@fcwilt said in IDEX CoreXY, With Only 2 Motors.:

Nice graphics!

Do you do that sort of work professionally?

Frederick

These are the Voron .step files. Someone has put a lot of work into creating them with all the correct colours. I am just building on it in Fusion 360.

I guess you could call what I do a profession haha. I quit my job in the Automotive trade to pursue my 3D printing business from what started out as a hobby 7 years or so ago. I mostly focus on engineering related 3d printing, but the bulk of what I print is PLA investment casting patterns (I dont do the castings, just supply the patterns). Before you ask, yes we print a lot of cool sh!t that gets cast in metal, but I generally cant share most of it. But one of the coolest ones was this public sculpture, all of the spheres and the bendy straw collars were 3d printed and investment cast in bronze, the straight pipe is off the shelf. We went big straight out the gate as this was the first thing we ever investment cast with 3d printing.

Another cool one was this motorbike Cylinder head. Any my ugly mug holding the very intricate printed pattern.

Hey guys, I wanted to share a relatively simple concept I thought of, that implements dual independent extrusion on a coreXY frame, without the need for any additional stepper motors, or drive belts.

My plan is to build a Voron 2.4, however I need reliable dual extrusion for the majority of printing work I do.

Looking through the design files of the Voron, I was trying to find a clean way of mounting 2 additional motors and belts to drive the Y axis, while the existing std drive lines would be responsible for the two X axis for each independent carriage. Realising this could not be done without heavily redesigning the majority of components, it occurred to me that there was a relatively simple method of achieving this, without adding a 3rd and 4th belt drive/motor.

I print dual materials all day long, pretty much solely breakaway support material used as an interface layer, for just about any part with an overhang. I don't care for dual colour printing, dual object printing, or mirror mode printing, my use case for this is very low and if someone want two of something, or a LH and RH, I'm billing them for two anyway. All I really care about is dual material printing for that clean overhang.

The thing is, with dual material printing, one carriage is always parked at one end of the gantry for the entire duration of the print. So my idea was this: Why don't we lock the parked carriage to the gantry by means of a servo , solenoid ect, which then allows the otherwise redundant motor to become responsible for directly driving the Y axis?

As you can see in my diagram, carriage 1 is locked into position on the gantry with a servo. The red motor now drives the Y axis directly, while the blue motor drives carriage 2's X axis.

At a tool change, carriage 2 is parked to the right of the gantry, servo 2 is engaged, then servo 1 is released and carriage 1 is free to more around. The kinematics of this directly correspond to that of Markforged, except at every toolchange, both X and Y motor logic is swapped and reversed.

I am eager to hear people thoughts on this setup, what problems can you foresee? Have you got any good locking mechanism ideas? Any feedback would be appreciated

Regards
Rich

Further to this, the servo lock would function by being mounted at 90 deg rotation to what I have sketched (was just easier to draw that way) allowing the servo to do a sort of 'slot and lock' function, where the servo arm is rotated down into a slot on the carriage. This way the servo does not need to apply a constant load to the carriage to hold it in position.

But, I am really interested to hear if anyone has a better idea.

@fcwilt said in IDEX CoreXY, With Only 2 Motors.:

Nice graphics!

Do you do that sort of work professionally?

Frederick

These are the Voron .step files. Someone has put a lot of work into creating them with all the correct colours. I am just building on it in Fusion 360.

I guess you could call what I do a profession haha. I quit my job in the Automotive trade to pursue my 3D printing business from what started out as a hobby 7 years or so ago. I mostly focus on engineering related 3d printing, but the bulk of what I print is PLA investment casting patterns (I dont do the castings, just supply the patterns). Before you ask, yes we print a lot of cool sh!t that gets cast in metal, but I generally cant share most of it. But one of the coolest ones was this public sculpture, all of the spheres and the bendy straw collars were 3d printed and investment cast in bronze, the straight pipe is off the shelf. We went big straight out the gate as this was the first thing we ever investment cast with 3d printing.

Another cool one was this motorbike Cylinder head. Any my ugly mug holding the very intricate printed pattern.

@o_lampe ahh yes your right about the energy thing at both ends, it will be equal so it will probably bind up and freeze. But I think it can be altered to accomodate. It is a little bit of a complex system though, electric servos are sounding pretty good at the moment haha

Alrighty, been a busy day, haven’t had much chance to ponder things, but here is my rough idea. It needs a lot more refinement and maybe it can be simplified further but hopefully this is good enough to portray the idea.

There is a brass bush in the carriage where a piece of linear rod can be inserted into to lock it in place.

The far left arm is actuated by the carriage moving to the park position. The secondary idler arm is similar to a servo saver, two seperate arms cut with a v groove allowing the lower arm that’s connected to the carriage actuator to rotate, while the upper arm connected to the locking pin stays in place until the lock pin meets the carriage hole, and snaps into place. A long connecting rod is attached to a mirrored assembly at the other end. Once the lock pin snaps into the parked carriage, it is released simultaneously at the other end.

