Skew Correction

Fixing Parts That Come Out Skewed (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.

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Will this actually help me?

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.

The 30-second test for whether you even have skew

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.

Why it happens (in plain English)

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.

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Before you start

• ⏱️ 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, and it's a one-tap undo.

Requirement: your printer needs the [skew_correction] section enabled. The OpenKE installer adds it for you (under the print-quality mods prompt). If the Skew button says "not enabled," see Enabling it at the bottom.

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Step 1 — Print a calibration square

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.)

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Step 2 — Measure the three lengths

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.

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Step 3 — Enter them on the screen

1. On the printer: Tune → Skew.
2. Tap each field and type the millimetre value (the keypad has a decimal point): A-C, B-D, A-D.
3. 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. 🎉

(Want to confirm? Re-print the frame and re-measure the diagonals — they should now match.)

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Undoing / clearing it

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.

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Enabling it

The OpenKE installer enables this for you (it ships a [skew_correction] section). If Tune → Skew shows "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).

Prefer to do it by hand? It's one bare section (no settings):

1. Open printer.cfg (Mainsail Machine tab, or over SSH).
2. Add this line anywhere above the #*# <---- SAVE_CONFIG ----> marker:

   [skew_correction]

3. 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.cfg and aren't lost by re-running the installer.

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How much can it fix?

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.