In this post we will cover five Fusion 360 functions that will be very useful when we make designs for 3D printing.
1. Apply clearance by parameters for 3D printer tolerance
Each 3D printer has its own tolerances in relation to many parameters. One of the most relevant is the type of material, and ideally in these cases is to adjust the model with enough clearance in parts where there are inserts or threads. It is usually 0.1 to 0.5 mm in FFF 3D printers.
First thing is to test the machine to know the tolerances that it has. There are several models in Thingiverse that you can print to confirm what you need for a specific material and 3D printing setting. Here you have an example of tolerances test.
With the slicer you can use the horizontal expansion parameter to modify the size of the part in the horizontal plane and offset for the material shrinking. But this affects the whole part and it may happen that you only want to apply this toa hole for example, or a hole in a vertical orientation that would not be affected by expansion that is only horizontal.
In this case your option is to modify the design. In Fusion 360 we have the tool Modify – Press/Pull (shortcut key ‘Q’) that allows you to offset one or several faces. In a hole, simply select the hole inner face and move it out (-0.2 mm in the example, so -0.4 mm in diameter).
In a threaded hole, you have to apply the same by selecting all inner faces of the thread.
The beauty of working with parametric software such as Fusion 360 is that you can convert this -0.2 mm value in a parameter that you can change any time, and use it in all Press/Pull operations that you have applied, or will apply.
For this we create a parameter “holgura” in Modify – Change Parameters. (“holgura” is the translation of clearance in Spanish, use you own term)
Once created you can modify the Press/Pull operation by replacing -0.2 mm value with “holgura” (or your preferred term). And you can use it in the following operations to adjust tolerance.
Thanks to having parameters, if you need to change of material or machine, you only need to modify the “holgura” parameter value and export to STL again to have the model adjusted to the new material or machine.
2. Simulate slicing with Section Analysis
We all want to avoid supports when we design for 3D printing. A good way to check what you are doing is to use Inspect – Section Analysis. It allows you to check the section of a part.
Before we begin with this it is ver recommended to deactivate Incremental Move so you can move section plane without jumps.
Apply Section Analysis and select the XY plane (TOP plane). Don’t push OK. With this you make an horizontal section. The tool lets you set where you want the section to be by moving the plane with the arrow.
If you orbit to see the part from above, you will see that when moving the section plane up the part shows with the same appearance when you use layer Preview in a slicer. With this trick you can identify object parts that can be overhangs or angles that you do not want to have, even if they are inside the object.
This is a good trick to work in advance with the model if you want to avoid or reduce the amount of suports for 3D printing with filament (FDM) or resin (SLA / DLP).
Another alternative is to apply Section Analysis but on the XZ plane (FRONT plane) to show a vertical section of the part an where it is more obvious that an angle is an overhang. In this case we are talking about a first visual inspection, you can use Inspect – Measure to measure angles between faces with precision.
3. Check overlap between solids with Interference
Today’s slicers make automatic repairs of STLs, and it is possible that you have never found this problem that happens when solids self-intersect, or parts of solids are occupying the same space and so overlapping. The slicers merge the parts automatically and we do not know about the issue although the STL mesh is not correct.
We show below an example of two cubes that are not joined so they create faces that cross themselves when exporting to STL. The usual slicers will consider this a single part by repairing the STL.
With Interference Analyis you can detect if any interference exists between one of the bodies and solve it if it is your intention. On the contrary, if two objects go together, it is better to apply a boolean operation with Modify- Combine Join than to let the slicer decide for you.
4. Export several STLs in one shot
The usual way to export your design is to select the body and with right mouse button apply Save as STL. A dialog box appears where you can select mesh density (in Refinement) with three standard options and a customized one. If your design has curves, then you can decide whether to use medium and high density.
If you have several bodies that you want to export, an option is to select the root component (with the file name) and apply Save as STL with right mouse button. When ou have several bodies you can choose in Structure field to export in a single STL with all bodies in it (One File), or to export a different STL file for each body (One File per Body).
You can also export components to STL, in this case it will include all bodies within the component. If you want to export some bodies at the same time, but not all of them, this would be the grouping option to use. The body groups (Group) are groups of bodies you can create, like a folder, but unfortunately at publication date it is not possible to export a group to STL.
There is one last way to export STLs, using the File menu. If you use File – Export with STL extension Fusion 360 will convert the format, usually in the cloud, but you do not have any option to choose conversion criteria so I do not recommend to use it. In addition it takes longer and provides low res meshes. This option could be interesting if you want to export in OBJ format.
5. Effect of 3D printing fillets and chamfers
We often tend to use rounded edges with Fillet because of aesthetics, but it can create problems for 3D printing if you apply it to horizontal edges at the bottom faces of the parts. In fact, some fillets should be printed with supports due to the angle they start with at the beginning of the curve.
In the example below you can see that a Fillet on below face could require supports, while for lateral and top edges it is not needed.
On the other hand a chamfer with Chamfer tool has normally an angle of 45°, like on the left of the first image, or in any case an angle that you can control to avoid supports..
You also have to take into consideration the scale of things. Maybe applying a 0.5 mm Fillet when in fact this is going to be 3 printed makes no noticeable difference compared to a Chamfer with the same short distance.
To know more on this topic I recommend a video from Maker’s Muse where it compares 3D printing of fillets and chamfers and how this affects the outcome..
I hope these tricks help you improve your designs for 3D printing and to reduce the number of iterations you need to make in a design.
If you want to learn Fusion 360 from scratch, with best practices for solid design and more content related to 3D printing, I encourage you to enroll en my online Fusion 360 course (in Spanish). In this link you will find more information abut the course, its methodology and content.