Chapter 03 — Build plate¶

One page per step

Read this chapter one step per page — big pictures, prev/next, and the same tick marks. This page is the whole chapter in one scroll.

Prepares the 355×355×10 mm heated plate and bolts it to the bed extrusions, so the frame has its datum surface and the plate's three leads lie loose above the deck, ready for the bed WAGO breakout in Ch 09.

What you're building in this chapter: the heated bed, as a stack of four things. The build plate is a cast, ground aluminium slab with a mains-powered silicone heater pad and a 125 °C thermal fuse already bonded to its underside — both are factory-fitted on this kit, so two of the official manual's pages become inspections. On top of it you laminate the magnetic pad, an adhesive magnetised sheet, and onto that drops the flex plate: removable spring steel, the surface prints actually stick to and the reason you can pop a finished part off by flexing it. The whole stack sits on four thumb-nut spacers on the two bed extrusions from Ch 01, held by four bolts of which only one is ever tightened — the other three let a 355 mm aluminium plate expand as it heats instead of buckling. Nothing is wired here; the plate's three short leads stay loose above the deck, for the bed WAGO breakout Ch 09 fits on the left bed extrusion.

Revali checking with a magnifier — The bed is your datum. A wave you ignore today will introduce itself in every print.

Time: 1.5–2.5 h hands-on, first build (survey §7.2).

Sessions: 4 × ~30 min — the Pause: lines below break the chapter into 4 segments; every minute figure is a first-build estimate.

Prerequisites:

Ch 01 — Frame. Squared, and the bed extrusions positioned with 65 mm from the centreline to each inner face — a 130 mm clear gap, 150 mm centre-to-centre (manual p.20; Ch 01 Step 01.19).
Ch 02 — Z drives and idlers. Deck panel and deck supports fitted (manual p.28–29); the wire opening in the deck must be clear and unobstructed.
Printed parts: none. No print batch gates this chapter. The 2.4r2 mounts the plate straight onto the bed extrusions with metal hardware — there are no printed feet, bed mounts or spacers anywhere in p.52–61. The bed WAGO mount is supplied printed by LDO and is fitted in Ch 09, not here.

Tools

Hex 2.5 mm
Plastic scraper, squeegee or an old credit card (magnet application)
Sharp craft knife with a fresh blade (trimming the magnet at the bolt holes; cutting the liner at Step 03.9)
Masking tape (marking the back edge at Step 03.2; the hinge for the magnet at Step 03.9)
Steel rule or straightedge ≥360 mm (flatness check and the 38 mm offset)
Digital caliper

Consumables: IPA ≥90%, lint-free cloth, nitrile gloves. The plate's protective film goes in the bin.

Printed parts

STL	Qty	Colour
— none —	0	—

Hardware (chapter totals)

Fastener / part	Qty	Note
Build plate, cast 5083, 355×355×10 mm, heatpad and 125 °C fuse pre-applied	1	LDO 350 Rev D BOM
Magnetic Pad 2.4-350	1	applied in this chapter
Spring Steel Flex Plate 2.4-350	1	drops on, no fasteners
M3×20 SHCS	4	not the manual's M3×16
M4 knurled thumb nut	4	used as the spacer, not as a nut
M3 roll-in T-nut, 2020	4	bed extrusion top slots
M4×6 BHCS (bed PE)	0: pre-fitted to the plate	verify only, do not remove (washer: verify on bench)

Read first

The heater pad (p.55) and the thermal fuse (p.56) are already on your plate. Both pages are verify-only. Do not peel, re-seat or re-bolt anything. src
Trim the magnet at the four bolt holes immediately after you roll it down and before you bolt anything. Discovering it at p.59 means peeling the magnet or drilling through it (survey §5.2 W6).
Use M3×20 SHCS, not the manual's M3×16 — this plate and these spacers are thicker. src
The magnet goes on with the hinge method at Step 03.9 — one shot; read the whole step before you peel anything.
Only one of the four bolts gets tightened (p.59). A bed clamped hard at all four corners while cold, then heated fast, tacos.
A part missing, damaged or wrong: stop, photograph it and ask Fabreeko. Questions about LDO's own parts go to #ldo_motors. Both are set up at Step 00.31.
No wiring happens here, and no bed lead goes through the deck. Manual p.60 feeds the bed wires through the opening; this kit's plate leads end at the bed WAGO breakout above the deck (Ch 09), and only the kit's extension leads go below, in Ch 10. Leave the three leads loose above the deck. src

