K2 OpenKlipper

Open-source mainline Klipper for the Creality K2: strain-gauge probe, CFS multi-filament box, closed-loop motors and touchscreen, without Creality's closed control stack.

The Creality K2 normally runs a closed fork of Klipper: the nozzle probe (prtouch_v3), the CFS box driver, the closed-loop X/Y/E motor control and the screen are compiled binaries, and Creality's master-server drives the printer. This project replaces all of that with upstream Klipper plus open Python modules, so the K2 can be driven, tuned and extended like any other Klipper printer: Mainsail, Moonraker, your own macros, OrcaSlicer, Klipper input shaping and pressure advance.

It runs on the printer's own board. No external host or hardware changes are needed, and the stock firmware stays installed for a one-command rollback. Optionally, Klipper can run on a separate PC over one USB cable (external host).

Install: step-by-step guide, about 15 minutes.

Status: alpha (v0.4.2-alpha.1). It is in daily use on one K2 (F021, K2 / K2 Combo) and has completed full prints, CFS loads and multi-slot jobs. It is still experimental printer firmware: supervise prints, keep the rollback path, and read Project status first.

What works

Area	Open implementation
Klipper host	Upstream Klipper (pinned commit in K2-BUILD-MANIFEST)
Z probe	Open re-implementation of the K2 nozzle strain gauge (PRTouch): precise Z home, adaptive mesh, contamination guard
Z reference	PA15 optical bottom switch, used at every print start (start sequence)
X/Y/E motors	Closed-loop motor bus: wake-up, stall homing, parameter read/write, telemetry (motor controller)
CFS	Load, purge, unload, tool changes, steady feed, take-up tension, per-slot filament records, error retry (CFS protocol)
Pressure advance	Measured with the nozzle strain gauge: PA_CAL_RUN SLOT=x picks PA per CFS slot (PA calibration)
Input shaping	Head accelerometer (LIS2DW on the nozzle board) via [lis2dw_k2], standard SHAPER_CALIBRATE
Touchscreen	Hark Screen: themeable landscape UI, CFS slots, load/purge, PA calibration, Wi-Fi (screen and camera)
Camera	Chamber camera as a plain MJPEG stream in Mainsail (and usable by AI failure detection)
Klipper extras	Ideas from Kalico as add-on modules: RELOAD_GCODE_MACROS, PID_PROFILE per CFS slot material, BED_MESH_CHECK
Klipper on a separate PC	Optional: Klipper and Moonraker on any Linux PC over one USB cable; the K2 board only relays its serial ports (external host)
Print safety	[hark_safety]: pauses on a dead hotend or part fan, cancels on an X/Y motor fault, pauses on an extruder fault (clog or jam)
Runout refill	When a reel runs out, another CFS slot with the same material and colour takes over and the print carries on, like stock. With no match it pauses, and RESUME loads and purges the new spool before carrying on. A warning names the next slot as soon as the reel's end passes the CFS
Chamber fan	The exhaust fan vents the chamber above 35C while printing, like stock; the slicer's chamber target (M141/M191) raises it
Updates	Tested releases from GitHub: an Update button in Mainsail and on the touchscreen; your settings live in printer-overrides.cfg and are kept
AI failure detection	Optional, on the host PC: Obico model every 10 s plus a local vision model (Qwen3-VL) as a second opinion (ai-detect)
Web UI	Mainsail Hark K2 edition (CFS panel, control centre, appearance presets) on port 4409, Moonraker on 7126

What is different from stock

• One heat cycle before probing. Load and purge at print temperature over the chute, cool-wipe once, measure Z with a clean nozzle, scrape on the bed strip, then mesh. That is about 5 minutes faster than stock and causes less ooze.
• Pressure advance from real nozzle pressure. The strain gauge measures the pressure response to flow steps; the result is stored per CFS slot. Creality only offers camera-based flow calibration, and only on the K2 Plus.
• Everything is visible and editable in Mainsail: macros, CFS slot data, motor parameters.

Supported hardware

Model	Status
K2 / K2 Combo (F021)	Developed and tested here
K2 without a CFS (rear spool)	Supported: found automatically at each start (details); tested on our K2 with the CFS unplugged
K2 Pro (F012)	Same motor tuning and boards as the K2 in Creality's config; untested
K2 Plus (F008)	Supported: tested on a real K2 Plus without a CFS from 31 Oct 2026 (homing, Z tilt, probing, chamber heater, full prints, touchscreen). docs/K2-PLUS-BETA.md is the step-by-step first run; a K2 Plus with a CFS is still untested

Earlier snapshots described the test machine as a K2 Plus; it is an F021 K2.

