ME 514
Team #4
April 5, 2024
Apple Airpod Pro ULTRA Comfort Project Update
Scanning
First, a wax ear plug was pressed into a group member’s right ear, creating a mold of their inner ear geometry. A 3D scan of the mold was performed at the MakerSpace, using the Creaform Handyscan 700. The scanner had difficulty detecting the intricate details of the mold because the wax is partially translucent. This reduced the overall quality of the scan, and the resulting 3D model had several surface defects. These imperfections made the model unsuitable for 3D printing. To solve this problem, a different wax/mold material was needed that is more compatible with the scanner. The material that was chosen was a tan, opaque silicone putty that is commonly used for earplugs. The exact product that was purchased can be found here: (Amazon.com). The material was once again formed into the shape of a group member’s inner ear, and the same scanning procedure was performed. The scanner successfully detected all of the object’s surfaces, resulting in a high quality scan. The scan was able to be exported to a solid 3D model with no surface defects, which means it is suitable for 3D printing.
Modeling
With a 3D model of the ear geometry prepared, the next step involved integrating it with the geometry of an Apple AirPod Pro. The 3D model of an Apple AirPod Pro was sourced from Sketchfab (Sketchfab.com) and imported into Blender alongside the ear geometry as .STL files. Utilizing Blender, the orientation of the AirPod Pro model within the ear scan model was adjusted to mimic its natural positioning in a user’s ear, as illustrated in Figure 3. The X-ray view in Figure 4 further depicts how the two geometries are overlaid. Next, a boolean operation was performed, where the Airpod model was subtracted from the ear scan model. This action yielded a hollow space within the ear scan geometry, as shown in Figure 5. Finally, the resultant geometry was exported as an .STL file suitable for 3D printing processes.
3D Printing
The ULTRA comfort custom-made AirPods were made using Stratasys F370 printer and an FDM additive manufacturing process. The choice of this printing technology was informed by its ability to produce parts quickly and cost-effectively. Additionally, the printer’s capability to work with flexible materials was essential for enhancing the comfort and fit of the AirPod sleeve. Therefore, Thermoplastic Polyurethane (TPU) was selected as the printing material. Prior to printing, the slicer software (Preform) automatically rectified the model by addressing minor surface glitches and ensuring its watertightness, subsequently converting it to a “.print” file. The outer (lateral) side of the mold, as depicted in Figure 2, was selected as the base of the print that would be nearest to the build plate. Printing duration totaled 0.77 hours (46.2 minutes), while post-processing required 8-12 hours. Removal of support structures, situated on the lateral side of the model as depicted in Figure 2, was accomplished by immersing the part in a Stratasys bath until complete dissolution of the support material was achieved.
Figure 1: Inner Side of Printed Mold
Figure 2: Outer Side of Printed Mold
Figure 3: Assembly of Mold and Airpod Model
Figure 4: Assembly of Mold and Airpod Model (X-Ray View)
Figure 5: 3D Scanned Model With Cutouts
Figure 6: Printed Mold in Ear
Results and Future Improvements
First, the fit and comfort of the printed part were assessed. The component snugly fits into the team member’s ear; however, several aspects of its design necessitate improvement. The surface of the printed component, as depicted in Figures 1, 2, and 6, showed visible layer lines and was slightly rough, resulting in discomfort. Smoothing these surfaces, particularly those in contact with the ear, may be necessary to improve comfort. Alternatively, adopting a different printing method, such as Stereolithography (SLA), could mitigate surface roughness issues. While SLA typically entails longer printing and post-processing times, it yields highly detailed parts with superior surface finishes. The MakerSpace offers several Formlabs (SLA) printers that could be viable options, as they are capable of printing in flexible resins. Two potential flexible resins include Formlabs Flexible 80A, and Formlabs Elastic.
Next, the fit of the Airpod within the part was evaluated. Unfortunately, the AirPod did not fit inside the printed component, with two main factors potentially contributing to this issue. Firstly, the online-sourced AirPod Pro model might not have been entirely dimensionally accurate. Alternatively, some degree of shrinkage may have occurred during printing. For future iterations, it is imperative to verify model dimensions and obtain information about standard shrinkage rates for the additive manufacturing method of choice.