The V-Core 4.1 is Rat Rig's open CoreXY kit, sold in 300, 400 and 500 mm sizes, with Hybrid and IDEX upgrades and optional carbon filtration. It is for experienced makers who want a Klipper printer they build and tune themselves.
Does the Rat Rig V-Core 4.1 3D printer work with SimplyPrint, OctoPrint, Mainsail and Fluidd?
Each way of connecting it, what it needs, and how to set it up.
Ships with Klipper: OctoPrint only runs on top of it, through the OctoKlipper plugin
What works with SimplyPrint
Connected through Klipper (Moonraker), SimplyPrint supports most of what it offers on the Rat Rig V-Core 4.1: the camera and AI failure detection, remote printing, skipping objects, temperature and movement control and AutoPrint. Not yet in SimplyPrint through Klipper (Moonraker): download the file before the print starts.
Every SimplyPrint feature, for each way of connecting it to SimplyPrint
Connected to SimplyPrint through
SimplyPrint feature
Klipper (Moonraker)
Compatible
Monitoring
Live status and progress
Yes
Webcam
Yes1
AI failure detection
Yes1
Time left
Yes
Layer progress
Yes
Temperatures
Yes
Printing
Starting a print
Yes
Pause, resume and cancel
Yes
Skip objects
Yes
Printer control
Change temperatures
Yes
Moving with the controls
Yes
Homing
Yes
Extrude and retract
Yes
Change print speed
Yes
Fan speed
Yes
Baby stepping
Yes
Send G-code
Yes
Calibration
Change filament
Yes
Bed leveling
Yes
Z-Offset Calibration
Yes
Automation
AutoPrint
Pro
Yes
Download the file before the print starts
No2
Connected to SimplyPrint through Klipper (Moonraker)
Compatible
Monitoring
Live status and progressYes
WebcamYes1
AI failure detectionYes1
Time leftYes
Layer progressYes
TemperaturesYes
Printing
Starting a printYes
Pause, resume and cancelYes
Skip objectsYes
Printer control
Change temperaturesYes
Moving with the controlsYes
HomingYes
Extrude and retractYes
Change print speedYes
Fan speedYes
Baby steppingYes
Send G-codeYes
Calibration
Change filamentYes
Bed levelingYes
Z-Offset CalibrationYes
Automation
AutoPrint ProYes
Download the file before the print startsNo2
Works
Depends
Not supported
Needs a camera
SimplyPrint doesn't support this through this connection yet.
What slicer to use for the Rat Rig V-Core 4.1
None of the slicers in SimplyPrint's cloud has a ready-made profile for the Rat Rig V-Core 4.1, but it takes standard G-code: start from a similar printer's profile and set the bed size, height and nozzle to match.
We only list slicers you can use in the SimplyPrint cloud, so there may be others for the Rat Rig V-Core 4.1.
Cloud-Based Slicer for Rat Rig V-Core 4.1
All supported slicers - directly in your browser with SimplyPrint's online cloud slicer. No installation required. Slice your Rat Rig V-Core 4.1 models from any device, anywhere in the world!
Automatic Profile Updates: Profiles are automatically checked and fetched from the slicer GitHub repositories every day, as well as from our own open-source community-driven slicer profile database. This ensures you always have access to the latest profiles.
Note: Other slicers, such as Simplify3D, ideaMaker, SuperSlicer and KISSlicer, aren't in our cloud, so we don't track their profiles. They may still work well with your Rat Rig V-Core 4.1: check the slicer's own documentation or forums for a profile. You can also contribute profiles to our open-source slicer profile database on GitHub.
The app for the Rat Rig V-Core 4.1
Rat Rig doesn't make an app for the Rat Rig V-Core 4.1. SimplyPrint works as its app: on your phone and in any browser, with a slicer in the cloud.
There's no plate swapper or auto-ejection kit for the Rat Rig V-Core 4.1 in SimplyPrint yet, but AutoPrint can still keep it printing: once the plate is clear, it starts the next job from your queue.
CoreXY printers push their prints off
The Rat Rig V-Core 4.1's bed only moves up and down, so the usual way to automate it is a G-code routine that lets the toolhead push the cooled print off the front of the plate before the next job starts.
Ways to automate it
Push prints off with the toolheadOn a CoreXY printer, a G-code routine can push the cooled print off the front of the plate before the next job starts.
Your own ejection G-codeWrite the routine that clears your plate, and AutoPrint runs it after every print.
Rat Rig V-Core 4.1 specifications: bed size, print height and more
Its size, temperatures, multi-material and how it connects, from the maker and our own research.
