Week 15: System Integration¶
As I had spent significant time on sketching, and design thinking, so I though I would dedicte a chunk from this week to explaining those design decisions.
Design Choices¶
Despite Fusion offering a timeline where you can change features and dimensions, I did not want to commit changes on my main models. I had concerns that things could have gone in wrong directions, and I would need to redo the models from scratch. Indeed, I had ended up making 3 of the complete model of the device, as I could not change some features efficiently. So remaking a complete new CAD model was more time friendly [or I haven’t discovered good practices of CAD modeling yet].
The Hinges¶
I first began experimenting with the hinge designs, and whether they would open beyond 90 degrees. Not to damage the main file I first opened a new draft file on Fusion to understand the measurements. After all, the doors were one of the key features of the case.
Once I had the final design for hinges, after one more iteration I made a small adjustment – a slit to push out the rods keeping the doors in place.
Failed Results¶
In reality, I first thought that a print-in-place door would be a good idea. I did not take into account that fact that these hinges are very small and detailed, and so an in-place print was a bad idea. Mid-testing I got concerned that the springs might even dislocate the doors, even though their presence post-deployment is not critical.
The Springs¶
The inverse cones with slits letting the springs slide in and not out. On the doors’ undersides I also added a “railing” for the springs looped ends.
Initial Feature¶
In the right image the knob “holds” the spring in place. In reality I knew that this would not have functioned well, but I simply wanted to test how the sping would behave when supressed. Once I had taken these measurements, I designed a invers cone-like shape, which would not let the springs slide out.
The Latch¶
I colored the model in three colors to differenciate the individual objects. Red is the main body, yellow is the top door with the lever eye [this also holds the bottom door in place], and in grey is the hooked lever with two holes connected to the servo.
Why is the lever separate and not printed?
To begin with, I prefer printing the case in a sideways orientation, where here the print direction badly reflects on the lever. Moreover, if the lever gets damaged, I simply cannot replace it. Nevertheless, if the siffness is not optimal for the servo’s pull, I cannot waste a whole case – 150 g of filament, and ~10 hrs goes to waste.
In this image below you can see how the lever is screwed into the case.
The Parachute Loop¶
As I wanted a unibody design, but a detachable parachute, I needed a loop that would attach the parachute to. But i could not simply be a loop, because the moment the parachute deplys there is a lot of pull tension on it. So when slicing I added a modifier to change the infill density.
Now, inside the case there is a cone-like infill which acts like a root system, connected more securily to the whole body. You can see the embedded structure in the video below.
Conclusion¶
Overall I am very satisfied with what I had achieved in this design. I am a person who does not like praising myself, but I like the directions I had taken, and the ideas I had come up with to have functional parts. Based on this I am counting on a good learning curve for my CAD skills.