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Ch 05Before you start

Before you start Chapter 05

Before you start · Chapter 05 — Gantry: X and Y axes, XY joints, X carriage, titanium backers

Builds the complete gantry on the bench — XY bridge, both Y axes with their MGN9 rails, both XY joints, the X extrusion with its MGN12 rail, and the titanium extrusion backers — and ends with the X axis riding on the Y carriages. Unlocks Ch 06 (gantry install, Z belts, squaring).

What you're building in this chapter. The gantry is the entire moving upper half of the printer — a rectangle of aluminium extrusion that later hangs on four belts and slides up and down, with the toolhead riding inside it. Its back edge is the XY bridge, the cross-beam that carries the A and B motors you built in Ch 04. Two side extrusions, the Y axes, run forward from that bridge; each has a linear rail along one face and a front idler block at its front end that turns its belt back. Spanning the two sides is the X beam, capped at each end by an XY joint — the printed blocks that ride on the Y carriages and turn each belt around from its Y run to its X run. Bolted to the face opposite every rail are the titanium backers, flat strips that stop a steel rail bowing its aluminium extrusion as the chamber heats. Nothing in this chapter gets belts or squaring: both belong to Ch 06/07, and both would undo work done here.

Revali turning a hex key
Build the gantry on the bench, not in the frame. Clear the whole table, including that pile.

Time: 5.0–7.0 h hands-on, first build, two people (survey §5.1 P05 / §7.2).

Sessions: 12 × ~30 min (first-build estimate; each Pause: line carries its own segment minutes).

Prerequisites:

  • Ch 04 — A drive, B drive and both front idler assemblies built and checked (manual p.62–81). This chapter consumes them whole.
  • Ch 00 — all seven rails cleaned and packed with grease before they go on an extrusion (LDO rail grease guide); jigs Tools/MGN9_rail_guide_x2.stl and Tools/MGN12_rail_guide_x2.stl printed (batch B00). The rails still wear their Ch 00 end bands (Step 00.17) — they come off at Steps 05.11 / 05.33.
  • Print batches: B04 (XY joints + X carriage, plate B04-P1, 8.6 h, black) and B02-P3 (the blue accent plate — cable bridge, endstop pod and the four upper Z-belt clips) (print plan §B04). B04 needs Gate B (Step B00.7).
  • Titanium backer set (Fabreeko/LDO, 350 size) unpacked and counted, plus 58 M3 roll-in T-nuts counted out from the kit bag: 29 for the rails and extrusion ends, 29 for the backers. The backer set ships none.
  • Ch 01's bagged C ×2, D ×1, E ×1 extrusions.

Tools

  • Hex drivers 2 / 2.5 / 3 / 4 mm; a ball-end 2.5 mm helps at the XY joints
  • T10 Torx driver — strongly preferred for the backer M3 FHCS; hex cams out of a countersink easily (backers README)
  • Printed rail-centring jigs MGN9_rail_guide_x2, MGN12_rail_guide_x2
  • Steel rule 300 mm and a caliper — to equalise the rail overhang at both ends
  • Masking tape (carriage retention) and the kit's rubber rail stoppers
  • 2.5 mm flat screwdriver (cable-chain latches, if you dry-fit the chain end)

Printed parts

Parts arrive in the bins named below (see the bin map in print/README.md#bins); check the bin label's list before you start.

Looks like STL Bin Qty Colour
xy_joint_left_lower_MGN12.stl 05-XY 1 Black
xy_joint_left_upper_MGN12.stl 05-XY 1 Black
xy_joint_right_lower_MGN12.stl 05-XY 1 Black
xy_joint_right_upper_MGN12.stl 05-XY 1 Black
[a]_xy_joint_cable_bridge_2hole.stl 05-XY 1 Blue
XY_cable_chain_bridge-Igus-3mm_backer.stl 05-XY 1 (alternate — fit whichever clears the backer) Blue
x_frame_V2TR_MGN12_left.stl 07-X 1 Black — staged here, fitted in Ch 07
x_frame_V2TR_MGN12_right.stl 07-X 1 Black — staged here, fitted in Ch 07
probe_retainer_bracket.stl 07-X 1 Black — staged here, fitted in Ch 07/08
[a]_endstop_pod_D2F_switch.stl 05-XY 1 Blue — staged here, fitted at endstop wiring
[a]_z_belt_clip_upper_x4.stl 05-XY 4 Blue — fitted here under the idler and drive M5×16 (p.91, p.93, p.95), loaded with belt in Ch 06

Do not print [a]_endstop_pod_hall_effect.stl, [a]_xy_joint_cable_bridge_3hole.stl, or any xy_joint_*_MGN9 — wrong variants for this kit (print plan §7).

