My printer was always a little disappointing at speed. Push the feedrate up and the corners bulged, the surfaces rippled, and anything with detail turned to mush. I had assumed this was simply what the machine was: a cheap-ish 8-bit board doing its best, and its best was not very fast. Then I tried Klipper, and it turned out the limitation was almost entirely the board, not the mechanics underneath it.
the actual idea
The clever bit of Klipper is that it stops asking the printer's little microcontroller to think. Traditional firmware like Marlin runs everything on the board: parsing G-code, planning moves, doing the trigonometry, driving the steppers, all on a chip with the computational budget of a pocket calculator. When that chip runs out of maths per second, it just moves slower or stutters.
Klipper splits the job. A Raspberry Pi does all the heavy planning and the kinematics, then streams precisely timed step commands down to the board, whose only remaining job is to fire steppers when told. The board becomes dumb hardware. The Pi has more than enough headroom to plan moves the old firmware could never keep up with.
what changed in practice
The first thing I noticed was pressure advance. Klipper can model the way molten filament lags and oozes under pressure, then compensate ahead of time. Tune it once and the corners stop bulging and the seams tidy up. My extrusion suddenly looked deliberate instead of approximate.
The second thing was input shaping. Run an accelerometer test, get a graph of your printer's resonant frequencies, and Klipper shapes the motion to avoid exciting them. The ghosting and ringing I had assumed were permanent features of a budget frame mostly vanished. I could push accelerations far higher without the surface artefacts coming back.
The configuration is all in one printer.cfg text file, which after years of flashing firmware to change a single setting felt like a small liberation.
[input_shaper]
shaper_freq_x: 41.6
shaper_freq_y: 38.2
shaper_type: mzv
Edit, save, RESTART, and the new behaviour is live in a couple of seconds. No recompiling, no reflashing, no praying you picked the right board variant in the menu.
The catch, and there is one, is that you now have a Raspberry Pi to look after. It is another thing that can fall off the network, fill its SD card, or refuse to boot at the worst moment. But the trade has been overwhelmingly worth it. Same motors, same frame, same nozzle, and prints that come off both faster and cleaner than the machine had any right to produce. The hardware was never the bottleneck. The eight-bit brain in the middle was.