Rat Rig V-Core 3 and 3.1 compatible hybrid upgrade.

The files and BOM provide everything you need to port the VC4 hybrid functionality on to your existing VC3. other than the long shaft motors and the front belt tensioners.

I recommend you use these belt tensioners on your hybrid upgrade. https://www.printables.com/model/1131528-rat-rig-v-core-3-hybrid-belt-tensioners

This mod is an VERY SIMPLE to retrofit to any of the open front, OneBox or Rat Rig version of their  enclosed Rat Rig V-core 3 and 3.1 printers.

You can opt to just install the much improved XY joiners or do the full hybrid upgrade. Even if opt to just upgrade your XY joiners should expect to get excellent gains in Klippers input shaper recommended accelerations. I ran my own printer like this for several months before adding the other hybrid upgrade parts.

A key focus has been on providing compatibility with your existing VC3 and forward compatibility with standard Rat Rig VC4 parts. This means you can source parts from Rat Rigs existing parts inventory and that you might be able to take advantage of some future upgrades and updates from Rat Rig.. There were no design or functionality compromises required in porting the VC4 hybrid operation onto the VC3. I saw no need to reinvent the wheel.

For example, this entire mod is fully compatible with your existing 3.1 compatible print head, EVA, Microlight, etc. 

This upgrade will not ready your printer for full width IDEX operation, because it does not increase the width of your printer. It is designed as a simple and cost effective performance update to give you the same functionality as the newer Rat Rig V-Core 4 printer in hybrid mode.

If you wish to move your belt tensioners off your print head and mount them on the front vertical extrusions of your printer (highly recommended for ease of maintenance and using modern print head designs like the Microlight), then please see my other mods. Funssor also include my design of front belt tensioners in their hybrid upgrade kit available from Aliexpress.

The files attached include much improved XY joiner assemblies for Rat RigV-Core 3 and 3.1 printers. They use standard Rat Rig VC4 XY joiner top plates.

If your just doing the XY joiner upgrade the only custom metal parts required are the bottom XY joiner plates and the spacer tubes. 

If you are doing the full hybrid upgrade The above plates and some optional lower motor mount plates (which are shaped to better seal an VC3 enclosure) are available from Funssor on Aliexpress. For the full hybrid upgrade you will also need the front belt tensioners for the extra hybrid belts.

All non custom VC4 metal parts, like the top XY joiner parts and the motor mount plates used in this design are standard Rat Rig VC4 parts.

This mod also moves your Y linear rails to the top of the Y extrusions, where they are more readily accessible for cleaning and maintenance.

Coffee fund
I except no kick backs or royalties from third party companies such as Funssor who manufacture stuff I model and post on Printables.

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

Notes:

1. The bottom XY joiner plates are different from the VC4 bottom plates. This is required to get the necessary spacing for the two bottom cap screws that bolt into T nuts in the 2020 X gantry extrusion because the 2020 extrusion does not insert as far into the XY joiners on the VC3.1.
    
2. I have split the printed extrusion locators in the XY joiners into two parts in a different manner from the VC4 XY joiners. This makes thse parts eaiser to print flat on the bed without supports.
    
3. The VC3 Hybrid XY joiners locate the extrusion and bearings in the correct planes for the 3.1  which are different for the VC4. This means no other frame or print head upgrades or modifications are required to upgrade your VC3.1 to hybrid operation.
    
4. The countersunk bolts and cap head screws are different lengths from the VC4. I have given careful attention to the design to ensure that the length of all screws are readily available lengths.
    
5. The printed hybrid belt retention parts and other hardware that screws to the top of the XY plates are the same as for the standard VC4. You can download these parts from Rat Rig's CAD files.
    
6. I have also included remodelled optional lower CoreXY motor mount plates to fit the rear shelf of the V-Core 3.1 Open front, OneBox and V-Core 3.1 2.0 Enclosure frames. These are optional but look tidier and will allow you to better seal your enclosure. I have included a picture of this fitted to a V-Core 3.1. These should be cut from alumininum plate and are included in the Funssor VC3 hybrid upgrade kit.
    
