| Previous blogs | Description |
|---|---|
| #1 - Introduction, the plan and materials preparation | In this blog post we describe the project's main concept and some initial high-level design of it. |
| #2 - Materials and casing assembly | Our journey with selecting proper materials, cutting and assembling the drawer and its casing! |
| #3 - Modelling, cutting, planting! | The title says it all: this part describes some modelling we did before cutting some holes in the drawer and finally planted some vegetables! |
| #4 - Plants, harvests, and fertilisers | First harvest, problems with plants and used fertilisers. All that went off-script for our plants in the artificial environment. |
| #5 - Piping and pumping - water and liquid fertiliser delivery system | Design and development of water supply system. |
| #6 - Mix of fixes - various fixes to water supply, lighting and hardware | Polish and fixes of various components of the system, all the small things. |
| #7 - Ride the lightning - Wiring diagram, pinout and components discussion | Diagram of the circuit, pinout for most components, wire choices and their connections |
| #8 - Pulling the strings | LED and Fan control circuit, overview of BJTs and MOSFETs with a handful of useful general information |
| Next blogs | Description |
|---|---|
| #10 - Software, architecture and the benefits of good preparation | Big explanation of the software and its architecture |
| #11 - Summary | Our final post before the end of the challenge! |
Intro
It is finally time to show off how we utilised the miracle known commonly as 3D printing! I suggest to look through this post if you are interested in 3D printing, as I will be sharing some of my tips and stuff I have learned so far when it comes to printing and modelling things to print! If you are not so keen on it, there is a plenty of nice pictures and renders below, so feel free to look through those 
. As you might have seen in the previous blogs, many 3D printed parts appear in our project, interacting with each subsystem of it in one way or another. I have learned a lot about 3D modelling and printing throughout this project as you will probably be able to see from the design quality 
.
Meet the printer: Prusa I3 MK3S
This project would definitely have been much more time consuming and some of it maybe impossible if not for this beautiful machine! I am in no way sponsored by Prusa, but I truly must admit that this is a work of art. So if you are ever considering to buy a 3D printer, definitely do check this one out!
3D Model
Since the project is constantly evolving, our 3D model of it is changing as well! All parts used in our project were modelled by us in Fusion 360, so here is a render of the up-to-date version:
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| View at an angle |  |
| Front view |  |
| Bottom view |
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The designs
Below each design visible in the render above is displayed with its 3D model and the actual printed part, along with a short history of that particular element . As you will soon find out, I am a huge fan of engravings on 3D prints, which is a neat trick and fairly easy to do! Also they make the prints look much more professional (in my humble opinion at least).
Here is a list of those elements (in chronological order):
- MDF board clip
- Outer cover rectangular legs
- Support wheels
- Capacitance sensor horizontal holder
- Capacitance sensor vertical holder
- Bed clip (Not used)
- Motor holder + wheels
- Irrigation hose holder
MDF board clip
The clip itself was a very simple design, but necessary as our top part of the Envidrawer's cover is made up of 2 parts. This clip has 2 purposes: the first one is holding those two parts together. The other one is to tie the clips to the bed so that the front part of the cover doesn't dip in the middle. With that in place the Envidrawer can freely move under the cover. The clip simply slides on the cover and the assembly is done!
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| MDF board clip model assembly | |
| View at an angle next to the actual 3D print | The clips were printed using Prusa's Gentleman's Grey PLA.
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Outer cover rectangular legs
The cover legs are a slightly longer story. The first version came out a bit too wide and the screw hole was slightly too big. By version 3 they fit perfectly in place and were extremely easy to install with a single screw each. Because of the nature of 3D printing, The parts were modelled so that the only overhang is very easy to print and generally a semi-complex object was turned into a very simple print! This is something I recommend everyone does when modelling things to be printed - think of the orientation of the print while designing, whether it will need supports, if so maybe it is best to design them yourself.
| {tabbedtable} Tab Label | Tab Content |
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| Rectangular legs model assembly | |
| Legs during print |
There is a neat trick I used here: The actual 3D model doesn't have a hole in it, or rather it is there, but there is a thin layer (exactly 1 layer height) of material before the hole. This makes the overhang so easy to print! Instead of working around the hole, the extruder can go over it! Then all you have to do is to puncture the single layer and the print is ready to be used!
The legs were printed using Prusa's Gentleman's Grey PLA.
For reference, see the 3D models to which I will post a link at the end of this blog.
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| Leg adapter model | Below is a model for an adapter for version 1&2. With it in place, they can be used as working legs, no need to recycle them just yet!
