCB size. One coordinate frame: origin at the outer bottom-left-front corner of the base, +Z up. Board features are given in board coordinates, as on the board's drawing, and converted through to_world() (which applies pcb_rot), so every cutout is dimensioned from the PCB origin, never from the wall (wall-referenced cutouts drift when the wall changes). Expose part = assembly | exploded | base | lid | section | check; only base/lid (and extra printable parts) are exported.

Structural columns — the single most common failure

Every screw lands in a hollow column that runs floor to mating face, tied into the shell. Never a thin flange, never a boss floating on a wall — that is a lever arm with a layer line at its root.

• 2–4 triangular gussets per column, thickness = wall, height 60–80 % of the column, reaching about as far as they rise. The 45° is for stiffness: a rib standing on the floor prints at any slope, because each layer sits inside the one below. Route ribs away from the board (the template runs them along the wall of the zone that holds the column).
• Fillet gusset roots and the column-to-floor junction.
• Boss OD is at least the final CAD bore Ø + 2 × required radial wall and the profile minimum. Derive layout from the resulting OD.
• Heat-set inserts: use the actual insert manufacturer's hole shape, diameter, depth and installation guidance. Coupon-tested CAD bore dimensions already include process compensation. House M3 defaults are uncalibrated; straight bore, no mouth chamfer, and 1 mm relief are defaults for that example, not all insert products.
• ≥ 4 columns up to a 100 mm span, one more per additional ~70 mm, plus one beside any connector that takes insertion force — a USB port pushed 200 times is a fatigue test of whatever holds that wall. The exception is the corner where two connector walls meet (Raspberry Pi): the board fills it, so three columns plus the register close the lid; add a fourth by hand if the lid must seal.
• Lid columns and PCB standoffs are separate: a column must never pass through the board's footprint.

PCB fit and connectors

• Lateral clearance ≥ the profile's slip tol per side (template default 0.5 mm; clones vary), located by standoffs, or by rails and stops when the board has no holes (template mount_holes = []). Never press-fit a PCB.
• ≥ 2 mm above the tallest rigid top-side component. For a devkit with soldered headers and top-entry Dupont leads, use the assembled wiring envelope, never the bare-board component height: default wiring_top_h = 28 mm above the PCB top when no physical measurement exists (22 mm only for a pre-bent, restrained harness), plus the normal 2 mm closure margin. Soldered pins below the PCB are part of the bottom stack, separately from comp_bot: default pin_tail_h = 4 mm when unmeasured, standoffs ≥ pin-tail height + 1 mm (5 mm is the normal minimum for pinned devkits), and pins and solder joints must not touch the floor, rails, keyhole heads or cable ties. The full stack-up table is in references/pcb-and-components.md §2.
• Header placement is per board edge, before pcb_rot. One-sided soldering and right-angle headers are asymmetric geometry: set header_edge_clear = [x0, x1, y0, y1] to the connector/harness projection beyond each edge, zero on unused edges, expand only the affected face, and keep its envelope clear of rails, stops, columns, vents and the lid register. Do not centre the board to hide an asymmetric header unless that still preserves every port and antenna constraint.
• Cutouts +0.5 mm all round; +0.75 mm and a 1 mm lead-in chamfer on user-facing ports.
• Plugs must reach their sockets. A plug's overmold is wider than the socket; if the socket sits more than ~1.5 mm behind the outer surface, recess the outer face to overmold size so ≤ 1 mm of wall remains (template overmold field). A connector also needs its wall close to the board edge: the template puts the board against every wall that carries a connector and moves the columns to the other sides. Give each cutout by board edge and set pcb_rot to choose which wall that edge meets.
• Cutouts never cross the lid split unless deliberately split between both halves.
• Headers with Dupont wires plugged from above use wiring_top_h, independently of comp_top; do not hide connector and bend allowance inside a guessed component height. Wiring that leaves the box, a second module, a battery or a switched load: the electronics and wiring reference. Give those runs a wiring bay (bay_front / bay_back) on the long side without connector cutouts, a zip-tie anchor at each exit, and a hole chamfered so the jacket cannot chafe. Keep a service loop to every part on the lid.

Ventilation

Required when anything dissipates > ~0.3 W or the brief names a heat source.