7. I have included a replacement Y rear end stop mount as the original V-VCore 3 ones won't work with the hybrid joiners. Note there is also a file included for a detent that is a press fit into the botoom of these.
    
8. I have included front Y axis bumpers. These have been remodelled from the VC4 Y axis bumpers to suit the length required for the VC3.
    
    

Instructions
For assembly of the motor mounts just follow the VC4 online instructions. 
https://ratrig.dozuki.com/Guide/04.+Motion+system+-+CoreXY/242
The one mototr plate that is slightly different on each side is postiioned as the second plate up from the bottom on each side.

Assembly of everything else is self evident.

When you print out the XY joiners measure and check the stack height of the two plastic parts. They should have the same stack height as the two long internal aluminium support tubes (43mm). Remember some materials like ABS will have some shrinkage when you print it and you may need to compensate fo this shrinkage in your slicer settings.


Klipper hybrid configuration
A V-Core 3 hybrid upgrade is not yet included in RatOS configuration wizard.
I just selected the RatOS configuration for the V-Core 4.
I then made the following changes to my printer.cfg file.

[stepper_x] # Gantry is narrower on a V-Core 3 and the end stop is offset from the V-Core 4.
position_min: 0
position_max: 300
position_endstop: 0

[stepper_y] #Y end stop is at th back of a V-Core e and at the front of a V-Core 4
position_min: 0
position_max: 300
position_endstop: 0

Add this toyour printer.cfg file

[gcode_macro RatOS]
variable_bed_margin_x: [0, 0]
variable_bed_margin_y: [0, 0]


Bom
Please not the following Bom does not include the parts you will reuse from your VC3.
Funssor include everything you need as below in their VC3 hybrid upgrade kit , other than the longer shaft motors.

Bom for XY joiners.
2 x V-Core 4 top XY joiner plates. 
2 x V Core 3 hybrid joiner lower plates

XY assembly hardware and spacers
All spacers for the XY joiner assemblies can be cut from a length of 10mm OD X 5mm ID aluminium tubing.

4 x 43 mm spacer 8mm OD/5 mm ID
2 x 29 mm spacer 8mm OD/5 mm ID

2 x 16 mm  spacer 8mm OD/5 mm ID
2 x 13mm spacer 8mm OD/5 mm ID

Countersink screws and  nylock nuts
8 x M5 x 55 x 0.8 countersink 
2 x M5 x 28 x 0.8 countersink 
8 x M5 X 0.8 Nylock nuts

Cap head screws

4 x  M5 x 12 x 0.8 countersink 


Bom for mounting X-stop bumper
2 x M3 x 4mm OD  x 5mm long threaded inserts (OD and length not critical, use what you have).
1 x M3 x 16 socket head cap screws.



Bom for Y bumpers
1 x M6 x 10mm cap head scew



Additional stock VC4 parts required if you wish to use these improved XY joners to also upgrade to hybrid operation.

• Left and right VC4 CoreXY and Y motor mount assemblies.
• 4 x LDO-42STH48-2504AH(S37) motors, 37mm or longer shafts. Longer shaft motors can eaisly be shortened with an cutting disc on an angle grinder or dremel.
• 2 x front belt tensioners.These can be found here:
  https://www.printables.com/model/918098-mfbs-generic-front-belt-adjusters-for-3d-printers
• 2 x additional belts for the Y motion system (I recommend reusing your existing CoreXY belts for the Y motion system and purchasing two new belts to replace your existing CoreXY motion system belts.
  
  The following Y clamp hardware:
   
• Y belt clamp printed parts and mounting screws.
• 4 x M3 x 12 x 0.5
• 6 x M3 x 8 x 0.5
• 6 x m3 x 4.6 x 4 brass inserts
  
  
  BOM for motor mounts assemblies for V-Core 3.1 hybrid upgrade
  Does not include parts already included with V-Core 3.1
  
  Motor mount plates
  One set of 8 x VC4 motor mount plates
  
  or better option to help seal enclosure.
  
