Getting Your File Ready To Print

Introduction

The following instructions will assist you in getting your file ready to take to the FabShop for printing. The goal is an error-free file which will print on the first try.

Before getting started, you’ll need to download and install Netfabb here. Netfabb is a free program, although there is additional functionality you can only use if you pay for Netfabb. We're only going to use the functionality available in the free trial version, complemented with Netfabb's Cloud Service for things we're unable to fix in Netfabb.

What is Netfabb

Netfabb is a free program that can check and edit 3D files. The program also has basic 3D file editing features such as analysis, scaling, measuring, and repairing. Netfabb can open the following file types: PLY, STL, OFF, OBJ, 3DS, COLLADA, PTX, V3D, PTS, APTS, XYZ, GTS, TRI, ASC, X3D, X3DV, VRML, ALN.

Measure

Once you've completed your 3D modelling, you may find that your model is the wrong scale. For instance, you may design a ring, but when you go to print it, you discover that your model file is more the size of a bracelet. This can happen because you've accidentally moved from millimetres to centimetres, or centimetres to inches, or because "real life" measurements were not taken into consideration while modelling.

To check your file's dimensions, open your file in Netfabb and click on the model so that it turns green. On the bottom of the right hand side bar, you will see some important information about your model.

1. Bounding box dimensions: This is how long, wide and deep your whole model is. Bearing in mind that our UP printers have a printable area of 255mm x 205mm x 205mm. Does your model exceed these dimensions?
2. Volume: This is how much space (in cubic centimetres) your model occupies. If volume reads "--" it because something is wrong with the mesh and the program can't determine an enclosed surface to calculate the internal area.
3. Area: This is the surface area of your model, given in square centimetres.
4. 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. The FabShop will reject files of more than 50,000 polygons (or 3mb).
5. If you see the red, triangle ! sign, this means there is something wrong with your model that will prevent it from printing properly.

Ideally, any scale errors will be picked up and fixed in the program you've used to model your object. If you're happy to resize your model in Netfabb, go to the Part menu and click Scale. You can enter a FACTOR to scale your model, either as a global scale factor or just in one dimension. Note that choosing to scale in one dimension only will squash and distort your model, not scale it evenly. Entering a factor of 0.5 applied globally will reduce any measurements to half of what they were previously.

Check

Netfabb is a great tool for checking your model for printability. Netfabb can analyse all the features of your model to make sure the surface will make sense to the printer.

In 3D geometry, models are composed of 3 elements, vertices (points) edges (lines between points) and faces (surfaces between lines). In order for a 3D file to be printable, it needs to have “manifold”, or "water tight" geometry. When a 3D file is manifold, every edge is connected to only two faces. When Non-Manifold geometry is found in a model, 3D printers will have issues reading the file.

To check a model, click on the Extras menu. Then click New Analysis > Standard Analysis. From the resulting information on the right hand side bar, what you want to see is the following:

Holes, Boundary edges, Flipped triangles, and Bad edges should all read 0. Surface should be closed and orientable. If this is not the case, most errors (but not all) can be repaired in Netfabb.

Repair

When repairing in Netfabb, your model will be refined to have the following qualities:

• Zero Holes: model will be manifold, without any gaps between faces and edges.
• Zero Border Edges: a border edge is an edge on the side of a hole.
• Zero Invalid Orientations: The orientation of a face is shown in green if it points outward, red if it points inward. If you have red faces pointing outward, its orientation is not valid.
• Positive Volume: All the green faces face out and the red face in, otherwise the printer will think that everything outside the model is to be printed.
• Closed Surfaces: A closed surface means that there are no holes or border edges.
• Orientable Surface: All faces must be defined as in or out, with no stray edges or vertices.

If your model has some errors, run the automatic repair tool by clicking the red + sign on the top menu bar. This changes your tools to relate to the Repair tool. Notice that the side bar has changed and the Part navigator now highlights the Repair tool, and that your model will now show the mesh polygons which make up your file. Some problem areas might show red polygons. Bear in mind that although you may not be able to see the problematic polygons, these will be shown in the analysis data.

The bottom right of the screen, click Automatic repair to fix any problems. Choose either default or simple repair. Click Apply repair to finish. It will ask if you want to Remove old part. Say yes - but first make sure it hasn't done something you don't want, like covering over part of your design to fix a problem. The values for shells, invalid orientation and holes should go down, preferably to zero.

Now that your Mesh is repaired, click on the file name to return to the main toolset. If you are happy with the repair, run the Standard Analysis again to check that the errors have indeed been eliminated. To save, click Part menu, click Export part > as STL. Netfabb may ask if it can run an Optimisation algorithm as it saves, and if it does, you should say yes to this.

Netfabb Cloud Service

If the automatic repair tool didn’t work to fix the errors in your model, it’s worth trying the functionality in the more powerful Netfabb Cloud Service. Once you've registered with Netfabb Cloud (this is also free) you can simply upload your file to the service and wait a few moments for the repair to be completed automatically. It can then be downloaded and opened again in Netfabb for checking. Although Netfabb’s Repair Tool is automatic, mistakes may still occur. Always check your model thoroughly afterwards to make sure it didn’t close any of the wrong holes or delete any important geometry.