Sources for this chapter:

Voron 2.4r2 assembly manual (pinned de7e89d) pages 52–61 — plate orientation, magnet, bed-extrusion verification, spacers, the DON'T TIGHTEN rule
LDO Build Notes (Rev D) — p.55 and p.56 skipped (heater and fuse pre-applied), M4×6 PE screw, M3×20 instead of M3×16, trim the magnet now
LDO 350 Rev D BOM — plate, magnetic pad, flex plate and thermal-fuse line items
LDO wiring guide § Wiring the Bed Heater — where the three bed cables actually terminate (Ch 10)
magnet lamination demo — the lamination demo the manual links from p.54
survey §5.2 W6
The two mirrored images in this chapter, the plate's underside at Step 03.4 and the build-plate mapping at Steps 03.14 and 03.19, are LDO Motors', used with attribution; see assets/remote/03-build-plate/SOURCES.txt and assets/remote/10-wiring/SOURCES.txt. Each original URL stays on its step's Source: line.

Video coverage (Steve Builds, pre-release LDO kit — differs from Rev D+): Part 1 @0:45:02 (+5m)

Step 03.1 — Unpack the plate and read the end state¶

What you're looking at: Manual p.52: the finished bed and its three parts. The build plate is a 355 × 355 × 10 mm cast aluminium slab with the AC heater pad bonded underneath. The magnetic pad laminates on top. The flex plate is the removable spring-steel print surface.

Parts:

staged: build plate ×1
staged: magnetic pad ×1
staged: spring steel flex plate ×1

Do: Take the plate out flat, never on edge; a dropped corner dents a 10 mm cast slab. Lay it on a clean towel. It ends up on the two bed extrusions, cables above the deck.

Check

Three cables leave the plate at the back-centre edge, with the M4×6 PE screw beside them. Washer type (verify on bench).

Source: Voron manual p.52 · LDO 350 Rev D BOM · Video: Part 1 @0:44:56

Step 03.2 — Work out which side is which¶

What you're looking at: Manual p.53: the plate's two faces. The top is the one whose four corner holes are counterbored, a pocket that lets the bolt head sit below the surface. The bottom carries the heater, the thermal fuse and the earth screw.

Parts:

staged: build plate
consumable: masking tape
staged: M3×20 SHCS ×1, fit test, back in its tray

Do:

Find the four corner mounting holes. The counterbored face is the top.
The face carrying the heater, thermal fuse and PE screw holes is the bottom.
Mark the back edge, where the cables leave, with masking tape.

Check

Drop an M3×20 SHCS into a corner hole from the top; the head sinks into the bore. From the other side it stands proud.

Helper: Points to the magnet side and the heater side and names each one.

Source: Voron manual p.53

Step 03.3 — Strip the protective film¶

What you're looking at: Manual p.54: the ground top face under its protective film. The face is Blanchard-ground, the swirl pattern you will see. The film has to come off before the magnet; adhesive will not bond through it.

Parts:

staged: build plate

Do: Peel the blue/clear protective film off the top face and bin it. Work from one corner; do not use a metal tool on the ground surface.

Check

No film left in the counterbores or under the edges. The ground surface is bare metal, matte, with visible Blanchard swirl.

Caution

Rev D+ / LDO: the manual never mentions the film — LDO adds this. Remove it now; the magnet will not bond through it. src

Source: Voron manual p.54 · LDO Build Notes (Rev D)

Step 03.4 — Verify the heater pad (do not apply one)¶

What you're looking at: Manual p.55 shows the official manual applying a heater pad, a page you skip. The LDO photo beside it is your plate from below: the silicone AC pad bonded and screwed down, the thermal-fuse patch, the cable exit. Compare layout, not ratings.

Parts: none.

Do:

Turn the plate bottom-up.
Confirm the AC heatpad is flat and centred: no lifted corner, wrinkle or trapped air.
Confirm every pad screw is present. Do not tighten them, add adhesive or re-press a lifted edge.

Check

Pad flat and centred; every pad screw present and untouched, head type (verify on bench); nothing peeling at the cable exit.

Helper: Counts the pad screws aloud and points out any lifted corner.

