Full Frontal Gantry mod for Rat Rig V-Core

The Full Frontal Gantry mod for all models of Rat Rig V-Core 3 and 4 printers, other than IDEX.

Compatibility:
V Core 3 and 3.1 (MFBS hybrid upgrade)
V-Core 3.2h (Rat Rig's hybrid upgrade)
V-Core 4 
V-Core 4 hybrid 
OneBox and 
Enclosure 2
All Ultralight print heads.

Current Ultralight print heads released:
Dragon Ace
Rapido 2
Rapido 1
More coming….

Please note testing of this mod has now been completed and I am EXTREMELY pleased with the results.
I am achieving 40K accelerations on an otherwise near stock V-Core 300 with zero ringing visible. Videos of this have been posted in the Rat Rig Discord.

This is mod is fully compatible with both the V-Core 3 hybrid and V-core 4 hybrid. If you have a V-core 3 or 3.1 and want to upgrade it to hybrid please click here for the that, but use these XY joiners instead.

Why

1. The Full Frontal Gantry mod dramatically reduces the distance of the nozzle from the Centre of Rotation of the MGN12 carriage in the Y and Z dimensions. reducing nozzle movement due to play/flex in the carriage rail mounting interface to increase printing precision.
    
2. The The Full frontal mod also dramatically reduces the distance from the belt attachment points from the Centre of Rotation of the MGN12 carriage in both the Y and Z dimensions, reducing the moment of torque applied by the belts to the Centre of Rotaion of the MGN12 carrigage to increase printing precision.
    
3. The Ultralight core mounting plate template will provide a simple fixutre for a variety of print tools. Print tools could be things like the upcoming Bondtech INDA a pen a drag knife, etc.
   
    

Coffee fund
If you download and print this design or get a thrid party such as PCBway to print these parts for you I receive no compensation for my design work or my cost for the CAD software I have to pay an annual license for.

If you decide to make a donation to my coffee fund (which keeps me up late at night doing more of this stuff) I would appreciate it. There is absolutely no obligation for you to do this. My PayPal account is [email protected]

Please remember to post feed back as it is always valuable to me for future iterations.

Many thanks.
Liam Venter
MFBS Design

A STEP file of the Ultralight Core tool head mounting plate is included for those who want to mount other print heads or tool changers.
The core mounting plate is easily modified to support the mounting of a range of tools and print heads. I will release a version of this mounting plate to suit the Bondtech INDX tool changer as soon as Bondtech release the mounting template.

The Ultralight Core tool head mounting plates should be CNC'd or 3D printed in alumimium. PCBway charge about $26 to print these.

Files for the Dragon Ace Ultralight tool head are included.
PCBway charge about $32 to print the Dragon Ace Ultralight from aluminium.

Files for the Rapido 2 Ultralight tool head are included.
PCBway charge about $32 to print the Rapido 2 Ultralight from aluminium. You will also need Funssors stand off tube kit with this version of the Ultralight.

Files for the Rapido 2 Ultralight tool head are included.
PCBway charge about $32 to print the Rapido 1 Ultralight d from aluminium. You will also need Funssors stand off tube kit with this version of the Ultralight.
 

Modular back plate.
I have made the back plate modular. 

1. Top  (includes unmbilical cable mount
2. CPAP pipe
3. Ducts for part cooling.

Making these three parts modular makes it easier to swap these out for alternative part cooling  options.

I have also created drafts of of other Ultralight print heads for the following hot ends that I will update when they are finished.

Phaetus Rapido (original)
Triangle Labs Rapido Ace
Peopoly Lancer


Belt Wedge-Lock  retaining system.
For the Ultralight tool heads, I have devised a new  belt wedge lock retention system which sares the same Open Source license as all other aspects of this design.

1. The belts are pushed all the way through curved and tapered slots.,
2. Then a short 8mm length of filament is placed in about the 4th belt groove from the end,
3. The belt is then withdrawn out of the slot until the filament and belt jams in the narrowing taper of the slot.,
4. A small section of belt is left protruding out the slot so that when you want to release the belt you can just pull on the section sticking out with a pair of pliers to release the short piece of filament and then fully with draw the belt from the slot.,

Pros: 
Initial testing of the Wedge-lock belt retention systemshows that belt retention is very secure. 
The system is simple, compact and does not require any screws. 

Cons: 
A little bit fiddly to fit, but probably quicker than most other systems. 

