Mechanical Design, Machine Design
Tasks:
Make a machine, including the end effector, build the passive parts and operate it manually.
Automate your machine. Document the group project and your individual contribution.
This time it is a group task in which we have to build a machine that MAKEs something. For our group assigment, we decided to build a Solar Drawing Machine
The first one is to track the sunlight and focus it on one beam. The second is to use this focused beam to either engrave or draw something on a material that can be burnt, melt or cut.
To view the group's MTM page, please click on this Link
Even thought it is a group assigment, we have to document the individual contribution!
I tried to get involved in as many parts of the project as possible, starting from the idea and design, finishing with the electronics and programming of the machine! The reason for that is LEARNING. Some of my collegues have a design background, some have a good knowledge of programming, and I wanted to catch up in everything.
Because we are going to focus the sun light into one point, we had a discussion about the lens that we should use. The choice was between the Fresnel Lens and the Magnifying Glass.
After some research (source) we decided to use the Fresnel Lens! They are not quite expensive, so we purchased one from eBay wich has the dimensions of 31x31 cm.
One of my tasks was to build the frame for the lense, so we can attach it to the whole structure, and make it controllable by a motor!
This is the sketch of how I visualized the frame!
I designed the 3D model using 
. I used simple shapes like rectangles and circles to draw the sketches, after that I extruded them. I was planning to use 8mm acrylic because of its transparency which will not block the sunlight!
The idea is to fix the lens between the frame, and wedge it by locking all 4 sides using "key" joint! The holes in the middle are made to attach the rod which then will be attached to the sides of the whole structure
The final 3D model looks like this:
The 3D model is useful to have a visualization of how the final result should look like. I export the sketches as .dxf file, and prepare it for the lasercutter!
To lasercut the frame, I used the following settings:
After I assembled the parts and fixed the lens in between, this is how it looks:
As I mentioned before, I designed a through hole joint which is fixed by a "key". This will keep the structure stiff!
To attach the frame to the rest of the structure, I used the M6 threaded rod, which I fixed from both sides using two nuts screwed in different directions, and also attached a pulley which will be controlled by a motor using a belt
Another task which I was working on is to make the mechanical part where the lens will be attached.
The problem here is that we will have to focus the fresnel lens on the bed manually, that is why I cannot design a fixed attachment, I simply do not know the distance between the lens and the bed.
I came up with a solution which will make the length adjustible, so we can manually focus the lens on the right position, and also change it anytime whenever we need it.
As you can notice, I designed it in a way that you can slide the attachments up and down, and when the right position is found, we fix it by screwing the bolt and nut on the back side!
Here is what I mean by attachments:
On the front side of the slider the lens will be attached, and on the back, the slider will be fixed in position by screwing the bolt. This mechanism gives us freedom and flexibility, and allows us to adjust the hight anytime we want
This is how the 3D model looks like:
Let's mill it!
To cut my design, I will be using the big CNC monster.
In FabLab Kamp-Lintfort we have a CNC portal milling machine by e(sign: Easy Worker MasterPro 2513.
It’s working area is 2600 x 1400 x 300mm and it comes with a vacuum table. We primarily us it for wood milling but with its HSD Spindel (3.9KW; 24.000U/min) it is also capable to mill metals easily.
The material which I will be using is 18mm Plywood
At first, I place the wood sheet on the CNC bed, and after I aligned it, switch on the vacuum. After I exported the .dxf file, I used 
to edit the design before importing it into the machine CAM software.
To set the X,Y and Z Zero Positions, I home the machine by pressing the home button in the software (or on the remote control).
Now I have to find the Z axis, which I do using the special tool which comes with the machine:
I split the job into two: the inside cut and the outside cut. These are the settings which I used for the inside:
After the job is done, I launch the outside cut with the following settings:
After the mill is done, I sandpapered the pieces, and this is what I get:
For the attachment sliders, I had to drill the holes manually! Because I was planning to use M5 bolts, I drilled a hole of 6mm and a bigger diameter of 12mm around it. The result looks like this:
Problem
When I tried to attach and screw the bolts to fix the slider, I noticed that the elastic properties of the plywood are not enough for my needs. The force applied by the bolt was too big, and the wood was braking.
I decided to 3D print the sliders, using PLA instead of wood. I exported the sketches from Fusion 360 into 
, and printed the model using the following settings:
I did not make any support because the 3D shape which I intended to print looked pretty fine without it!
And I was right!
On the front side of the slider, I lasercut small rings of acrylic with outer diameter = 10mm and the inner diameter = 6.5mm which are supposed to act as berings, and hammered them inside the predisigned hole:
To attach the lens to the slider, I cut two threaded rods with 12cm length, one from each side of the lens
After I assembled everything together, fixed the slider in the right position, attached a pulley for the mottor to the threaded rod, and fixed everything using nuts, this is what I get:
And here we are! We have got the structure, and the lens attached to it, a freely rotating axis fixed to a pulley, controlled by a mottor using a belt!
Download Files:
Mechanical Structure Fusion360 (.f3d)
Mechanical Structure CNC (.dxf)
*Special THANKS to our local instructors Daniele Ingrassia and Karsten Nebe, and the BEST TEAM from FabLab Kamp-Lintfort. We did a great job and had a lot of fun!