Caution

Rev D+ / LDO: SKIP manual p.55 entirely — the heater pad is pre-applied on Rev C and later kits. This step is inspection only. If the pad is genuinely lifting, stop and raise it in #ldo_motors before you bolt the plate in. src · wiring guide § Wiring the Bed Heater

Source: Voron manual p.55 · LDO Build Notes (Rev D) · LDO wiring guide § Wiring the Bed Heater · image: LDO build_plate_bottom_view.jpg

Step 03.5 — Verify the thermal fuse (do not fit one)¶

What you're looking at: Manual p.56, the fuse installation you skip. The thermal fuse is a one-shot cut-out that opens permanently at 125 °C, wired in series with one heater lead, so a runaway heater loses supply. It works only pressed flat against the aluminium. See the glossary.

Parts: none.

Do:

Find the 125 °C thermal fuse on the bottom face by the cable exit.
Confirm its body is pressed flat to the aluminium, its single screw and washer tight.
It is wired in-line with one heater lead.

Check

Fuse flat to the plate, screw tight, no strain on either leg of the fuse where it joins the heater wire.

Caution

Rev D+ / LDO: SKIP manual p.56 entirely — the fuse is pre-installed. Inspect only; the page's M3×12 SHCS and M3 washer are not needed. src

Source: Voron manual p.56 · LDO Build Notes (Rev D)

Step 03.6 — Verify the PE screw and identify the three cables¶

What you're looking at: Manual p.57: the plate's cable exit. Three cables leave here: two thick braided AC leads, N and Bed L, and one thin two-pin BED TH thermistor cable. Beside them the protective-earth M4×6 BHCS bonds the plate to earth. Washer (verify on bench). See the glossary.

Parts: none.

Do:

Identify the three cables at the back edge: N, Bed L, and the BED TH ATC Semitec 104NT thermistor.
Find the M4×6 BHCS beside them, the bed PE point.
Leave it in place until Ch 10.

Check

Three labelled cables, no chafe or cut in the braid, no exposed conductor. PE screw present, snug.

Caution

Rev D+ / LDO: the manual calls for an M3×6 BHCS you supply. Your plate ships with an M4×6 BHCS already attached — use that one. src

Caution

Rev D+ / LDO: do not wire the PE, the heater leads or the thermistor here. The bed harness is a breakout design: the plate's L and N land on the bed WAGO mount above the deck and its thermistor on the 2×2 XH splicer PCB, both in Ch 10; extension leads carry on below. src

Source: Voron manual p.57 · LDO Build Notes (Rev D) · LDO wiring guide § Wiring the Bed Heater

Good stopping point · ~30 min since the last one

the plate is unpacked and identified top from bottom, the film is off, and the pre-applied heater, thermal fuse and PE screw are all inspected and left alone. The magnet is still in its backing. Do not start Step 03.9 until you can run 03.8–03.10 straight through: the magnet is a one-shot lamination.

Step 03.7 — Check the plate for flatness before the magnet goes on¶

What you're looking at: The bare ground face and a straightedge. This is the last moment the aluminium is visible. Once the magnet is on, a dish or crown can only be inferred from a bed mesh, and neither mesh nor quad gantry level corrects it.

Parts:

staged: build plate
tool: steel rule or straightedge

Do: Stand the straightedge on edge on the ground face and sight against a light: one diagonal and one centreline, two minutes. Do it now; once the magnet is on you cannot inspect this surface again.

Check

No daylight under the straightedge. Flatness tolerance is not specified; raise it in #ldo_motors only if a sheet of paper slides under.

Helper: Holds a torch behind the straightedge and says if any light shows under it.

Tip

a cast, Blanchard-ground 5083 plate is deliberately thick and stress-relieved; a visible dish here does not get corrected by mesh or QGL later. src

Source: Voron manual p.53 · LDO 350 Rev D BOM

Step 03.8 — Clean the top face¶

What you're looking at: The top face, IPA and a lint-free cloth. Oil, dust or a fingerprint left on the surface becomes a permanent bump under an adhesive sheet you cannot lift again.

Parts:

staged: build plate
consumable: IPA
consumable: lint-free cloth
consumable: nitrile gloves

Do: Wipe the whole top face with IPA and let it flash off completely, so no solvent is trapped under the adhesive. Wear gloves from here on.

Check

Surface dry, no lint, no residue in the counterbores.

Helper: Holds the plate flat on the towel and checks afterwards for missed patches.

Source: Voron manual p.54

Step 03.9 — Apply the magnet sheet¶

What you're looking at: Manual p.54 and the magnetic pad: a flexible sheet of magnetised rubber with a pressure-sensitive adhesive back under a liner. Laminated to the plate, it holds the spring-steel flex plate down. On this kit it is a separate BOM line, not factory-applied.

