Cams in Motion

What is a Cam?

A cam is a way of converting rotary motion into reciprocating (back and forth) motion. You can download the parts to make your own cam here. By changing the shape of the cam a variety of different types of motion can be created. Cans are often used in automata to help bring moving characters to life.

Where are Cam Mechanisms used?

Cams can be found in a wide variety of machines and devices, including:

Engines - Camshafts - are essential for controlling the opening and closing of engine valves
Appliances - Sewing machines, dishwashers, washing machines, etc.
Manufacturing & Automation - Automatic machine tools and textile machinery often rely on cams to control feeding mechanisms and other repetitive movements

Common Types of Cams Used in Automata

Snail Cam

This type of cam is known as a snail cam, because it is shaped like a snail shell. As the cam turns, the push rod raises at a steady rate. At the top of the rise the cam follower suddenly drops down and the process starts again.

The graph below shows how the rotation of the cam changes the position of the can follower.

The shape of the cam is known as the cam profile. Change the cam profile and change the story!

Double Snail Cam

By making the cam profile into a double snail profile the cam follower moves twice as fast.

Check out how the output movement changes in the graph below.

Dwell Cam

By carefully shaping the cam profile it is even possible to make make the cam follower pause. In this cam the follower pause for a quarter of a turn at the top and at the bottom. This is known as dwell.

You can see the dwell in the graph below.

Cam Shapes are Infinite

Cams come in all shapes and sizes, it depends on what linear motion you are trying to accomplish. Using a Motion Graph like the ones pictured above can help you create your custom cam!

Graph Your Story

Use Google Sheets to create a visual representation of the cams you would like to create to tell your automata story. Follow the steps below to get started.

*You will need at least 2 cams in your automata

1.) Input Data

Create a new Google Sheet
Set your cells up as shown

The cam rotates 360° in the automata project. You will type in the height you want your cam to be at each 30° increment. The larger you make your radius, the higher the follower/prop will rise.

Minimum Cam Radius - 0.5"

Maximum Cam Radius - 1.25"

Input the desired radius for each cam angle

2.) Create a Linear Graph

Select all data
Insert -> Chart
In the customize tab, select series and change the point size to 7px

3.) Create a Radar Chart

Select data
Insert -> Chart
Insert the second chart & change the chart type to Radar

The radar chart shows the shape of your custom cam. You can now use these measurements in Inventor to create a custom cam for your automata project!

4.) Create a Second Cam Motion Graph/Chart

On the same Google Sheets Document, move down the page and redo steps 1-3 above to create data, a linear and a radar chart.

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