Week 5 : 3D scanning and printing¶
Week 5 assignment could be categorized as follows:
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Group assignment
- Design rules test of a 3D printer
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Individual assignment
- Design and 3D print of a non-substractive object
- 3D scan of an object
Design rules test of a 3D printer¶
General info about 3D printing
Common 3D printing process :
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Fused deposition modeling (FDM)/fused filament fabrication (FFF) : melts plastic filaments and extruding it through a heated nozzle, depositing material layer by layer to build the part. Filament is usually 1.75 mm thick and is pressed through a nozzle to a much smaller diameter (usually 0.4mm)
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Common FDM materials :
- Polylactic acid (PLA) : inexpensive, ideal for decorative objects or components with low loads, good recyclability
- Polyethylene terephthalate glycol (PETG) : more robust than PLA, good for functional components that need to withstand high forces/loads
- Other characteristics :
- These materials below are hygroscopic - absorbs moisture and degrades with time
- Low levels of ultrafine particles (UFP) and so safe to use in open environments More information could be found at Prusa's filament material guide
- Start by assuming that these materials are not food safe
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On anisotropy : A printed object’s strength and properties depend on the direction it was printed.
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Slicer takes 3D model into thin horizontal layers and then generates printer instructions (e.g. temperatures, speed, etc) in the form of G-code file.
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Stereolithography (SLA): use UV laser to cure (i.e. harden) liquid resin layer by layer.
- Comparison with FDM/FFF :
- Processing might be faster, but a lot of post-processing required.
- Higher accuracy and finer details
Reference : Formlabs
3D printing is a form of additive manufacturing, in which layers are added to form an object rather than subtracted (material removed to obtain the form of desired object).
In this study, the FDM process is investigated using the Bambu Lab A1 mini. The printer specifications and settings (including material) used for the test are provided in the following tab.
| Specification | Details |
|---|---|
| Build Volume | 180 × 180 × 180 mm |
| Nozzle Diameter | 0.4 mm |
| Maximum Nozzle Temperature | 300 ℃ |
| Maximum Bed Temperature | 80 ℃ |
| Supported Materials | PLA, PETG, TPU, PVA |
| Parameter | Details |
|---|---|
| Material | PLA |
| Layer Height | 0.2 mm |
| Extrusion Temp | 220 ℃ |
| Bed Temp | 60 ℃ |
| Infill | 15% (Grid) |
About Bambu Lab Mini AMS
The Automatic Material System (AMS) on the Bambu Lab Mini allows for multi-color and multi-material printing. However, the filament is exposed in the storage cartridges, so humidity and moisture absorption may affect print quality.
If the filament has absorbed moisture or is otherwise degraded, issues such as poor layer adhesion, stringing, bubbles, or weak prints may occur.
The AMS uses NFC tags embedded in the filament spools to automatically detect the filament type and color.
Source: ChatGPT by OpenAI, February 2026
Overhang and bridging test¶
Aim of test : To determine the maximum overhang length and bridging test before "spaghetti" could be observed.
Observation :
- Overhang test : Even at the 1 mm overhang, the spaghetti could already be observed at the bottom part of the overhang
- Bridge test : this sagging feature could not be seen even until 20 mm distance gap
Possible cause :
- Tension that is created at both ends of the bridge keeps the filament to stay suspended
- Insufficient rapid cooling prevents the filament to solidify quickly enough
Clearance test¶
Aim of test : To determine ideal spacing/clearing of moving and interlocking parts. The diameter of the axle is 2.5 mm, and the numbers engraved on the 3D print indicate the circular gap in each rectangle (e.g. for 0.3 mm clearance, the actual circular diameter is 2.8mm)
Observation : Transition from loose to tight fit starts with the 0.3 mm clearance. Therefore from that point onwards (i.e. 0.2, 0.1, etc), it would be impossible to create moving parts.
Possible cause :
- None
Wall thickness test¶
Aim of test : To discover the thinnest wall the printer could produce.
Observation :
The initial three layers (0.1–0.3 mm) were omitted.
Possible cause :
This parameter can be adjusted in the slicer. However, since this test only aims to determine the minimum printable wall thickness, further investigations were not done.
Angle test¶
Aim of test : To determine angles in which the prints are clean without the spaghetti.
Observation :
From 40° up to a fully vertical orientation, the print quality becomes noticeably cleaner.
Possible cause :
At lower angles, each new layer extends further outward and has less material underneath to support it. From 40° upward, more of each layer is supported by the previous one, reducing sagging.
Design and 3D print of a non-substractive object¶
A functional enclosure that houses battery, controller, and electronic components would be needed for the final project (see final project tab) - and so a test is done to explore the design of integrated features such as a conical hinge, embossed text and snap-fit lid into a single printed part.
The results are based on the 0.2mm Standard @BBL A1M, with the following parameter adjustments applied to reduce printing time:
- Layer height : 0.28 mm
- Sparse infill density : 5%
The trapped geometry conical hinge can only be manufactured with additive process. It would require multiple separate parts, manual assembly and enough physical access for the subtractive process such as CNC milling. Nevertheless, this method introduces its own challenge especially on determining the correct orientation for the 3D print even without caring much the anistropic aspect of the end result. The rotation angle of the lid will always be below 40° considering the shape of the hinge and therefore, support structures are required.
The embossed text perhaps could technically be produced by either process. However, printing text with a different color and making it directly embedded on the object of interest within a single production step is only possible by additive manufacturing. Although the print failed during fabrication, the process provided valuable insights and are summarized below :
- Longer print duration : multi-print coloring requires unloading and reloading of filament. These transitions interrupt continuous extrusion and add processing time at every swap. Extra 30 minutes are required in comparison to the single-print option.
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Increased material waste : besides the longer duration due the color transition, it is also observed that the height of a wipe tower - auxiliary structure printed beside the object of interest in which printer extrudes leftover filament from nozzle during color change - therefore, the higher the placement of the text on the object, the taller the wipe tower will be.
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Text integration workflow : text in CAD models is exported as mesh geometry in common 3D file formats (e.g., STL, 3MF) for use in slicers. In contrast, adding text directly in the slicer preserves its vector-like form, making it easier for the software to detect and assign different filament colors.
Bambu Studio filament assignment
In Bambu Studio, the assignment of filament colors can be a bit confusing. The number of filaments to be used is set before clicking the “Print Plate” button, but the selection of the specific filament for each color is done after this step.
3D scan of an object¶
Basics of 3D scanning
3D scanning method :
- Laser scanning/Light detection and ranging (LIDAR) : captures object geometry by projecting a laser beam onto a surface and measuring its reflection distance and position.
- Photogrammetry : captures object geometry by taking multiple photographs from different angles and are then used to reconstruct (i.e. stitch) a 3D model based on the images. Works with most smartphones.
These scans would result in point clouds in 3D space that represents the surface of a scanned object. Each point has data on it's position in space and sometimes additional data like color.
A mesh is a 3D surface made of many small connected polygons (usually triangles) that together form the outer shape of an object. A software will try to connect neighboring points to become vertices, edges and faces. Limitation is that smooth surfaces could become sharp edges due to this translation. A good mesh is airtight (i.e. no holes, fully closed surface)
Tips :
- Free of black (i.e. will absorb light) or reflective surfaces.
- Done in a controlled environment. Avoid direct sunlight as lighting may change. Plain and non-reflective background to avoid scanner confusing object's shape with surroundings.
Only the iPhone Pro series has an embedded LiDAR sensor and so for this test only photogrammetry based 3D scanning must rely could be done. The software Polycam was used and a video compilation of the sequence of captured images and the result could be seen below:
The resulting 3D scan is quite accurate and visually detailed such as cloth wrinkles, especially considering that it was conducted outdoors with uncontrolled lighting conditions. Since the goal is 3D printing the object rather than achieving perfect scan quality, the current result is deemed sufficient, and no further post-processing is done except the need to flatten the bottom part of the object (else the 3D print will not be mechanically stable). At the time of writing, the free version of Polycam only allows export in GLB format - fortunately, Onshape accepts this file format and simple extrusion is sufficient to achieve the desired outcome.
The 0.08 mm High Quality @BBL A1M setting with 5% infill density was used for this 3D print. This allows a qualitative comparison (additionally with more complex features like cloth wrinkles) with the previously printed enclosure using the standard setting.
The result shows that smoother surfaces are achieved with the finer 0.08 mm setting with individual layers being much less visible compared to the standard setting. Only minor deformations, mainly due to overhangs, were observed—particularly around the chin—but overall the print quality is deemed satisfactory.