Parts:

Magnetic Pad 2.4-350 ×1
consumable: masking tape
tool: plastic squeegee or card
tool: knife or scissors for the liner

Do:

Position the pad on the plate, liner down, and tape the back edge as a hinge.
Fold it back, peel and cut 40–50 mm of liner, squeegee it, then draw the liner out and press the sheet down.

Check

No bubbles, no wrinkles, pad square to the plate edges, borders even all round.

Tip

measure the pad first (verify on bench): at 355 mm lay it edge-flush to the back edge and one side; if smaller, centre it and note the border.

Tip

lift the first strip immediately if it lands crooked; past a few centimetres it will not reposition. Bubbles worked to an edge come out, ones in the middle do not.

Tip

The liner side is the adhesive; the plain rubber face is the magnet. Keep the unlaid pad lifted so adhesive never touches ahead of the squeegee.

Caution

Rev D+ / LDO: the magnetic pad is a separate line item in the 350 Rev D BOM — it is not laminated at the factory, unlike the heater and fuse. If your plate did arrive with the magnet already on, skip to 03.10 and check whether the four bolt holes are already cut. src

Source: Voron manual p.54 · LDO 350 Rev D BOM · magnet lamination demo

Step 03.10 — Trim the magnet at the four bolt holes¶

What you're looking at: The laminated magnet with four dimples where the plate's counterbored corner holes sit underneath. The mounting bolts pass through those holes and a hex key has to reach their heads, so the magnet is cut away over each one.

Parts:

reused: the applied magnetic pad
tool: sharp craft knife
staged: M3×20 SHCS ×1, fit test
tool: 2.5 mm hex key

Do:

Press down to find the four counterbored holes as dimples.
Cut the magnet away over each one, following the bore, in light repeated passes.
Do not gouge the aluminium; a burr stops the bolt head sitting flush.

Check

All four bores fully open. Test each with an M3×20 SHCS and the hex key before you go anywhere near the frame.

Caution

Rev D+ / LDO: LDO's note at p.54 exists because the magnet gets applied here and the bolts do not go in until p.59. Trimming now costs two minutes; discovering it at p.59 costs the magnet (survey §5.2 W6). src

Source: Voron manual p.54 · LDO Build Notes (Rev D)

Good stopping point · ~30 min since the last one

the top face is cleaned, the magnet is rolled down bubble-free and all four bolt holes are cut clear through it and test-fitted with an M3×20 and a hex key. The lamination is finished, so nothing is mid-adhesive. Lay the plate flat, magnet up, and cover it.

Step 03.11 — Verify the bed extrusion position¶

What you're looking at: Manual p.20: the bottom frame in plan, the two bed extrusions 65 mm each side of the centreline, 130 mm apart. They carry the plate's four mounting points, so you re-check Ch 01's placement here.

Parts: none.

Do:

With the printer upright, measure between the facing inner faces of the two bed extrusions: 130 mm clear.
Centre that gap, 65 mm from the centreline to each inner face.
Measure at both ends; both must match.

Check

130 mm clear gap between the facing inner faces, so 150 mm centre-to-centre, 65 mm from the centreline to each, the same at both ends.

Helper: Holds the rule on one inner face and reads the gap at each end.

Source: Voron manual p.58 · Voron manual p.20

Step 03.12 — Load the four M3 T-nuts¶

What you're looking at: Manual p.58: four M3 roll-in T-nuts in the top slots of the bed extrusions, two per extrusion. Each is the thread one corner bolt picks up. The plan view places the front pair.

Parts:

M3 roll-in T-nut, 2020 ×4

Do: Roll two T-nuts into the top slot of each bed extrusion. Centre the front pair 25 mm behind the front rail's inner face, the rear pair under the plate's rear corner holes. Leave them loose to slide.

Check

Four T-nuts, all in the top slot, all rotated so their threads face up and they cannot fall out.

Caution

Rev D+ / LDO: extrusion and roll-in T-nut tolerances on this kit are tight. Test-fit each nut and, if a slot is stiff, pick the extrusion face that accepts it best — do not force one and gall the slot. src

Source: Voron manual p.58 · LDO Build Notes (Rev D)

Step 03.13 — Fit the four thumb nuts as spacers¶

What you're looking at: Manual p.58: four knurled thumb nuts, used as spacers rather than nuts. They hold the plate a fixed height above the extrusion; the bolt passes through the thumb nut's bore into the T-nut below. Any substitute must be the same length and heat-resistant.

