# Fabrication Plan — Tunable Snare Frame Array ## Maker Nexus Tools Required | Tool | Use | |------|-----| | Plasma cutter (Hypertherm 45XP or similar) | Frame flat blank + lug ears | | Slip-roll (e.g. Jet R-3 or Di-Acro 12") | Roll shell cylinders | | TIG welder (Miller Dynasty or similar) | Butt-weld cylinder seams | | Angle grinder + flap disc | Seam flush-grind + deburr | | Drill press | Lug holes in shells | | Brake press | Frame flange bends | | Belt grinder / file | Bearing edge chamfer | | Drum key, chromatic tuner | Head tensioning + pitch verification | --- ## Step-by-Step Sequence ### Stage 1 — Cut Blanks 1. Mark stock 1.0 mm CRS for three shell blanks; cut with plasma or shear: - Shell A: 798.0 mm × 60.0 mm - Shell B: 637.7 mm × 50.0 mm - Shell C: 477.5 mm × 40.0 mm 2. Mark stock 1.5 mm CRS for frame: 450.0 mm × 131.5 mm; plasma-cut three circular holes: - Drum A hole: ⌀256 mm at x=60, y=65.75 (center of 131.5 mm frame) - Drum B hole: ⌀205 mm at x=185, y=65.75 - Drum C hole: ⌀154 mm at x=310, y=65.75 - Also plasma: 12× M5 clearance holes (⌀5.5 mm) around each circle at ±20 mm from edge 3. Plasma 16× lug ear blanks from 1.5 mm CRS: 60 mm × 40 mm each. Mark fold line at 15 mm. 4. Deburr all plasma-cut edges with file/grinder. ### Stage 2 — Form Cylinders 5. Slip-roll Shell C (smallest) first as coupon. 3-roller setup; pass blank through at progressive settings until ⌀152 mm OD achieved. Measure OD with calipers or wrap tape measure. - Overshoot by 1–2 mm then spring back; iterate. 6. Check seam alignment: butt edges should meet flush within 0.5 mm gap. 7. TIG butt-weld seam: 1.0 mm CRS, 40A, DCEN, ER70S-6 filler. Tack 3 spots, then run seam bottom to top. Avoid warping — short passes, let cool. 8. Grind seam flush: flap disc until OD is smooth. Confirm OD within ±0.5 mm of nominal. 9. Repeat for Shell B, then Shell A (each progressively larger radius is easier to roll). ### Stage 3 — Bearing Edge + Lug Holes 10. File or belt-grind 45° × 1.0 mm chamfer on top rim OD of each shell. Run finger along edge — zero sharp burr acceptable. This is the head bearing edge. 11. Drill 4× (Shell C) or 6× (Shell A, B) M5 clearance holes (⌀5.5 mm) at 15 mm from top rim using drill press + V-block fixture to hold cylinder. Mark positions with transfer punch. 12. Deburr all holes inside and outside with countersink. ### Stage 4 — Form Frame 13. Brake press: bend top flange (20 mm) 90° inward at y = 25.74 mm from top edge of blank. 14. Brake press: bend bottom flange (20 mm) 90° inward at y = 25.74 mm from bottom edge. 15. Check flanges square with combination square. Both flanges fold toward drum-mounting side. 16. Fold 16× lug ear blanks: 90° bend at 15 mm mark (brake or vise + block). Base tab is 15 mm × 60 mm; ear body is 25 mm × 60 mm. ### Stage 5 — Weld Lug Ears to Shells 17. Position 4 ears (per Shell C) or 6 ears (per Shell A, B) on shell OD at lug hole positions. Align ear base tab with lug hole. Tack-weld. 18. Verify ear angle perpendicular to shell axis using square. 19. Complete weld all ears. ### Stage 6 — Assembly 20. Drop each shell into its frame cut-out. Lug ears pass through frame from drum side; M5 bolts secure from frame side. 21. Install counter-hoop and drum head: seat Remo Ambassador 6/8/10" onto shell rim; place counter-hoop; install tension rods through counter-hoop → lug → rod. 22. Finger-tighten all rods. Equalize with cross-tension pattern (see `tuning-notes.md`). 23. Install snare mechanism: snare wires lay across batter head bottom edge; thumb-wheel tensioner mounts to lug ear or dedicated bracket. ### Stage 7 — Tune and Validate 24. Tension drums to target frequencies (see `tuning-notes.md` and `validation.csv`). 25. Verify all acceptance targets in `validation.csv`. 26. Mark lug rod extension with paint pen at target tension for repeatability. --- ## Material Stock Required - 1.0 mm CRS sheet: 1× sheet 300 × 900 mm covers Shell A + B + C blanks - 1.5 mm CRS sheet: 1× sheet 500 × 500 mm covers frame + lug ear stock - ER70S-6 TIG rod, flap disc, M5 hardware --- ## Inspection Gates | Gate | Criteria | Point | |------|---------|-------| | Shell OD | ±0.5 mm of nominal after weld + grind | After Stage 2 | | Seam flush | < 0.5 mm proud | After Stage 2 | | Bearing edge | No sharp burrs; smooth 45° chamfer | After Stage 3 | | Lug holes | ±0.5 mm position; no raised burrs inside shell | After Stage 3 | | Frame flatness | < 1 mm bow over 450 mm span | After Stage 4 | | Head seating | Head seats with no visible gap around rim | After Stage 6 | | Pitch | Center fundamental within ±50 cents of target | After Stage 7 |