Optical QC: plate every 5 records, how plates avoid scratching

User, 19 Oct 2026: one plate every 5 records; how do we make sure the
plates don't scratch the records.

- Plate every 5 (10 per 50-record stack, ~15 kg a stack).
- Scratch rules: groove-guard profile keeps grooves off the plate (QRP);
  plate flat, larger than the record (306 to 310 mm), deburred; clear
  anodised (cost estimate, CNY 16 to 28/m2 China reference); vertical
  handling only; no grit (trimmer extraction, ionised blow-off and wipe
  on return, covered carts and racks); numbered plates, monthly check;
  station compares scratches on plate faces vs record faces.
- About 700 plates for a 24 h queue (25 sheets, THB 245k to 315k cut,
  + 35k to 105k anodising, estimates); 200 to 260 for 8 h.
- Plate trial adds bare vs anodised and the scratch comparison.

docs/equipment/inline-optical-qc.md

@@ -429,34 +429,68 @@ October 2026).
     Record Pressing pulls the spindle at 50
     ([VRTX](https://vrtxmag.com/articles/how-to-press-vinyl-locally)).
     Fifty 180 g records weigh 9 kg; a day of output is about 58 stacks.
-  - **A flat aluminium cooling plate every 10 records** to start with, as
+  - **A flat aluminium cooling plate every 5 records** (decided October
-    at MY45 ([oberflaeche.de](https://oberflaeche.de/en/knowledge/topics/electro-plating/a-vinyl-renaissance/the-great-comeback-of-the-record-3));
+    2026), so 10 plates in a stack of 50. MY45 lays one every ten
-    Mobineko lays one under every record
+    ([oberflaeche.de](https://oberflaeche.de/en/knowledge/topics/electro-plating/a-vinyl-renaissance/the-great-comeback-of-the-record-3)),
+    Mobineko one under every record
     ([Mobineko](https://mobineko.com/vinyl-quality-standards)). The
     Classic places the plates itself ("automatic cooling plate handling",
     [Newbilt](https://vinyl-pressing-plants.com/blog/newbilt-classic-12-inch-vinyl-record-press));
     at the Duplex the operator lays one by hand. Full flat discs, not ring
     spacers: a warm record held only round the label sags into a dish.
-  - **Plates cut locally.** 5052 aluminium (5083 if they are anodised),
+    A stack then weighs about 15 kg: 9 kg of records and 10 plates of
-    3 mm thick, with the diameter and centre hole of Newbilt's plate so
+    0.6 kg at 3 mm (0.4 kg at 2 mm).
-    the Classic's magazine takes them; thickness and alloy are our
+  - **Plates cut locally.** 5052 aluminium, 3 mm thick, with the centre
-    estimate until Newbilt's drawing arrives. A 1220 × 2440 mm sheet nests
+    hole of Newbilt's plate so the Classic's magazine takes them;
-    28 discs of about 305 mm, and a 3 mm sheet costs about THB 8,300
+    thickness and alloy are our estimate until Newbilt's drawing arrives.
-    before VAT
+    A 1220 × 2440 mm sheet nests 28 discs of up to about 310 mm, and a
+    3 mm sheet costs about THB 8,300 before VAT
     ([OneStockHome](https://www.onestockhome.com/th/product_categories/aluminum-sheet-thickness-3-mm),
     grade 3003, October 2026): about THB 300 of metal a plate, THB 350 to
     450 with cutting and deburring (estimate). Cut on a fibre laser or a
     waterjet. Chiang Mai has several laser shops (SK Laser Cut and Laser
     CNX on Rattanakosin Road, among others), but many cut only acrylic and
-    wood, so ask for 3 mm aluminium. Edges and the centre hole are
+    wood, so ask for 3 mm aluminium.
-    deburred and rounded, because a burr marks the record. Every plate is
+  - **Keeping the plates from scratching the records:**
-    checked on a surface plate (no gap over 0.1 mm, our target).
+    1. **The grooves never touch the plate.** Record dies have a thick
-  - **How many:** one plate per 10 records over the full 24-hour queue
+       label area matched by a thick outer edge, so pressed records stack
-    needs about 350 plates (13 sheets, THB 120,000 to 160,000, estimate);
+       without the groove area touching while they cool
-    an 8-hour queue about 100 to 130. Two sheets come first, for the
+       ([Quality Record Pressings](http://qualityrecordpressings.com/index.cfm?go=Record-Weights)).
