Tag Archives: CoreXYU

3D Printing: Ashtar C IDEX (Independent Dual Extrusion)

Status: just a draft


  • 2021/01/14: quick start with a rough draft


Well, after the IDEX option designs – still as drafts – worked for Ashtar K (Prusa i3), Ashtar M (Moving Gantry) and Ashtar D (Classic XY), I thought, why not also target Ashtar C (Core XY).

Ashtar D IDEX is definitely a narrow design, so I thought to reuse two parts of it for Ashtar C as well, and hopefully the A and B belts route around – and well, it seems mechanically to work out.

On the firmware part it seems this CoreXY plus additional X motor is called CoreXYU and supported by Duet RepRap firmware – but details need to be researched in more depth. On the first glance the “traditional” CoreXYU setup routes the U belt off the X beam and not place a motor on it as I do, but routes at the end of the frames so the motor is stationary – definitely something also to look at.



Issues to Resolve

  • Firmware supporting CoreXY IDEX:
    • E1: X & Y provided through CoreXY by motors A & B
    • E2: X provided by X motor, Y provided by CoreXY where X=0 remains (both motors A & B have to operate to provide X=0 while Y is moved)
    • Duet RepRap firmware provides CoreXYU support, and it seems it would cover my use case here
    • Marlin firmware as of 2.x does not support CoreXYU yet
  • Moving the X motor – or U motor as in CoreXYU context – off the X beam and route a much longer belt and place the motor stationary like the motors A & B of CoreXY
  • Ooze prevention (same issue as with Ashtar D IDEX)

As I progress I will update this blog-post, and summarize also the developments in the Ashtar C project page.


  • CoreXYU: Dual Head for CoreXY, another more complex approach where 3rd motor is also stationary

That’s it.