Klipper
Open-source printer firmware that splits the work: a small program on the printer's microcontroller does the stepping, while a host computer — usually a Raspberry Pi — does the heavy motion maths. The result is faster, quieter, more precise printing from the same hardware.
If you want to push an ageing or mid-range printer well past its stock limits — and you don't mind flashing firmware and editing a config file — Klipper is the upgrade. Pair it with Moonraker and a web UI like Mainsail or Fluidd and you get input shaping, pressure advance and remote control on hardware that previously topped out at a fraction of the speed.
What it is
Klipper is firmware for FDM 3D printers, but it is architected differently from the usual single-board approach. Instead of running all the motion planning on the printer's own microcontroller, Klipper runs the planner on a separate host computer — typically a Raspberry Pi — and reduces the printer board's firmware to a tiny program that just executes precisely timed step commands sent over USB or serial. The host does the trigonometry; the microcontroller does the timing.
Because the host is a full Linux machine, Klipper can afford expensive maths the printer's own chip never could: high step rates, look-ahead, and per-move acceleration shaping. The whole machine is described in a single human-readable printer.cfg file — kinematics, pins, limits, macros — so the printer's behaviour is configuration-as-code that you can version and share. Klipper does not ship a UI of its own; it pairs with Moonraker (a web API) and a front-end such as Mainsail or Fluidd.
Where it wins
- Speed and quality from the same hardware. Input shaping cancels ringing/ghosting, and pressure advance sharpens corners and seams — both let you run higher speeds and accelerations than stock firmware allows.
- Config-as-code. The entire printer lives in
printer.cfg. Tuning is editable, diffable text, and proven configs for common machines are easy to find and adapt. - Powerful macros. Klipper's macro system lets you script start/end routines, calibration and conditional G-code logic that would be painful or impossible elsewhere.
- Open and networked. GPL-3.0, with Moonraker exposing a clean API so Mainsail, Fluidd, mobile apps and your own scripts can all drive the printer remotely.
Where it still hurts
- You must flash the board. Klipper means compiling and flashing firmware onto the printer's microcontroller — straightforward once you've done it, intimidating the first time, and a hard requirement rather than an optional step.
- Steeper setup. An extra host computer, a config file to populate, and calibration to run before the first good print. It rewards tinkerers; it punishes "plug in and go".
- No stock LCD by default. The familiar printer screen typically goes dark — you drive the machine from a phone or laptop, or add a dedicated touchscreen. Some find that a downgrade for quick at-the-printer tweaks.
- Another box to maintain. The Raspberry Pi (or equivalent) is now part of your printer, with its own SD card, updates and failure modes.
The AI angle
Klipper's split architecture is quietly ideal for the AI era: the host is already a Linux SBC with spare compute and a network, so it is the obvious place to bolt on a camera and run inference. Moonraker's open API means failure-detection, first-layer vision and automatic tuning tools can read state and issue commands without hacking the firmware. Projects that watch the print and pause on spaghetti, or that tune pressure advance from a few test runs, all plug into this surface — and an LLM agent can read and edit printer.cfg as plain text. We dogfood this directly: ender-pi (github.com/2nth-ai/ender-pi) is our real Raspberry Pi 4 Klipper server for a Creality Ender 3 V2, where flashing Klipper onto the stock 4.2.2 board is the firmware step that unlocks the rest.
Start here
- Read the official docs and install guide at klipper3d.org.
- Source and releases: github.com/Klipper3d/klipper. Note: Kalico is an active fork (descended from Danger Klipper, December 2024) with experimental features and faster release cycles — worth watching if you want bleeding-edge hardware support.
- Use the KIAUH helper to install Klipper, Moonraker and a UI on your Pi in one place.
- Slice with OrcaSlicer and run its calibration tests once input shaping and pressure advance are tuned.
- See how it fits the bigger picture: the Klipper stack explained — Klipper, Moonraker and Mainsail as four layers.