FuseBox2/FuseBox2R

A new CoreXY 3D printer design. This design has 2 variants:

• FuseBox2R: An improved version using an MGN12 linear rail gantry.

• FuseBox2: The original design using a dual 8mm rod gantry.

Specifications

• Rigid 2020(top and sides)/2040(bottom) aluminum extrusion frame
• Non-crossing CoreXY belt path
• 210x200x210mm (FuseBox2) or 210x205x210mm (FuseBox2R) build area
• 390x340x412mm size
• PCB heatbed with 3 point leveling
• Powerful 2040 part cooling blower
• E3D V6 compatible hotend + Bowden extruder
• 24v + 32 bit electronics recommended - SKR 1.3 and Duet are good options

Improvements over original FuseBox

• Slightly more compact
• Slightly larger build area
• Much greater frame and z axis rigidity
• Belt tensioning improvements - much easier to tension; screw-clamped to prevent slipping out
• Clamped bearing and rod mounts - no more structural zip ties
• Proper belt idlers instead of 625 bearings - eliminates belt rubbing
• Extrusions (optionally) joined via tapped ends + screws instead of corner brackets
• Lowered part count
• Better endstop mounting

Variants

FuseBox2 v1.0.1

• Minor change from 1.0 - added adjustment screw for more precise Z offset adjustment. Eliminates 2 M5x8mm screws and t-nuts, and needs 1 additional M3x25mm (or longer) bolt and 2 additional M3 lock nuts.

FuseBox2R v1.1

Switches out the twin 8mm rods on the gantry for a single MGN12 rail. Improvements include 30% gantry weight savings for less ringing and higher speeds, lowered bearing noise, easier belt tensioning, and a modular fan duct. Relatively inexpensive ($10-$15) MGN12 rails can be found on Aliexpress, so it's recommended to build this configuration if starting from scratch. The printed parts for the 2R gantry are in the rail gantry subfolder in the stl folder. Don't print anything from the stock gantry folder if building the rail gantry version, and vice versa.

Changes from FuseBox2

The entire CoreXY movement will need to be changed out. This includes all the parts on the gantry itself as well as the motor mounts and idler blocks.

Compared to the stock gantry, the belts may need to be shortened slightly.

Changes in FuseBox2R v1.1

Revised XY movement to simplify assembly and address issues with v1.0 rail gantry:

• X-end rigidity improvements
• Belts moved closer to centerline of MGN rail - alleviates x-end bending from belt tension; should further reduce ringing
• Corner idler brackets made more robust and compact - allows for a few mm more Y travel
• Homing direction reverted to x-min
• Thicker, more rigid 8mm rod holders with looser unclamped fit for easier rod installation

BOM

Item	Quantity
Extrusions
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
Thermistor for 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: cut off the microswitch from one endstop to use on the x axis)	3
40mm axial fan	1
2040 radial blower	1
Mechanical
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 (recommended) or all 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 other hardware
M5x8mm button head bolt	49
M5x12mm button head bolt	28
M5 T nuts (drop-in recommended)	49
M3x8mm socket head bolt	16
M3x10mm button head bolt	36
M3x25mm button head bolt	14
Bed leveling spring, nut, and bolt set	3
Extruder spring	1
M3 lock nut	50
Adhesive felt feet	4
Misc
~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 for bed	4

FuseBox2R MGN12 upgrade BOM

Item	Quantity
250mm MGN12 Rail + MGN12C Block	1
M3x10mm bolt (button head)	2
M3x6mm bolt (socket head)	4
M3x10mm bolt (socket head)	4
M3 lock nut	1
M3x25mm bolt (button head)	-6
M3x18mm bolt (button head)	4
300mm 8mm smooth rod	-2
LM8LUU bearing	-2

Note that the upgrade requires new fasteners and parts, but also gets rid of some. If upgrading, get only the positive quantity items. If building from scratch, add item amounts to base BOM.