Read more by the manufacturer
Size
Build volume
300 x 300 x 300 mm
Bed type
Square
Bed size
300 x 300 mm
Max print height
300 mm
Printing
Enclosure
Partly enclosed
Motion system
CoreXY
Max extruder temperature
350 °C
Has heated bed
Yes
Max bed temperature
120 °C
Number of nozzles
1
Toolheads
1
Direct drive
No
Probing tool / Auto Bed Leveling
Yes
Filament width
1.75 mm
Multi-material
Toolchanger or hotend changer
No
IDEX (independent dual extruders)
No
Connecting
Supports serial printing
No
Shipped firmware
Klipper
Files and slicing
Supported file formats
G-code (.gcode, .gco, .g)
The printer
Printer manufacturer / brand
Rat Rig
Printer model name
V-Core 4.1
Made by a company from
Portugal
Launched
December 2025
Still made
Yes
Disclaimer:
We strive to keep this information as current and accurate as possible, but cannot guarantee its completeness or reliability. Our data is based on user submissions and manufacturer references.
What filament can the Rat Rig V-Core 4.1 print?
Filament compatibility for the Rat Rig V-Core 4.1: the materials Rat Rig lists for it.
Filament
Suitability
Notes
PLA
Great
On the maker's list of materials for this printer.
PETG
Great
On the maker's list of materials for this printer.
TPU & flexibles
Great
On the maker's list of materials for this printer.
ABS & ASA
Great
On the maker's list of materials for this printer.
Nylon (PA)
Great
On the maker's list of materials for this printer.
Polycarbonate (PC)
Great
On the maker's list of materials for this printer.
Carbon-fiber & glass-filled
Great
On the maker's list of materials for this printer.
Tip: this is a general guide from the printer's specs - always check your filament's recommended settings. With SimplyPrint you can save a profile for each spool and track exactly what filament you have in stock.
Best filament for the Rat Rig V-Core 4.1
Filaments the Rat Rig V-Core 4.1 prints well, Rat Rig's own first, then the best known.
Choose the V-Core 4.1 if you enjoy building and customising your printer and want it to grow: Rat Rig's page offers a size choice, electronics included or not, a Hybrid upgrade with higher acceleration and an IDEX upgrade for two materials or copy and mirror modes. Enclosing panels are not included (Rat Rig supplies DXF files), so it is not ready for ABS or classrooms as bought. We found no independent review for this version. If you want a printer that arrives ready to run, the Prusa CORE One+ is the easier route.
Pros
Sold in 300, 400 and 500 mm sizes, so you pick the build volume (Rat Rig).
Hybrid and IDEX upgrades add higher acceleration or a second extruder for two materials or copy and mirror modes (Rat Rig).
An optional Rat Pack carbon filter for ABS, ASA, PC and nylon fumes (Rat Rig).
Open design with a plug-and-play wiring harness in the electronics kit (Rat Rig).
Works with SimplyPrint through Klipper.
Cons
A kit you assemble yourself, with the enclosing panels not included (Rat Rig).
Not an out-of-the-box printer: tuning and Klipper configuration are up to you.
Some parts are on backorder or pre-order, and the final cost depends on size, electronics and upgrades (Rat Rig).
We found no independent review of the 4.1.
Who it suits
SchoolsNot a good fit
An open kit that students would have to build and tune; the open frame leaves moving parts exposed.
HobbyistsGreat fit
A flexible Klipper platform for tinkerers who like building and upgrading.
BusinessesCan work
Capable and configurable, but variable by build and not supplied ready to run.
Print farmsNot a good fit
Every unit is a custom build to assemble and tune, so a fleet would be uneven and slow to deploy.
Compare the Rat Rig V-Core 4.1 with similar printers
Printers from the same maker, of a similar size, printing the same engineering materials or multi-material like it, that you can buy today. Compare up to four side by side, with their specs and how each connects.
Who makes the Rat Rig V-Core 4.1, and how open Rat Rig leaves you: whether its printers run without its cloud, take any filament and slicer, and can be repaired. Each area is rated from public sources.
Openness: Open (5.0 of 5)
Open
Walled gardenOpen
Rat Rig is a Portuguese company near Faro that designs and sells do-it-yourself kits for large CoreXY 3D printers and CNC machines, mostly to buyers abroad. Its V-Core printers come as kits you assemble, run on RatOS, Rat Rig's Klipper distribution, and suit makers who want a big machine they can upgrade and repair themselves.
Founded:
2014 ·
Headquarters:
Near Faro, Portugal ·
Ownership:
Privately held; founder and CEO Miguel Carvalho (2024) ·
People:
About 30 employees (2024) ·
Website:ratrig.com
Published designs, a GPL Klipper distribution, standard parts and no cloud leave the owner in control. The one limit is that the design files may not be reused commercially.
Firmware and custom firmware ●●●●●
RatOS, Rat Rig's Klipper distribution, is developed in the open on GitHub under the GPL-3.0 and was still being updated in 2026 (2.1 release line); plain Klipper and Mainsail can be used instead.
[8][7]
Local control and integrations ●●●●●
RatOS runs Klipper, Moonraker, Mainsail and KlipperScreen on a Raspberry Pi in the printer, on your own network, and Moonraker's API is documented. Rat Rig has no printer cloud or account.
[7][17]
Third-party filament, slicers and parts ●●●●●
The machines use standard parts (MGN and HG rails, Gates belts, LDO and BigTreeTech electronics, Orbiter extruders) that Rat Rig and others sell, any filament, and any slicer; OrcaSlicer ships V-Core 3, V-Core 4 and V-Minion profiles.
