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Hlidskjalf (Odin's Chair)

by Prot0typ1cal, published

Hlidskjalf (Odin's Chair) by Prot0typ1cal Sep 26, 2016
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"Hlidskjalf" is my dual CoreXY, extremely expensive 3D printer.
"CoreXYU" coined by dc42 on the RepRap forums.

Extruders are done: http://www.thingiverse.com/make:258333

Build volume covered by both heads: 13.37" square x 15.75" High, or 34 sq x 40cm Tall.

Left print head: "Hugin", E3d-v6 300c 24V hot end with Toranado extruder.
Right print head: "Munin", Prometheus v2 300c 24V hot end with Toranado extruder.

RADDS v1.5 board with 2x driver extension and 8x RAPS128 stepper drivers
6x NEMA17's 76oz-in for axis, 2x NEMA 14's 15.6oz-in 0.9deg for extruders
Arduino Due r3 microcontroller with 7" Panel Due touch screen
RepRap 24V PCB Heatbed 300mm x 300mm

2x RM1605 x 550mm ballscrews with anti-backlash nuts and FF12/FK12 end supports
8x MGN x 500mm linear guides with12x MGN12H guide blocks
Misumi USA aluminum extrusions

Odin, give me the strength to finish this project, because I've already spent my wealth!

How I Designed This

Hlidskjalf project guide

My inspirations:


Design challenge:

2 head open frame driven by core-XY with CNC capabilities.
Phase1, Single core-XY. SIngle head prints.
Phase2, Dual core-XY, 2x head implementation.
Phase3, link X-carriages for CNC, flexible shaft Dremel for spindle.


  1. Optimize XY torque and precision at 100mm/s feed rates, rapids up to 300mm/s.
  2. Minimum print build of 300 x 300 x 400mm, with heated bed.
  3. Maximize rigidity with open frame construction.
  4. Minimize reciprocating mass.
  5. 300c direct drive extruders.
  6. Aesthetics and DFMA.


  1. 24V system to maximize stepper and heater efficiencies.
  2. Linear guides for best of class rigidity and low coefficients of friction.
  3. Z axis ball screws to position work for CNC. Max torque 25mm/s, Rapids 150mm/s.
  4. Core-XY with steel cord Urethane GT2 belts. 2:1 primary XY drives, 10mm/rev output.
  5. 32 bit micro controller for dual core-XY to achieve speed and accuracy.

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Now have power, 1000 Watts of 24VDC.
Will be replacing the 2x stepper driver extension with a 3x that includes 2x more fan outputs, so will wire up extruders when that arrives.
Plus will get the ATP-5 1/4" tooling plate soon for the bed, so will be able to wire up the heatbed at that time as well.
PanelDue working, in process of hacking firmware to support CoreXYU.

Jun 15, 2017 - Modified Jun 15, 2017
jneilliii - in reply to Prot0typ1cal

Are you using standard CAT-5 cable to wire your motors, etc.? Is that a large enough gauge wire to supply the correct loads for hot ends, etc.?

Actually. it's CAT3. It's 24 AWG and the cables don't move. Also used same for the stationary end stops for Y and Z.
At 24VDC (1.4A stepper) is only a 1.5% voltage drop over 1.5 meter cable length, that's half of the max recommended of 3%.

For the hot ends have ultra-flexible multi-strand 15 wire 22 AWG cable going to the carriages and will use 4 wires, 2 each for the negative and positive leads for the cartridge heaters. Plus 2 for the thermistor, 2 for the heat sink fan, 3 for the filament cooling fan, and 4 for the NEMA 14 direct drive (total 15). The smaller cables that go to the carriages now are for the X endstops only, and is only 26 AWG.

Amazing. I will follow up your progress!

This is absolutely beautiful. I'm designing my own CoreXY and came across yours when researching stacked belts vs crossed belts to see if the torque form stacked belts really matters. Does your independent system work reliably? My design is very similar to yours using 4 linear guide rails for the z axis, and 2 for the y, but I hadn't considered doing independent heads for dual extrusion. The design of this machine is phenomenal. The only change I think I would make for mine would be to use E3D's Aero heads for each extruder/hotend.

Hey buddy, i plan to replace my crappy Prusia I3 rework by your awesome build!
Does the current version usable or not?

I loved your project.. it is the innovation community seeks (at least I seek) =) waiting for your machine to print! I want to build this, but so complicated to understand with pictures. Can you post 3D cad files for us to examine the completed machine?

As soon as it's done I'll be posting the final assembly. Still a "work in progress".

Feb 13, 2017 - Modified Feb 13, 2017


Really like this project. Go big or go home!

I've got a large build underway as well but single extruder based on one of Jetguy's "Big-Boy" printers. Mine is a four lead-screw Z-lift with a 14"x14"x36" build volume: "Tall-Boy". Z-travel is a work in progress; its hard to keep things really square over this much travel.

Question: where did you source the high quality GT2 belt? All I've found is the fiberglass core Chinese stuff.

Thank you much,

Mark Napier

Hate to say it, AliExpress.

Each X-carriage required 4.85 meters of belt (2 loops) for the coreXY.

The more I look at this design the more I like it. I think the only change I can see making is proably the XY axis looks heavier than it needs to be unless you plan to do some light milling as well.

Feb 6, 2017 - Modified Feb 6, 2017
Prot0typ1cal - in reply to ChrisT88

Absolutely, some light milling as well. Plan is linking the two X-carriages with a single spindle mount plate.
Beauty is, with dual coreXY, I'll have 4x motors driving the milling head.

