Everything you need to know to prepare a file for 3D printing
Whether you're printing your first prototype or your hundredth, correctly preparing the 3D file is the most important step to achieving a quality result. This guide contains everything you need: the fundamental rules of modeling for 3D printing, errors to avoid, choosing the right format and material, and tips for saving costs. These tips are also useful for correcting models generated with artificial intelligence, which often contain geometric errors. Read our A guide on how to 3D print AI-generated models
If you already have the file ready, you can Upload it directly for an instant quote. If the file contains errors, we'll let you know and help you fix them.
The 5 rules for a printable file
Whatever software you use for modeling, your file must follow these fundamental rules to be 3D printed without problems.
1. The model must have volume
In modeling for rendering or animation, it is common to create surfaces without thickness. For 3D printing, each element must be a solid with volumeA real object always has some thickness, even a minimal one. If your model contains individual surfaces, you must extrude or thicken to obtain a solid.
2. The model must be closed (watertight)
A model is "closed" when it has no holes or openings in its geometry. Imagine filling it with water: if the water leaks out, the model is not watertight. 3D printers need to know exactly what's "in" and what's "out" to deposit the material correctly.
3. The geometry must be manifold
Manifold This means that every edge of the mesh is shared by exactly two faces, and that the geometry has a well-defined interior and exterior. non-manifold The most common errors are: duplicate internal faces, overlapping vertices, edges shared by more than two faces, and separate bodies that only touch at one point. Most CAD software offers tools to identify and correct these errors.
4. Normals must be oriented correctly
Normals are vectors perpendicular to each face of the mesh that indicate which side is "outside." If any normals are inverted, the printer cannot distinguish between the inside and outside of the model. Almost all software has a command to automatically recalculate the normals.
5. The dimensions and thicknesses must be adequate
Each printing technology and material has specific limitations: maximum print area size, minimum wall thickness, and minimum detail size. Walls that are too thin can break during production or post-processing. Always consult the data sheet. Technical details of the material you intend to use.
Common errors in 3D printing files and how to avoid them
Mesh not closed or with holes
This is the most serious error: if the model has gaps, the printer cannot generate the print layers. Solution: Make sure your software reports the model as “closed” or “solid.” Use automatic repair tools (such as Make Manifold in Blender, Repair in Fusion, Check in Rhino) before exporting.
Inverted normals
Normals that point inward instead of outward confuse the printer about the direction of the surfaces. Solution: recalculate normals (in Blender: Shift+N, in Rhino: UnifyMeshNormals, in Fusion it is handled automatically).
Unjoined overlapping bodies
Models composed of multiple bodies that intersect without being fused generate double walls and ambiguous geometries. Solution: join all bodies with boolean operations before exporting (in Blender: Boolean → Union, in Fusion: Combine → Join, in TinkerCAD: Group).
Mesh resolution too low
An STL file with few triangles shows faceted surfaces, especially on curves. Solution: Export at an appropriate resolution. Typically, a tolerance of 0.01-0.05 mm is sufficient. More detailed files generate larger files with no visible benefits in print.
Mesh resolution too high
The opposite excess: huge STL files (over 40-50 MB) slow down processing without improving print quality. Solution: reduce the number of polygons with the modifier Decimate (Blender), Reduce (Rhino/Fusion) or lower the resolution in the export settings.
Incorrect units of measurement
A model designed in inches but interpreted in millimeters will be 25 times smaller than expected (and vice versa). Solution: Check the document's units before exporting. For 3D printing, you typically work in millimeters.
Walls too thin
Even if the model is geometrically correct, walls smaller than the minimum material thickness will be brittle, incomplete, or will break. Solution: see the fact sheet chosen material to find out the minimum guaranteed thickness.
STL, OBJ, or 3MF: Which Format to Choose?
STL (Standard Tessellation Language)
It's the most popular format for 3D printing. It contains only the model's geometry in the form of triangles. It doesn't include information about colors, materials, or units of measurement. It's supported by all software and printing services.
Use STL when: molds in a single color/material (plastic, resin, metal).
OBJ (Wavefront Object)
Contains the geometry plus material and texture information, saved in a separate .mtl file. Texture images are referenced as external files.
Use OBJ when: color molds with the material multicolor powder or when the model has textures applied.
Note: When you load an OBJ file for printing, create a .zip archive containing the .obj file, the .mtl file, and any referenced texture images.
