5. 3D Scanning and printing¶
For this week we had to:
-
Group assignment:
- Test the design rules for your 3D printer(s)
- Document your work on the group work page and reflect on your individual page what you learned about characteristics of your printer(s)
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Individual assignment:
- Design and 3D print an object (small, few cm3, limited by printer time) that could not be easily made subtractively
- 3D scan an object (and optionally print it)
Group assignment¶
Details of our group work can be found here.
Differences in working with MakerBot Replicator 2 and Creality Ender-3 v1 3D printers¶
Table characteristics¶
The MakerBot printer’s platform is acrylic with adhesive tape and no heating function, while the Ender-3 has an aluminum static platform with a heating function and a special coating. The Ender-3’s platform cannot be removed, but there is a risk of the printed model detaching if the height-to-area ratio is high without using a “raft” to increase adhesion to the platform, resulting in higher material usage. Attached photos illustrate this issue.
Some characteristics¶
| MakerBot Replicator 2 | Creality Ender-3 v1 | |
|---|---|---|
| Usable printing materials | Only PLA | PlA and ABS |
| Extruder nozzle | 0.4 mm static nozzle | switchable nozzle |
Print detail depending on Meshing options¶
Most 3D printers work with STL files. In the STL file, information about an object is stored as a list of triangular faces that describe its surface, and their normals. The quality of the surface of the prototyping object depends on the number of polygons that make up the surface.
We work in the FreeCad graphics program that supports conversion to STL file format. The conversion depends on two parameters, Surface deviation and Angular deviation.
As part of the group work, we decided to construct a sphere with a radius of 18 mm, cut from below by 6 mm. Let’s set different values for Surface deviation and Angular deviation and look at the results.
Converting to STL format with maximum fidelity might seem like the best option, but it can result in large file sizes, up to 1 GB for large models, which can slow down your workflow. Therefore, it is better to find a balance between the quality of Model 4 and Model 5 that will not significantly affect print quality.
Individual assignment¶
3D printing¶
Bearing on a 3D printer¶
As part of this week, I’m going to design a bearing, of course it will be different from a metal bearing, which is designed to solve important problems. But I am very interested in this question, because within our laboratory there are tasks in which there is a need to create a moving axis, and if the experiment is successful, then in the future I can bring this solution to other projects.
Back in the day, before 3D printers were a thing, prototypes and products had to be made using subtractive methods. If an object had moving parts, each piece had to be created separately and then put together. But with 3D printing, that’s not the case anymore! It’s way easier to create mechanisms with empty spaces between parts, which allows them to move freely.
I am going to implement the project in FreeCad. FreeCad makes it possible to make the design parametric, if in the process it becomes necessary to edit the drawing, then by changing several parameters the drawing will be automatically generated.
My bearing will be characterized by 8 parameters
- Outer race radius
- Outer race thickness
- Inner race radius
- Internal race thickness
- Bearing width
- Sphere radius
- Sphere backlash
- Number of spheres
Let’s create them in FreeCad and give preliminary values. This is done in the Speadsheet section.
Variables are created and now it’s time to pre-design itself. In the section Part there is a wonderful tool tube with whose help you can create our races (races).
Now I will combine the two into one using the Make a union of several shapes tool, which is also in the Part section.
Now you need to create a passage for the spheres. This can be done in the Part section using the torus solid tool.
To create a passage, it remains to remove the torus from our races. To do this, first select the race and then the torus and click on the tool Make a cut of two shapes.
Now let’s create spheres. This is done using the Sphere tool. Now we need to set parameters for it. Set its radius and location along the Z axis equal to half the width of the bearing, as well as the location along the X axis using the formula so that it is located in the center of the passage of spheres.
Now we need to increase the number of spheres. To do this, go to the Draft section. Using the Array tool, create a circular array relative to coordinates (0, 0, 0) with the number of elements we need.
Combine races and spheres with the Make a union of several shapes tool in the Part section.
At the moment we have a parametric drawing of the bearing, but in order to print it on a 3D printer, you need to create a G-code. But to create a G code, Mesh Design is needed.
We need to go to the Mesh Design section, mark all our elements and click on the Tessellate shape tool. Then select the parameters and click on the OK button. Our design will be generated, but with the difference that it already consists of triangles and equilateral quadrilaterals (equilateral quadrilateral).
This will already be clear to the G-code generation program. In my case, I will use MakerBot and UltiMaker Cura. Now you need to export the resulting Mesh Design in *STL format.
