AutomaticRecordDigitalizer

Sourcing pass, September 2026 — corrections to the bill of materials

Every line of docs/04-bill-of-materials.md priced against live German shop pages on 10 September 2026, incl. 19 % VAT, delivered to Germany. Amazon.de and Conrad.de block automated fetching, so they were excluded rather than guessed at.

The itemised result, with product links and three ways of ordering it, is in bom-shopping-list.md.

The headline: the BOM’s estimate of ≈ 865 € holds up in aggregate, but only because it is the sum of two large errors in opposite directions plus a lot of accurate lines. The corrections below have been absorbed into the repo docs.

Corrections

Micro linear servo: 12 € is wrong by 10×

Material · affects docs/04-bill-of-materials.md

No sub-30 € linear servo is in stock at any German or EU shop. Verified: Actuonix PQ12-S 123,49 €, MightyZAP 6N 90,95 €. An MG996R metal-gear servo at 6,65 € driving the existing printed pusher rod does what the cue lever needs — a bracket change, not a design change.

Vacuum switch: the 12 € sensing set cannot cover it

Material · affects docs/04-bill-of-materials.md

Industrial vacuum switches start at 95,30 € in Germany. An Adafruit MPRLS absolute-pressure breakout at 30,90 € plus a software threshold replaces it — but see the open question below, because it moves where the check lives.

The solenoid valve must be direct-acting

Important · affects docs/04-bill-of-materials.md

Pilot-assisted valves (the common 2V025 type) do not open at zero differential pressure, i.e. under vacuum. Verified suitable: 2/2-way G 1/8″ NC, FKM, 12 V, direktgesteuert, 0–16 bar — 42,44 €.

Motedis cannot supply the extrusion

Important · affects docs/04-bill-of-materials.md

It is named first under suggested sources, but Motedis carries no V-slot profile at all — only B-Typ Nut 6 and I-Typ Nut 5, which have no wheel-running surface. Use shop.bohrers.de at 12,90 €/m, or Dold at 14,00 €/m plus a 0,50 € cutting fee.

The computer becomes a Raspberry Pi 4B rev 1.1, 2 GB

Change of plan · affects docs/03-electronics-and-software.md

Already owned, two of them. One CSI port instead of two, so the wrist camera takes the USB branch the doc already sanctions and the CSI-HDMI extender leaves the BOM entirely. WAVs go to an external USB 3.0 SSD, never the card — about 860 MB per side, 40 GB per magazine. Everything USB on a powered hub with udev-pinned device names. rev 1.1 refuses e-marked USB-C cables.

Where does the GRIP post-condition live now?

Material · affects docs/06-open-questions.md

docs/03 puts the vacuum switch on a controller end-stop input and has GRIP wait on it inside Klipper. An MPRLS is an I²C device on the Pi, so that check moves to the orchestrator and a failed grip no longer aborts inside the motion queue. Either keep a cheap digital switch purely as the Klipper interlock, or accept the latency and document it. Needs deciding before anything is wired.

Are 720p label photographs enough for Discogs matching?

Change of plan · affects docs/06-open-questions.md

The wrist camera now tops out at 720p. If the tagging stage needs better, the answer is a static high-resolution label camera at the station — not a heavier camera on the moving wrist.

Donor table: three corrections

Change of plan · affects docs/04-bill-of-materials.md

Add the Ender 3 Max Neo near the top — 300×300 frame, dual Z with two motors, 32-bit board, 350 W supply. Add the Ender 3 S1 family as avoid: its frame is smooth-faced extrusion, not open V-slot, so frame and wheels are useless here. And note that TMC drivers on Creality 4.2.x boards are soldered down, so they cannot be harvested.

Raspberry Pi 4B: the gotchas worth reading before wiring

• rev 1.1 boards refuse power from e-marked USB-C cables — use the official supply or a plain cable. Verify the board with cat /proc/cpuinfo, which should show a03111.
• rev 1.1 puts the SD-card voltage regulator on the underside next to the slot, where it is easy to knock off. Set the card up once and leave it alone.
• Inside a closed electronics box under sustained vision load, a Pi 4 wants a heatsink and a fan.
• The Pi 4 budgets roughly 1.2 A across all four USB ports. Put the Scarlett, the SSD, the webcam and the relay card on a self-powered hub, and pin every device with a udev rule so /dev/video* and the ALSA card index do not shuffle across reboots.
• Do not run the Pi from the servo’s 5 V buck converter: an MG996R stalls at about 2.5 A and will brown the Pi out.
• CPU is roughly 2 to 2.5× less than a Pi 5. The workload absorbs it because the only sustained vision load is the deck camera tracking the headshell in a known ROI — keep those frames at about 640 × 480, 10–15 fps, and process the 12 MP label shots one at a time.

Errata from the consistency check, 14 September 2026

Checking the bill of materials against cad/params.py and the planner’s actual travel changed these lines after the pricing pass. The shopping list above still shows the lengths as priced; order these instead.

• 2040 cross beam: 940 mm, not 800. The frame is 860 mm wide over the panels and the X carriage plates sit outside it. The 800 mm cut is the concept’s 80 cm frame, which the CAD widened to 86 and the cut list never followed. Same profile, same shop; about 2 € more.
• 2020 end tie: 880 mm, not 800, over the two X beams. Still cut from the 1 m length.
• End panel: 842 × 830, not 800 × 830. It sits between the side panels’ inner faces.
• Plywood: two 1500 × 3000 sheets, not one — panels on one, both carousel discs on the other — and a third if the bench top is cut rather than existing.
• V-wheels: 12, not 9. Four per carriage plate, three plates, six eccentric spacers as priced.
• A 24 → 12 V buck, about 3 €, was missing altogether: the pump, the valve and the LED strip are 12 V parts and the list has only a 24 V supply and a 5 V buck.
• Cable chain: three chains, 700 + 600 + 600 mm. The Y carriage travels 625 mm along the cross beam, which the concept forgot. The 3 m priced covers it with a metre spare.
• PU tube: 7 m, not 5. With the electronics on the frame the run from the pump to the cup is 4.5 m with wiggle room, and a 2.1 m stub carries the vacuum to the pressure sensor beside the Pi.
• Not on the list at all: about 6 m of 4-core, 12 m of 3-core and 4 m of 2-core extension wire, because the motors come with about 1 m of lead and the sensors with none; a 2 m USB 2.0 A-to-A extension for the wrist camera; and a 3 m USB-C cable from the Pi to the Octopus, now that the two sit at opposite ends of the frame. The 0.5 m camera ribbon is right: the Pi mounts on the deck-end panel, 30 cm from the camera. The routed lengths are tabulated in docs/08-assembly-instructions.md.

Decided since, 14 September 2026

• The GRIP post-condition lives in the orchestrator, on the MPRLS alone; no switch, no Klipper interlock. docs/05-design-decisions.md.
• The electronics sit on the frame, not in a box; the Pi is on the deck-end panel and the 0.5 m camera ribbon is right.
• 720p label photographs: still to be tried on a batch. The 1080p webcam already on hand is the first fallback.

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