I did experiment with using a toothed wedge instead of a piece of filament, but the filament worked so well the toothed wedge was just an unnecessary complication and easy part to drop on the floor and loose....so is the filament...but you can always find another 8mm long piece of filament! (edited)


Full Metal XY joiners
While all parts of this design have a non commercial license, I may offer a license to one manufacturer (yet to be selected) to offer these for sale as per the XY joiners for my previous V-Core 3 hybrid upgrade.

If you want the alternative XY joiners that are designed to be CNC machined rather than the ones in the files here that are designed to be aluminium 3D printed, please click on this link.
https://www.printables.com/model/1430210-full-frontal-gantry-cnc-version-of-xy-joiners

Both the printable ones and the CNC ones have exactly the same bearing offsets and both work really well. Both use the exact same Build of Materials (BOM)

XY joiners BOM
2 x M5 x 28 Flat Head Cap screws. (Ganty retaining top)
2 x M5 x 10mm Socket Head Cap screws. (Gantry retaining bottom)
7 x M3 x 8mm flat head cap screws (bearing stack retaining) 
1 x M3  x 6 mm flat hed cap screw for (bearing stack retaining)
4 x Aluminium threaded spindles 14 x 50D x 3mm ID (centre of bearing stack).

Assembly.
Only the XY joiners and the Ultralight Cores are 3D designed to be 3D printed from aluminium. All other parts should be printed from your favourite plastic.

When fitting on a  V-Core 3or 3.1 it is necessary to shorten each end of the linear rail by 5 mm with an angle grinder fitted with a cutting disk. Takes about 20 seconds per end. This is not necessary on a V-Core 4.


Aluminium 3D printable version of XY Joiners:
I currently use these versions on my printer.
The two of the bearing stacks installed in the shorter clevis's must be installed before the gantry is fitted. They can not be installed after the gantry is fitted. These will only fit into place if installed from behind the XY joiners. It is not possible to access the rear of the XY joiners once the gantry is intalled.
The other two bearing stacks can be fitted before or after the gantry is installed.
These XY joiners use two plain bearing spindles in each joiner.

Alternative aluminium CNC machinable version of XY Joiners:
Machining the XY tuners will be more dimensionally precise than printing them. These machined ones are just 1~2 grams heavier than the 3D printed ones.
All bearing stacks can be installed and removed once the gantry is fitted. 
These XY joiners use one plain bearing tube and one stepped bearing spindle in each joiner.

Ultralight:
Depending on the accuracy of the aluminium printed part, which can vary by as much as 0.1mm you may need to fractionally open up the entry point for the belt slots. This can be easily accomplished with a 1.5 mm drill bit.

Ultralight BOM
4 x M3 threaded inserts (5mm OD x 4mm long) 
https://www.aliexpress.com/item/1005001407970757.html
2 x M3 x 32mm Flat Head Cap Screws (Back plate vertical screws).
2 x M3 x 10 mm Flat Head Cap Screws (Front part cooling Duct mounting).
2 x M3 x 6 mm Flat Head Cap Screws (MGN Carriage).
2 x M3 x20 mm Flat Head Cap Screws (Fan mounting).
2 x M3 x 8mm Socket Head Cap screws (X-stop mounting).
2 x M3 x 8mm Socket Head Cap screws (Orbitor mount).
1 x 2.5 mm x 200mm  Zip tie (Orbiter clamp, optional)

Dragon Ace Ultralight: Requires tapping of:
2 x M3 x 0.5 holes for X-stop switch mounting.
2 x M3 x 0.5 holes for Orbiter mounting.

Rapido 2 Ultralight: Requires tapping of:
2 x M3 x 0.5 holes for X-stop switch mounting.
2 x M3 x 0.5 holes for Orbiter mounting.
3 x M1.6 holes for Rapido heater block mounting.

Rapido 2 Ultralight: Requires tapping of:
2 x M3 x 0.5 holes for X-stop switch mounting.
2 x M3 x 0.5 holes for Orbiter mounting.
3 x M1.6 holes for Rapido heater block mounting.

Updates

8/Sept/2025 increased diameter of heat sink hole in Dragon Ace version of Ultralight print head to make fitting easier.
08/Sept/2025 Increased clearances on XY joiners for belts.
14/Sept/2025 further increased the clearances on the XY joiners for the belts.
15/Sept/2025 Published Rapido 2 Ultralight STL and STEP files.
18/Sept/2025 Published Rapido 1 Ultralight STL and STEP files.
19/Sept/2025 Published CNC versions of XY joiners.
14/Oct/2025 Updated part cooling duct to give more clearance on heater blocks and it now also has an internal splitter to better direct airflow. 
30/10/2025 Added grub screw retention of the heat break for the Rapido 2 Ultralight