  6 X VC4 motor mount plates &
  2 x VC3.1 hyybrid upgrade motor mount plates available from Funssor
  
  Extra Hardware required for Left Motor mount BOM
  
  4 x Cap head screw M6 x 50mm
  
  2 x Cap head screw M5 x 45mm
  1 x Cap head screw M5 x 85mm
  
  2 x Countersink Screw M3 x 40mm
  6 x Countersink Screw M3 x 6mm (motor mounts)
  
  1 x Button head screw M5 x 35 mm (X stop mount)
  
  1 M6 T-Nut Drop in for 3030 extrusion
  1 x Hex Locking Nut M5
  
  4 x Aluminium Spacer 6 ID x 10 OD x 30 mm
  1 x Aluminium Spacer 5 ID x 8 OD x 14mm
  2 x Aluminium Spacer 5 ID x 8 OD x 10mm
  6 x Aluminium Spacer 5 ID x 8 OD x 4mm
  2 x Aluminium Spacer 3 ID x 6 OD x 30mm
  
  6 x  Ball Bearing F695ZZ
  2 x Ball Bearing 695ZZ
  
  1 x Timing Pulley 2GT-20T for 9mm belt
  
  Extra Hardware required for Right Motor mount BOM
  
  4 x Cap head screw M6 x 50mm
  
  2 x Cap head screw M5 x 45mm
  1 x Cap head screw M5 x 85mm
  
  2 x Countersink Screw M3 x 40mm
  6 x Countersink Screw M3 x 6mm (motor mounts)
  
  1 M6 T-Nut Drop in for 3030 extrusion
  1 x Hex Locking Nut M5
  
  4 x Aluminium Spacer 6 ID x 10 OD x 30mm
  1 x Aluminium Spacer 5 ID x 8 OD x 17mm
  2 x Aluminium Spacer 5 ID x 8 OD x 10mm
  5 x Aluminium Spacer 5 ID x 8 OD x 4mm
  2 x Aluminium Spacer 3 ID x 6 OD x 30mm
  
  6 x  Ball Bearing F695ZZ
  2 x Ball Bearing 695ZZ
  
  2 x Timing Pulley 2GT-20T for 9mm belt
  
  Long shaft motors
  4 X LDO 42STH48-2504AH(S37) 
  
  You may find it easier and cheaper to source the slightly longer shaft version of the same motors, LDO 42STH48-2504AH(S55). If you source the longer shaft motor the shafts are quick and easy to trim with an angle grinder with a cutting disc as I did.
  
  
  
  Atrtribution: 
  This hybrid upgrade is a derivative of the original Rat Rig VC3 and the VC4 printer.
  Some parts of this upgrade are derivatives of the excellent design of the Rat Rig VC4 hybrid printer.
  These two printers have different open source licenses, The VC4 has an Open Source Non Commercial license and the VC3 had a Open Source license, Hence parts of this upgrade inherit the VC3 license and are covered by the Commercial use license and parts of it inherit the VC4 Non Comercial license. 
  
  
  Updates
  5th August 2024: 
  Corrected error in upper and lower right hand side XY joiner printed parts and strengthened upright tab on lower left printed part.
  
  13th August 2024: 
  Included raised Y endstop required to work with hybrid XY joiners.
  
  18th August 2024: 
  Added BOM for VC3.1 hybrid upgrade motor mounts. 
  
  24th August 2024:
  Corrected 0.4mm offset error, in the location of the 2020 extrusion tube, in the right hand joiner printer parts.
  
  8th Dec 2024
  Added Y Axis bumpers
  
  23/12/24
  Added a X-stop bumper
  Modified top left XY joiner printed part to mount X-stop bumper.
  
  25/12/24
  Corrected bottom left XY joiner STEP file (The STL file had the correct sizing for the 2020 extrusion but the STEP file was incorrect.
  
  28/04/25
  Corrected BOM from 1 x Timing Pulley 2GT-20T for 9mm belt,  to 2 x Timing Pulley 2GT-20T for 9mm belt.
  
  16/06/25
  Added new Y  end stop mount.