6. 3D Scanning and Printing¶
Week assignment
- Test the design rules for your printer(s)(group).
- Document my work and explain what are the limits of your printer(s)(in a group or individually)
- Design and 3D print an object (small, few cm3, limited by printer time) that could not be easily made subtractively
- 3D scan an object, try to prepare it for printing (and optionally print it)(individually)
Characterize the 3D printers and test the design rules¶
2 types of printers were available in the lab for us to test: SLA (Stereolithography Apparatus) and FDM (Fused Deposition Modeling). The group slpit so that each of us could test something different and then share results.
Printing Technology: FDM (Fillament)¶
Test: Reprap 1 using Filaflex - Thermoplastic Polyurethane (TPU)¶
I downloaded Cura and chose the machine I was going to use. Then, import the test file. Then I found that I didn’t have the parameters to print TPU (Filafex). So, I moved to the 3D printing area and used the computer there.
We all used the same file for the test. In this way we also made sure not to have errors not linked to the printers themselves.
The machine set to print using TPU is the RepRap 1. These are the paremeters I used for this material:
- Printing temperature: 240C
- Printing temperature initial layer: 240C
- Initial printing temperature: 235C
- Final printing temerature: 235C
- Build plate temperature: 40C
- Build plate temperature initial layer: 40C
- Flow: 100%
The printing time estimation was 1h 48 min using a draft of 0.2mm and 25% infill.
For this material the recommended speed is between 15 mm/s – 25 mm/s to ensure high-quality prints.
Issue¶
Half an hour into the printing process, the piece began to detach from the sides. We had to stop the printing, remove the part, clean, apply a fixing spray and start over.
The temperature was too hot and the retraction too low. We changed the retraction from 3.5 to 2 and the temperature to 230.
Changeing the filament¶
Steps to change the filament on the Reprap 1
- The nozzle has to be previously heated.
- Unscrew the screw and open the filament small gate.
- Push the material in place until it extrudes a bit and then pull up.
- Cut the tip of the new filament at a 45º angle.
- Push the tip between the gears until the nozzle start extruding the material.
- Close the small filament gate without tightening the screw too much.
Each printer has a slightly different way to change the filament.
Adjusting the bed¶
We noticed that the nozzle was touching the bed on one side. So we rotate the side bar to level the nozzle.
Conclusion¶
TPU is a highly flexible material but it doesn’t have a smooth surface finish. Easily comes off the bed, which is a problem if it happens in the middle of printing. Also, it’s printing speed is significantly slower than PLA.
Test: Reprap using PLA¶
- Filament: PLA
- Noozle diam: 0.6
- Cooling fan part: No
- Bed temperature: 40C
- Filament temperature: 250
Test: Prusa using PLA¶
- Filament: PLA
- Noozle diam: 0.4
- Cooling fan part: Yes
- Bed temperature: 60C
- Filament temperature: 215
Test: Anycube using PLA¶
- Filament: PLA
- Noozle diam: 0.4
- Cooling fan part: Yes
- Bed temperature: 40C
- Filament temperature: 215
Printing Technology: LCD-based SLA 3D Printer (Resin)¶
Testing Anycubic Photon S¶
The detailed specs of the machine:
- Light-source : UV integrated light（wavelength 405nm）
- XY DPI : 47um (2560*1440)
- Y axis resolution : 1.25um
- Layer resolution : 25 ~ 100um
- Printing speed : 20mm/h
- Rated Power : 50W
- Printer size: 230mm200mm400mm
- Printing volume : 115mm 65mm 165mm (4.52″2.56″6.1″)
- Printing material : 405nm photosensitive resin
Differences between SLA and FDM¶
In FDM, a strand of material (in this case: thermoplastics) is deposited in layers to create a 3D printed object. During printing, the plastic filament is fed through a hot extruder where the plastic gets soft enough that it can be precisely placed by the print head. The melted filament is then deposited layer by layer in the print area to build the workpiece.
