Week | 6
3d Scanning and Printing
How I’m making a 3D print of an object I’ve designed and another one of an object I’ve scanned.
24 February 2018 01:06:
3D Design and Print
My idea for this week was to design something simple, so that I could use the time to learn how to 3D print rather than spending it to design an object.
Having lived in a few cities in the last years, I decided to model a cube, that could be used as a candle cover, and have in each side of the cube a pattern representing these places:
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Rio de Janeiro, Brazil.
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Santos, Brazil.
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Sao Paulo, Brazil.
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Berlin, Germany.
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Barcelona, Spain.
Since most shapes are simple, I have modelled them in Fusion and mainly used the sketch mode and extruded the planes. Then, I aligned and joined each separate side to create the cube, leaving one side free so that I could put the (electronic) candle inside.
Here’s the model:
27 February 2018 13:06:
After talking to our instructor, I realised I had to make some small updates on the model, so that the 3D print could have higher changes of going well. I changed the bottom part of the cube so that the pattern most likely to bend would be in contact with the machine surface, therefore, with plenty of support and no chances of falling. I also had to change the direction of one of the patterns, so that it could be printed with more support as well. See below:
This is the model that ended up being printed:
I have used Cura to generate a G code and export the file to the printer.
The cube is about 8 cm, so, it would take too long to print with a detail quality, specially for this kind of test, so, I’ve changed some parameters like increasing the layer height to 0.3 mm and the print speed to 60 mm/s.
Find here a more comprehensive documentation about parameter setting, put together by Ilias Bartolini as part of our group assignment for this week.
The printer I’ve used for this test is a Formbytes we have here at the lab. What’s really interesting about this printer is that it doesn’t have an enclosure, so you get to see its parts and components working together and the interface is quite straightforward. Here’s a very nice tutorial on how to use and setup the Formbytes at Cura.
Here are some screenshots of parameters used at Cura. Cura slices the 3D part and generates the G-code for the 3D printer:
You can simulate the print job and see how it’s going to be printed by using the layer view:
I copied the file from Cura to an SD card and started the job. Another interesting aspect of Formbytes is that it allows you to adjust the speed during the printing process, so, you can regulate the speed as your model is being printed. This is particularly useful when you see that your model is being printed well and does not require lots of details, so you can increase the speed to save some time. I’ve set mine to approx. 115%.
I had a small setback during the printing: we had a power cut at the lab when I had approximately 80% of the job done! This printer does not remember it’s position, and resumes automatically, so I had to send it to print again.
Here’s the result:
Printing issues:
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My biggest problem was with the bridges (a stretch of plastic that is extruded between two raised points).Probably because of the size of the gaps between the model’s columns and potentially due to the speed of the extrusion, which might have been too fast and created too much vibration and made the filament unstable.
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The infill pattern was visible from the outside. Probably due to the wall/shell thickness.
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Some cracks in the object. Probably the base layer didn’t cool before the following one, adhering to the second layer and creating the tiny holes.
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Fine details didn’t print correctly and generated artefacts. Probably because of the choice of the layer height (should be smaller) and perhaps the nozzle size.
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Stringing: there were some strings of plastic between parts of the model. Probably because some filament has dripped from the nozzle when the head moved.
I believe most issues happened due to the parameters I have chosen. Since this is just a test to get familiarised with the 3D printing process, I didn’t believe it was worthy to change the parameters and print once again, but, if I had more time I would change parameters to have more detail, make the cube smaller (approx. 6 cm), thicken some pattern parts and use the white PLA instead (the yellow one was the one already connected to the machine).
Here’s a really interesting compilation of common 3D printing problems and their likely solutions: link.
In general the use of 3D printing is an advantage when you want to develop something quickly. From finishing the design to having the actual piece in your hands usually takes a few hours, and that is not comparable to a traditional manufacturing process. On the other hand, choice of materials is still somewhat limited to the general public and it has too much reliance in plastic, which is not environmentally friendly. Equipments and materials are also expensive, if compared to traditional manufacturing.
In the case of the cube I’ve designed above, it would not be possible to do it using a subtractive process (such as laser cutting or Milling a wax block or a block of wood) with the tools we have at the lab, the cube has 5 walls and it’s empty on the inside, all interconnected, so 3D is indeed the best option for this prototype.
A video showing the steps to model the cube in Fusion:
3D Scan and Print
The other part of this week’s assignment is to scan and print something. I decided to use a Kinect sensor (bought an used one from this shop for 10 euros) and the Skanect software for this.
Here’s my (very) improvised rig:
My initial idea was to scan my dog and a small object, but I have realised the graphics card (Intel HD Graphics 515 1536 MB) of the Macbook Air I’m using does not support CUDA, so I had to use the CPU implementation instead, which was slower and much less accurate than the GPU version. I decided to go for a much simpler and somewhat dull task, which was to scan myself. So, considering the lack of time, light and graphics card, this is the result model I got:
I have tried to improve my model using MeshMixer, and I did succeeded in slightly smoothing my face (pretty much just trying to use different settings and brushes in the sculpt > refinement tool), something really random, like this:
But, the model is still very bad due to the graphics card / light limitations I had., as you can see below:
While using MeshMixer and watching some tutorials, I realised that there is plenty you can do with it in order to improve your scan, including adding pre-modelled small body parts that weren’t really nicely scanned due to their size, so, I decided to play a bit more with it and added some bunny ears to my model : /
Here’s the model:
And the final print:
