Phone Armband 「GK-1123」

We combined 3D printing and polyester to make this Phone Armband. Our goal is to make it comfortable and customizable while also keeping the manufacturing simple. This Instructable is an entrant for the Back To School Student Design Challenge from the Rochester Institute of Technology.

Hardware:

• A 3D Printer that can print PLA, TPU, and PETG (Artillery Sidewinder SWX2 used for this project)
• PETG and/or PLA Filament
• TPU Filament (Shore Hardness 85A)
• Polyester fabric sheet
• Fabric scissors
• Blue tape
• Tape measure

Software:

• Autodesk Fusion 360
• Ultimaker Cura

Use a tape measure to measure the circumference of your upper arm. If you will be wearing an armband with your clothes on, measure the circumference of your upper arm with your clothes on.

Download our three f3d files and open them in Fusion.

For each files, click "Change Parameters" in "Modify" Section. Then, you can enter your phone dimensions on the top three parameters. Click "OK" after you enter the dimensions of you phone, and the CAD will change automatically based on your phone dimensions. 

After you enter your phone dimensions, click "File" on the top of the window, then click "Export". In the export window, change file type to "STL Files (* .stl)". Then, click blue "Export" button. Repeat this step for the remaining two files.

We need to know the length of the bottom edge of the bottom box. Use the "Measure" command in Fusion 360 (the shortcut is I) to get the number of the length of the bottom edge.

According to the data you get, draw the red outline on the elastic fabric.

Use a good scissors to cut out the fabric according to the red outline.

Fold the fabric as shown above. (Fold the two ends to the center)

Place the folded fabric in the center of the printing bed and secure it with blue tape.

Import your Bottom Case STL file into Cura. For better adhesion of TPU to polyester, you need to make some adjustments to the temperature. Please see the picture above for specific parameters.

Use TPU filament to print the Bottom Box directly onto the fabric. Using a auto-leveling sensor like the BLTouch or the one on the Artillery Sidewinder SWX2 make this easier. Heating the bed helps smoothen the fabric, so increase the bed temperature if the fabric is not smooth.

The lid part uses two filaments on the same part - TPU is used for the flexible and stretch pattern portions, while a hard filament (preferably PETG because of its higher strength and similar printing temperatures to TPU) is used to make the connection parts on either end rigid. To achieve that, we need change some settings in Cura. Firstly, use default TPU setting. Then, click "Extensions" on the top of the window. In that section, click "Posting Processing", and then click "Modify G-Code".

In the "Modify G-Code" window, click "Add a script" and select “ChangeAtZ". For the specific data, please see the second and the third picture. Then, click "Add a script" again, and select "Pause at height". For the specific data, please see the fourth picture.

Use TPU firstly to print the Lid. When the printer stops on its own, replace the material with PETG and continue printing.

The Top Box part should be printed vertically with a hard filament. PETG can be used but we found that using PLA on the default Cura settings resulted in more successful parts.

Using the rail, insert the Upper Box into the Bottom Box. (If it is difficult to insert, you can put some oil onto the rails for lubrication.)

Join the female connector of the top section of the Bottom Box to the male connector of the Lid.

Congrats!! You're finished!