sl-mechanical
61c716ee58
3× MaUWB ESP32-S3 follow-me UWB system: 1 wearable tag, 2 robot anchors. chassis/uwb_tag_enclosure.scad Belt-clip enclosure for MaUWB PCB (~50×25×10 mm) + TP4056 micro-USB charger + 18650 cell. Snap-fit PETG shell + TPU 95A bumper sleeve. IP44-ish 4 mm overlap + 2-turn labyrinth seam. Open antenna window in lid (no PLA within 10 mm of UWB antenna). Power switch cutout (Y− face), micro-USB port (X− face), LED window hole (Y+ face). Belt clip integrated (PETG spring arm, 42 mm belt slot). RENDER: body/lid/tpu_bumper/assembly. chassis/uwb_anchor_mount.scad Stem-mounted anchor bracket for 25 mm OD stem. Split D-collar with M4 thumbscrews (tool-free), M4 hex nut pockets, M4 set screw height lock. Anti-rotation flat tab on front half prevents axial rotation without stem modification. USB cable routing channel in rear half. Module bracket tilted 10° outward — antenna faces horizon, clears stem metal. Back-wall cutout behind antenna section (10 mm clearance). 250 mm anchor spacing (RENDER "pair" shows both on stem section). RENDER: collar_front/collar_rear/ bracket/assembly/pair. chassis/uwb_assembly.md Full assembly notes: antenna clearance rules, IP44 seam description, stem positioning diagram (anchors at 450 mm + 700 mm), USB cable routing, complete BOM (~300 g total, tag ~130 g). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
205 lines
7.6 KiB
Markdown
205 lines
7.6 KiB
Markdown
# SaltyBot UWB System — Assembly Notes + BOM
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**Rev A — 2026-03-01 — sl-mechanical**
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**Issues: #57, #61, #62**
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---
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## System Overview
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Follow-me UWB ranging using 3× MaUWB ESP32-S3 modules:
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| Role | Qty | Location | File |
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|------|-----|----------|------|
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| Tag | 1 | Operator belt ("Tee") | `uwb_tag_enclosure.scad` |
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| Anchor | 2 | Robot stem, 250 mm apart | `uwb_anchor_mount.scad` |
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---
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## Antenna Clearance — CRITICAL
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The DW3000 UWB chip antenna requires:
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- **10 mm clear zone** around antenna — no metal, no carbon fibre, no metal-fill filament
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- Use **plain PLA or PETG** only in these parts (no conductive additives)
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- Tag lid has an **open window** directly over the PCB antenna area
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- Anchor bracket **back wall has a cutout** behind the antenna section of the PCB
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- When installing modules, orient antenna end **away from stem** (faces outward)
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---
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## Part A — UWB Tag Enclosure (`uwb_tag_enclosure.scad`)
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### Printed parts
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| 1 | `body` | 1 | PETG | 4 perims, 35% infill, 0.2 mm layer |
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| 2 | `lid` | 1 | PETG | 4 perims, 35% infill |
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| 3 | `tpu_bumper` | 1 | TPU 95A | 3 perims, 20% infill, 25 mm/s |
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> **Print orientation:** body — floor on bed; lid — inside face down; TPU bumper — flat.
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### Internal layout diagram
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```
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X− ←────────── ~75 mm ──────────→ X+
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┌──────────────────────────────┐
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USB → │[TP4056] [ 18650 cell ] │
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│─────────────────────────────│
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│ [ MaUWB ESP32-S3 PCB ] │ ← antenna faces UP
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└──────────────────────────────┘
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↑ ↑
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micro-USB LED window
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(charging) (Y+ face, small hole)
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Power switch cutout: Y− face, centred
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Belt clip: Y− face (back)
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```
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### IP44 seam
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Lid rim overlaps body 4 mm with a 2-turn labyrinth ridge (water must turn
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90° twice). No holes on the top face. All ports on side/back faces.
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**Not suitable for rain immersion — use for light splash protection only.**
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### Heat-set insert option
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For improved thread strength, replace M2 clearance standoffs with **M2 × 3 mm
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heat-set brass inserts** pressed into the standoff posts with a soldering iron.
