You have an idea, you have a design — but when you send the file to a 3D printing service, something goes wrong. Sound familiar? The culprit is almost always file preparation. Here's everything you need to know to get it right the first time.
Start With the Right File Format
Most 3D printing services — including us here at 3D PrintWell — work with STL files as the standard. STL (Standard Tessellation Language) converts your 3D model into a mesh of triangles that slicing software can understand. Almost every CAD application can export to STL, including Fusion 360, SolidWorks, Blender, Tinkercad, and FreeCAD.
Increasingly, 3MF files are becoming preferred over STL because they retain colour, material, and scale data that STL strips away. If your software supports 3MF export, it's worth using.
We also accept STEP and OBJ files — useful if you need us to make minor adjustments before printing.
Check Your Model Is Watertight (Manifold)
A watertight model means every surface is fully closed — there are no holes, gaps, or overlapping faces. Think of it like a container: if you filled it with water, none should leak out. Slicing software gets confused by non-manifold geometry and can produce print errors or simply refuse to process the file.
The easiest way to check and fix this is with a free tool called Meshmixer (by Autodesk) or the online repair tool at Netfabb. Many slicers like PrusaSlicer and Bambu Studio also have basic auto-repair built in.
Quick tipIf you're working in Fusion 360, always export from the "Bodies" folder rather than the component level to reduce geometry errors.
Get Your Scale Right
This is the number one mistake we see. Always verify your model is in the correct units before exporting. STL files don't carry unit data — so a model designed in millimetres might import into the slicer as inches, making it 25x too large.
Best practice: design in millimetres and confirm the exported dimensions match your intended real-world size before sending. We always check this at our end, but confirming it saves time for everyone.
Think About Wall Thickness
For FDM printing, walls need to be at least 1.2mm thick (ideally 1.6mm or more) to print reliably. Thinner walls may not form correctly because the nozzle diameter determines the minimum printable line width — typically 0.4mm, with most walls requiring at least 2–3 lines.
For resin printing, you can go thinner — down to around 0.5mm — but very thin sections are fragile and prone to warping post-cure.
Consider Overhangs and Supports
FDM printers struggle to print angles steeper than around 45° without support structures. If your model has significant overhangs — like a T-shape, a horizontal hole, or a bridge — it will need supports, which are removed after printing and can leave surface marks.
Where possible, orient your model to minimise overhangs. We'll always advise on the best print orientation when you get in touch — it's often a simple rotation that makes a big difference to surface quality and material use.
Summary Checklist
- Export as STL or 3MF
- Check the file is watertight (manifold) — use Meshmixer or Netfabb
- Confirm your model is scaled correctly in millimetres
- Ensure wall thickness is at least 1.2mm for FDM, 0.5mm for resin
- Minimise overhangs or plan for support removal
- Send us a reference image or sketch if you have one — it helps enormously
Not sure if your file is ready?
Send it to us anyway. We review every file before printing and will flag any issues, suggest fixes, and advise on the best approach — all as part of our free quote process. No CAD experience required.
Ready to get your design printed? Get a free, no-obligation quote from the 3D PrintWell team.
Get a Free Quote →You have an idea, you have a design — but when you send the file to a 3D printing service, something goes wrong. Sound familiar? The culprit is almost always file preparation. Here's everything you need to know to get it right the first time.
Start With the Right File Format
Most 3D printing services — including us here at 3D PrintWell — work with STL files as the standard. STL (Standard Tessellation Language) converts your 3D model into a mesh of triangles that slicing software can understand. Almost every CAD application can export to STL, including Fusion 360, SolidWorks, Blender, Tinkercad, and FreeCAD.
Increasingly, 3MF files are becoming preferred over STL because they retain colour, material, and scale data that STL strips away. If your software supports 3MF export, it's worth using.
We also accept STEP and OBJ files — useful if you need us to make minor adjustments before printing.
Check Your Model Is Watertight (Manifold)
A watertight model means every surface is fully closed — there are no holes, gaps, or overlapping faces. Think of it like a container: if you filled it with water, none should leak out. Slicing software gets confused by non-manifold geometry and can produce print errors or simply refuse to process the file.
The easiest way to check and fix this is with a free tool called Meshmixer (by Autodesk) or the online repair tool at Netfabb. Many slicers like PrusaSlicer and Bambu Studio also have basic auto-repair built in.
Quick tipIf you're working in Fusion 360, always export from the "Bodies" folder rather than the component level to reduce geometry errors.
Get Your Scale Right
This is the number one mistake we see. Always verify your model is in the correct units before exporting. STL files don't carry unit data — so a model designed in millimetres might import into the slicer as inches, making it 25x too large.
Best practice: design in millimetres and confirm the exported dimensions match your intended real-world size before sending. We always check this at our end, but confirming it saves time for everyone.
Think About Wall Thickness
For FDM printing, walls need to be at least 1.2mm thick (ideally 1.6mm or more) to print reliably. Thinner walls may not form correctly because the nozzle diameter determines the minimum printable line width — typically 0.4mm, with most walls requiring at least 2–3 lines.
For resin printing, you can go thinner — down to around 0.5mm — but very thin sections are fragile and prone to warping post-cure.
Consider Overhangs and Supports
FDM printers struggle to print angles steeper than around 45° without support structures. If your model has significant overhangs — like a T-shape, a horizontal hole, or a bridge — it will need supports, which are removed after printing and can leave surface marks.
Where possible, orient your model to minimise overhangs. We'll always advise on the best print orientation when you get in touch — it's often a simple rotation that makes a big difference to surface quality and material use.
Summary Checklist
- Export as STL or 3MF
- Check the file is watertight (manifold) — use Meshmixer or Netfabb
- Confirm your model is scaled correctly in millimetres
- Ensure wall thickness is at least 1.2mm for FDM, 0.5mm for resin
- Minimise overhangs or plan for support removal
- Send us a reference image or sketch if you have one — it helps enormously
Not sure if your file is ready?
Send it to us anyway. We review every file before printing and will flag any issues, suggest fixes, and advise on the best approach — all as part of our free quote process. No CAD experience required.
Ready to get your design printed? Get a free, no-obligation quote from the 3D PrintWell team.
Get a Free Quote →