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| V1 and V2 with adapters installed |   |
| Leg with a screw before installing |  |
| Envidrawer cover with legs installed |
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Support wheels
Since the project itself ways quite a bit, we decided to add some support wheels underneath it so that the full weight won't be supported just by the motors. We found some old skateboard bearings, so we decided to use them here. The caster wheel support along with the axel and the nut were made out of PLA while the tyre itself was printed with filamentum flexfill 98A, a TPU polymer which has a similar hardness to hard rubber. When printing with a flexible material, it is important to run the print slower and loosen the idler which pulls on the filament, to prevent it tangling around it or jamming. Although I never experienced a jam with this material, I always followed those instructions, so keep that in mind . The wheel again went through some changes during the development process, increasing the thickness of some parts, adding the nut and threads to the axel to prevent it falling out.
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| Support wheel model assembly | |
| Flexfill tyre with bearing inside | The tyre design actually required some maths in order to be symmetrical, but turned out quite nice
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| Caster assembly | Here are all caster wheels already assembled and after positioning them and temporarily securing in place with some tape, they were attached to the drawer with some screws.
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Motion subsystem
The Envidrawer is supposed to move on its own from under the bed and hide under it at the end of the day. In order for that to be possible, there needs to be a way for it to know when it is fully under the bed or completely visible. For this purpose we utilise 2 capacitance sensors, but more on that in the motion subsystem blog, to be released soon! The sensor holder designs derived from the simple yet effective MDF board clip design, cause why not reuse what you have already made .
Capacitance sensor horizontal holder
This too went through some iterations, Version 1 was a bit too fragile and hard to manipulate, But with a wider gap in the new version and stronger links the holder fit just right! I personally really hate 3D printed supports and removing them, so whenever I can I try to avoid them. A helpful tip is to always consider how you can split the part in order for it to be printed without supports. I then simply add some pegs on one part holes on the other with around 0.5mm of wiggle space and we got a ready part!
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| Capacitance sensor horizontal model | |
| Capacitance sensor horizontal holder V1 | Here we can see the small "pegs" as they are guided into their holes to secure the part in place.
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| Capacitance sensor horizontal holder final side view |  |
| Capacitance sensor horizontal holder final front view + rendered model | The holder was printed using Prusa's Gentleman's Grey PLA.
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Capacitance sensor vertical holder
This design derived from the horizontal holder. The first version unfortunately was too big and did not fit inside of the drawer. The second one was a bit harder to print, with a tough overhang, nevertheless it printed flawlessly . With the modified design it also was easier to assemble
and disassemble (see the animation below). Another friendly 3D printing tip: round holes can be easily printed on a vertical wall, without any supports (nobody likes supports!). Additionally make sure to test your printers bridging capabilities before a print
with big overhangs to avoid failed prints. Luckily for me, Prusa i3 MK3S is an amazing machine and printed it without a sweat . Both V1 and the final version were printed in Prusa's Gentleman's Grey PLA.
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| Capacitance sensor vertical model assembly | |
| Capacitance sensor vertical holder v1 | Version 1 worked similarly to the horizontal holder, with two parts being attached together, this unfortunately proved to be a bit to tall and did not fit under the Envidrawer's cover. The parts were printed at the same time and assembled afterwards
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| Capacitance sensor holder final side view |  |
| Capacitance sensor holder final + rendered model |   |
Motor holder + wheels
With support caster wheels in place, capacitance sensors attached it is time to combine it with the motors and print some bigger wheels! The tyres were a remix of the caster wheel tyres with slight improvents and everyting else was designed from scratch.
| {tabbedtable} Tab Label | Tab Content |
|---|---|
| Motor + coverr + wheel assembly | |
| 3D printing it | The plate connecting the drawer and the motor was printed using PLA, the tyre was printed with Filamentum Flexfill 98A (0.2mm layer height) and the wheel support was printed with black powdered Devil Design PETG (0.3mm layer height).
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| Plate v1 | Nothing goes to waste! I used the failed v1 plates as soldering stands for the motors
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Summary
Wow! that was long! for those that managed to get through all of this, I am sharing the last video of the day, my second ever 3D printing timelapse! As I already have a ton of embedded videos, this one will be linked to yt: https://youtu.be/FqjGjHK1LWg
All in all, there was a lot of 3D printing and modelling involved in the making of Envidrawer, still some to be made (an electronics box, other smaller designs). This was quite a piece of writing, took me much longer than I anticipated! We finally see the light in the tunnel as we close in on the deadline, stay tuned for an update on the Motion subsystem and more!
Szymon, Jakub & Michał
| Previous post | Next post |
|---|---|
| #8 - Pulling the strings | #10 - Software detailed discussion |
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