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Chapter 05: The Gantry

The gantry is the heart of the CoreXY motion system. It's the assembly that moves in the X and Y directions, carrying the toolhead. This chapter covers the construction of the Y-axis arms, the X-axis rail, and how to combine them with the A/B drives and idlers from the previous chapter to form the complete gantry.

Overview of the gantry components Overview of the gantry components

An overview graphic showing all the components that form the gantry: the A/B drives and idlers, the X and Y extrusions, linear rails, and the XY joints.

Section 1: Y-Axis Arms

You will build two Y-axis arms, which are mirror images of each other.

  1. Prepare Extrusions: Take your Y-axis aluminum extrusions and insert the required M3 and M5 T-Nuts into the channels as shown in the diagrams.
  2. Mount Linear Rails: Attach an MGN9 linear rail to each Y-axis extrusion. Use a printed alignment tool to keep it centered. Remember to secure the carriage with tape to prevent it from falling off.
  3. Attach End Pieces: Fasten the printed idler-end pieces (which hold the Y-axis belt idlers) to the front of each Y-axis arm. Ensure they sit perfectly flush with the end of the extrusion.

Assembling a Y-axis arm Assembling a Y-axis arm

Illustration of a Y-axis extrusion with the linear rail mounted and the printed idler-end piece being attached.

Section 2: XY Joints

The XY Joints connect the X-axis rail to the Y-axis arms. You will build one left and one right mirrored joint.

  1. Preparation: Install the M5 nuts into the printed joint housings.
  2. Bearing Stacks: For each joint, create the bearing stacks on the integrated posts using F695 bearings and M5 shims. An M5 bolt can be used as a temporary alignment aid.
  3. Install Idler: Screw the GT2 20T idler into place. Do not overtighten this bolt; the idler must spin freely.

Exploded view of an XY Joint assembly Exploded view of an XY Joint assembly

An exploded diagram showing the components of a single XY joint: printed parts, bearings, shims, idler, and screws.

Section 3: X-Axis Rail

Prepare the X-axis rail by mounting the MGN12 linear rail onto the X-axis extrusion. As before, use an alignment tool and secure the carriage with tape. Prepare the rail by inserting the necessary T-Nuts for the X-carriage and belt clamps.

Preparing the X-axis rail Preparing the X-axis rail

The X-axis extrusion with the MGN12 linear rail being mounted and T-nuts inserted into the channel.

Section 4: Final Gantry Assembly

Now it's time to connect everything together.

  1. Attach Y-Arms to Drives: Connect the two Y-axis arms you built in Section 1 to the A-Drive and B-Drive assemblies from the previous chapter. This will form the back and sides of the gantry.
  2. Attach XY Joints to Y-Arms: Slide the left and right XY Joints onto the carriages of the Y-axis linear rails and secure them.
  3. Install X-Axis: Fit the X-axis rail between the two XY Joints and fasten it securely. Your gantry should now be a single, rigid assembly.

The fully assembled gantry The fully assembled gantry

Illustration of the final, fully assembled gantry, showing all components connected together.