Print directly¶
First I tried to print the bearing with the original parameters on MakerBot. Generated G-code in MakerBot. But the result did not please me, since I could not in this program to generate such support (supports) to be in the right place, namely under the spheres. And the result is this:
Then I decided to use UltiMaker Cura. The initial results also did not please me. The spheres were glued to the races.
In the future, I decided to increase the scale of the bearing by 2 times with the program UltiMaker Cura. As a result, the spheres broke away from the part during the printing process.
Then I increased the bearing in the program UltiMaker Cura by 1.5 times from the initial size. The bearing printed normally, but since there was a lot of space between the balls, the balls crawled out of the structure and the bearing turned out to be unstable, did not retain its appearance and functionality.
As a result, based on the failed experiments, it became obvious to me that the distance between the balls should be as small as possible.
And the best solution would be to print the bearing on Ender-3, and create G-code using UltiMaker Cura
I ended up printing a part with the following specifications.
| Parameter | Meaning |
|---|---|
| Outer race radius | 15.00 mm |
| Outer race thickness | 3.30 mm |
| Inner race radius | 4.50 mm |
| Internal race thickness | 3.30 mm |
| Bearing width | 9.00 mm |
| Sphere radius | 3.70 mm |
| Sphere backlash | 0.20 mm |
| Number of spheres | 8 |
Here is the print result
3D scanning¶
Working with Meshroom¶
I have no experience with 3D scanning. I am more comfortable working with a computer than with a phone, for this reason I chose the Meshroom program for the scanning task. I downloaded this program here.
As a scanned object, I chose the wing of a drone that was present in our laboratory.
I made 43 photo drawings from different angles and threw them into the program.
The result was such that the 3D model was not scanned, the download did not go through.
Then I learned that in order for the part to be scanned, it needs to be fixed from the bottom side and the camera needs to capture it from different sides. Since I was not familiar with scanning, I thought that the part can be twisted as you like and the program that produces a 3D model based on photos will understand this and generate a 3D model.
Working with the WIDAR mobile application¶
To give some results, I decided to use the WIDAR mobile application. Looks very promising as it saves time. You can bypass some processes.
Since the connection with the shaft is also important for the drone, and in order to somehow scan this part, I decided to fix the *** screw *** on a thin stick. I launched the application and followed the instructions and started making photogravures directly in the application. As a result, I took 100 photos.
The result I got amazed me: Almost everything that fell into the camera lens was scanned, except for the necessary.
I don’t have a downloaded 3D file, because it was necessary to make a paid subscription for downloading, and since the scan was not successful, I did not make a subscription. But for a free subscription, you can only view the 3D model. The scanned 3D model can be viewed by following the following link.
Working with the KIRI Engine - 3D Scan & Edit mobile application¶
Although I was very disappointed with the result of two tests, I still wanted to see at least some result and for this reason I decided to try another mobile application for scanning and another object. My colleague Anoush Arshakyan said what app she used and most importantly, she got the result and was able to download it.
I downloaded the KIRI Engine - 3D Scan & Edit app from Google Play and registered. For a free subscription, there is the possibility of 3D scanning based on 70 photos, and with a paid subscription, based on 200 photos.
After doing 70 photogravures, I uploaded them to generate a 3D model.
When the photos loaded, it took extra time for the 3D model to be generated.
I then exported it in .obj format and then imported it into FreeCad. The object I needed was scanned, but next to it, something that I didn’t need was also scanned.
Since the 3D model is Mesh, I went to the Mesh Design section. It can be seen from the model that the whole model is a separate model, and if you apply the tool Split selected mesh into its components to it, then the model will be divided into unrelated models.
After deleting the models I don’t need, the following remains:
There are still some leftover parts. There is a nice tool Cuts a mesh with a picked polygon that cuts out parts of the model. Let’s use this tool.
After cutting out some unnecessary parts, the resulting result cannot be considered ideal and suitable for printing on a 3D printer, but it is worth noting that it looks like the original. Let’s visually compare the model obtained as a result of 3D scanning with the real one, from different angles.
Conclusion¶
I especially liked working with the 3D printer. I also liked the fact that as a result of the unsuccessful results, I learned the intricacies of the work. Although 3D printers have changed our lives a lot, in particular, we can make the thing we need if we don’t find it on sale, but to get a complex part, you need to take into account some nuances, some of which we wrote in our group work and which I tried to write about in my individual work.
Regarding 3D scanning, there are also some nuances. But if you are interested in this activity, I advise you to conduct your experiments and find your working style.