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An Introduction to Mechanisms
- A mechanism is a device that takes an input motion or force and outputs a different motion or force.
- Gears trains, for instance, are a type of mechanism.
- This gear train takes rotary motion as input, and outputs rotary motion. The difference between the input and output is the speed and direction of the motion.
- In this project you're going to be looking at different type mechanism called a Cam Mechanism.
- Cam mechanisms turn rotary motion (round and round) into reciprocating motion (up and down)
- A cam mechanism is made up of three main parts: cam, slide and follower. In the image below, the slide (or guide) is the red ring.
- The cam rotates continually. The follower is a rod that rests on the edge of the turning cam.
- The follower moves up and down, but can't move to the side because of the slide or guide.
- This means the cam follower can only:
- We can draw what are know as
displacement graphsfor any cam mechanism.
- A displacement graph shows how the follower moves as the cam rotates.
- Follow these steps to create your own displacement graphs. This one is for a pear cam.
Badge It - Silver
- Click on the following link to complete the quiz on different types of cams and displacement graphs.
- Let's try and make one of the Cams in SolidWorks
- We'll make a pear-shaped Cam.
- If you've forgotten how to get started in SolidWorks, then ask your teacher for some help.
- First we'll need a couple of circles, as shown below
- Notice the little symbol between the circles like this.
- This means they have a tangential relationship (look up the word tangent if you don't know what that means)
- You can give sketch elements a tangential relationship by shift-clicking both elements and choosing
tangentfrom the menu on the left
- The centre of the two circles also have a
- Now draw two straight lines as shown below. Don't let them touch the circles yet.
- We can now give the lines a tangential relationship with each of the circles.
-Then use thew trim tool to cut away the lines you don't want
- Lastly you can add a small circle in the cam, where doweling would go.
- Once completed, you can extrude the sketch.
- Note that this is just practice and not your actual cam, which will need to have a different center cut-out.
Badge It - Gold
- Using SolidWorks, produce either a heart, drop, irregular or ratchet cam.
- The Cam's diameter must not exceed 60mm.
- Screenshot your finished sketches including the part where it states your sketch is fully defined.
- We can animate cams in SolidWorks as well.
- Create a new assembly and import in one of your cams.
- Now select
New Motion Studyfrom the tool bar.
- Near the bottom of the screen, the motion study will appear. In it's tool bar is the symbol for a motor - click it.
- Now you'll need to select the inner face of the cam, to choose what part the motor will turn.
- You should see it populated in the menu on the left. You can make other changes here as well, such as the speed of rotation.
- Once you're done, watch the animation using the play buttons.
Badge It - Platinum
- SolidWorks can be used to produce animations.
- Independently (or with a little help from your teacher), produce an animation of one of your cams rotating.
- Using the save icon, you can produce a video of you cam moving.