• Slots 1.5–2.5 mm wide, ≤ 25 mm long, pitch ≥ slot + one wall — webs are structure.
• Vertical-wall slots print unsupported; on horizontal faces use short bridged slots or a vertex-up hex grid.
• Chimney: inlets in the lowest 25 % of one wall, outlets in the top 25 % of the opposite wall or the lid, so air crosses the heat source.
• Above 1 W maximise open area (aim ≥ 25 % of the vented wall) or add a fan.
• Children/animals: no opening > 4 mm in any direction, none directly above the PCB — offset louvres so there is no straight line from outside to electronics.

Sensor compartments

Read references/sensors.md for per-sensor geometry. Universally: own chamber behind a full-height divider with its own vents; ≥ 15 mm from any heat source plus a ≥ 3 mm air gap or a slot through the divider (the template builds a two-skin divider); no dead air pockets; serviceable without desoldering.

RF

No conductive material, insert, column or rib inside the profile's antenna keepout radius. Antenna over open plastic near an edge, minimum plastic in front of it; set antenna and the template stretches the column zones until the inserts clear it. Filled materials attenuate 2.4 GHz — say so and recommend an RSSI check.

Electrical and safety

Printed plastic is not a qualified insulator, especially filled grades, and layer lines are not food-safe. ≥ 3 mm creepage from any mains/HV net to the wall; never rest a bare conductor on plastic. For mains, tell the user the safe path is a certified supply so the printed enclosure sees only low voltage. Anything reachable by children or pets: no detachable small parts, battery compartments that need a tool, magnets fully captured.

Assembly and serviceability

• Default closure: lid screwed into insert columns and located by the register above. Other closures: references/fits-and-fasteners.md — check the profile before any elastic feature.
• One tol drives the fit table (press / slip / loose). Measure and record it for the printer, material, and process; reuse it across mating pairs, then revalidate after process changes.
• Screws from the least visible face (the template drives them down through the lid; the fasteners reference covers screwing up through the floor). Hide the parting seam on a chamfer (template seam_ch).
• Rubber-foot recesses (Ø 8 × 1 mm). For a wall, ears (wall_mount = "ears", nothing inside can collide with them) or keyholes (Ø 7 / 3.5 mm, hidden, need a board deep enough to leave floor between the standoffs).
• Strain relief on every cable exit: a zip-tie anchor 10–20 mm inside the wall, so a pull never reaches a solder joint. tie_anchor() and cable_exit_cut() are in the library; the template places one of each per cable_exits entry.
• Deboss part name + version 0.4 mm deep, ≥ 3 mm tall, on an internal face.

Clean CSG

Every cutter overshoots the faces it cuts by EPS; use $fa/$fs, coarser in preview; no minkowski(); assert() every invariant that would otherwise print fine and fail in assembly (fit, minimums, envelope, keepouts, cutouts vs split). Use at least 64 segments for functional circular holes in final exports.

Output contracts

Write files to disk when the user asked for a model; do not paste a long script into the reply when a file is what they will print. Export one file per part, bed face on z = 0, following references/mesh-and-export.md. Without file tools, use one fenced block per file.

Part being designed or cleared to print

## Process
<FDM / resin / SLS> on <profile>. <Why this process.>

## Orientation
Bed face: <which face, and why>
Load path: <where tension and bending sit relative to the layers>
Sacrificed face: <none, or the face that may carry support scars>

## Geometry
<Walls, fits, fasteners, and the shapes changed so it prints and holds.>

## Mesh
<When a file was written: one solid, bed on z = 0, and the check_stl.py line. Report the actual Bambu Studio result; investigate any repair prompt or warning there, since the mesh checker is advisory for some edge patterns.>

## Print plan
<Layer height, walls, infill, brim, supports, nozzle, drying, and any pause-at-layer height. Use Bambu Studio setting names and the A1 Mini preset in references/slicer-and-troubleshooting.md unless the user named another slicer. Supports must read "none" unless a face was sacrificed on purpose. X-Y hole compensation is 0 when the model already has hole_comp. Make overhangs printable stays off.>

## Watch-out
<The single most likely failure, and the check that prevents it.>

## Assumptions
<Every value the user did not give.>

For a design review, replace Geometry with a punch list ordered as: will not print, will fail in use, will look bad. Quote the dimension that is wrong and the dimension to use.

For a failed print, use the diagnosis shape in references/slicer-and-troubleshooting.md: most likely cause, the observation that confirms it, one fix. Geometry first, then a single slicer change.

For a mesh review, report units, bounding box, and manifold status first, then the punch list. Say which checks ran with a tool and which were done by reading the model.

