Introduction: Clamp for Car Seat Phone Mount

This instructable is about a clamp I made for a phone mount I have in my car.


3d printer using white PLA filament (can be any color you like)

Tinkercad website for CAD editing

Thingiverse 'Super Clamp with customizer' model:

Step 1: Problem

I found this great mount for my phone years ago that fastens to the seat rail mount. The arm is very stiff and helps to hold the phone properly in place without having to permanently stick something on the dashboard or bolt something to the air conditioning vent (it gets hot in Texas!).

The only problem is that the arm shakes or wiggles as you drive. In the past I've used an oversized spring clamp to fix it to the nearby console so that it wouldn't shake, but this was a very unelegant solution. And I didn't want to dedicate the clamp for that purpose! (In the pic I'm holding the arm to the console, showing where I need a clamp).

Now that I have a 3d-printer, I wanted to 3d print a solution so I added this to the list of things to 3d print someday.

Fast forward 1 year -- I'm printing some clamps with the 3d-printer for something else and remember this project I've been meaning to do.

Let's get to it! I'll go here through the larger steps of the process I use to build something useful in the real world using my 3d printer.

Step 2: Measure and Simulate

As I often do with any designs that need to interface with something in the real world, the first thing I did was to measure the diameter of the phone mount arm and the width of the console using a digital caliper.

Initially, I measured 23mm for both, but then I went back again after my first 'draft' and adjusted the measurements to 22mm for the console and 21.6mm diameter for the arm. "Measure twice, cut once" as they say.

A trick: I took a strip of scrap paper, wrapped it around the arm and marked it to get the circumference. Unwrap the paper, measure it with the caliper and divide by PI (3.14159...).

Then I went to Tinkercad, a free online simple CAD tool that is surprisingly powerful, and simulated the console as a gray cuboid (3d rectangle) with a width of 22mm. Then I added a black cylinder with a diameter of 21.6mm to represent the arm of the mount.

Step 3: Thingiverse Model

I then went to Thingiverse and found an appropriate model. The Super Clamp with Customizer seemed to fit my need and appeared to be used by many for any sort of need for a clamp:

I then downloaded and imported into Tinkercad.

Step 4: Edit the Clamp

After the model was in Tinkercad, I modified the clamp to fit both the console and the arm.

For basic stuff like this, I tend to use Tinkercad, it's simple to use, available anywhere with a simple browser, and does everything I need for 3d model editing.

To modify the clamp, I first made 2 copies of the clamp. Then I used a 'hole box' (negative space cuboid) to 'cut' one clamp on one side, and another hole box to cut the other clamp on the other side. Then I aligned them together and grouped them. This basically made a larger clamp. I stretched out part of one clamp on one side. Finally, I added another hole box and a 'hole cylinder' to serve as a cutout for the arm and voila, a new clamp!

The screw included with the model was also too long for what I wanted so I did the same thing there: made 2 copies of the screw, cut one at one end, cut the other at the other end, then grouped them back to make a shorter screw!

The last step with Tinkercad was to select the clamp model (pink) and export it to an STL file. Same with the shortened screw.

NOTE: The clamp model does have an OpenSCAD file in case you want to use that to modify it. I figured that the OpenSCAD wouldn't support the cutout needed for the arm without a lot of digging into the code, but you might be more comfortable doing that instead of using a CAD editor.

Step 5: Slice It!

Then I brought the STL into my Cura slicer (a slicer is a program to 'slice' the 3d model into code that tells the 3d printer how to print the object, layer by layer). I used the same profile settings I had done before to print similar clamps.

Since this is a functional print, to improve strength I made sure to have:

  • 3 walls
  • 35% infill
  • Cubic infill pattern

I used PLA here but you could use any material you like. If I start to have problems with the clamp in the car during the summertime, I'll probably have to go back and reprint it in ABS instead, which has a higher melting/softening temperature than PLA.

Step 6: Test Template

Something I often do when something needs to fit with something in the real world, is that I only let the printer complete the first few layers of the object before stopping it. That's what I did here, after maybe like 3 layers I paused and aborted the print.

This partial print served as a template that I could compare against the real arm and console to see how good the fit was. This saves both time and material. (Measure twice...)

In this case, after a quick check of the template, it looked like I needed to move the 'hole cylinder' (the round cutout) in the model a few mm, indicated by the black marks I made on the template.

Then I went back to Tinkercad, made the necessary adjustments, generated the STL again via export from Tinkercad, generated GCODE again from the Cura slicer, and started printing again!

Step 7: Final Print

This time I had to let the print finish. It took about 6 hours for the main clamp, and another hour for the bolt/screw and little cap.

This print may still not be the final version but it represents the first real 'dress rehearsal' of the part. It all depends on the final test fit!

Step 8: Test Fit

Success! It fit perfectly!

The only minor issue was that both the cap on the bolt and the console in the car are so smooth that the clamp would slip off, due to arm pulling forward. I added a small bit of double-stick tape on the cap (second picture) to help hold it in place, and that's it!