Start with wall thickness
FDM printing has a minimum wall thickness that depends on the nozzle diameter in use — typically 0.4mm to 0.6mm. Walls thinner than this will either fail to print or print with significant gaps. A common guideline is to keep walls at minimum 1.2mm, and 1.6mm or more for anything structural.
In your slicer or modeling tool, check for thin-wall warnings before exporting. What looks solid in a render may have walls that will not hold during printing.
Check for non-manifold geometry
A manifold mesh is a closed, watertight surface — every edge shared by exactly two faces, no holes, no self-intersections. Non-manifold geometry looks fine on screen but causes slicer errors or print failures. Most CAD tools have a mesh repair or analysis function. Meshmixer, Netfabb, and PrusaSlicer all have built-in repair tools.
Exporting from a solid modeling tool like Fusion 360 or SolidWorks in STL or STEP format usually produces clean geometry. Meshes built in polygon modeling tools like Blender or ZBrush often need more attention.
Consider print orientation before sending
Orientation affects surface finish, strength, and support requirements. FDM parts are weakest along the Z-axis — the layer-to-layer bond. If a part has a critical load direction, that should be noted in the quote request so orientation can be reviewed. Flat surfaces printed face-down will be smoother than surfaces oriented vertically.
Do not assume the shop will figure out the best orientation — include your expectations and use case so the review can account for them.
Minimize unnecessary supports
Support structures are printed under overhangs that exceed 45 degrees. They add print time, material cost, and cleanup labor. Supports that are deep inside a part or in hard-to-reach geometry can also damage the surface when removed.
If possible, design overhangs at 45 degrees or less, add chamfers instead of horizontal bridges, and split parts at natural break points to eliminate overhangs entirely. Mention any surfaces where support marks are not acceptable — that affects orientation choices and quoting.
Export settings matter
When exporting an STL, the chord deviation and angle tolerance settings determine how smoothly curves are represented. Too low and the file is enormous and slow to process. Too high and curved surfaces are visibly faceted. A chord deviation around 0.02mm and angle tolerance around 1 degree is a reasonable starting point for most parts.
STEP format preserves the original geometry exactly and is often preferred for accurate review. Send both if available — STL for slicer preview, STEP for geometric accuracy review.
What to include with the file
The file alone is not enough for an accurate quote. Include: the intended use case, material preference, required quantity, color, whether the part is indoor or outdoor, any heat or load concerns, and the target date. For replacement parts, include photos of the original and critical dimensions. The more complete the request, the faster the quote.