How to make 3D printed sandals

This Instructable will show you how to design and print something simple and useful: your own sandals (also known as flip flop)!

The size of sandal you can print is a function of your printer and your willingness to spend time on CAD and assembly. If you are limited to a 4 inch by 4 inch print bed, such as on a Makerbot Cupcake, then you can print sandals for a 5 year old if you do it in two parts. If you have a Makerbot Replicator or a Printrbot+, on the other hand, you can print full sized adult sandals in two parts.

What you'll need:

Paper
Pencil
Ruler
Scissors
A CAD program such as Google Sketch-up & basic knowledge on how to use it
A 3D printer that uses ABS plastic or similar robust material and knowledge about how to print
9/16" nylon webbing or similar (3 feet should be enough to give you one free mistake)
Small file or sandpaper
Acetone or similar ABS solvent + eye dropper or q-tip
Hot glue
2 small nails
wire cutter or hack saw for cutting nails (optional)

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Step 1: Size the sandal and design the base

Before you start, you need to figure out what size sandal you are going to make. If you are determined, you can print an adult sized sandal on a small bed printer by putting together 6-8 separate pieces, but to avoid over-complicating things, I suggest limiting yourself to whatever you can print in two pieces, and that is what this Instructable will describe. For example, if you only have a 4"x4" print bed, then you should limit yourself to something you can make that is approximately 4"x8" or smaller. That's what I started with, but it was enough to create shoes for my daughter who is nearly 5 .

Once you've made sure you can actually print a sandal of a reasonable size, the first step is to have the person who will ultimately end up wearing the sandals stand on a piece of paper, so you or a helper can trace their feet (see image 1). Make sure that you also trace between the big toe and 2nd toe, since that is where the strap will go (image 2).

After you've traced both feet, get out your ruler and draw rectangle a little bit (say 1 cm) outside your foot outline. You want the sandal to have a little space around the foot. Now convert the rectangle into a polygon by cutting off corners with the ruler until you have a shape that looks more sandal-like. Six sides should be enough for something that looks reasonably good (image 3).

When you have something that you are happy with, double check that the same measurements work on the other foot. If you find that one foot is smaller than the other, use the dimensions for the larger foot. When you are done, you should have a simple shape that will serve as the outline for both the left and right sandals and the measurements you need to create in your CAD program.