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FuseBox2 CoreXY 3D Printer

by _AlexY, published

FuseBox2 CoreXY 3D Printer by _AlexY Jul 7, 2017
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STLs and full BOM are now available!


Github: https://github.com/alexyu132/fusebox2
Update 11/14/17: Modified extruder arm to allow for greater tension and prevent bottoming out on smaller diameter extruder gears.

FuseBox2 Printing

An affordable and robust CoreXY printer loosely based on the original FuseBox. Materials cost ranges from $300-400 largely depending on what hotend and electronics you choose to use.


Benchy print: https://www.youtube.com/watch?v=cd1lirX5iP4
Movement test: https://youtu.be/IUSiRgaVAkE


  • Rigid 2020(top and sides)/2040(bottom) aluminum extrusion frame
  • Non-crossing CoreXY belt path
  • 210x200x210mm build area
  • 390x340x412mm size
  • MK2 or MK3 PCB heatbed with 3 point leveling
  • Strong part cooling blower (4020s)
  • E3D V6 or Lite6 + 40mm cooling fan and Bowden extruder
  • 24v + 32 bit electronics recommended


Improvements over original FuseBox

  • Slightly more compact
  • Slightly larger build area
  • 2020 frane for much greater rigidity
  • Belt tensioning improvements - much easier to tension and screw-clamped to prevent slipping out
  • Clamped bearing and rod mounts - no more structural zip ties
  • Proper belt idlers - eliminates belt rubbing
  • Extrusions (optionally) joined via tapped ends + screws instead of corner brackets
  • Lowered part count - y rods integrated into motor and idler mounts
  • Vertical gantry for easier hotend installation/removal and better cooling
  • Better endstop mounting and easier adjustability

Print Settings


Any well-calibrated printer










Some parts may require your printer to be decent at bridging (carriage, idler blocks).

PETG or other temperature resistant filament should be used for the hotend cooling duct and is also recommended for the bed mounts and hotend carriage. PLA is fine for the rest of the printed parts.


Finishing printed parts

The hotend carriage has a piece of integrated support under the fan duct. Simply peel it off the finished part.

Make sure to get rid of stringing or other rough areas where the linear bearings and rods attach to make installing those parts easier. Some parts may have a tight fit depending on your printer.

Connecting extrusions

FuseBox2 does away with corner brackets and instead uses a tap and drill method to join the extrusions - this results in a lower part count, a cleaner appearance, and likely greater rigidity.

To connect 2 extrusions perpendicularly, use an M5 tap to tap the end of the first extrusion. On the second extrusion, drill an access hole where you want the first extrusion to connect. Partially screw in a 12mm M5 bolt to the end of the first extrusion, and slip its head into the channel of the second extrusion. Tighten down to attach the pieces rigidly together.

A more detailed explanation of how to connect extrusions using this method is available here: http://forums.reprap.org/read.php?177,601562

BOM (Make sure to get plenty of extra fasteners, zipties, wires, etc.)

Item Quantity
2020 extrusion, 350mm 2
2020 extrusion, 340mm 6
2020 extrusion, 184mm 1
2020 extrusion, 202mm 2
2040 extrusion, 184mm 1
2040 extrusion, 350mm 2
2040 extrusion, 300mm 2
Heaters, motors, electronics
MK2 compatible PCB heatbed 1
15A 24v PSU or 30A 12v PSU 1
E3DV6 compatible hotend with PTFE tube and coupler 1
Any electronics (32 bit preferred, mounts available for azsmz board+lcd) 1
NEMA 17 stepper (60+ oz in/42+ N cm preferred) 3
NEMA 17 short body stepper (up to 30mm motor body length) 1
IEC socket with fuse and switch 1
~5A 250v fuse 1
IEC power cord 1
Mechanical endstop (Note: remove the microswitch from one of them to use on the x axis) 3
40mm axial fan 1
2040s radial blower 1
Thermistor for heatbed 1
8mm OD smooth rod, 300mm length 6
LM8LUU linear bearing 6
T8 leadscrew+nut, 250mm length, 2mm pitch preferred 1
16T GT2 idler for 6mm belt(6 toothed/2 smooth or 8 smooth) 8
20T GT2 pulley for 6mm belt 2
3m GT2 belt, 6mm 1
625zz bearing 1
5mm to 8mm flex coupler 1
MK8 extruder gear 1
Fasteners and Hardware
M5x8mm button head bolt 51
M5x12mm button head bolt 28
M5 T nuts (drop-in recommended) 51
M3x8mm socket head bolt 16
M3x10mm button head bolt 36
M3x25mm button head bolt 13
Bed leveling spring, nut, and bolt set 3
Extruder spring 1
M3 locknut 48
Adhesive felt feet 4
~200x213mm glass sheet 1
~200x213mm PEI sheet with adhesive 1
Zip ties Varies
Cable mesh (optional) Varies
18AWG wire for AC input Varies
14AWG wire for heatbed and main DC power Varies
Small binder/bulldog clips 4

