5. 3D Printing and Scanning - Kathryn and Wilson¶
This week’s group assignment is to test the design rules for our 3D printer, which was the Bambu A1 mini. Our group focused on a torture test and infill tests for our FFF 3D printers.
Work Distribution¶
| Member | Role |
|---|---|
| Kathryn and Wilson | Documentation |
| Kathryn | Terms |
| Kathryn | Torture Test |
| Wilson | Infill Testing |
Terms - Kathryn¶
Design Considerations:
| Term | Definition |
|---|---|
| Dimensions | Measurements of a print in the X, Y, and Z axes |
| Clearance | The space between parts to ensure proper fit |
| Wall Thickness | The thickness of the outer walls of a print |
| Anisotropy | A material property where strength differs in X, Y, and Z directions |
Printer Components:
| Term | Definition |
|---|---|
| Extruder | The assembly that feeds and melts filament before deposition |
| Hotend | The heated part of the extruder that melts the filament |
| Nozzle | The tip of the extruder that deposits melted filament |
| Build Plate | The surface where printing occurs |
| Cooling Fan | Blows air onto the filament to solidify layers quickly |
| Filament | The material used in FDM printing (e.g., PLA, ABS, PETG). |
| Resin | A liquid photopolymer |
Print Layers & Structure:
| Term | Definition |
|---|---|
| Layer Height | The thickness of each layer in a print; smaller heights yield finer resolution |
| Perimeters (Shells) | The outermost layers of a print |
| Infill | Internal structure of a 3D print; affects strength, weight, and print time |
| Bridging | Printing filament in mid-air between two points without supports |
| Overhang | Any shape that extends outward, above the previous layer, and doesn’t have direct support |
Support & Adhesion:
| Term | Definition |
|---|---|
| Supports | Temporary structures that stabilize overhangs and bridges, removed post-printing |
| Tree Supports | A branching support structure that reduces material usage and is easier to remove |
| Bed Adhesion | Methods to keep the first layer attached to the build plate |
| Raft | A thick, sacrificial base layer that improves adhesion and levels the print |
| Brim | A thin perimeter around the base of the print to enhance adhesion |
| Skirt | An outline printed around the object to prime the extruder before printing |
Print Speed & Motion Control:
| Term | Definition |
|---|---|
| Print Speed | The speed at which the nozzle moves while printing |
| Travel Speed | The speed of non-printing movements |
| Acceleration | The rate at which printhead speed increases |
| Retraction | A setting that pulls filament back during non-printing movements to prevent stringing |
Common Print Issues:
| Term | Definition |
|---|---|
| Over-extrusion | Too much filament is extruded, causing blobs and rough surfaces |
| Under-extrusion | Too little filament is extruded, leading to weak and incomplete layers |
| Stringing | Thin strands of filament between parts due to improper retraction settings |
| Ghosting/Ringing | Vibrations causing repeated echoes of a feature |
| Warping | The curling of a print’s edges due to uneven cooling |
All-in-One Torture Test - Kathryn¶
For my work, I referred to Angelina, Collin, and Kabir’s group work as well as Richard and David.
I downloaded the .stl file for the all-in-one torture test here. I was originally thinking of using a Prusa printer, so I opened the .stl file in PrusaSlicer.
I sized it down 80% before slicing it, but I got an error about overhang, which was to be expected.
Using the Prusa, I would constantly get issues with my print, such as the terrible adhesion that lead to clumping because the nozzle would drag the filament that was already laid down.
So, I switched to a Bambu printer. Because they are faster, I was less limited by time and chose to retain the original size of the design. My print got through 60% until it ran out of filament. I thought I had enough, but the machine gives an alert when there is around a meter left, and does not print the rest.
I switched out the filament spool with another one that was the same color, but full and would definitely be able to finish my design. However, the new layer with the new filament did not add smoothly to my design, also clumping after a few passes.
I restarted the print on the Bambu again, and it went perfectly!
There were three main parts on the torture test that I noted. First was the overhang, how as the angle increases, the the surface becomes less smooth because the lines are spread farther apart. It made sense, because the printer layers the filament in horizontal layers. At around 50 degrees, I saw a notable difference in the surface quality.
Next, also on the overhang, I noticed that some of the filament underneath the sections that are very angled would sag and create a bump on the bottom surface. It was all fine until 80 degrees. This could also be attributed to the widening distance between each line and less surface of a layer connected to the one below it. Also gravity.
On the bridges, I also saw some sagging especially on the longer ones that have more distance between each of the poles that offer support. It was at around 0.86 mm that I started to see the filament dropping.
Infill Testing - Wilson¶
For the infill testing, I also referenced Angelina, Collin, and Kabir’s work. I first designed a 1x1x1 box in Fusion 360 using the box tool and exported the file as an STL.
Next, in Bambu Studio, I imported the file and used the system’s 0.16mm Optimal @BBL A1 setting as a preset. Then, I modified the Sparse infill density to 15%. I sent it my A1 Bambu Lab printer and stopped the print at around 40% completion. By stopping the print in the middle, the infill density can be clearly displayed.
I would then repeat this process for a total of 3 cubes, changing the infill from 15% to 30% to 60%.
15% on the left, 30% on top, 60% on the right.
After printing all these, I used a hammer to smash each box to test the strength. After smashing, I found that the 15% infill broke easily, the 30% infill was slightly stronger, and the 60% infill ended up surviving more than 15 strong hits. Here is what the 60% infill looks like after hitting it.
As you can see, it was barely damaged no matter how many times I hit it. Based on these results, I can conclude that for faster, semi-strong prints, between 15% and 30% is good. For prints that need to withstand more, somewhere around 40%-60% should be sufficient.
Files¶
Torture Test Infill Test for 15%