Netfabb supports the following file types: .3mf, .3ds, .amf, .binvox, .CLI, .CASE, .x3d, .gts, .nfpbproject, .sldprt, .ply, .stl, .wrl, .vtu, .obj, .zpr, .zip, .ncm.
If you are exporting a file from another program to open in Netfabb, be sure to save it with one of these file extensions.
The Netfabb information sidebar
Click on the model so that it turns green. On the bottom right side bar, you can find important information about your model:
Bounding box dimensions: How long, wide, and deep your whole model is.
Volume: How much space (in cubic centimeters) your model occupies. Sometimes this shows a dash if the model contains errors that need to be resolved.
Area: The amount of surface area your model has.
Triangles: These are the smallest shapes that a 3D model can be described with. The more shapes, the more complicated and the larger the file can become. Shapeways will accept uploads of up to 1,000,000 polygons and/or 64mb. More polygons means that your model is less likely to print faceted.
If you see this 
sign, it means there is something wrong with your model that will prevent it from printing correctly. You can use the repair tool to fix most common issues.
The repair tool
Click the red + sign on the top bar, this will change your toolkit to be repair-related.
In the "statistics" side bar a few values are red, click update to see which ones they are.
Shells the number of separate 3D objects that are in this file. They may be separated by space or overlapping.
Invalid orientation means that the normal value of a face is in the wrong direction.
Think of a 3D model as being an origami made out of paper that is infinitely thin, as an individual face has 0 thickness. A face can only “face” in one direction, so if it's blue, it is facing outward, and if it is red that means it's facing inward. If there is red facing out, the printer will not recognize it correctly, and the model can't print.
Holes occur when the model's mesh is not a cohesive, continuous surface, or when it's not “watertight.” Like the origami analogy, because faces of the model are infinitely thin paper, the space between them is the thickness. If there is only one piece of paper without another across from it, there really isn't anything for the printer to print, again, which will confuse it.
Border edges that are not connected (although they may be overlapping) will be yellow, these count along holes too.
Click "run repair script" to fix these problems, and if there are are overlapping faces, the script will merge them together so that the whole model has a continuous shell. You can choose between default, simple, or extended repair.
When you're sure you're done, click "apply repair" to finish. It will ask if you want to discard, say yes but make sure that it hasn't done something unintentional to your mesh. Notice that the values for shells, invalid orientation, and holes should go down, preferably to the lowest number possible. If the repairs haven't worked perfectly, Shapeways will run another repair through a different tool (called "mesh-medic") to check for any remaining errors after you upload your model.
Now that your mesh is repaired, click on the file name to return to the main tool set.
Before:
After:
Tip 3: Measuring sidebar menu
We need to check if the model meets our design guidelines for the specific material you want to print in. Every material has its own unique set of guidelines that our engineers use to check your model's printability.
Click the "measurements" tool in the top tool bar to go to the measuring menu.
Here you can find useful measuring tools, allowing you to measure distance from a point, an edge, a radius or a distance on a circle, a surface distance, an angle, and even a wall's thickness. The latter is perhaps the most useful tool for adhering to our design guidelines.
After measuring this model, it doesn't look like it will meet the design guidelines: the wires are too thin, and according to the bounding box measurements, the model is too small.
You can use the scale tool to change the dimensions of all three axis proportionately. Some software packages don’t export the accurate size of the model, but you can use this tool to change the model to whatever dimensions you would like.
Click: Modify > Scale:
Choose the target size of any axis, changing the Y to 10 will change all the other axis if "Fix Scaling Ratio" is selected.
Notice that the bounding box went up, the volume is much higher, but the number of triangles are unchanged, because you only changed the dimensions of the model, not its geometry.
Now that the model is bigger, we can check if it meets the Design Guidelines again. When using the measuring tool, you'll see that the wires are much thicker:
Tip 4: Cutting tool
If you want to get an even better look at how your model is made, you can use the cutting tools:
These sliding bars represent the X, Y, and Z axis. You can click into the slider range to determine where to cut your model. Then, click the arrows on either side of the slider to decide of you want to move left or right of this location.
This tool works great alongside the measuring tools if you want a better view of the model without anything in the way, and if you want to make sure that all the faces are oriented correctly.
Tip 5: Design guidelines
When checking your model in Netfabb, make sure to measure against design guidelines published in the Shapeways material hub. We recommend that you design above the guidelines whenever possible to ensure that your model will survive the print and post-print processes.
For example, our Versatile Plastic requires a 0.7mm wall thickness, while Fine Detail Plastic can go down to 0.3mm wall thickness (but this makes it quite fragile).
You can review all of our guidelines on each material's dedicated info page here.