-    plate trial (next steps).
+       A flat plate rests on the same two rings. That holds as long as the
-  - **Clean plates:** dust on a plate ends up on the record, so the plates
+       plate is flat (checked on a surface plate, no gap over 0.1 mm, our
-    are wiped on their way back to the presses and kept covered.
+       target) and the Newbilt dies have this profile (to confirm).
+    2. **The plate is larger than the record,** about 306 to 310 mm
+       against 302 mm, so the record's rim sits on the flat face and never
+       on the plate's edge. All edges and the centre hole are deburred and
+       rounded; the centre hole sits under the label.
+    3. **Clear anodised** (about 10 to 15 µm): a hard, closed surface
+       that does not smear grey aluminium onto the record and keeps its
+       finish longer. Roughly CNY 16 to 28 a square metre in bulk in China
+       ([YF CNC](https://yfcncmachining.com/reference-price-for-domestic-surface-treatment-in-china/));
+       THB 50 to 150 a plate for a small Thai batch (estimate). The first
+       two sheets test bare against anodised.
+    4. **Straight up and down only.** Records and plates go onto the
+       spindle and come off it vertically; nothing slides across a
+       record. Lint-free gloves, plates lifted by the rim that stands out
+       past the record.
+    5. **No grit between them.** Grit trapped under 15 kg is what
+       scratches. Flash from the edge trimmer goes into the trimmer's
+       extraction, not onto the stack. Each plate passes an ionised-air
+       blow-off and a wipe on its way back to the presses, plates travel
+       on a covered spindle cart, and the racks are covered.
+    6. **Plates are numbered** (laser mark on the band outside the
+       record) and looked at under a raking light every month; a dented
+       or scratched plate is taken out.
+    7. **The station proves it.** It knows each record's place in the
+       stack, so it can compare scratch counts on faces that lay on a
+       plate with faces that lay on another record. If the plate faces
+       come out worse, the plates are the cause.
+  - **How many:** one plate per 5 records over the full 24-hour queue
+    needs about 700 plates (25 sheets): THB 245,000 to 315,000 cut, plus
+    THB 35,000 to 105,000 for anodising (estimates). An 8-hour queue
+    needs about 200 to 260. Ask Newbilt how many plates come with the
+    Classic. Two sheets come first, for the plate trial (next steps).
+
 - **At the station.** The finishing operator takes each record off the
   cooled stack and puts it on the infeed, and lifts each cooling plate
   onto the plate cart that goes back to the presses. Good records leave the outfeed
@@ -605,11 +639,13 @@ vision share is not yet confirmed.
    cycle, side; see [digital factory](../digital-factory.md)).
 4. **Warp sensors.** Choose between two point lasers and a line profiler
    once the trials show whether a thickness map is worth the extra cost.
-5. **Plate and settling trial.** Cut two sheets of plates (56). Press one
+5. **Plate and settling trial.** Cut two sheets of plates (56), half of
-   job with a plate every 5, 10 and 25 records, and read edge run-out and
+   them anodised. Press one job with a plate every 5, 10 and 25 records,
-   dish on the station after 1 hour and after 24 hours. That sets the
+   and read edge run-out and dish on the station after 1 hour and after
-   records per plate (black, colour and specials apart) and shows whether
+   24 hours, plus the scratch counts on plate faces against record faces.
-   a 1-hour reading predicts the settled one.
+   That confirms 5 records per plate or shows that 10 is enough (black,
+   colour and specials apart), and shows whether a 1-hour reading
+   predicts the settled one.
 6. **EtherCAT bench.** Before the frame is built, run one A6-EC kit, the
    EK1101 with its terminals and the spindle encoder from the mini PC
    with qitech_lib on EtherCrab: eight tests and pass marks are in the