Parts:

M4 knurled thumb nut ×4

Do: Stand one M4 thumb nut over each T-nut, knurl up, bore concentric with the T-nut thread. Do not thread anything into the thumb nut; the M3 bolt passes straight through its bore.

Check

Four thumb nuts standing on the extrusions, none tipped, each aligned with the T-nut under it and all four the same height.

Source: Voron manual p.58

Step 03.14 — Lower the plate on, cables above the deck¶

What you're looking at: Manual p.60: the plate coming down onto its four spacers, cables first. This kit skips the page's wire passthrough: the plate's three short leads stay above the deck and end at the bed WAGO breakout on the left bed extrusion.

Parts:

build plate, magnet applied ×1

Do:

Two hands, plate flat, magnet up, cables at the back.
Lay the three leads toward the left bed extrusion, none through the deck.
Lower the plate onto the four thumb nuts, cables clear.

Check

Plate rests on all four thumb nuts, none knocked over. All three leads loose above the deck, none through it, none trapped.

Helper: Holds the three leads toward the left extrusion while you lower the plate.

Caution

Rev D+ / LDO: skip the manual's wire passthrough. The plate's leads end at LDO's bed WAGO mount above the deck, so the plate lifts off. Only Ch 10's extension leads go below: Layout v3 L, N, PE via the round hole, TH via the notch; LDO layout all four via the hole. LDO § Wiring the bed heater

Source: Voron manual p.60 · LDO wiki build-plate mapping · review/2026-09-23-bay-mods/layout-v2/layout-v2.md § How each requirement is met · Video: Part 2 @1:36:04

Step 03.15 — Start the four bolts¶

What you're looking at: Manual p.59: the four M3×20 bolts. They are longer than the official manual's M3×16 because this plate is 10 mm thick and sits on a spacer. Start them by hand so the T-nuts can still slide to meet each hole.

Parts:

M3×20 SHCS ×4

Do:

Start an M3×20 SHCS by hand through each trimmed corner hole and thumb nut into the T-nut below.
Nudge a T-nut if a bolt misses the thread.
Run all four down only until they just take up.

Check

All four bolts engaged and turning freely, plate still sitting flat on the spacers, no bolt cross-threaded.

Caution

Rev D+ / LDO: M3×20 SHCS, not the manual's M3×16. This plate is 10 mm and the spacer stack is taller, so an M3×16 will not reach enough thread. src

Source: Voron manual p.59 · LDO Build Notes (Rev D)

Step 03.16 — Set the 38 mm front offset and centre the plate¶

What you're looking at: Manual p.60: the plate's position in plan. The 38 mm setback puts the plate where the toolhead can reach it. Equal side gaps keep it clear of the vertical extrusions and Z rails, tight for a 355 mm plate in a 350 mm machine.

Parts:

tool: steel rule
tool: caliper

Do:

With the bolts loose, slide the plate until its front edge sits 38 mm behind the frame's front edge.
Split the left and right gaps evenly, then re-check the 38 mm.
Run a finger round the perimeter.

Check

38 mm at both front corners, left and right gaps equal, nothing touching a vertical extrusion or a Z rail.

Helper: Reads the rule at each corner and calls the number back to you.

Source: Voron manual p.60

Step 03.17 — Tighten one bolt only¶

What you're looking at: Manual p.59 and its DON'T TIGHTEN rule. One bolt locates the plate; the other three stay loose so the aluminium can grow as it heats. Clamped at all four corners and taken to 110 °C, a plate this size buckles for good.

Parts:

reused: the four M3×20 SHCS
tool: 2.5 mm hex key

Do:

Tighten any one bolt fully. Use the front-left one so you remember which.
Leave the other three slightly loose. They locate the plate, not clamp it.
Torque is not specified: snug by hand feel, no torque driver.

Check

One bolt tight, the other three turnable with a fingertip on the hex key. A free corner gives slightly and returns.

Caution

Rev D+ / LDO: none — the manual's DON'T TIGHTEN rule stands unchanged (p.59). Aluminium at 110 °C grows against a steel-bolted frame; three loose bolts are what lets it grow.

Source: Voron manual p.59

Good stopping point · ~35 min since the last one

the plate is on its four thumb-nut spacers, set 38 mm behind the frame's front edge and centred, one bolt tight and three deliberately loose, cables loose above the deck. This is the natural stop: the plate is bolted and the assembly is stable. Do not tighten the other three bolts.

