Industrial Product Design

Industrial Product Design

Make the product credible before making the drawing polished. Integrate user tasks, architecture, form, interfaces, motion, CMF, manufacturing, service, and safety into one revision-bound design.

Portability Contract

• Keep the workflow independent of Codex, Claude Code, a CAD vendor, and a specific MCP namespace.
• Discover actual tools and capabilities before selecting a modeling route. Never invent a tool call or validation result.
• Keep editable native CAD as the design authority. Treat STEP, GLB, STL, renders, PDF, and DXF as derived evidence.
• Preserve source files and unrelated geometry. Use document IDs, revisions, configurations, and absolute paths to bind every mutation and output.
• Mark missing inputs TBD, skipped checks NOT_EVALUATED, and assumptions explicitly. Do not turn missing evidence into a pass.

Skill Boundary

• Use this skill upstream for product intent, concept selection, architecture, proportion, interaction, form language, interfaces, configurations, motion, CMF, and design maturity.
• Use mechanical-drafting-gbt downstream for GB/T views, dimensions, fits, GPS/GD&T, BOMs, manufacturing notes, DRC/DFM, plotting, exchange verification, and release packaging.
• Do not duplicate drafting rules here. Do not start release drawings while the product-design gates for the claimed maturity are unresolved.

Required Workflow

1. Classify maturity. Choose discovery, concept, design-development, engineering-candidate, or release-candidate. State what the requested output can and cannot prove.
2. Write the brief. Record users, scenarios, functions, critical actions, interfaces, environment, loads, anthropometry, size, cost, process, service, safety, appearance intent, retained features, prohibited features, and deliverables. Separate supplied, derived, assumed, contradictory, and TBD requirements.
3. Build architecture. Define functional blocks, energy/signal/material flows, purchased-component envelopes, motion axes, interfaces, assembly direction, cables/hoses, thermal paths, service volumes, and hazard keep-outs.
4. Generate concepts. For a new product or major redesign, compare at least three materially different architectures or silhouettes at the same scale. Color, fillet, or trim variants of one idea do not count.
5. Select and codify. Record the selected direction and why. Define primary/secondary/tertiary masses, control lines, section strategy, curvature/radius families, seams, openings, interface treatment, detail density, and CMF zones.
6. Pass the capability gate. Read cad-capability-contract.md. A primitive-only backend may prove packaging but may not claim refined surfaces, parametric assembly, or product rendering.
7. Create the skeleton. Model named overall dimensions, datums, component envelopes, support footprint, human contact zones, motion axes, interfaces, cable paths, thermal volumes, service access, and safety keep-outs. Preview immediately from common views.
8. Develop by subsystem. Add one logical feature or subsystem at a time. Read back actual feature identity, parameters, hierarchy, material role, bounds, and associations after each mutable stage. Roll back on unexplained mismatch.
9. Model configurations and motion. Use component instances and transforms, not duplicated loose geometry. Define fixed components, mates/limits, degrees of freedom, named configurations, motion envelopes, and interference evidence. See configuration-motion-render.md.
10. Review through separate channels. Judge design intent, ergonomics, architecture, geometry, motion, manufacturing, service, safety, and physical performance separately. A valid B-rep or attractive render is not an overall pass.
11. Handoff deliberately. Freeze the selected revision and configuration, list TBD and NOT_EVALUATED items, then invoke mechanical-drafting-gbt for manufacturing definition and release evidence.

