IDEX BOTH ON CORE XY

[cgrosbeck]

Is it possible to currently set up IDEX as both heads driven CORE XY?

So 4 motors driving the CORE XY at all times but one head would stay outside the print area until commanded.
This seems doable just, I just don't know if the kinematics in the firm ware can handle the logic of the head that is not in use and still work in conjunction to move the gantry.

My background 30 years designer spatialized equipment.
Mechanical Engineer Designer

Chris T Grosbeck
MiMe.Global

[oliof]

@cgrosbeck a pure CoreXY setup for IDEX involves a lot of belts and pulleys, and you need to stack belts in three to four layers instead of the normal two.

It's simpler and easier to go for Dual Markforged / Hybrid CoreXY where the Y axis is driven by two motors linearly, and both carriages are driven with a Core-style indirect motor drive.

This approach solves several problems: First of all, you get double the motor power for the heavy X gantry. Second, you get shorter belts for Y which are easier to tune since they are a simple loop. Third, you save on belt stacks. Fourth you save on pulleys. You still have three belt layers, but the Y layer is separate from the XU layers.

[MJLew]

@cgrosbeck What @oliof says about belts might well be true, but my next printer is likely to be a dual-gantry like the DuellingZero.

My plan is to stretch it along the y-axis to give a printing area of about 150 by 300mm. The short x-axis will allow it to be light and to use some nice THK rails that I acquired second hand a couple of years ago. I find my Duet-powered Voron 0 to be a very nice printer for my purposes, so a larger bed is not important to me.

[cgrosbeck]

@oliof Four layers of belts is fine as this will also use four motors the cost is in consideration as commercial design for 600mm sq and up, This is not being designed cost for the home hobbyist, The team also is asking for filament change and purge on the fly with each head. So this is a large machine and the concern of stacking belts is not a problem, I am not software / firmware savvy so need help on the software / firmware side, So can this be done in the current firmware with a proper config.

Chris T Grosbeck
Sorry if I sound rude about home hobbyist but that market is out of China and we are not looking to compete at that level!
we are targeting $10000 base printer to 30000 with IDEX and dual on the fly material changing 4 or 8 per head!

[oliof]

@cgrosbeck I was not arguing about cost, but complexity. A commercial machine should reduce complexity and part count to avoid maintenance load and reduce per-unit cost.

[droftarts]

@cgrosbeck Yes, the firmware supports CoreXY IDEX, and has for a long time, so not "doable just"! And yes, it can handle the logic, the computations are not very difficult, see the diagrams below.

Machine kinematics are set by M669; see https://docs.duet3d.com/en/User_manual/Reference/Gcodes#m669-set-kinematics-type-and-kinematics-parameters
There are presets for the common machine types. I think what you are describing is actually what we refer to as a CoreXYU. A CoreXYUV would have two completely independent CoreXY gantries, including the X carriage (like @MJLew suggests). M669 already has support, and a preset, for CoreXYU and CoreXYUV. M669 allows setting up of custom kinematics, too. User @deckingman built a machine that had three separate CoreXY gantries, dubbed a CoreXYUVAB.

There are two ways of doing a CoreXYU (or CoreXY IDEX); the first is as you describe, with 4 motors for the X, Y and U motion:

The second is a CoreXY with a Markforged U axis, and uses three motors, and less belt and other hardware:

Both are supported by RRF, using the M669 K5 CoreXYU kinematic. There isn't any great advantage using the first over the second, while the first adds to the complexity.

M669 also supports the dual Markforged kinematic @oliof suggests. I believe @RogerPodacter has built one of these, see https://forum.duet3d.com/post/303241

(From this thread: https://forum.duet3d.com/topic/21021/dual-markforged-kinematics)

Ian