For a little while I’ve been working on a little project with @Joshua_Rowley and @Sanjay_Mortimer from E3d.
It arose as a result of some idle chit-chat about printer designs and Josh came up with a rather genius idea to provide direct drive without an extruder above the hot end. We’ve christened it core XE for obvious reasons. None of us appear to have time to prototype the design at this stage so we wanted to release it to the community for further development. The linked blog post covers the basic concept. I’ll post some follow up renders and the Inventor files we’ve put together so far.
Please let me know if you’re interested in participating in this and E3d and I will provide as much support as we are able.
http://forum.e3d-online.com/viewtopic.php?f=12&t=189
@Tim_Rastall this caught my attention the other evening in the google hang out. Someone has prototyped this, correct? I understood it took the weight off the extruder by placing the motor on the carriage, I did not understand where the linear motion was carried through. Most obvious through the drive gear, but to acquire a high quality hexagonal linear bearing seemed to be a challenge to me.
Am I seeing all this right or off on a different planet?
I think it should be called core XYE as core XE would imply just one axis plus extruder (e.g with a bed moving in Y) where as this plan involves all three!
Looks fantastic though! Are there any issues with the torque differences between the extruder and axis being driven by the same motors?
How do you bind the belt so it can go through the extruder assembly at the splice?
@Camerin_hahn closed loop belt. The design allows for everything to be built around the belt.
@Hannes_Lilliefeldt closed loop belts are available in 50mm size increments from http://sdp-si.com. The x axis is vslot, so easily scaled to fit.
Here’s a render https://plus.google.com/116889746506579771100/posts/DHApHguzTuz
@Shauki this, was our concern too but without testing we will never know. Something not included in the current model is a matching set of bevel gears on the other side of the carriage. Inverted obviously. This would ensure perfect equilibrium on both sides of the carriage. I assume you get why this would be awesome if it worked though?
Ccing @Nick_Parker
@Shauki true, but sometimes it’s fun to work on new things :). I’ve never been very good at finishing things anyway - there is always another fun project waiting to start.
@Shauki I have some igus 8mm shafts and bearings for Ingentis. Just haven’t got around to using them 
QR Ingentis sounds awesome.
The main issue I see is that the belt will be continually run through the extruder and therefore cannot have any joins. @Tim_Rastall
@Matt_Kraemer True but a closed loop belt is fine with the current design. All the components can be assembled around the belt. and the belt can be tensioned by shifting the mounting plates for the idlers in the 4 corners.
Ahh different planet.
Can you buy custom length closed loop belt? If so I really like this idea and want to try it.
Hmm. I’ve been hankering to build another printer, and was already leaning towards making one with this form factor. And it’s an intriguing alternative to Bowden. It’s a very tempting project. 
@Matt_Kraemer many many length options from SDP-SI. In case it’s not obvious The closed loop belt that drives the Y axis needs to be chosen to compliment the XE closed loop belt length. It will be much easier to adjust the XE belt to fir, given that all 4 corner mounting points could be moved.
This closed belt needs to be PU steel reinforced T2.5 or T5 or you’ll have problems with stretch.
@Matt_Kraemer or just wider. 9mm gt2.