I am currently developing the fastening mechanism of the enclosure and it’s location/integration within the casing design. This will be partially determined/influenced by the way that the product will be manufactured.
A couple of fastening design ideas are shown above. Both solutions involve the use of a tab (protruding from the cap) that fits within a cavity in the base component on which the Raspberry Pi board will be held.
The sketches at the top of the image show a plan view of a prong-style clip, much like those used on backpacks and nylon straps, where the two prongs are pushed through a pair of teeth, locking the components together until they are pulled apart.
The sketches at the bottom show a side-on, cross section profile of a different design, where the tab would flex upwards to then interlock with a groove in the corresponding cavity. This may be a cleaner, more visually appealing solution which may be easier to fabricate.
The parts involved will be 3d printed. In order to maximise the strength, and therefore, the longevity of these fastening solutions, it is important to consider the orientation that the parts will be printed in. FDM 3D printed parts have inherently anisotropic properties, meaning they are much stronger in the XY direction than the Z direction (Redwood, 2020). This is illustrated in Figure 1 (below), showing how layer direction relates to the strength of 3D printed parts (3D Hubs, 2020: online).
“For functional parts, it is important to consider the application and the direction of the loads. For example, FDM parts are much more likely to delaminate and fracture when placed in tension in the Z direction compared to the XY directions” (Redwood, 2020).
As a result, the parts would be printed flat to the printing surface as shown below.
This orientation would also accommodate the fastenings being printed on the sides of the enclosure (which I will be exploring in further development), potentially allowing a more secure fit (as two fastenings would be used instead of one) and more intuitive use.
Figure 1: Redwood, B. (2020) How layer direction relates to the strength of 3D printed parts.: 3D Hubs. [Online Image] [Accessed on 31/10/2020] https://www.3dhubs.com/knowledge-base/how-does-part-orientation-affect-3d-print/
Redwood, B. (2020) How does part orientation affect a 3D print? : 3D Hubs. [Online] [Accessed on 31/10/2020] https://www.3dhubs.com/knowledge-base/how-does-part-orientation-affect-3d-print/
P.S. I found it challenging to write this in a clear manner since I needed to briefly explain the properties of 3d printed parts in order to elaborate on my design decisions, so I apologise if it’s difficult to understand. I also feel the need to better define the names and functions of the parts involved to enable improved written communication of design ideas. This will be the focus of an upcoming post.