Install and rollback

Step-by-step guide: docs/INSTALL.md (root access on the touchscreen, one SSH session, about 15 minutes). In short, on the K2 as root:

python3 -c "import urllib.request as u; open('/tmp/install.sh','wb').write(u.urlopen('https://raw.githubusercontent.com/grant0013/K2-OpenKlipper/main/install.sh').read())" && sh /tmp/install.sh --check
sh /tmp/install.sh                                        # install (backs up first)
sh /mnt/UDISK/k2-mainline-20260729-v62/uninstall.sh      # back to stock

It installs next to the stock firmware and backs up every system file it changes. Never install, switch or uninstall while a job is printing or paused. See OPEN-STACK.md for the architecture and CONTRIBUTING.md before testing on your own printer.

Warnings learned the hard way

• Do not enable the motor speed-loop "FAL" parameter (ID 0x5e). It worked in motion, but left idle it locked both X/Y motor controllers off the bus until a full power cycle. See motor controller.
• The CFS feed must be armed for any sustained extrusion. Without it the extruder drags filament off the spool against the take-up tension and slips.
• Never write motor flash parameters (opcode 07). Everything here writes RAM only, so a power cycle always restores factory values.
• The board MCUs still run Creality's firmware (Klipper warns about deprecated features). It carries the K2-specific commands this stack depends on, so do not flash stock Klipper MCU firmware.

OrcaSlicer

Use:

START_PRINT EXTRUDER_TEMP=[nozzle_temperature_initial_layer] BED_TEMP=[bed_temperature_initial_layer_single] TOOL=[initial_no_support_extruder]

Replace Creality's legacy Change filament G-code with:

G90
G1 Z{max(z_after_toolchange, 0.6)} F600

The full explanation is in config/ORCA-K2-PROFILE.cfg.

Repository layout

• klippy/ - pinned upstream Klipper plus the K2 modules in klippy/extras/: prtouch_mainline.py + prtouch_open/ (strain-gauge probe), k2_cfs.py + hark_cfs_slots.py (CFS and slot records), k2_motor_bus.py (closed-loop motors), k2_z_align.py (bottom reference), lis2dw_k2.py (head accelerometer), pa_pressure_log.py + pa_analysis.py (PA calibration)
• config/mainline_stage2.cfg - the full working printer configuration and macros (start sequence, CFS, nozzle cleaning, purge line, PA calibration)
• harkscreen/ - touchscreen app; harkcam/ - camera streamer
• host/ - running Klipper on a separate Linux PC: the K2-side USB relay and boot script, host udev rule, systemd units, nginx site and config overrides
• tools/ - deployment helper, PA plotting and simulation, motor parameter scan and A/B test tools, boot-animation generator, ai-detect/ print-failure watcher
• system/ - Mainsail (Hark K2 edition build, source in grant0013/mainsail), Moonraker service and compatibility patches
• docs/ - protocol and design notes: CFS, PRTouch, motor controller, PA calibration, start sequence, screen and camera, external host, project status

Help wanted

• Testing on K2 Pro (F012) and K2 Plus (F008), and on other firmware revisions
• Motor controller parameters: the notch filters and ripple compensator are locked in the motor firmware; any safe way to reach them
• CFS electrical interface and multi-box setups
• Long-print, power-loss and runout recovery testing

Use the issue templates and include exact versions, logs and the phase being tested. Do not publish credentials, serial numbers, Wi-Fi details or other private data.

Legal and what is not in this repository

No Creality code is included or redistributed: no .so wrappers, no firmware images, no decompiled code and no Creality scripts (the installer edits the printer's own files in place, after backing them up). Protocol knowledge comes from observing the printer and its traffic, studying how Creality's software on the printer behaves, Creality's published configuration and GPL sources, and interoperability testing, as UK law (CDPA 1988 s.50B and s.50BA) allows for interoperability. The Klipper-derived code is GNU GPLv3 (see COPYING); bundled third-party components keep their own licences (see THIRD_PARTY.md).

Not affiliated with or endorsed by Creality. Modifying printer software may void Creality's warranty and can damage hardware. You use this at your own risk.

Credits

Built by Hark Tech (Grant Harkness), a UK 3D printing and electronics repair workshop, on top of Klipper (Kevin O'Connor and contributors), Moonraker and Mainsail.

With thanks to:

• Jacob10383 (K2 Plus custom firmware, GPLv3): motor reply decoding and fault handling, PRTouch tap selection and probe safety, and CFS status codes, runout purge and path tracking are adapted from his code. Each file that uses it says so.
• Dmitry Butyugin (Klipper): pa_tester, the load-cell pressure advance calibration behind PA_CAL_STATIC.
• CNC Kitchen (Stefan Hermann): the PATuner method behind PA_CAL_RUN.

Keywords: Creality K2, K2 Combo, K2 Pro, K2 Plus, mainline Klipper, open source firmware, root, PRTouch, strain gauge probe, CFS, Creality Filament System, multi-material, closed-loop servo, pressure advance calibration, input shaper, Mainsail, Moonraker, OrcaSlicer.