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### Fasteners
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 4 | M2 × 6 BHCS | 4 | MaUWB PCB to standoffs |
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| 5 | M2 hex nut | 4 | Alternative if no heat-set inserts |
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| 6 | M3 × 8 SHCS | 2 | Belt clip to enclosure back |
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| 7 | M3 hex nut | 2 | Captured in clip back plate |
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### Assembly sequence — tag
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1. Install TP4056 board in body, micro-USB port aligned with cutout
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2. Solder TP4056 leads to 18650 spring contacts (or use 18650 holder PCB)
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3. Snap 18650 into battery cradle (+ end toward spring contact at X+)
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4. Seat MaUWB PCB on M2 standoffs; tighten M2 × 6 bolts (0.3 N·m — soft)
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5. Route USB data + power cable from MaUWB to TP4056 B+ / B− pads
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6. Press power switch into cutout (Y− face)
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7. Close lid — press corners until 4 snap clips engage (audible click ×4)
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8. Slide TPU bumper sleeve onto body from below
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9. Attach belt clip to Y− face with 2× M3 × 8
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---
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## Part B — Anchor Mounts (`uwb_anchor_mount.scad`)
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### Printed parts (per mount × 2 mounts)
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| # | RENDER | Qty per mount | Total | Material | Notes |
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|---|--------|---------------|-------|----------|-------|
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| 10 | `collar_front` | 1 | 2 | PETG | Flat-face-down; has thumbscrew recesses |
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| 11 | `collar_rear` | 1 | 2 | PETG | Has hex nut pockets + USB cable channel |
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| 12 | `bracket` | 1 | 2 | PETG | Flat-face-down; back wall on bed |
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### Anti-rotation
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The front collar half has a **flat tab** (3 × 8 mm radial tab at +X) that
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protrudes from the collar outer surface. This tab:
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- Bears against the module bracket arm, preventing rotation during clamping
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- Creates a positive mechanical register — mount always faces the same direction
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- No modification to the stem required
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### Anchor positioning on stem
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```
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TOP OF STEM
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│
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──┼── ← Sensor head (sensor_head.scad, at ~800–900 mm)
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│
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══╬══ ← Upper anchor (ANCHOR 2) ┐
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│ │ 250 mm
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══╬══ ← Lower anchor (ANCHOR 1) ┘
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│
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──┼── ← Battery carousel (stem_battery_clamp.scad)
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│
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BOTTOM OF STEM (base plate)
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```
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Recommended Z positions (above base plate):
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- Anchor 1: **450 mm** (just above battery carousel top)
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- Anchor 2: **700 mm**
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This places anchors in the mid-stem region, maximising horizontal separation
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from each other and from nearby metal (battery packs, base plate).
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### USB cable routing
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Each anchor is powered via USB-A from the Jetson Orin. Cable routing:
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1. Cable exits Orin USB hub, runs up stem through cable ties
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2. Enters anchor bracket through USB notch on left side wall
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3. Plugs into MaUWB USB-C port (programming and power)
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4. Excess cable loops into rear collar USB channel groove, held with a cable tie
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### Fasteners (per mount)
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 13 | M4 × 25 SHCS (thumbscrew head) | 2 | Collar clamping bolts (tool-free: slot for coin) |
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| 14 | M4 hex nut | 2 | Captured in rear collar half |
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| 15 | M4 × 10 set screw | 1 | Collar height lock (front half) |
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| 16 | M4 × 20 SHCS | 2 | Bracket to collar arm boss |
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| 17 | M4 hex nut | 2 | Under collar boss for bracket bolts |
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| 18 | M2 × 6 BHCS | 4 | MaUWB PCB to bracket standoffs |
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| 19 | M2 hex nut | 4 | PCB standoff nuts |
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### Assembly sequence — anchor (×2)
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1. Press M4 hex nuts into collar rear half nut pockets
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2. Press M2 hex nuts into bracket standoff counterbores
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3. Seat MaUWB PCB in bracket on M2 standoffs; tighten M2 × 6 BHCS (0.3 N·m)
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4. Bolt bracket to collar front-half arm boss with 2× M4 × 20
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5. Align anti-rotation tab with bracket arm edge
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6. Wrap collar halves around stem at desired height
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7. Align micro-USB / USB-C port direction, tighten M4 thumbscrews finger-tight
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8. Tighten set screw on front half to lock height
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9. Route USB cable through rear channel, cable-tie every ~100 mm along stem
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---
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## Full Mass Estimate
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| Part | Material | Est. mass |
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|------|----------|-----------|
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| Tag body + lid (PETG) | PETG | ~45 g |
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| Tag TPU bumper | TPU | ~12 g |
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| 18650 cell | Li-ion | ~47 g |
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| TP4056 + MaUWB PCBs | PCB | ~20 g |
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| Tag total | | **~130 g** |
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| Anchor collar set × 2 (×2) | PETG | ~80 g |
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| Anchor brackets × 2 | PETG | ~40 g |
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| MaUWB PCBs × 2 | PCB | ~30 g |
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| Anchor fasteners | SS | ~20 g |
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| **Total (tag + 2 anchors)** | | **~300 g** |
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---
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## Bill of Materials Summary
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| # | Description | Qty | Source hint |
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|---|-------------|-----|-------------|
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| A | MaUWB ESP32-S3 module | 3 | AliExpress / MakerFabs |
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| B | 18650 Li-ion cell (≥2000 mAh) | 1 | Panasonic NCR18650B or equiv. |
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| C | TP4056 micro-USB charger board | 1 | Standard TP4056 module |
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| D | Slide power switch 13×7 mm | 1 | SS-12D00 or equiv. |
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| E | M2 × 6 BHCS | 12 | (4 tag + 4 anchor-1 + 4 anchor-2) |
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| F | M2 hex nut | 12 | |
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| G | M3 × 8 SHCS | 2 | Belt clip |
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| H | M3 hex nut | 2 | |
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| I | M4 × 25 thumbscrew SHCS | 4 | Slot-head preferred for tool-free use |
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| J | M4 × 20 SHCS | 4 | Bracket-to-collar |
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| K | M4 × 10 set screw | 2 | Height lock |
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| L | M4 hex nut | 8 | |
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| M | USB-A to USB-C cable 1 m | 2 | Anchor power from Orin |
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| N | PETG filament | ~200 g | Any brand |
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| O | TPU 95A filament | ~30 g | For tag bumper |
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| P | Loctite 243 blue | 1 | Structural M4 bolts |
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| Q | Cable ties 100 mm | 10 | Stem cable management |
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