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Any chance you make a version with the two main motors flipped so that they are not sticking up out the top of the frame?

How can I use "alignment jig"?

The jig is used to drill access holes through the side of the extrusions. Align the larger side of the triangle with the end of the extrusion, and use a bolt/nut in the hole on the smaller side to secure the jig to the extrusion. Drill through the hole closer to the larger side.

How can I set endstops positions? (I don't have heatbed, and I have different thickness glass sheet)

To adjust the z, there's a sliding piece on the bed assembly held in by a single bolt. Loosen the bolt and move up/down to adjust the z endstop positioning. The y endstop mount can also slide forward and backward. The x axis is not adjustable.

I found it, thanks. :)
Would not it be simpler and more accurate to have a screw at the top of the alu profile? (I have rostock mini pro)

I wasn't able to find a way to do it without the z endstop sticking out the back, which would probably make it more vulnerable to getting bumped. The current way is also slightly lower in part count, since usually you would need a spring or lock nuts to hold the screw in place.

Please when will you publish, at least a small assembly tutorial of the structure? I'm kind of missing out on the use of the bolts and nuts.

A bit busy right now, but I'll try to get to writing a tutorial when I have time. For now, here's a quick explanation of what each bolt size is for.

The M5x8 bolts are used with T nuts for fastening the 3D printed parts to the frame. The M5x12 bolts are for screwing into the tapped ends of the extrusions - they hold the frame together. 10mm M3 bolts are used with lock nuts to secure the smooth rods, endstops, and x/z carriage linear bearings. 8mm M3 bolts are used for mounting the steppers and PSU. 25mm M3 bolts are used to attach the hotend and all belt idler pulleys, hold together the LCD, and secure the gantry to the Y bearings.

Thank you for the improved concept. Working on it right now, just got the extrusions!

However, the provided file of the bed center mount seems to be empty/not working. Cura wont load it. Can you update the file on github?

Fixed now, thanks

The instructins were not clear and I got my cat stuck in the ceiling fan. Pls send help.

I did not find the specifications of the linear guides and the bearings. Where can I find? Is the same as v1.5 fusebox1 (LM8LUU and roll 625zz)?

Full BOM coming soon - the linear bearings are the same, but the pulleys are swapped to 16T GT2 idlers - like these: https://www.banggood.com/8Pcs-16T-2GT-Aluminum-Timing-Drive-Pulley-Without-Tooth-For-DIY-3D-Printer-p-1121574.html?rmmds=search

This design looks great! Are you willing to release the design files in a format compatible with Solidworks?

What kind of formats are compatible?

STEP files would be ideal!

Doesn't look like sketchup can export STEPs, but I'll see what I can do.

I wonder if it would be possible for you to upload the design to OnShape? Then people could download whatever format they wanted. I love the design, but without a BOM its hard to build.

BOM will be coming soon - I still have to figure out the quantities of each item. I could upload to OnShape as well.

Do you have any gain in print quality, or print speed with non crossing ?

Not sure about that one - I've only had experience with the stacked belt path.

What's the difference for crossing and Non crossing CoreXY belt path ?

Non crossing CoreXY stacks the belts so that they don't change height. This design and most newer CoreXY designs use this arrangement since it should be easier on the belts and bearings.