MEEN 4110 – Mechanisms Design Fall - 2010 Lecture 09 CAM

Up on completion of this chapter, the student will be able to Chapters Objectives Up on completion of this chapter, the student will be able to Understand how to design a CAM-FOLLOWER Systems.

Cam Follower

Cam A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice versa. It is often a part of a rotating wheel (eg. an eccentric wheel) or shaft (eg a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower which is a lever making contact with the cam. The reason the cam acts as a lever is because the hole is not directly in the centre, therefore moving the cam rather than just spinning. On the other hand, some cams are made with a hole exactly in the centre and their sides act as cams to move the levers touching them to move up and down or to go back and forth.

Design of Cam Systems The first stage in designing a cam system is the creation of a displacement diagram. A typical plate cam with an in-line roller follower is shown below with a displacement diagram. This figure shows the following characteristic features. The rise- This is when the follower is moving away from the cam centre. The slope reflects the follower velocity. The dwell- the is the period when the follower is stationary The return - This is when the follower moves back towards the cam centre The base circle on the cam is the smallest full diameter of the cam The prime circle is centered on the cam rotation centre with radius at the follower roller centre when the follower is on the base circle The cam profile is the shaped surface of the cam defining the follower motion

Cam Design

Types of Cams

Types of Joint Closers (cam/follower joint)

Follower Motion

Types of Followers

Obtaining the S Diagram

Unwrapping/Linearizing a Cam

Unwrapping/Linearizing a Cam

The S Diagram

Why S Diagram Cannot Have Negative Values New

SVAJ Diagram

SVAJ Diagram

SVAJ Diagram

Type of Motion Constraints

Type of Motion Program RF = rise-fall RFD = rise-fall-dwell RDFD = rise-dwell-fall-dwell

Double-Dwell Cam Design- Choosing SVAJ Functions

How Not Meet Cam Design Specifications (Linear Function)

SVAJ Diagram

SVAJ Diagram

Cycloidal Motion

Cycloidal Motion – SVAJ Diagram

a Diagram

v Diagram

s Diagram

Cycloidal Displacement Function

Polynomial Function

Polynomial Function

Polynomial Function

SVAJ Diagram

Polynomial Function

Polynomial Function

Polynomial Function

Polynomial Function

Double Dwell Cam Design

Double Dwell Cam Design

Double Dwell Cam Design

Double Dwell Cam Design

Double Dwell Cam Design

Single Dwell Cam Design

Single Dwell Cam Design

Single Dwell Cam Design

Single Dwell Cam Design

Single Dwell Cam Design

Single Dwell Cam Design

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