Like FDM, SLA is an additive method: Models are built layer by layer. SLA, however, uses a curable photopolymer (Generally a liquid resin) that is hardened by applying focused light or UV light (this process is called curing). SLA printers usually build the models from top to bottom, the build platform lifts the model upwards, out of the resin bath.
| Technology | Materials tested | Printers tested | Dimension accuracy | Surface finish | Supports required | Post-processing process |
|---|---|---|---|---|---|---|
| FDM | SLA, PLA | Prusa, RepRap,Anycubic | ± 0.08 - 0.2mm - | Lower quality | Depending on the angles | Not always required |
| SLA | Resins | Photon | ± 0.01 - 0.1mm - | Smoother surface | Always required | Always required |
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Materials and colors
- FDM printers typically use PLA, PETG, or ABS filament. Also, nylon, PVA, TPU and a variety of PLA blends (mixed with wood, ceramics, metals, carbon fiber, etc.)can be used. Filament’s palette color is huge. Standard filamente diameter could be 1.75 or 2.85mm.
- SLA has a more limited pallet of resin materials. The choice of colors is also limited for non industrial machines. I found this color kit from Formlabs that seems to let you create your colored resin.
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Precision and surface finish
- FDM: the printer’s resolution is a factor of the nozzle size and the precision of the extruder movements (X/Y axis). Also, the bonding force between the layers is lower than in SLA printing. The surface finish on fast printing is also lower.
- SLA printers produce higher resolution objects and are more accurate than FDM printers. The resolution is primarily determined by the optical spot size which is smallet than the nozzle of the FDM printers. Plus, During printing less force is applied to the model. This way, the surface finish is much smoother. SLA prints show details an FDM printer could never produce.
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Costs
- FDM consumables: Nozzles and filament rolls. The cost of a filament roll it’s lower than the resin. This depends on the material of choice.
- SLA consumables: Resin and resin tank. According to the specs the resin tank has to be replaced after 2-3 liters of resin have been printed (it lowers the precision). Some SLA printers have use proprietary material, therefore it is not as standardized as FDM. Also, it’s recommended to replace the build platform after some use.
Design and 3D print an object that could not be easily made subtractively¶
As I wanted to start doing some tests for my final project, I decided to do a quick 3D model of a two-piece object with a rail. To do this, use Rhino since it is the 3D modeling tool that I handle the best. The bottom piece has holes to pass the laces of the shoe. A rail and some spaces to place some mini neodymium magnets that I got for testing.
Before starting modeling, measured my shoe and make an initial box with all these measures. On the top view, I drew the base in 2D and extruded it about 2mm approx. Then in the side view, draw the profile of the rail and extruded it too. I did a boolean operation to join these volumes. Finally, in the other side view, I drew the top of the rail with the spaces for the magnets.
Consider an initial tolerance of 0.2 for the top piece. But instead of extruding volumes, I started with a volume to which I apply boolean operations to subtract parts and add the ears.
On my first attempt, I printed a piece with a rail that I wanted to test for the final project. I wanted to print the base in TPU but I faild to the balance between the temperature and retraction. Also, the surface finish was far from smooth. At least, I learned that adding support to 3D print with Filaflex is a very bad idea.
I ended up printing both pieces on the Prusa. I leant that to be an optimal design, I should have adjusted the angles of both the holes and the sides. However, as the piece was small, this didn’t impact the surface.
Parameters I used:
- Infill: 15%
- Layer height: 0.2 mm
- First layer height: 0.2 mm
- Perimeters: 2
- No support
This object can not be easily be made subtractively because you’ll need a 5 axes milling machine. On the one hand, the fact that it has a rail makes it more complex, but the stop piece where the magnets go makes it much more difficult to manufacture by subtraction. The other reason is that I wanted to do a try this piece in Filaflex. So, to do something similar I would have to develop a mold to be able to make a silicone casting.
Find all the files here:
3D scan an object, try to prepare it for printing¶
During the class we learn how to 3D scan using the Kinect. I was the subject scanned. We used a basic platform that rotates and as I was standing up still, someone was rotating the platform and the tallest one was scaning with the Kninect.
I decided to try photometry but for some reason I couldn’t get pass form 1% download. I try lowering the resolution, the amount of photos, but nothing. Until it finlly was uploaded and downloaded. The final result was far from an object.
I ended up using an app, Capture. the main dificulty was the fact that I needed to capture the image with the front camera. While this might be useful for a face, it’s definitly not for an object.
Although the image was not good I decided to try fixing it in Blender. So, I exported it to .slt and imported it into Blender. I found out that this was not even near a mesh. It looked more like a cloud of dots. I cleaned it a little bit but it mas impossible to do anything with this.
Find all the files here: