# Fabrication Plan — Modular Pedestal Drum Stack Keyed to Maker Nexus tooling. Total estimated shop time: 18–22 hours including finishing and final assembly. ## Sequence overview ``` [1] CUT → plasma + shear ↓ [2] DEBURR → bench (edge sander, scotch-brite) ↓ [3] FORM → slip-roll + finger brake + lathe ↓ [4] JOIN → TIG weld ↓ [5] DRESS → bench grinder + flap disc + polish ↓ [6] DRILL → drill press (lug holes) ↓ [7] FINISH → spray booth (clear or matte black) ↓ [8] ASSEMBLE → hardware install, head + hoop, tension to target Hz ↓ [9] INSPECT → acoustic + ergonomic + safety per validation.csv ``` ## Phase 1 — Cut (plasma, ~3 h including queue) - Mount 24" × 48" × 1.2 mm CRS sheet on plasma bed. - Load `cnc/shells-and-brackets.dxf` nest. - Verify origin and material file ("Mild Steel 18 ga, Hypertherm 45A"). - Run nest — 5 shell blanks + 15 bracket blanks. - Reload bed with 16" × 16" × 6 mm 1018 plate. - Cut base plate disc + tapped-hole pilots. - Reload bed with five 1 m lengths of 3 mm × 18 mm flat bar OR shear strips from a 3 mm sheet. ## Phase 2 — Deburr (~1 h) - Edge-sander all blank perimeters. - Scotch-brite all faces. - Light file on hole perimeters. - **Stop and inspect:** No burrs. No corners > 0.3 mm radius. Mark each blank with part name in marker. ## Phase 3 — Form (~5 h) ### 3a. Roll shells Refer to `cnc/setup-sheet.md` slip-roll chart. 1. Calibrate slip-roll: bend a test scrap of 1.2 mm CRS to a 50 mm radius (drum-5 spec). Check spring-back. Adjust roller pre-load until spring-back < 5°. **If spring-back exceeds 5° on the test, drop drum-5 to 1.0 mm stock and re-cut that blank.** 2. Roll drum-1 first (easiest): 3 pre-bend passes, then full curl. Cylinder should close with a 3 mm overlap; trim to butt fit. 3. Roll drums 2-5 in order, smaller = trickier. ### 3b. Roll counter hoops Same procedure for 3 mm × 18 mm flat bar. Roll to drum OD, trim to butt fit. ### 3c. Bend internal brackets Finger brake, 90° bends at 20 mm and 40 mm marks. Make 1 test piece first to verify bend allowance from `bend-table.csv` (~3 mm BA per 90° bend in 1.2 mm CRS). ### 3d. Turn pole socket 50 mm round bar 1018, ~50 mm length. In 3-jaw chuck: 1. Face one end. 2. Drill ⌀25.2 mm bore through. 3. Turn OD to 40 mm. 4. Part off to 30 mm length. 5. File chamfer top and bottom. ## Phase 4 — Join (TIG, ~5 h) ### 4a. Shell seams (5×) Per `cnc/setup-sheet.md` TIG settings. 1. Tack at 4 points (12, 3, 6, 9 o'clock) — clamp in a V-block fixture. 2. Inspect tack alignment — gap should be 0–0.3 mm with no overlap. 3. Continuous root pass closing the seam in a single direction. 4. **Stop and inspect:** No porosity visible. Weld height ≤ 1.5 mm. Shell roundness deviation < 1.0 mm (indicator-check on a surface plate). ### 4b. Counter hoop seams (5×) Same as shells but smaller. Faster — these can be lap-or-butt depending on slip-roll precision. ### 4c. Internal brackets to shells (15×) Each shell gets 3 brackets at 120° spacing inside, set at the shell mid-height. Tack each bracket at 3 points (top, bottom, middle of the U-channel back) using a fixture to hold the bracket flush to the inner shell wall. ### 4d. Base plate to socket Tack socket centred on base plate, gap-check 0 mm. Run continuous 3 mm fillet all the way around the socket-plate joint. Flip plate, run a partial fillet on the underside (3-5 mm tacks every 60°) for redundancy. ## Phase 5 — Dress (~2 h) - Grind shell seams flush with parent material using a bench grinder + flap disc. - Sand inside of shell to remove weld spatter. - File any sharp edges on the inward bearing-edge chamfer. ## Phase 6 — Drill lug holes (~1 h) - Use a laser-cut paper template wrapped around each shell to mark 6 lug positions evenly at 35 mm above the bottom edge. - Drill ⌀5.5 mm holes with a drill press; back the hole with a wood block inside the shell to prevent burring. - Each lug needs 2 holes 25 mm apart vertically — drill the second row 25 mm below the first. - Total: 12 holes per drum × 5 drums = 60 holes. ## Phase 7 — Finish (~2 h work + 24 h cure) - Wipe all parts with acetone. - Hang in spray booth. - Apply 2 coats of satin-clear urethane OR matte-black 2K. The clear lets the weld lines and steel texture show; the black hides imperfections and matches professional drum-kit aesthetics. Pick one. - Cure 24 h at room temp before assembly. ## Phase 8 — Assemble (~2 h) 1. Slide pole through base socket; tighten setscrews on a flat lower mount. 2. Slide drum-1 (largest) onto pole at the lowest position; align with rubber puck below; tighten the 2 bracket setscrews into the pole. 3. Repeat for drums 2-5 in ascending order. 4. For each drum: - Install 6 lugs with M6 screws (use Loctite blue on threads). - Drop head onto bearing edge. - Drop counter hoop over head flesh-hoop. - Hook the 6 claws over the counter hoop. - Install 6 tension rods with nylon washers. - Hand-tighten + 1/4 turn per rod, star pattern. 5. Tune each drum per `tuning-notes.md` procedure. ## Phase 9 — Inspect Run through `validation.csv` row by row. Fill the `measured` column. Anything in `pending` state is a gate the next round must satisfy before the instrument is declared v0.2-physical. ## Tool-skill matrix | Tool | Skill required | Alternative | |---|---|---| | Plasma CNC | basic operator | manual shear + jigsaw (slow) | | Slip-roll | intermediate | small ring-roll for hoops; shells need slip-roll | | TIG welder | intermediate-advanced | MIG ok for shell seams if cleaned up; TIG for brackets | | Lathe | basic | hand-file the bearing edge (much slower, less consistent) | | Drill press | basic | hand drill with guide | | Spray booth | basic | brush-on enamel (lower finish quality) | If TIG access is unavailable: the entire welded-seam architecture can be swapped for **lap-and-rivet** construction (sheet-metal screws or pop rivets at the seam), with a polymer sealant in the lap to prevent rattle. This is a v0.2 fabrication alternative; document if substituted.