New enclosure design

Deliver in this order:

1. <product>_enclosure.scad — parametric, using enclosure_lib.scad.
2. enclosure_lib.scad alongside it, unless the user already has this version. If the user needs a single self-contained file (online renderer, paste into the editor), inline the used modules instead and say so.
3. One CLI export line per part: openscad -D 'part="base"' -o base.stl <product>_enclosure.scad
4. BUILD NOTES — per part: orientation and why, brim yes/no, bounding box vs envelope; layer height, material, supports (must read "none"), profile operator notes; fastener BOM with quantities and lengths (the template echoes one).
5. WIRING — when the brief has more than one module, a battery, a switched load or a cable leaving the box: power budget, pin map, wiring table, protection, harness notes, as in electronics-and-wiring.md §9. For a wiring question with no box, this section is the whole deliverable.
6. ASSUMPTIONS — every value the user did not specify.
7. SELF-CHECK — the list below.

Chat iteration protocol

The user will iterate ("move the USB 3 mm left", "thinner", "add a button"):

1. Return the complete updated file, not a fragment (unless asked for a diff).
2. Keep parameter names stable so Customizer presets and -D overrides keep working. Add parameters; don't rename them.
3. Change the minimum — prefer a parameter or list entry over restructuring.
4. Re-run the static check and re-render what changed before replying.
5. Reply with a short CHANGES list naming the parameters touched, any new assumption, and the self-check items affected — not the full contract again.
6. If a request conflicts with a rule (1 mm walls, snap-fits in PETG-CF), do it if it is merely suboptimal and name the consequence; push back only when the part would fail to print or fail its job.

Self-check before answering

For every part being designed or cleared:

• No part needs supports; no overhang beyond the profile limit; no support lands on a fit, seal, or sliding face.
• The critical load is not peeling layers, or the part was reoriented.
• FDM walls are a whole number of extrusion widths from the profile in force.
• Each fit has a named clearance. Every functional vertical hole carries hole_comp or a drill note, and not both hole_comp and slicer hole compensation.
• Body and lid locate each other with the slip clearance on each mating face. A rim-to-rim plate fails this check even when the two solids do not intersect.
• Every part fits the profile's build envelope, or the split and the fasteners are specified.
• Profile bans are respected. On house PETG-CF that means no snaps, clips, or living hinges unless the user insisted, the profile limits are applied, and the risk is stated.
• Any exported file is one part per file, in print orientation, with functional holes at $fn ≥ 64. Every STL has passed the reported topology, envelope and bed checks; sampled island findings have been inspected in the slicer. Self-intersections, wall thickness and strength are not certified by the checker.
• The print plan names the Bambu Studio printer, process, and plate presets when that is the slicer, and it leaves hole compensation and overhang rewriting off.
• Heat, UV, food, and mains were either handled or marked not applicable. Printed plastic is not a certified insulator or a flame barrier unless the spool says so.

For enclosures, additionally state the verdict on each:

(a) every screw has a gusseted, filleted column that avoids the board; (b) every sensor has a vented, thermally decoupled chamber; (c) antenna keepout respected; (d) all cutouts referenced to the PCB origin through their board edge, and plugs can reach their sockets; (e) assert() statements present and passing; (f) export commands match the part values; (g) context rules applied (heat/vents, sealing, batteries, children/pets) or not applicable; (h) when the brief has more than one module, a battery, a switched load or a cable out: a power budget, a pin map, a wiring table, a fuse at the source, and a keyed/latched or screwed power connection; each cable exit has a zip-tie anchor and an anti-chafe hole; (i) the vertical stack uses the assembled board: bottom soldered-pin envelope, standoffs, PCB, top header/Dupont envelope, bend radius, and 2 mm closure margin; with the actual harness installed, a section/check view shows no contact with the lid, seam, columns or floor — a bare-board height check fails (i); (j) every soldered header is assigned to its actual PCB face and edge; asymmetric top/bottom and x0/x1/y0/y1 envelopes are preserved through pcb_rot, and unused sides do not receive invented clearance — a single symmetric header allowance fails (j).

If a check fails, change the part before replying. Do not ship the failure as a note or a caveat where geometry was the answer. If the native renderer or slicer was unavailable, identify the checks that remain unverified. Never infer a mesh or physical-fit pass from static source checks.

OpenSCAD compatibility

Target OpenSCAD 2021.01 syntax; it runs unchanged in development snapshots, which render far faster with the Manifold backend. Avoid experimental features unless the user runs a snapshot. Docs: https://openscad.org/documentation.html