L8 - MEEG439 Lecture Cams Introduction A cam is an...

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Unformatted text preview: MEEG439 Lecture Cams Introduction A cam is an irregular shaped machine member which serves as a driving link and which imparts motion to a driven link called the follower Examples: Translating roller follower cam cam Translating flat-faced follower cam cam Rotating roller follower Rotating flat-faced follower Terminology Stroke: distance or angle of maximum follower travel Rise: the interval during which the follower is moving away from the center of the cam Dwell: an interval during which the follower is stationary Fall: the interval during which the follower moves toward the center of the cam Intervals are measured in terms of the cam rotation angle rather than actual time in seconds so as to maintain the same cam- follower relationships regardless of cam speed rise Fall SVAJ Diagrams These are used to define the motion of the follower as functions of cam rotational angle s v a j h rise High dwell fall Low dwell Bad design Four segments Let = total angle of a segment in radians Boundary conditions During rise s=0, v=0, a=0 s=h, v=0, a=0 During fall s=h, v=0, a=0 s=0, v=0, a=0 Polynomial Functions n n x C x C x C x C x C C s + + + + + + = 4 4 3 3 2 2 1 Represent the follower displacement by Where s =follower displacement and = x To design the cam, we need to solve for the coefficients C j (for j =0, 1, , n ) based on the boundary conditions The degree of the polynomial will be n = k-1 , where k is the number of chosen boundary conditions Example 1 s h rise High dwell fall Low dwell Consider the cam design specifications: =1 rad/s Low dwell: zero displacement for 90 ; Rise: rise h in 90 ; High dwell: zero displacement for 90...
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This note was uploaded on 02/06/2012 for the course MEEG 439 taught by Professor Scf during the Spring '11 term at The Petroleum Institute.

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L8 - MEEG439 Lecture Cams Introduction A cam is an...

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