Introduction: Belt Clip for Protecting Phone & Headphone Cord

This instructable will show you the design components necessary to create a belt clip to protect your phone and headphone clip.

Necessary tools & materials:

* 3D printer (higher resolution preferred but not necessary)

* CAD software

* calipers (or ruler)

* headphones or earphones

* phone or mp3 player

Step 1: Understanding Clearancing and Tolerancing

In order to create a phone case that allows your phone (or mp3 player) to fit snuggly (without rattling), it is incredibly important to focus on the printer's resolution. This includes understanding tolerances for FDM printers that expand or contract in certain areas after drying completely.

For clearancing, setting 0.001 & 0.007 inches respectively as minimum and maximum seems to be a pretty good standard. By using 0.004 as the average when tight or loose fit is not important, it is easy to increase or decrease 0.004 for specific applications.

For FDM printers, it is important to realize that inner dimensions will be smaller than planned and outer dimensions will be larger than planned. This occurs because the FDM printers get incredibly hot to melt the filament. During the cooling of the part, these inner & outer dimensions change slightly. For printers that use UV curing (such as the Objet Model 500 Connex, which is used in the preparation of the first prototype shown in this instructable) this is not an issue. Depending on the type of printer (as well as the accuracy) you are using to create your own case, you may or may not have to tolerance for accuracy.

The picture above is of a shaft collar (please contact me if you are interested in designing and developing shaft collars since I am currently creating a custom prototype), which is an ideal example to show when clearancing is important.

Step 2: Start Designing on Your CAD Program

First & foremost you must choose the CAD program you want to use. The ones I would recommend are Autodesk's Inventor & Fusion 360. Solidworks is also an incredibly solid option. For this example I used Fusion 360.

With your CAD program open, you can follow the steps below to design your own case. There are multiple ways to create a case like this. The steps below are just one suggestion as to how you may go about creating your own.

Choose a plane to start your sketch on. Draw two rectangles, with their center's both being (0,0,0). The width and height of the inner rectangle should be the dimensions of the phone (plus case if you have one) plus the clearance (0.004 inches average). If you are using a FDM printer, it is important to take into account the amount the prototype shrinks/expands in certain directions. This may include printing samples to figure out the exact amount of shrinking/expanding for your exact printer. In this example, I have used the X-Y plane. Once you choose the desired thickness of the case (0.15 inches for my example), extrude the area between the rectangles. The depth of the extrusion is the entire depth of the phone plus clearancing amounts.

Step 3: Adding the Hole for the Headphone Cord

Start a new sketch on the bottom plane of the extrusion. Draw a rectangle the exact size of the inner rectangle used in the initial extrusion.

Use your calipers to measure the exact distance between the exterior of the phone and the center of the hole for the headphone jack.

Use your calipers to measure the diameter of the hole as well as the exterior of the headphone jack on your headphone cord. The larger measurement is the one you should use for the size of the hole you draw in the sketch. Make sure to include clearances so your headphones will easily connect to your phone/mp3 player. Use the extrusion command to add the bottom plate with headphone jack hole to the model.

Step 4: Designing Custom Shapes for Lightweighting

Steps (a) & (b) are interchangeable (AKA it does not matter which one you do first). The picture above shows the simple design used in the first prototype.

a) Start a new sketch on the front plane (X-Z plane in this example) to decide the custom design you want to remove from the front printing area (and possibly back of case) to not only save money during printing (since model material is more expensive than support material) but also to ensure the final product is lightweight yet sturdy. Use the cutting command to remove the material from the initial extrusion.

b) Start a new sketch on the side plane (Y-Z plane in this example) to decide the custom design you want to remove from the initial extrusion. Use the cutting command to remove the material from the initial extrusion.

Step 5: Incorporating the Clip

The first step is to start a new sketch on the side plane (Y-Z plane in this example). Using the spline drawing tool, it is straightforward to draw the curve for the clip since it is so simple. In the example shown here, the curve is copied and moved down and to the right of the original to create a clean looking product with a symmetrical design, but that once again is up to you as to how you want to create this component. If it is printed using a partially flexible material combination, the space between clip and case can be less than the amount shown in the first picture above.

The second step is to extrude the sketch the entire width of the case. Feel free to make this component smaller or make two or three small clips if you so please.

The third step is to fillet all the necessary edges so it easily slips over your belt. The most important fillet to include is shown in the second picture above.

The fourth step, which is necessary to ensure the clip is strong enough, is to check that the design you extruded out of the front and back does not also remove material from the area that the clip is in contact with the case. This is shown in the third picture above.

Step 6: Modifying for Ease of Use

There are three actions that you will perform by modifying your phone as you are walking around and listening to music, an opera, a lecture, an audiobook, etc. First is changing the volume by using the up and down buttons. The second is removing and reinserting the phone to change the song, lecture, book, etc. The third is the ability to easily insert and remove the headphones from the phone.

This means it is necessary to ensure there is significant space around each of the above-mentioned features.

Fillets are incredibly important to include all over your case since it will give it a smooth look and feel. Always be sure to triple check that you have filleted every possible edge. Worst case scenario is that you use sand paper to sand down any edges that were not filleted in the CAD model.

Step 7: Print!

Save your 3D model as a STL file type. If you have your own 3D printer then you already know how to print so have fun. If you do not have your own, then you can get creative (as to where to find and use a 3D printer) or go to your local TechShop or online 3D printing service (such as

Step 8: Possible Options for Post-Printing Modifications

One possible option is spray painting your print. I decided not to go down this route because I had access to the second option, which is sandblasting. The technique for both is the pretty much same. The main difference is that you need to get a strong grasp on your model while sandblasting, which is not necessary for spray painting. Be sure to take your time and be patient while giving your model an even coat. An example of sandblasting is shown in the picture above.

If you are using a FDM printer, you have a cool opportunity to try a fun method for adding strength to your model if you are feeling adventurous :)

Necessary Materials:

* FDM 3D Printer

* Drill w/ Drill Bit slightly larger than the hot glue gun tip

* Hot Glue Gun & Hot Glue (certain types are better, such as the one shown in the picture above, which is the best for this application)

First, set the fill on the 3D printer to as small as possible. After you have removed the support material from your part, grab a drill with a drill bit slightly bigger than the tip of your hot glue gun. Fill the empty cavities of the model with hot glue for strength. I personally recommend the hot glue shown in the picture above.

Step 9: Creative Uses for Your New 3D Printed Phone Case

1) Juggling

2) Working Out

3) Dancing

4) Stretching

5) Standing While Working

6) Meditation / Yoga

7) Making cool things in machine/wood shop

8) Snowboarding/Skiing (waterproof case Instructable TBA)

9) Create awesome improvements such as my new addition of a hook on the side to hold the headphone cord (look out for addition of a step to this Instructable that will be added in about a month)