As a 3d printer, the non printing head adds it's motors to moving the "heavy" Y-gantry in Y, while the other head prints in X and Y.
Acceleration calculations shows the CoreXYU arrangement to be more efficient than a standard CoreXY, especially on 45/135 degree moves.

I can't wait to see this working, I wish to build it already, only thing I would rather do instead of a pure corexy is a system like d-bot with no crossing belts?

Congratulations on this awesome work.

Well, amazing & interesting, fisrt for the big build size, second for the two x-axis independent Heads.
But: wich software ist capable to control that?

RepRap firmware can (has been) be expanded to support the dual X in a CoreXY, know known as CoreXYU.
Most slicers already support dual extruders, though Hlidskjalf will have modified Repeteir Host to provide desired control of both heads.

Waiting for all the wires and connectors... also waiting for the last of the fasteners, and the plywood top and sides.

pfft, I hate waiting :p

Based on what you have so far it will be worth it. Can't wait to see it in action and see the BOM.

impressive work
can you put a x_t file of the whole assembly please

Just adding as I go along ATM.
Plan on releasing a full model, with Bill of Material when complete.

I am really looking forward to see this printer working, or at least moving the first steps!!!!

A really great work.

Thanks :)
Added a new photo of the frame.
You'll see the right print head is belted (lower run). Hope to cut the plywood sides and top this weekend.
With just the one head, it will be compatible with the current Repitier firmware (Phase 1)
After the one head is proved out, can modify the software to run two heads (Phase 2).

Closer to phase 1 today.
Frame is bolted together and will begin wiring for a single head CoreXY.
Will add the plywood sides and top when weather allows.

Comments deleted.

Updated pics to show belt routing. Almost done 3d printing all the required pieces for assembly.
There's a few more parts that are pending:

  1. Spool holders. 2 will be on the back side under where the belts twist. Need filament guides as well, maybe sensors too.
  2. Machine Feet. Getting some isolation pads from McMaster-Carr and will design around those.
  3. Printer face. Includes mounting for the 7" display and electronics. Thinking a pull out drawer.

This assembly uses twenty (20) of these POM idlers:

Turns out, illustrious Chinese comrades bored from both sides to leave a step in the center so the bearings don't push through. Good solution, yet creates a defect when you pass a bolt and tighten it, it locks up the bearings because they don't mate on the inner race.

Had to press out all the bearings, which breaks the center POM ring, good thing it's POM as it shears clean. Then reassemble with a washer/spacer. Sure the bearings may walk out (very slim), but at least they turn.

Nov 28, 2016 - Modified Dec 1, 2016

I have no words about the amount of work you are doing, but i'm watching closely your project, this is the best i have seen on this site!!!!

Every day I do a little more. Today I finished machined the toothed idlers, by boring the 5mm stock I.D. out to 11mm and then turning the nose off on a lathe to make perfect idlers from these that I got from eBay: http://www.ebay.com/itm/231825108382 and http://www.ebay.com/itm/291694937751

Only the motor mounts and drive pulley brackets left to design. Will be bolting it all together soon so I can start on the wiring. The software will be RepRap/Repetier with modifications to support the dual CoreXY drive.

That PSU is 600$

Yea, it's overkill. The whole printer is...

Nice job, I'm assuming is gonna cost you a fortune get all the pieces milled, a question, what's the purpose of milling the bore of the ball screw support? Is just because was tight?

Sorry if the pic is misleading. Actually just truing up the bolt surface (with the 6 holes), by milling a light cut. And that's the Z-Flange, AKA nut mount. The supports are named "Anchor" and "Floater", to indicate which end of the ball screw they reside.

Nov 4, 2016 - Modified Nov 4, 2016

If you don't mind, i can suggest you that the last file posted can be printed upside down, with much better result and less plastic, as the support is not required then, and the piece can have a much better look, the angles are not critical upside down.(is just a comment, nothing important) :-)

The "Anchor" (for the ball screw) had almost 2mm curling on the corners printed at 0.2 with the large side down (original version), even with raft. So flipped it and added supports (version 3), now it prints flat and parallel. Better to use a little more material and have a usable part. FWIW, I'm printing PLA and don't have a heated bed on my rep2.

Thanks for your comments :)

If you manage to have this up and running i'll buy one from you, no matter how much it cost!!!!!!
This is the printer of the year :-))

Busy printing Z-FLANGEs (2), Z-CARRs (4) and TOP90s (8). Printing red pieces at 0.2 res/4 shells/50% infill, and grey bits 0.1 res/4 shells/50% infill. Running out of filament as most that I print is prototypes and get versioned into the obsolete bin. If a part stays in the Thing files for more than a few days means it's in the current build. Probably about 6 to 8 printed pieces left to design.

Need to mill some reliefs in the top 2020 cross bars, the retainer nut for the ball screw fixed support needs more room than allowed by the 20mm gap. Plenty of space for the 10mm to 5mm shaft coupling. Also one the machining list is boring the toothed idlers for bearings.

Realized the cheap MGN12 linear guides and extra H blocks from China are complete crap. Replaced bearings in one from McMaster-Carr and tweaked the wire retainer so it didn't bind the ball return. So far it's the only usable carriage, you get what you pay for...

When all will be done, do you think that we Can expected à BOM ?

Amazing job man!!
I am watching you.......

This is gonna be The Printer!!!!

Eventually... Next will print out a Y carriage to check dimensions, adjust because it never prints perfect. Then print two once it meets my specs.

Nice Job Man!!!!!

Nice design, let's see what your pen is capable to do :-))

Thanks, we'll see if my Makerbot Rep2 can make parts that fit :p