Printer calibration block

One test print that measures your printer — and tells you which numbers OwlCAD takes and which belong in your slicer.

Almost every print-aware decision — whether a face needs support, whether a wall is too thin to lay down, how much slack a joint needs — rests on a number that belongs to your machine rather than to your model. OwlCAD ships defaults for those, and they are averages for a printer nobody owns. This is the part you print once to replace them with your own.

Slice it with supports off, and no raft. This is the one setting that decides whether the print means anything: supports prop up the overhang fins and the bridging beam and pack the fuse gaps, so three of the ten banks come off the bed looking like passes when they are not — and those readings go straight into your settings. A raft does the same to the first-layer block, which only reports elephant foot when it is printed against the bed itself. A brim is the one exception, and only on the plate: it changes none of the ten readings there, and a plate this wide can lift a corner. Keep it off the loose first-layer block — snapping a brim away leaves a burr on exactly the base edge you put the calipers on.

Set the nozzle before anything else. It is not a dimension of the part; it is the scale every ladder is derived from. The wall comb steps from half a nozzle upward, the clearance and fuse ladders step by an eighth of one, and the engraved values follow. That is the thing a downloaded test STL cannot do: at a 0.2 mm nozzle a fixed 0.4-derived comb starts three stations above anything you can use, and answers a question you did not ask.

The readings do not all go to the same place, and the panel says which is which.

Feeds OwlCAD. The *overhang fan* gives you the shallowest angle your printer holds unsupported, in degrees from horizontal — the same convention as the 3D Print panel’s Overhang angle, so it goes straight in and PrintCheck starts flagging your printer instead of an average one. The *thin wall comb* gives you the thinnest wall that comes out solid; that is Minimum wall, which the wall gauge and every generator read-out compares features against. The *clearance ladder* gives you the gap a hole needs over its pin: put it in the Fit control on snap-fits, pin hinges, ball joints and adapters, as the Custom gap.

Feeds your slicer. The *dimensional gauge* is a pad and a bore at engraved nominals — measure them and the difference is your XY size compensation. The *stringing towers* test retraction, the *cooling spike* tests your fan curve and nozzle temperature, and the *first layer gauge* is elephant foot. OwlCAD deliberately never writes a slicer profile: your slicer owns the machine, the material and the settings you have already tuned, and a guess from CAD would either duplicate that or quietly override it. So the block measures these, tells you where they go, and stops.

For reference. The *fuse gap* is the distance below which two separate parts weld into one lump — useful every time you lay parts out on a plate, though nothing here reads it automatically. The *bridging spans* tell you how far this printer bridges unsupported, which is what decides whether a hole needs support. The *fine detail* ladder is the smallest rib and groove still visible on a surface, which is a different question from the wall comb: a standing wall and a surface detail fail at different sizes on the same machine.

Two parts print separately, and both have a reason. The gauge pin is loose because a fit is read by putting one part into another. The first-layer block is loose because elephant foot only happens on the first layer — a pad raised on top of a 3 mm plate has no first layer of its own and would report nothing.

Make it fit your bed. Every bank has its own switch, and the plate packs itself around whichever ones are left on, so a block for a 180 mm bed is a matter of turning off what you are not asking about today. The Footprint read-out is the whole part including the loose bodies.

If clearance is all you need, the fit test coupon sweeps it on its own with more stations and both feature kinds — a round bore and a flat slot are not the same measurement on the same machine.

1. Open the Generate panel from the left sidebar and choose Calibration block (under Calibration).
2. Set Nozzle diameter first. Every ladder on the block is derived from it, so this is what makes the walls, clearances and gaps bracket what your printer can actually resolve.
3. Switch off any bank you do not need. The plate repacks itself around what is left, and the Footprint read-out tells you whether it fits your bed.
4. Slice it with SUPPORTS OFF and no raft, and print it in the material you actually build with. Supports would prop up the overhang fins and the bridges and fill the fuse gaps — three banks that would then read as passes — and a raft lifts the first-layer block off the bed, which is the only place elephant foot happens. A brim is fine on the plate — it changes none of the ten readings, and a plate this wide can lift a corner. Keep it OFF the loose first-layer block, whose base edge is the surface you measure.
5. Read each bank off the printed part — the value is engraved beside it.
6. Put the OwlCAD numbers in: overhang angle and minimum wall go in the 3D Print panel, and the clearance goes in the Fit control (choose Custom) on any joint you build next.
7. Put the slicer numbers in your slicer profile. OwlCAD does not write those.