Precision Gantry for the Prusa INDX

Precision Gantry for the Prusa INDX

Tool pickup and storage on the INDX is delicate, and interference or torque on the extruders can result in failed pickup or storage.

This modification applies a simple geometric principle: by making the tubing runs nearly identical and minimizing lateral stress, when a tool moves in the X-direction its tubing arch contracts rather than sweeping sideways into the other stored tools. With this geometry, when the tubes do touch, contact occurs high on the arch, well away from the extruder.

I’ve tested this on several long prints, including the Prusa Octopus. At this point, I’m at roughly 6,000 tool changes with zero failures.

It is compatible with the OneTop for the INDX/Core One. This modification now allows me to run prints with the top in place, something I couldn’t do with the previous feedthrough and gantry design.

A short video of the gantry in operation is here.  Taken as the Prusa Octupus was finishing.

The design goals were:

1. Minimize tubing bends, avoid compound curves, and reduce interaction between Bowden tubes.

2. Minimize torque — especially lateral torque — on the individual extruders.

3. Make installation straightforward for the DIY crowd.

4. Make the entire system printable on an MK4 bed.

I mounted the filament passthrough by drilling and tapping three 3 mm holes in the upper frame. Use the part itself as a drill guide.  This makes the passthrough very solid. If you don’t have a 3mm tap, you can alternately use a nut to secure the passthrough.

To allow the gantry to fit on the MK4 print bed, the upper crossmember is shortened and its corners beveled and the passthrough is printed in two pieces with a built in joint.  The tower geometry adds the gantry material back in the assembled structure, restoring the required span without requiring a splice in the horizontal member.

Use 3 mm heat-set inserts in the gantry and secure it with 10 mm screws.

The PTFE tubing should be long enough for tools 1 and 8 to reach the opposite side of the bed without excessive stress.  Test this during tubing install by moving the printhead the full range with the tool attached.

Printed in PETG with 4 perimeters and 15% gyroid infill.

Finally, I repurposed the Core One light bar, which is removed during INDX installation, to act as a bumper along the front edge so each tube has the same resting point. See the photos.

Let me know if you have any questions in the comments.