Step 03.18 — Verify the plate floats level¶

What you're looking at: The four corners and a caliper. The plate rides on four bolts above the two bed extrusions; the gap under each bolt is what you measure, and all four should match. A short corner is a permanent tilt every bed mesh has to fight.

Parts:

tool: caliper

Do:

Measure the gap between extrusion top and plate underside at each bolt.
Sight along the plate at eye level, front and side.
A short corner means an unrolled T-nut, a tipped thumb nut or a tight bolt.

Check

All four gaps equal to the thumb-nut height and to each other. Press each corner in turn: no rock, no click.

Helper: Reads the caliper at each corner and writes the four gaps down.

Tip

do not level the plate to the gantry mechanically. Quad gantry level does that in software in Ch 13; this step only proves the plate floats evenly.

Tip

The CAD bed is the 10 in (254 mm) MIC6 plate on 370 mm bed extrusions (250). Yours is the 350 plate on the 350 frame: four bolts, four gaps.

Source: Voron manual p.59 · Voron manual p.58 · CAD: Voron 2.4r2 STEP @ de7e89d

Step 03.19 — Dress the bed leads above the deck¶

What you're looking at: The plate's three leads, loose above the deck. Nothing is terminated in this chapter. They end at the bed WAGO breakout Ch 09 fits on the left bed extrusion; Ch 10 terminates them.

Parts: none.

Do:

Lay the three leads toward the left bed extrusion's rear half, generous slack at the plate end.
Keep them out of the round hole and the notch, and off every thumb nut.

Check

Slack loop at the plate; no lead under tension, through the deck or touching a cut edge; the thermal fuse's legs undisturbed. Nothing tied down.

Caution

Rev D+ / LDO: do not zip-tie or terminate anything yet. The bed harness is a breakout design specifically so the plate can be removed from the top of the deck panel later. The bed WAGO mount is Ch 09; the terminations, the extension leads and the Omron SSR are Ch 10. src

Source: Voron manual p.60 · LDO wiki build-plate mapping · LDO wiring guide § Wiring the Bed Heater

Step 03.20 — Fit the flex plate, then cover the bed¶

What you're looking at: Manual p.61: the flex plate, the removable spring-steel print surface that clicks onto the magnet. It goes on once to prove it sits flat, then straight back in its sleeve; the magnet is not something you can resurface.

Parts:

Spring Steel Flex Plate 2.4-350 ×1
consumable: a sheet of cardboard

Do:

Drop the spring steel flex plate onto the magnet, coated side up, square to the edges. No fasteners.
Take it straight back off and into its sleeve.
Lay cardboard over the magnet for the next six chapters.

Check

Flex plate sits flat with no rocking and does not overhang the magnet on any side. Bed covered.

Caution

Rev D+ / LDO: the flex plate is an LDO kit item; the official manual's PRINT BED section ends at p.60 and p.61 carries no build content. src

Source: Voron manual p.61 · LDO 350 Rev D BOM

Good stopping point · ~20 min since the last one

the four-corner gap check is done, the plate's leads are dressed loose above the deck with nothing tied or terminated, and the flex plate has been test-fitted, removed and the bed covered with cardboard. Work through Checkpoint 03; the cover stays on for the next six chapters.

Checkpoint 03¶

Revali passing a gate — You built the heated bed, floating level on four spacers. 4 gummy worms.

Common mistakes¶

Applying the magnet over untrimmed bolt holes and only noticing at p.59. The fix is a peel-and-replace magnet or drilling through it — both bad. Trim at 03.10.
Using the M3×16 the manual calls for. It engages barely any thread through a 10 mm plate plus spacer, and strips the T-nut on first tighten. M3×20.
Tightening all four bolts because three loose bolts feel wrong. The plate tacos on the first fast heat-up to 110 °C and never comes flat again.
Trying to "fix" the pre-applied heater or fuse. Peeling a bonded AC heatpad to re-seat it wrecks it. Inspect and ask in #ldo_motors if something looks wrong.
Wiring the bed here, or feeding its leads through the deck. The plate's leads end at the bed WAGO breakout above the deck (Ch 09) and terminate in Ch 10. Landing or threading them now means undoing them.
Building on the bare magnet, or leaving the surface exposed. The magnet sheet is not a print surface, and everything you drop for the next six chapters lands on it.

Next¶

Ch 04 — A/B drives and idlers (manual p.62–81): the two gantry drive units and the front idlers, built on the bench with the bed covered.