Hardware (chapter totals)

Fastener / part Qty Where
E extrusion (XY bridge) 1 p.85
C extrusion (Y axis) 2 p.88
D extrusion (X axis) 1 p.101
MGN9H 400 mm rail 2 Y axes, p.88; carriage ships on the rail
MGN12H 400 mm rail 1 X axis, p.101; carriage ships on the rail
M5 roll-in T-nut 26 8 in E (p.85), 12 in the C pair (p.89, p.90), 6 in D (p.102)
M3 roll-in T-nut 29: 18 Y rails, 4 C-pair ends, 7 X rail 9 per 20-hole MGN9 (p.88), 4 in the C pair (p.90), 7 for the 16-hole MGN12 (p.101)
M3 roll-in T-nut, backers 29: 10 per Y backer, 9 on the X backer from the kit's M3 roll-in bag; the backer set ships no T-nuts
M5×10 BHCS 10 8 bridge-to-drive (p.86–87), 2 left XY joint (p.104)
M5×16 BHCS 10 4 front idlers, through the upper Z-belt clips (p.91, p.93), 4 rear drive joints, same (p.95), 2 right XY joint + cable bridge (p.104)
M5×30 BHCS 2 XY joints from below (p.104)
M5×40 SHCS 8 4 per XY joint (p.97–100)
M3×8 SHCS 25: 18 Y rails, 7 X rail one per marked rail hole (p.88, p.101): every other hole from the second, both end holes empty
M3×16 SHCS 6 XY joints to the Y carriages (p.106): 4 left joint, 2 right joint; all six fitted, none spare
M3×30 SHCS 2: bagged with the endstop pod at 05.46, fitted at 09.33 p.164 fits the pod through its body with 2× M3×30, not the M3×16 of p.106
M5 nut 6 3 per XY joint (p.96)
M5 precision spacer, brass 4 2 per XY joint stack — one below and one above the F695 pair (p.97, p.99) — replaces the manual's "M5 shim"
M5 washer, black 2 under the M5×30 heads (p.104) — replaces the manual's "M5 shim"
F695 bearing 4 2 per XY joint
GT2 20-tooth idler 2 1 per XY joint
Titanium backer, Y — from Ti backer set 2 one per C extrusion
Titanium backer, X — from Ti backer set 1 D extrusion, rear face
M3×8 FHCS, Y backers — from Ti backer set 20: 10 per Y backer tanaes Y_backer-350 DXF: 10 holes (verify on bench)
M3×6 FHCS, X backer — from Ti backer set 9 tanaes X_backer_chain-350 DXF: 9 holes, plus 4 chain pilots (verify on bench)

The West3D/Fabreeko titanium set ships 22× M3×8 FHCS and 10× M3×6 FHCS, two and one spare over the 20 + 9 holes, and no T-nuts (West3D).

Read first

  • The titanium backers go on during this chapter, not after it. Fitting them once the gantry is assembled or installed means a teardown (survey §5.2 W2). They mount on the face opposite the rail — top of the Y extrusions, rear of the X extrusion. "If you have a single MGN12 but decide to put a backer on top, you will be actively contributing to the problem of bimetallic expansion!" src
  • Do not tension the A/B belts and do not square the gantry here. Both are Ch 06/07, and the official squaring procedure begins by releasing A/B tension — tension it now and you undo it (survey §4.4 #2, §5.2 W1). Several joints in this chapter are deliberately left "slightly loose".
  • Every T-nut this chapter needs must go in before the drive and idler frames cap the extrusion ends. LDO: "Due to the tight tolerances of the extrusions and roll-in t-nuts it is advisable to either test fit before assembly … or to pre-load the t-nuts into the extrusions." src
  • Short a part? This chapter needs exact counts: 4 F695, 4 spacers, 2 20T idlers, the backer screws. Recount against your Ch 00 inventory sheet, then contact Fabreeko support; do not borrow from another chapter's bag.
  • Rails ship dry. If Ch 00's clean-and-pack pass has not been done, stop and do it — the flip-and-pack method needs access to the back of the rail (survey §4.4 #5).
  • Carriages slide off rails and are ruined by a drop (manual p.88, p.101). Tape or stopper every carriage the moment its rail is on an extrusion.
  • Orientation. Through p.105 the gantry is built the way it runs — motors hanging down below the bridge, Y rails underneath (p.85, p.116). p.106 turns it upside down (motors up, rails up) so the X axis can be lowered onto the Y carriages; it stays that way to the end of this chapter and is turned back in Ch 06 (Step 06.11). Every step that turns it over says so.

Sources for this chapter:

Video coverage (Steve Builds, pre-release LDO kit — differs from Rev D+): Part 3 @0:56:34 (+2m), Part 3 @1:19:23 (+16m), Part 3 @1:34:36 (+9m), Part 3 @1:43:29 (+5m), Part 4 @0:06:16 (+7m), Part 4 @0:34:10 (+9m), Part 5 @1:05:40 (+1m), Part 5 @1:20:27 (+13m)

helperHelper steps: 15 · 05.2, 05.4, 05.10, 05.11, 05.14, 05.16, 05.17, 05.24, 05.36, 05.40, 05.41, 05.42, 05.44, 05.46, 05.48

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