3D Printed Cuff

Learning Outcomes

• • Exposure to TinkerCad, a free 3D modeling tool for beginners

  • A sample design process that includes measuring

  • Concepts of 3D printing like design, resolution, and general expectations

In using TinkerCad, you will come to appreciate its strength and its weaknesses. By designing something that requires measuring, you will be familiar with steps you may take to solve other problems. As you see prints fabricated, you will learn more about the opportunities and limitations of 3D printing.

Determining Size

This is a two step process. First we'll use the measuring tape. If the units are not in millimeters, we will also use a calculator to convert inches to millimeters. We will then use a formula to take our circumference and determine diameter, which will give us a minimum size to work up from.

• • Measure your wrist, and write down the size and unit of measurement: __________. (You can skip the next step IF you have measuring tape with millimeters or centimeters.)

  • If it is in inches, this is the formula for converting inches to millimeters: inches x 25.4 = millimeters. You can also use Google's Unit Converter.

  • You now have the circumference of your wrist in mm. Because shapes in TinkerCad are measured across, like length, width, or diameter, we will convert your wrist circumference into wrist diameter for the minimum size of the cuff. Simply divide the circumference by π, or 3.14.

For example, if my wrist is 6 inches, I would multiply 6 inches x 25.4 = 152.4mm. And because I want to convert the circumference to diameter, I would divide 152.4 by 3.14 = 48.5mm. When I create my cuff in TinkerCad, the inside should be somewhat larger than 48.5mm -- closer to 55mm to be more comfortable.

3D Printing Limits and Consideration

Out of consideration to your peers and minimizing print time:

Your shape will be up to 5 or 6 mm in depth.

A note about designing efficiently for the 3D printer: a design that is "laying down" tends to print faster than a design that is "standing up" -- laying down has fewer layers, and standing up has more.

Using TinkerCad

Use the white cubes to resize objects.

Use the cone to raise and lower objects along the Z-axis.

Use the curved handles to rotate or flip objects.

Design Steps

There are many ways you can approach designing a cuff. Today we are going to:

• • select a shape

  • create the negative first (this is the diameter, plus 5-10mm)

  • then add the positive (the positive is what will be printed)

  • limit the depth of our cuff to 5-6mm

Create Space for your Wrist and Select your Shape

You will use one shape to represent your wrist, and one shape for the cuff. The shape for your wrist can be a cylinder or the same as the cuff. We encourage you to use a cylinder because it tends to print better. See example below for clarification.

• • Bring out the cylinder, or the shape you want cut out. Make sure it is the size of your wrist's diameter, plus 5-10mm.

  • Bring the cylinder or shape height up to 20mm so it stands tall.

  • Bring out the shape you want your cuff to be. Drag it out so it is larger than your wrist's diameter, and squish it so it is no more than 5-6 mm deep.

Check Alignment, if applicable

Select All, go to Adjust > Align. Click on a gray dot to align to Top/Middle/Bottom, or Left/Center/Right.

Select All and Group.

Bracelet to Cuff

Add a Box Hole to turn your bracelet into a cuff. The Box Hole should be between 25mm-40mm -- this depends on your wrist size. Use a lower number for smaller wrists, or a higher number for larger wrists. You can also try prototyping with cardboard or card stock to get a better feel for the dimensions. See below for clarification.

Name and Download

Click on Design. Select Properties to rename your file. When finished renaming, select Download for 3D printing. Select STL. Save your file. We'll collect files for processing in MakerWare and for printing.

Survey

Surveys are here: https://sites.google.com/site/cplmakerlab/surveys