Ch 05Checkpoint

Checkpoint 05

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

What you should have now — The whole gantry as one unit, off the machine: both Y extrusions, the X extrusion, both XY joints with the cable bridge; the X carriage halves are only staged, for Ch 07, with Chapter 04's drive units and idlers closing its four corners. Shown the right way up for comparison with Chapter 06 - Checkpoint 05 leaves it upside down on the bench, and Step 06.11 is where it is turned over and hung on the Z joints. CAD gantry is the 250: 350 mm Y extrusions and a 330 mm X extrusion. Yours are longer. The titanium backers are not in the CAD.

• E extrusion joined to both drive units with 8× M5×10 BHCS; drives parallel, no twist
• Both MGN9 rails centred and tightened on holes 2, 4 … 18, both end holes open, overhang equal at both ends
• MGN12 rail centred and tightened on holes 2, 4 … 14, both end holes open, overhang equal at both ends
• Every carriage retained by a stopper or tape; none dropped
• At each of the four C-extrusion ends: 2× M5 in the top (backer) slot, 1× M5 + 1× M3 in the rail slot beyond the rail end
• Titanium backers on the face opposite the rail — top of both Y extrusions, rear of the X extrusion — flat, all screws seated, none cammed out
• Both front idlers and both rear drive joints flush with the extrusion ends, each with a blue upper Z-belt clip under its two M5×16, clip notch pointing away from the idler or drive assembly
• Both XY joints: 3 M5 nuts, 4 M5×40 SHCS, 2 F695 flange-out between 2 precision spacers, 1 free-spinning 20T idler; the three joint bolts firm, the idler bolt snug
• Cable bridge fitted to the right XY joint with M5×16 BHCS; left joint on M5×10
• M5×30 BHCS with black M5 washers underneath, both lightly tightened
• XY joints bolted to the Y carriages: 4 bolts one side, 2 the other; all six M3×16 fitted; 2× M3×30 SHCS bagged with the endstop pod (p.164) for the right joint's two empty holes
• X axis runs the full Y travel with no tight spot
• A/B belts still unopened; nothing squared, nothing torqued down
• Gantry is upside down (motors up, rails up) with the right joint (bridge, endstop channel) on the A-drive side; it is turned back at Ch 06 Step 06.11

You built a complete gantry with the X axis riding on both Y rails. 12 gummy worms.

Common mistakes

• Fitting the backers after the gantry is built. Their T-nut slots are capped by the idler and drive frames, and the backer face is buried once the gantry is in the frame. It is a ~3 h teardown to fix (survey §5.2 W2).
• Putting the X backer on top of the X extrusion. With a single MGN12 on the front face, a top backer adds to the bimetallic bow instead of cancelling it, and it blocks the top slot the XY joints and cable bridge bolt into.
• Using the rails' end holes. The manual only forbids it on 300 mm builds; LDO forbids it on all of them, because the end holes sit exactly where the M5/M3 T-nuts of p.89–90 and p.102 have to live. Caught late, the rail comes off and goes back on.
• Forgetting the reserved T-nuts at p.90. Nothing in this chapter uses them, so they are easy to skip — and Ch 06's Z joints and Ch 10's chain hardware then have nowhere to bolt to. Count per slot — 2× M5 in the top slot, 1× M5 + 1× M3 in the rail slot — before the idlers go on.
• One spacer in an XY joint stack, or a flange facing inward. The pair drops 1 mm and its inner races are never clamped, or there is no belt channel at all; found in Ch 07 as belt rub, and both joints come apart again (3× M5×40 + idler each). Fix: spacer, flange down, flange up, spacer — read it from the side before closing the joint (p.97, p.99).
• Torquing the XY joints and "squaring" on the bench. The joints are meant to stay slightly loose and the gantry is squared in the frame with the belts slack. Tightening now, or tensioning belts now, costs a full de-tension in Ch 07 (survey §5.2 W1).
• Leaving the blue upper Z-belt clips off the idlers and drives. Nothing in this chapter loads them, but Ch 06 clamps every Z belt's second end under them (p.117, p.120). Fitting them later means backing out M5×16s on a gantry that is already in the frame.
• Over-tightening the 20T idler bolts. They thread straight into plastic and only locate the idler. Crushed pockets show up later as belt noise you will blame on tension.

Next

Ch 06 — Z axis: gantry install, Z belts and gantry squaring (manual p.108–123, plus the official 16-step squaring procedure); gated on batch B05 (Z joints + Z chain, 1 plate, 6.4 h) — start it now if it is not already printed. Keep the rubber rail stoppers: LDO uses them under the Z joints to rest the gantry during install.

Source: survey §7.5 · Voron manual p.107

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