STL Model Off the Build Plate

If an STL appears away from or below the build plate, check its minimum and maximum X/Y/Z coordinates as well as its size. A 20 mm span alone cannot tell you where the model was exported. Then use your slicer's placement controls deliberately and verify the resulting layer preview. A slicer may recenter or drop an imported model automatically, so the source coordinates and placed job are different evidence.

Same size, different source positions

Both are closed 12-triangle binary STLs of 684 bytes. On a hypothetical X/Y=0..200 mm bed, the shifted source is outside X and crosses Z=0. This is a coordinate observation, not a universal verdict about printer fit: the slicer can apply a placement transform, and a printer's usable area may differ from its nominal rectangle.

Observed PrusaSlicer placement contrast

In PrusaSlicer 2.9.6's CLI, the shifted cube with --dont-arrange produced “All objects are outside of the print volume” and no G-code. With --center 100,100, the shifted and origin controls produced byte-identical G-code in this run. Thus the tested centering workflow relocated the shifted geometry and placed it on the bed before slicing. The exported placed G-code is a software result, not proof that the original file was correctly located for an assembly.

The run used PrusaSlicer's default 200 × 200 mm bed, 0.4 mm nozzle, 0.45 mm extrusion width, 0.2 mm first and subsequent layers, two perimeters and rectilinear 100% infill. Other slicers or import settings may move the object differently. STL coordinates are unitless; all millimetre labels here are an explicit interpretation of the control.

Fix the placement without hiding an assembly error

1. Open the STL in STL Dimensions Checker. Read the minima and maxima as well as the X/Y/Z spans, under the intended unit assumption.
2. If Z is negative, inspect why the mesh extends below the bed. Use the slicer's drop-to-bed or place-on-face action only after choosing the intended contact face.
3. If X/Y are far away, review the slicer's move or arrange operation and confirm the resulting object footprint in the layer preview. A centred bounding box is not automatically the intended coordinate origin.
4. For multiple intended pieces, preserve and inspect their relative positions before moving them. Re-export from CAD when source placement is part of the design.
5. After slicing, review the actual extrusion and travel envelope. G-code outside the bed handles already sliced paths; printer fit handles model size and orientation.

Source reviewed 14 October 2026: Prusa's Move and Drop to bed controls and Auto-arrange documentation. Neither source establishes the placement behaviour of another slicer.