3MF (3D Manufacturing Format)
It's the most modern format, designed specifically for 3D printing. A single .3mf file contains geometry, colors, materials, textures, and metadata, including units of measurement. More and more software and printers support it.
Use 3MF when: Your software supports it and you want a compact file that includes all the information. Our service also accepts 3MF format files.
How to reduce the costs of 3D printing
The cost of a 3D print depends primarily on the volume of material used, the size of the object, and the complexity of its geometry. Here's how to optimize your model to save money:
Hollow the model
If your object doesn't need to be structurally solid, hollow it out by creating an internal cavity with walls of adequate thickness. This significantly reduces the amount of material used. In Blender, you can use the tool Hollow of the 3D Print Toolbox, in Fusion the command Shell, in Rhino the command OffsetSrf.
Choose the right orientation
The orientation of the object on the print bed affects the amount of supports needed, and therefore the cost. Position the object to minimize suspended surfaces (overhang) and the supports.
Reduce size where possible
Cost is proportional to volume. A scaled-down model of the 10% in each dimension takes up approximately 27% less volume. If size isn't critical, consider scaling the model down slightly.
Choose the right material
Not all projects require the most expensive material. For dimensional prototypes, the SLS white plastic (nylon) offers excellent value for money. For models requiring high detail, the standard resin is more suitable. For functional mechanical parts, evaluate the plastics for mechanical parts.
Merge multiple objects into a single file
If you need to print multiple small parts, place them close together in the same STL file. This optimizes space on the build platform and can reduce overall costs.
Minimum thicknesses and maximum dimensions for material
Each material has different technical specifications. Before modeling, check the limitations of the material you intend to use. Here's an overview of the most popular materials:
– White plastic SLS (nylon): excellent for functional prototypes, good mechanical resistance
– Standard resin: high definition, smooth surfaces, ideal for fine details
– Transparent resin: glass effect, suitable for aesthetic prototypes and architectural models
– Flexible rubber: for elastic parts, seals and soft prototypes
– Alumide: mix of nylon and aluminum powder, metallic appearance
– Multicolor sandstone: color printing with photographic quality
– Metals: stainless steel, aluminum, titanium for functional and final parts
See the sheet Technical details on each material page for minimum thicknesses, maximum dimensions and complete specifications.
Software Guides: How to Model for 3D Printing
We have prepared detailed, step-by-step guides for the most popular 3D modeling software:
– Blender: open source software for polygonal modeling, sculpting, and organic shapes
– Autodesk FusionParametric CAD for mechanical design and engineering
– Rhinoceros: NURBS modeling for design, jewelry, and architecture
– TinkerCAD: web application for beginners and educational projects
– SketchUp: 3D modeling for architecture and interior design
Each guide explains how to set up the project, check the geometry, fix errors, and export the file in the correct format for printing.
Frequently asked questions
What file formats do you accept?
We accept files in STL, OBJ, and SKP (SketchUp) formats. For models with textures and colors, upload a .zip archive containing the .obj file and the .mtl file with any images. Upload your file here.
What happens if my file contains errors?
If your file has geometric problems (open meshes, inverted normals, etc.), we'll notify you via email, explaining the type of error and how to fix it. In most cases, we can fix minor errors directly.
3d printing pricing
The cost depends on the volume of the model, the material chosen and the complexity of the geometry. Upload your file to receive an instant, free quote.
What's the best software to start modeling for 3D printing?
For those who are new to this, TinkerCAD It's the simplest and doesn't require installation. For mechanical designs, Autodesk Fusion is free for personal use. For organic and artistic forms, Blender It's free and very powerful. For design and jewelry, Rhinoceros It's the industry standard.
What is a mesh manifold?
A mesh is manifolds when each edge is shared by exactly two faces and the geometry clearly defines an interior and an exterior. A mesh non-manifold Contains errors such as edges shared by more than two faces, overlapping vertices, or internal faces. These errors prevent proper printing.
What is the minimum wall thickness for 3D printing?
It varies depending on the material: generally between 0.6 mm and 1.5 mm. For the exact values for each material, see the data sheet. Technical details on the material page.
How can I reduce the cost of 3D printing?
The main ways are: emptying the model (hollow) to reduce the volume of material, choose a material suitable for the actual needs, reduce the dimensions where possible and optimize the orientation to minimize supports.
Ready to print?
Upload your file for an instant quote or contact us for a consultation on your project.
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