How to prepare a model for 3D printing

A model does not need to be technically perfect before review. It should, however, describe the geometry, scale and purpose clearly. This checklist removes the most common sources of uncertainty before quoting.

Start with the use case, not the file format

The same shape needs a different approach as a decorative object, electronics enclosure, assembly fixture or loaded component. Add a short note explaining where it will be used, what attaches to it and what it must not fail to do.

What to include

• intended use and expected load,
• critical dimensions and tolerance,
• operating environment: temperature, UV, moisture or chemicals,
• deadline and quantity,
• visible faces and surfaces where support marks are unacceptable,
• assembly method: screws, press fit, snap, adhesive or moving joint.

Check that the model is a closed solid

The printer needs an unambiguous inside and outside. Open edges, overlapping faces, inverted normals and self-intersections can make the slicer omit geometry or fill the wrong region.

Use the solid check in your CAD tool. For scans and mesh models, run a repair function and remove accidental internal shells.

Match wall thickness to the function

A thin wall may be visible on screen but disappear during slicing or remain too fragile after printing. There is no single minimum for every process. Orientation, feature height, material and expected load all matter.

Review tall thin walls, sharp thickness transitions, bosses around fasteners, snap arms, embossed text and small ribs. Design them for their purpose rather than the theoretical machine limit.

Review overhangs, bridges and enclosed spaces

Surfaces above open space may need support. In FFF this means temporary deposited material; in SLA supports stabilise the part throughout the build.

Make sure supports can be removed. Closed channels, internal cavities and narrow pockets can trap support or uncured resin. A different angle, drain opening or model split can solve the issue.

Communicate orientation priorities

You do not need to place the model on the platform yourself, but identify the important faces. State which side should look best, where the part is supported in use and how the main load acts.

Orientation changes strength, appearance, supports and accuracy. Read orientation, layers and infill for the underlying rules.

Add clearance between components

Two CAD surfaces with zero gap will usually not assemble freely after printing. Moving and fitted parts need process-specific clearance; holes may need compensation or finishing.

For an important mechanism, describe the intended fit and consider a test coupon rather than guessing. See 3D printing tolerances and fits.

Which format should you send?

Format	Best use
STL	Common for finished geometry; verify units and mesh quality
3MF	Can retain units and additional model information
STEP	Useful for CAD parts and potential geometry changes
OBJ	Useful for meshes, organic models and surface data

When exporting STL, avoid a very coarse mesh that turns curves into visible facets. An excessively dense mesh also does not exceed the physical resolution of the process; it only increases file size.

Final checklist

1. The model has the correct scale and forms a closed solid.
2. Thin features match their intended function.
3. Supports can be removed from pockets and channels.
4. Mating parts have planned clearance.
5. Critical dimensions are identified.
6. The brief states environmental requirements or a verified material.
7. Quantity, deadline and finishing expectations are clear.