State: brain storming, early drafts

Updates:

• 2024/12/20: early idea to add tool changer as well
• 2024/12/16: adding more details with multiple extruders on same X gantry
• 2024/12/06: early ideas about single layer segmenting
• 2024/12/05: starting write-up

Introduction

While working on theoretical side of parallel 3D printing, I used the example of multi-gantry or Multi Gantry (MG) setup where a single bed is shared in Y – here a few rough sketches:

Gantry Details

There are several challenges, such as the Y- and the XZ motion system and making the thickness of each gantry as thin as possible to have as little “dead” or “unusable” space as it adds up and also limits the printable XY space.

Y motion system

We can share a single rail where each gantry rides hence Common Y Rails (CYR), then they can’t change the order, in that case the belt routing becomes the main issue of concern – whereas when each gantry has its own rail hence Dedicated Y Rails (DYR), and each gantry has a distinct height they can change the order (lift Z to the top and move over the lower one – hence each gantry has a different Z height, but with the filament and cabling the entanglement needs to be closely observed).

XZ motion system

We require to have two positioning axes to integrate here, the X and Z:

• two independent motion systems (X axis = 1 motor, Z axis = 1 motor)
• Core XZ system also using two motors, but having XZ motion combined

Slicing for Multi Gantry System

As I realized earlier, it makes no sense to statically segment Y-space for each gantry (e.g. Y-size/n) although it would make coding easier, but seamless printing would be impossible – in reality, we need slightly overlapping spaces to achieve zero space seams where the gantries print for the same piece, so we naturally choose flexible non-overlapping operations.

Layer Segmenting

Obviously one of the simple optimization is when we are looking at a single layer, and segment it area-wise to n-amount of gantries. For sake of consistency, a wall is assigned to a single gantry to have a seamless wall/perimeter.

• Infill areas are Y segmented
  • each area (e.g. A1-A4) is the same to distribute work equally
• Walls/perimeters are assigned to a single gantry
  • if walls intersect each other in Y, those are printed sequentially not in parallel to avoid Y collision

The layer segmenting approach makes it rather easy so all nozzles have the same Z, thereby segmenting print jobs becomes easy as well.

Mixing Multi Gantry (MG) with IMEX (IDEX & ITEX etc)

We can also mix Multi Gantry (MG) with IDEX (Dual) or ITEX (Triple), or in general Independent Multi Extruders (IMEX), something like this:

And like-wise segmenting layer areas in Y as before, and additionally segment in X for each printhead on Independent Multi Extruders (IMEX), in this example it’s IDEX (Dual).

As IMEX looks like scaling print parallelism further, one has to be aware of the spatial overhead for each printhead, e.g. a single printhead occupy ~40mm width in X, and similar in Y.

MG-MIEX 3×2

Early draft with more details based on Ashtar M, extended to MG, with Common Y Rails (CYR), with IDEX:

Challenges

• 1) When doing a MG-MIEX 3×2 (3 gantry with 2 extruders each):
  • X: 3*2 motors = 6 motors
  • Y: 3 motors
  • Z: 3 motors
  • E: 3*2 motors = 6 motors
    we end up 6+3+3+6 = 18 motors to coordinate & control.
• 2) Slim design of the gantry to reduce dead-space in Y.
• 3) Slim printhead design to reduce dead-space in X.
• 4) Slicer requires to coordinate 6 printheads (e.g. T0-T5) in non-colliding and efficient way.

Solutions

Slicer

A dedicated slicer is required which segments each layer into printable areas A₁ to A_n whereas n is the amount of gantries, and those areas might be further segmented by m-amount of printheads on the same gantry, so they share the same Y position but can have distinct X position but not switch order or collide.

As proposed above, a single printhead of a gantry is then assigned to print within the same Y-segment the walls/perimeters to have a clean wall, hence, the infills are distributed among all the printheads.

Firmware & Controller

The controller with its firmware we have a few options:

• Duet3D/RRF: Multiple motion systems
  • M400: wait for current moves to finish (when using T<n> with G1s together, applies to X, Y, Z, and also E)
  • M596 P<n> selects motion queue, prior each G0 or G1
  • M597: collision avoidance (at firmware level)
  • M598: sync up multiple motions (faster waits for the slower)
• Klipper
• Marlin
  • one controller per gantry, orchestrating between controller needed
  • simple setup, reliable

As the operation of the gantries are overlapping, they cannot have relative position, but rather have absolute Y position (relative position used to detect collision), the same for the X position.

Adding Tool Changer (TC)

In order to support a tool changer, the printheads need to reach a common position in order to deposit and pick up tools. In case of a single Y rail setup this seems at first sight challenging, only a dedicated tool change per gantry, at a particular a YZ position for example. The multi Y-rail setup allows any gantry to reach a common region in YZ, and so any printhead could deposit and pickup a tool from the common toolset.

References

• Parallel 3D Printing / Additive Manufacturing – Part 1
• Jon Schone’s Multi Gantry Setup (YouTube)