Making a Claw Machine

I wanted to build something special to take to the 2015 Nashville Mini Maker Faire, so I decide to build a claw machine. I wanted to build it entirely from parts that I had on hand. Other than buying a small piece of plywood and a longer piece of timing belt, I was able to keep that goal.


Part 1 - The Cabinet and Gantry

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As usual I drew the cabinet in SketchUp. This may seem like a waste of time to some people, but it is well worth for me to take the extra time to draw the cabinet in SketchUp first. This helps eliminate mistakes that can be made before the first piece of wood is cut. I also like the cut list add on that shows how many pieces to cut and the dimensions. In the long run, this not only saves time but it can also save money by eliminating wasted boards because they were cut to the wrong dimensions. Sketchup drawings for this project are available for download to Maker level patreons.

I used 3/4 inch plywood to build the cabinet. All of the pieces were cut on my table saw. I knew that cutting the large openings for the windows would be a task so I decided to cut them out using a jig saw. Then I went back with a router and cleaned up the cuts using a trim bit and a straight edge. This was a lot easier than trying to get an exact cut with the jig saw. It also cleans up and rounds out the corners of the windows.

Instead of using linear bearings for the gantry, I used a technique that I learned when building my first CNC machine. I used 3/4 inch angled aluminum and roller skate bearings. This is a really good way to make a cheap linear bearing. The main thing to consider is to keep the rails parallel. This can be achieved by cutting slots in the work piece with a table saw and placing the rails in the slots.

I used NEMA 23 stepper motors and XL timing belt to move all the pieces. All of the motor mounts, pulleys and gears were 3D printed. I'll post the pieces to Thingiverse at this location.


Part 2 - The Claw, Wire and Electronics.



For the claw I used the same 3D printed parts that I used in the Pac-Man clock video. The only modification that I had to make was to add a place to tie the string used to lower and raise the claw. You can find the 3D files at the Thingiverse link above. The actual claw pieces can from a broken claw game toy that someone gave me a few years ago. This saved time from having to design the claws and print them.

The electronics that control the game consist of a Teensy 3.1. Using a Teensy 3.1 may seem like overkill, but I used it because I had a couple on hand. A Teensy 3.1 also has enough pins to handle all of the input and drive 3 stepper motor drivers. There are a total of 7 switches on the machine. Three on the front and four limit switches on the gantry. I also needed three pins to control the LED strip and one for the servo on the claw. I used three Pololu 4988 series stepper motor drivers because I had a bunch of them left over from a previous project. I like these drivers because they a very small and can handle a lot of current. They are also more reliable than other drivers that I have used in the past.