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
V-Core 3.2h (Rat Rig's hybrid upgrade)
V-Core 3.5 Hybrid (MFBS hybrid upgrade)
V-Core 4/4.1 
V-Core 4/4.1 hybrid 
OneBox and 
Enclosure 2
All Ultralight print heads.

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

Please note the Ultralight FFG tool heads have now been moved to their own listing on Printables.
Click on the image below to go to the Ultralight print heads: 

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?
Faster more accurate printing with less artifacts.
Simpler and faster servicing.

Advantages of a Full Frontal Gantry.
With a rigid print head and XY joiners, most unwanted movement/play in the system is the carriage rocking on the X linear rail. With a top mounted rail all the weight ends up being cantilevered a long way in front of the C0R of the linear rail carriage.

Mounting the linear rail on the front of the gantry, moves the CoR of the linear rail carriage closer to the nozzle and belt mounting points on the print head.

The main performance advantages accrue from this. This shorter distance reduces the moment (lever) that the forces operate through, which means less torque (turning torque) is applied about the Centre of Rotation of the MGN12 carriage due to:

1. The inertia of the print head.

2. The forces applied by the belts.

3.  In addition, the all four belts attachment points are in the same plane as the mgn carriage

These three attributes mean that there is less rocking and twisting of the mgn carriage

In addition, because the offsets are less, there is also a corresponding reduced vertical and horizontal displacement of the nozzle for any given amount of twist of the print head that does still occur. This point is much overlooked.

The above means you can use much higher print head accelerations before you begin to see acceleration related artifacts in your prints.

Better and truer first layers with less pre-print heat soak times.

The other advantage of the having the linear rail mounted on its side on the front of the X gantry is that any bi metallic bending in the X gantry now distorts prints in the Y direction instead of the Z direction.

This may seem like a moot point with the excellent improvements in the latest RatOS pre-print processes and the new steel X tube in the V-Core 4.1 printers, but getting rid of the problem at source provide more advantages than just mitigating the issue. One of these advantages is a big reduction in pre-print heat soak times.


A Full Frontal Gantry enables us to engineer better print heads.
Having the rail mounted on the front of the gantry enables the design of much simpler, more compact, and more rigid print heads like the Ultralights as you don’t need to try and engineer rigid structures between the top  plate which is mounted to the carriage and an often separate front plate to which the hot end is mounted.

This enables a much lighter and less bulky print head. It's not until you have one in your hand that you realise how simple and tiny the Ultralight print heads are. Less weight allows higher accelerations with less ringing artifacts due to belt elasticity.

The Ultralights are also extremely rigid between the points where it counts. The hotend is virtually mounted (almost) directly to the carriage and the belts. There are no flexible structures or joints between the hot end and the belts or carriage.

Because the hot end heater blocks are also directly mounted to a heat sink, that is a monolithic part of this same face plate, there are also no flexible structures between the belt mounting points and the nozzle (other than the fastening system between the heater block and heat sink*)  again this means a reduction of acceleration artifacts in prints due to flex between the nozzle and the belts that move and position it…providing more precise nozzle location under fast accelerations.

* Depending which heater block you select this can also very rigid.

Simper Faster Servicing.
But the thing that seems to surprise people the most, is just how much easier any well designed FFG print head can be to work on. FFG lends itself to a much simpler print head design and construction and nearly every fastener can be accessed from the front.

The most service intensive part of a 3D printer is typically the print head.

In the case of the of the Ultralight FFG print head there are only  2 screws for the extruder and 2 for the back plate that are  accessed from the top and only the two beacon mount screws from the bottom. No screws are accessed from the back.

All belt attachments are accessed from the front with the very simple and reliable Wedge-lock attachment system.

The modularity of the back plate even makes swapping out fan ducts very fast and easy.

There are only 10 screws in the entire tool head assembly depending on what hotend you are using

2 x end-stop mounting screws
2 x heatsink fan mounting screws
4 x screws mounting the CPAP pipe and duct.
3 x screws mounting the heater block to the heat sink (or none in the case of the Dragon Ace Volcano hotend)
2 x screws to mount the Beacon

Now and them up and compare that screw count to number of screws in other hotends. Getting rid of screws not only reduces the weight, but also greatly reduces the servicing time.

This may seem like just convenience, but in a commercial environment like mine more uptime means a more productive and profitable tool.

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

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.

If you are using a Titanium X tube:
Several of us have discovered that the Titanium X tubes available are often very slightly oversized. Instead of being exactly 20 x 20 mm you might get one that is something like 20.1 x 20.3 mm and these may not fit standard sized 20 x 20 mm XY joiners, like these.

No problem. Using a small flat fine toothed file of say 18 mm width (Sometimes sold as a 'lathe' file, you can file out your joiners, with them held in a vice in about 20 minutes to fit.

To prevent the jaws of your vice marking your nicely anodized joiners you can use some leather cut from your spouses pants between the jaws of the vice and the joiners. To ensure a nice close sliding fit between the tube and XY joiners use some prussian blue (engineers blue) to indicate the high spots. I like a very slight interference fit that requires a couple of LIGHT taps to fit the joiners on the tube.

Updates:
08/Sept/2025 Increased clearances on XY joiners for belts.
14/Sept/2025 further increased the clearances on the XY joiners for the belts.
25th/ Feb/2026 move Ultralight print heads to their own listing on printables.

The terms FFG, Full Frontal Gantry, FRG and Full Rear Gantry are copyrighted by MFBS Design.