# Native engineering evidence - 28.6

Owner accepted publication as an upcoming prototype on September 19, 2026. The findings below remain open unless marked reconciled; no geometry repair is claimed.

## What changed in this review

Fusion was successfully updated from 2704.1.53 to 2705.1.15 through its own updater. The exact received F3D opened locally. Its native units are millimetres, and its design timeline contains 209 entries. All measurements below come from native Fusion B-rep solids in their current assembly positions, not from guessing positions from STL filenames.

The earlier STL report must be qualified: Plus, Minus, Talk and both optical pieces are approximately 5 mm higher in Y in the supplied STLs than in this Fusion assembly. Native checks remove the large side-button and optical collisions previously identified in the raw export coordinates. This is a substantive correction to the initial assessment, and demonstrates that the delivered mesh set is not positioned consistently with the supplied native assembly.

A translated individual STL may still be printable at the correct scale. The position mismatch does not by itself make its shape bad; it does make the set unreliable for assembly overlays and prevents treating this bundle as a verified matched assembly export.

## Confirmed native findings

| Interface | Native intersection volume | Interpretation |
|---|---:|---|
| Rear shell / battery | 40.761 mm³ | Actual modeled overlap. The battery is 62 × 38.5 × 8.5 mm, matching the previous maximum-pack envelope. Resolve the support/retention geometry without requiring battery compression. |
| Rear shell / PCB laminate | 36.336 mm³ | Actual modeled overlap. Board support and enclosure geometry need local correction. |
| Front shell / PCB laminate | 1.290 mm³ | Additional modeled board/shell intersection. |
| Front shell / play button | 11.536 mm³ | Play fit is still unresolved in the native model. Check the cap rim, shell opening and full travel. |
| Play-switch base / modeled switch body | 10.800 mm³ | Holder and nominal switch occupy the same space. Reconcile seat geometry and actual switch dimensions. |
| Front-shell Body1 / Body2 | 16.997 mm³ | The second frame-shaped body overlaps the main shell. Decide whether it is integral and should be united, or a separately manufactured part. |
| Front shell / acoustic film | 99.463 mm³ | The supplied acoustic layer intersects shell material. Resolve its intended trim and installed location. |
| Rim / rear shell | 1,549.969 mm³ | Substantial modeled overlap. Material/compression/retention intent is required before interpreting it as a defect or a deliberate fit. |
| Rim / front shell | 2,684.020 mm³ | Same qualification. Do not silently assume this is an acceptable flexible fit. |

The native Plus/rear and Minus/rear intersections are only 0.0093 mm³ each. Talk/rear is 0.0733 mm³. These are tiny residuals compared with the incorrect-position STL results and require local clearance/tolerance interpretation, not claims that the controls have the large rigid collisions previously shown. Talk's retained body name identifies it as a flexible grip; its material assignment still needs a release specification.

Both optical solids remain separate, but no positive-volume interference above 0.001 mm³ was found between them and the checked printed parts in the native placements. Their two-part identity, material, finish and optical performance still require documentation. No dynamic button-travel or physical fit pass is claimed.

Intersection volume is not penetration depth and is not a machining offset.

## Exterior and PCB placement

Native main-shell dimensions confirm 80 × 150 × 24 mm, excluding projecting details. The preceding design was 78 × 150 × 24 mm. This is a design change requiring alignment. Rim bounds confirm 84.2 × 154.2 × 28 mm.

The native PCB laminate is parallel to the case: bounds X -30..30, Y -58.04..21.96, Z -14.3015..-12.9715 mm, with thickness 1.33 mm. This is not the compound-tilted PCB arrangement developed for the prior R3.7/website 28.5 candidate. Its connected fit cannot inherit that candidate's verification.

## Native model health and hidden references

Five timeline entries report warning state 1 and missing references/cached geometry: Sketch3, Sketch9, Sketch23, Extrude23 and Sketch28. Fusion can display the current cached shapes, but references must be repaired and regeneration checked before treating the file as a dependable editable master. These warnings are not proof that every current solid is invalid.

Inventory: 1,775 B-rep bodies, of which 415 are solids and 1,360 are non-solid sheets within the PCB SIM8066 reference component. Attempting a volume on those sheets returns an API error; this is not 1,360 manufacturing-part failures. All 13 bodies corresponding to the 11 supplied print files are solids.

The saved assembly has 48 hidden solid bodies: 15 under Hardware and 33 under All wiring. A separate native check including them found 29 additional printed/reference intersections. Examples include volume-minus with a button wire, rear shell with coax, front shell with multiple battery/speaker/control wires, and LED housing with four LED leads. Hardware overlaps include screw/holder interfaces that may be intended and require classification. These are retained hidden references, not proven current build instructions. Their disposition must be explicit: update and include them, or retire them and model the intended replacement harness/hardware.

## Method and limits

- Read-only inventory of source component names, native/proxy bounds, solid status, volume, visibility and timeline feature health.
- Exact Fusion TemporaryBRepManager Boolean intersections on temporary copies; original model bodies were not modified.
- Copied-body bounds were independently compared with assembly-context body bounds and matched within 0.00001 mm, checking against a local/world transform mistake.
- Checked every pair of the 13 print bodies (78 pairs), with bounding-box screening, and printed-body intersections with 354 visible reference solids. A second pass included all 402 reference solids, including hidden hardware/wiring. No Boolean operation errors were recorded.
- Positive-volume reporting threshold: 0.001 mm³. Printed/reference checks do not constitute a full reference/reference collision audit. Non-solid reference sheets were excluded.
- Native shape comparisons establish static modeled fit only. Strength, wall adequacy, print tolerances, optical/acoustic/RF/electrical performance, full control motion, tool access and complete physical assembly remain unqualified.