Skew Correction
Do your prints come out as a slight parallelogram instead of a true square? A box whose lid won't sit square, holes that look a touch oval, a 100 mm part that measures 100 mm on each side but isn't quite square? That's skew — and OpenKE can correct it entirely from the printer's screen.
You don't need a computer or a slicer for this. Print one test frame from the screen, measure it with calipers, type in three numbers, and you're done.
Yes, if: your printer's axes aren't perfectly at 90° to each other (extremely common, usually by a tiny amount). The tell-tale sign: a printed square has two diagonals of different lengths, or parts that should be square come out leaning.
Probably not worth it, if: you only print models, figurines, or decorative things. Skew is a fraction of a degree — you'll never see it on a dragon, only on parts that must fit something. If you don't print functional/engineering parts, you can happily skip this.
Print any square (or the test frame below), pop it off the bed, and measure the two diagonals corner-to-corner with calipers. If they're the same length → you have no meaningful skew, nothing to fix. If they differ by more than ~0.2–0.3 mm → skew correction will tidy that up.
A 3D printer assumes its X and Y axes meet at a perfect 90° corner. In reality the frame can be off by a hair. Every layer then prints as a very slightly leaning parallelogram instead of a rectangle. No amount of bed leveling or meshing fixes it, because it's a geometry problem, not a height problem. Skew correction measures the error from a test print and shears every move by the opposite amount, so squares come out square.
- ⏱️ Time: ~15 minutes (a short test print + three caliper measurements).
- 🧰 You need: a pair of calipers (digital is easiest), and filament loaded. No computer, no tools.
- ↩️ Safe to try: it changes nothing until you enter measurements and tap Apply & Save. Undoing
it isn't a screen button — it's one console command (
SET_SKEW CLEAR=1, see Undoing / clearing it below) — but it is quick and fully reversible.
Requirement: your printer needs the
[skew_correction]section enabled. The OpenKE installer adds it for you (under the print-quality mods prompt). The Skew button always looks the same — if the section isn't enabled, tapping it pops up a message for a few seconds: "Skew correction isn't enabled. Add [skew_correction] to printer.cfg." If you see that, see Enabling it at the bottom.
You need one flat, square print to measure. Slice it with your own normal profile — that way the extrusion is dialed in for your printer and filament, and the corners come out crisp.
What to print: any XY skew calibration model, or simply a large flat square (a single- or double-wall frame, a few layers tall). Bigger is better — a ~150 mm square gives far more measurement resolution than a small one, because skew error grows with distance. Popular ready-made options on Printables/Thingiverse search for "skew calibration" (e.g. a frame with labeled A/B/C/D corners), but a plain 150 mm square box-bottom works just as well.
Slice it, print it, let it cool, and gently pop it off the bed. Keep track of which corner was at the front-left of the printer — that's corner A. (Mark it with a pen as you lift it off if that helps.)
Lay the frame flat. The corners are named like this, as the part sat on the bed (printer front toward you):
D (back-left) ───────────── C (back-right)
│ │
│ │
│ │
A (front-left) ──────────── B (front-right)
With your calipers, measure these three, outer corner to outer corner, as accurately as you can (to 0.01 mm if your calipers allow):
| Measure | From → to | What it is |
|---|---|---|
| A–C | front-left → back-right | one diagonal |
| B–D | front-right → back-left | the other diagonal |
| A–D | front-left → back-left | the left edge |
🎯 This is the whole trick: measure carefully and consistently. If there's no skew, A–C and B–D come out equal. The difference between them is exactly what the printer corrects.
- On the printer: Tune → Skew.
- Tap each field and type the millimetre value (the keypad has a decimal point): A-C, B-D, A-D.
- Tap Apply & Save.
That sends SET_SKEW and saves it permanently (the printer restarts briefly to lock it in). Done — every
print from now on comes out square. 🎉
Same three measurements, typed directly instead:
SET_SKEW XY=<AC>,<BD>,<AD>
SAVE_CONFIG
Replace <AC>, <BD>, <AD> with your measured millimetre values, in that order.
(Want to confirm either way? Re-print the frame and re-measure the diagonals — they should now match.)
If you ever want to remove the correction, run this in the Klipper console (Mainsail/Fluidd) and SAVE_CONFIG:
SET_SKEW CLEAR=1
That zeroes the correction. Re-running Steps 1–3 overwrites it with fresh measurements any time.
The OpenKE installer enables this for you (it ships a [skew_correction] section). If tapping
Tune → Skew pops up "Skew correction isn't enabled", the quickest fix is to re-run the installer
and answer Y at the print-quality-mods prompt, then Restart Klipper (if it shuts down with a
serialqueue error, restart once more — see Troubleshooting).
You don't need any of the steps below for a normal install — this is only for people who'd rather add the one bare section (no settings) by hand instead of re-running the installer.
Manual steps
- Open
printer.cfg(Mainsail Machine tab, or over SSH). - Add this line anywhere above the
#*# <---- SAVE_CONFIG ---->marker:[skew_correction] - Save and
FIRMWARE_RESTART.
A Creality firmware update can reset this. If the Skew button stops working after an update, just re-run the installer (or re-add that one line). Your saved skew values live in
printer.cfgand aren't lost by re-running the installer.
Skew correction handles the small, consistent frame-squareness error that's baked into the machine. It does not fix a part that physically rocks, a loose belt, or a bent axis — fix mechanical problems first. Think of it as the final polish for dimensional accuracy once the hardware is sound.
Note: Klipper's
[skew_correction]can actually correct three planes — XY, XZ, and YZ — but the on-screen Skew panel only exposes XY, since that's the plane nearly every Cartesian printer actually needs (X and Y are driven by separate motors that can be slightly non-perpendicular; X/Z and Y/Z rarely are on a machine like the KE). If you have a rare case that needs XZ or YZ too, you can set those from the console the same way —SET_SKEW XZ=<AC>,<BD>,<AD>/SET_SKEW YZ=<AC>,<BD>,<AD>, measured the same way but with the frame stood on its corresponding edge — the screen just won't show or edit those values for you.