Full hybrid upgrade for Rat Rig V-Core 3/3.1 printers

Rather than just repurpose VC4 hybrid parts as the 3.2H upgrade did, this mod is purpose designed and optimised for the VC3/3.1 printers.

It has:

1. Better motor mounting plates better suited to the VC3/3.1 frame.
2. It has lighter, and more rigid full metal XY joiners that more precisely align the X gantry.
3. This mod preserves the more optimal height of the VC3/3.1X gantry and this also means it is fully compatible with all existing 3, 3.1 compatible print heads, EVA, Microlight, etc. 

All parts (other than the long shaft motors) for this upgrade are now available on Aliexpress from Funssor.

Testing shows that the lighter weight and extra rigidity of the metal XY joiners provide surprisingly more gains in Input Shaper results than I expected. These are now also available from Funnssor. Unlike Rat Rig's hybrid upgrade XY joiners, both my options have the correct belt off-sets for all previous V-Core 3 and 3.1 print heads. 

The hybyrid belt tensioners are specifically designed to work on a a V-Core 3 hybrid. They have detents to help lock them into the front vertical 3030 extrusions (As I introduded with my Z  motor mounts years ago.)
Unlike the V-Core 4 ones, these mount with T-nuts in the extrusions to allow:

Fitting without drilling the frame
Fitting without custom side plates
Fine height adjustment for perfect belt alignment.

These 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.

If you want to take your upgrade to the next level of print quality and speed, consider jumping straight to the Full Frontal Gantry mod by just swapping out the XY joiners in this kit to the Full Frontal Gantry versions and using an Ultralight print head.

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

You can opt to just install just the much improved XY joiners or do the full hybrid upgrade. Even if you opt to just upgrade your XY joiners, you 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 (where there was no compromise in using them). This means you can source some 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.

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.

Coffee fund
I except no kick backs or royalties from third party companies such as Funssor for any of the parts in this upgrade.

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 VC3 Hybrid XY joiners locate the extrusion and bearings in the correct planes for the 3.1  which are different and more optimal than for the VC4. This means no other frame or print head upgrades or modifications are required to upgrade your VC3.1 to hybrid operation.
    

2. 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 printable parts from Rat Rig's CAD files.
    

3. I have also included remodelled the lower CoreXY motor mount plates to better 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 better seal your enclosure. I have included a picture of these fitted to a V-Core 3.1. These should be cut from alumininum plate and are included in the Funssor VC3 hybrid upgrade kit.
    

4. 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 bottom of these. You do not need to purchase a new Y end stop and keeping it mounted at the rear of the frame means you do not need to extend the wiring for it.
    

5. 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.
   

6. The XY joiner bearing stacks are designed to be held in place by 3mm screws that screw into the top and bottom of a 5mm OD aluminium tube (ferule) that sits in side the bearing stacks. 
   
   This arrangement is both lighter and more precise than using the usual 5mm screws.
   Feedback is invited and valuable.
   

7. All plastic parts should just be 3D printed in your preferred plastic.
   
    
    

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 the back of a V-Core 3/3.2 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.
BOM
2 x M5 x 28 Flat Head Cap screws.
2 x M5 x 10mm Socket Head Cap screws.
4 x Aluminium threaded ferules 14 x 50D x 3mm ID thread.
8 x M3 x 10mm Flat Head Cap screw.
8 x M3 aluminium countersunk washers.


Bom for Y end-stop mount and two Y bumpers.
3 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 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.
  
  
  
  BOM for 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 hybrid belt tensioners.
  4 x Rat Rig V-Core 4 tensioner arms.
  4 x M4 x 20 countersunk flat head cap screws.
  4 x M4 x 6 grub screws.
  6 x M6 T-nuts.
  6 x M6 x 24 socket head cap screws.
  
  4 x extra F695 bearings (you will also re-use the 4 from your original tensioners)
  2 x extra 695 bearings (you will also re-use the 2 from your original tensioners)
  
  
  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.
  Some parts of this upgrade are derivatives of parts on the Rat Rig VC4 hybrid printer.
  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
  
  18th August 2024: 
  Added BOM for VC3.1 hybrid upgrade motor mounts. 
  
  8th Dec 2024
  Added Y Axis bumpers
  
  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.