Hard Gates

Read design-gates.md for gate inputs and evidence. At minimum enforce:

• BRIEF_GATE: critical users, tasks, interfaces, constraints, maturity, and unknowns are recorded.
• CONCEPT_GATE: materially different concepts were compared or an authorized supplied concept is identified.
• ARCHITECTURE_GATE: component envelopes, flows, interfaces, motion, service, and hazards are coherent.
• DOCUMENT_IDENTITY_GATE: every mutation targets the requested document ID and expected revision.
• BACKEND_CAPABILITY_GATE: required modeling, selection, assembly, analysis, and render operations are actually available.
• SKELETON_GATE: same-scale multi-view review passes before detail.
• FORM_GATE: 360-degree massing, transitions, seams, interfaces, and detail hierarchy express one intent.
• CONFIGURATION_GATE: named states change component transforms without copying uncontrolled geometry.
• VERIFICATION_GATE: geometry, interference, wall/draft/surface, exchange, render, and physical checks are reported separately.
• HANDOFF_GATE: authoritative source, revision, configuration, units, dependencies, assumptions, and unresolved items are explicit.

Any failed identity, transaction, topology, or output-integrity gate is a hard stop. Attempt one bounded recovery, then switch to a verified backend or report blocked.

Evidence Rules

• Require requested, actual, and diff for mutable CAD operations. Treat unexplained postcondition differences as failure.
• Treat the semantic registry, native entity registry, and B-rep as one commit unit. When a native handle is erased or replaced, invalidate or replace its registry record in the same transaction; stale feature records block release.
• Prefer stable semantic feature IDs, named datums, and component IDs. Do not rely on volatile face or edge sequence numbers for automation.
• Require atomic transactions for multi-entity or multi-feature stages. A partial result is not a recoverable success.
• Require rollback evidence for entity/feature counts, registry rows, document revision, layers, and temporary outputs. An exception message alone does not prove rollback.
• Verify B-rep validity, body count, bounds, mass properties where meaningful, wall thickness, draft, surface continuity, and interference according to maturity and process.
• Label AABB overlap and sampled motion checks as broad-phase only. Distinguish containment, contact, permitted crossing, intentional motion overlays, and exact B-rep interference.
• Re-import required exchange formats and compare units, body count, bounds, critical dimensions, and configuration identity.
• Use deterministic named cameras and native/offscreen rendering for product review. Window screenshots and SendKeys are diagnostic fallbacks, not release evidence.
• Serialize AutoCAD MCP calls through the transport guard. A bounded queue, sliding-window budget, and hard response ceiling are release-safety controls; stop a campaign on E_TRANSPORT_*/E_MCP_* admission errors rather than retrying in parallel.
• Treat screenshots as file evidence: return path, dimensions, byte count, and SHA-256. Only embed image bytes after explicit opt-in and size verification, and prefer a fresh bounded review round after repeated context compaction.
• Bind every render to document ID, revision, configuration, camera, style, resolution, output path, content hash, clipping state, visible components, and material_render_verified. A linework image cannot pass a shaded/material review.
• Prepare revision-bound section planes/cut sets and exploded component transforms before requesting section or exploded evidence. Camera movement alone does not create either state.
• Treat FIT/NTS and fixed numeric plot scales as mutually exclusive. Verify paper, orientation, PDF MediaBox, viewport scale, and title-block declaration before release.
• Preserve a machine-written reports/round.json for each validation round with identity, transaction/rollback, readback diffs, DRC, render truth, plot truth, artifact hashes, cleanup, and lessons.
• Never infer strength, fatigue, thermal, fluid, electrical, safety, or compliance performance without inputs, method, thresholds, and evidence.

Workspace Contract

Use or map these portable folders under the project root:

specs/       brief, requirements, parameters, component/interface tables
scripts/     reproducible generators and validation entry points
models/      authoritative native CAD and exchange models
drawings/    downstream manufacturing drawings
previews/    revision-bound multi-view and configuration renders
reports/     design reviews, validation, interference, re-import evidence
outputs/     approved delivery package

Do not retain disposable CAD/PDF/PNG test artifacts after validation. Preserve compact JSON evidence, logs, hashes, and test summaries.

Final Response

State the current maturity, selected design decisions, user-confirmed requirements, assumptions, authoritative source/revision/configuration, checks that passed, checks that failed or were not evaluated, produced files, and the highest-value next test.