@o_lampe said in IDEX CoreXY, With Only 2 Motors.:

I'm trying to find a way to switch the locks without servos.
Just by moving against the far end of the printer, both carriers would simultanously push a springloaded switch, that toggles their lock/unlock hooks. Not sure yet, how to do this but it's there

You know what, I have done some finger paintings on my phone in bed, which I am not quite prepared to publish haha, but I think this may actually be possible. I will sketch something better in the morning

@o_lampe I have redesigned it so there are two cap screws and 2 c/sunk screws. The c/sunk ones are just hiding behind the belts. There is also an additional linear rail on the underside of the 2020 extrusion so in total, 8 bolts per carriage, a bit extreme. Edited* the belt clamps are secured with seperate bolts that run parallel to the gantry. They are not shown in the image, but it all still fits.

I too have been thinking about alternative locking mechanisms. I think the most ideal solution will be some kind of bushing in the carriage, that a machined shaft is inserted into to pin it in place. Its going to be crucial that the parked carriage has no movement otherwise this will translate into the print quality.

I have been scouring AliExpress for various bits of hardware that could be potential candidates but struggling to find something suitable. I did come across some small form 12v door latch solenoids that I liked the idea of, but I would be positive the solenoid pin will have some amount of play.

I figure if you can have 2 servos, latch/unlatch the carriages, you should be able to rig both latches to a single central servo with some actuator rods ect. But your idea of a full mechanical solution is a neat idea, I will have to give it some more thought, I’m not sure if it’s possible though as there will likely be a moment where both carriages must simultaneously move together which would likely loose the Y position, although this could be rectified with a home between tool change.

@3DPrintingWorld

It has crossed my mind, but it would require a coupler that was fairly acurate. I think I would probably end up with a result much like the toolchanger and park the tools off the carriage instead.

It just seemed so easy to throw on another carriage without much modification!

I think its a good thought, but I'm not sure I understand the purpose of locking the carriages to save a stepper. You would just be adding more moving weight, as the second motor on a dual markforged is parked on the frame.

You are welcome to check out my project, it might give you some ideas at the very least. https://github.com/3dprintingworld/MULDEX

I think the purpose of this would mostly be an effective way to add independent dual extrusion to an existing CoreXY printer, without the need to redesign a lot of key components.

Nice work on Muldex btw, it was the only DIY build IDEX printer I could find, and I do like it, but I thought it would be interesting to see what other options could potentially be possible.

Quite partial to the fixed bed, gantry z movement, and well designed form factor with no wasted space of the Voron, When I started looking over the design, I noticed there was no easy method to add additional belts and motors, not without redesigning all of the major components. That’s when I had the idea for a servo lock. It’s not flash, it’s relatively simple, but I think the concept of having only two motors responsible for the xy movement of two separate carriages, and how the firmware must interact to make it so is very intriguing, and perhaps this will spark other ideas.

Still unsure how racking would show? Lost steps and screeching carriers?

I think racking will boil down to how tightly build a gantry design is. Its hard to say without testing, and I dont know how racking would present itself in a print, possibly out of square corners, or misaligned layers. I think the best gauge would just be to see if you can feel for any play when trying to rock the gantry.

@o_lampe said in IDEX CoreXY, With Only 2 Motors.:

@RichardDuke
It's alive
The kinematic is the same as MarkForge (M669 K11) but I had to modify it, because my crossbeam is the Y-axis.
I've called it simple-IDEX or s-idex and linked the video to this thread.
Here's a short video with a fixed dummy U-axis.
Next I'll fix the Y-axis and work on the reversed kinematic.

Soooooo..... that is awesome! You're a superstar for testing this out! What an wicked post to wake up too.

I guess I am going to have to start ordering some parts and join in on the SIDEX action!

@fcwilt you and me both! I haven't even finished tuning my recent Cartesian IDEX build and I'm already looking for something else!

I guess the main idea behind this was to try implement indipendent dual extrusion to an existing platform without heavily modifying the original design. If it works, it would potentially be possible to a second carriage to just about any CoreXY printer.

@fcwilt yes the Voron is a CoreXY, designed for minimal racking, but with this modification the racking could become an issue as the gantry would now be pulled in the Y direction from opposite ends of the rail. It could potentiality be overcome with alternative belt routing, but that will require a design overhaul, in which case id probably look to just add an extra motor and belt anyway

@oliof a toolchanger could be an option, the coupling of the tools sound like it could be challenging though. Id probably look to retrofit the e3d carriage and park the tools off the gantry though.

@o_lampe I have had a conversation with Tony from Duet who doesn't think there will be an issue, but we will cross that path later.