[4][16]
Repairs and spare parts ●●●●●
Rat Rig sells parts one by one and publishes CAD, STL files, bills of materials and step-by-step build guides on its wiki. The design files are licensed CC BY-NC-SA 4.0, so they are free to use and modify but not for commercial reuse.
[6][10][2]
Data and privacy ●●●●●
Printing needs no account and everything runs on the printer's Raspberry Pi; RatOS's setup script even turns off the telemetry of the web framework its configurator uses. Rat Rig's privacy policy covers only its web shop.
[9][5]
Community and documentation ●●●●●
Rat Rig says its user communities (Facebook groups, plus an unofficial Discord) have many thousands of active members; documentation is public on its wiki and the RatOS site, and RatOS is developed openly on GitHub (by Mikkel Schmidt, per the RatOS docs). The documentation is split across the two sites.
[1][7][6]
Pros
Large build volumes, up to 500 mm, at kit prices.
Open, documented designs and standard parts make repairs and upgrades straightforward.
RatOS gives a ready-made Klipper setup that runs entirely on your own network.
Sold as kits: you assemble, wire and tune the printer yourself.
Design files are licensed for non-commercial use only (CC BY-NC-SA), unlike GPL projects.
Documentation is split between the Rat Rig wiki and the RatOS site.
Track record
2026: Rat Rig began selling the V-Core 4.1, a revised kit with a steel X gantry and newly written build documentation, together with a 4.1 upgrade kit for V-Core 4 owners.
[2][3]
November 2024: 3D Printing Industry shortlisted the V-Core 4 (IDEX and Hybrid), released earlier in 2024, for Desktop FFF 3D Printer of the Year.
[14][15]
September 2024: Dinheiro Vivo reported that Rat Rig had received about 200,000 euros of regional development aid for its first expansion and had been granted about 100,000 euros more from the Algarve 2030 programme for trade fairs and equipment.
[12]
August 30, 2024: Rat Rig released the IDEX upgrade that adds a second toolhead to the V-Core 4; it told Dinheiro Vivo it sold hundreds in the first 24 hours.
[12]
December 2022: Rat Rig won the 3D Printing Industry Award for Company of the Year (Personal).
[13]
2021: Rat Rig released the V-Core 3, a high-speed CoreXY kit in 200 to 500 mm sizes, with its design files on GitHub.
[11][15]
Researched from 17 sources, last checked October 18, 2026. Show sources
Is the Rat Rig V-Core 4.1 compatible with SimplyPrint?
Yes. You can connect the Rat Rig V-Core 4.1 to SimplyPrint via Klipper (Moonraker), then slice, queue, start and monitor prints from your browser or the mobile app.
How do I connect the Rat Rig V-Core 4.1 to SimplyPrint?
Follow our step-by-step setup guide for the Rat Rig V-Core 4.1. It shows how to connect it via Klipper (Moonraker), what you need for each, and which to pick.
What slicer should I use for the Rat Rig V-Core 4.1?
Cura, PrusaSlicer and OrcaSlicer all work with the Rat Rig V-Core 4.1, and you can run any of them in SimplyPrint's online browser slicer - no install needed, on any device.
Can I use OrcaSlicer with the Rat Rig V-Core 4.1?
Yes, but OrcaSlicer has no built-in profile for the Rat Rig V-Core 4.1 that we know of: start from a similar printer's profile and set the bed size, height and nozzle to match.
What filament can the Rat Rig V-Core 4.1 print?
Rat Rig lists PLA, PETG, TPU & flexibles, ABS & ASA, Nylon (PA), Polycarbonate (PC) and Carbon-fiber & glass-filled for the V-Core 4.1.
Does the Rat Rig V-Core 4.1 work with OctoPrint or Klipper?
The Rat Rig V-Core 4.1 works with Klipper (Mainsail and Fluidd), and SimplyPrint connects to it through them - so you get cloud access, a queue and camera monitoring on top.
What is the Rat Rig V-Core 4.1's bed size and build volume?
The Rat Rig V-Core 4.1 has a 300 x 300 mm print bed and prints up to 300 mm tall, a build volume of about 300 x 300 x 300 mm. See the full specifications table above for bed type, temperatures and more.
When did the Rat Rig V-Core 4.1 come out?
Rat Rig launched the V-Core 4.1 in December 2025.
Can the Rat Rig V-Core 4.1 eject prints automatically?
There's no kit for it that we support yet, but SimplyPrint's AutoPrint can push prints off with the toolhead, or run your own ejection G-code, and then start the next job from your queue.
Where can I buy the Rat Rig V-Core 4.1?
From Rat Rig's own store, which has shops for everywhere else. The links on this page go to those stores; some are affiliate links, so we may earn a commission at no extra cost to you.
Affiliate disclosure: Some links on this page are affiliate links. We may earn a commission if you make a purchase, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
Portugal
Klipper (Moonraker) 
PrusaSlicer
OrcaSlicer
BambuStudio
ElegooSlicer
CrealityPrint
Cura
Kiri:Moto
