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sd30=dtat/6
sd29=h/2*(1-cos((180/dtat)* sd30))
sd26=2*dtat/6
sd25=h/2*(1-cos((180/dtat)* sd26))
sd23=3*dtat/6
sd22=h/2*(1-cos((180/dtat)* sd23))
sd20=4*dtat/6
sd19=h/2*(1-cos((180/dtat)* sd20))
sd17=5*dtat/6
sd16=h/2*(1-cos((180/dtat)* sd17))
sd10=dtat
sd11=h
/* Graph4(the displacement and angle of sine acceleration in rise travel)
sd30=dtat/6
sd29=h*((sd86/dtat)-(1/(2*pi))*sin(360*sd30/dtat))
sd26=2*dtat/6
sd25=h*((sd3/dtat)-(1/(2*pi))*sin(360*sd26/dtat))
sd23=3*dtat/6
sd22=h*((sd6/dtat)-(1/(2*pi))*sin(360*sd23/dtat))
sd20=4*dtat/6
sd19=h*((sd8/dtat)-(1/(2*pi))*sin(360*sd20/dtat))
sd17=5*dtat/6
sd16=h*((sd9/dtat)-(1/(2*pi))*sin(360*sd17/dtat))
sd10=dtat
sd11=h*((sd11/dtat)-(1/(2*pi))*sin(360*sd10/dtat))
In the same way, the displacement-angle relations of far stop travel, return travel and nearly stop travel, can be input.
3.3. Sketch cam theoretical curve
By use of variable section sweep tool, each part of cam can be gotten which correspond to four motion stages, shown as Figure 3. Each trajectory for the sweep was fragmented arc on Front plane, which took half of base circle radius as its radius and cam angle as its central angle. Sweep’s section is a rectangle gone through the control point of sweep’s trajectory, which took cam’s width as its width and its length was associated with displacement line graph by Trajpar’s parameter in relations, so as to control cam profile.
By setting rise-travel parameter ‘tui’ and return-travel parameter ‘hui’, the systems can auto-chose corresponding displacement line graphs according to different motion laws, so as to get proper size’s cam section, furthermore realized 16 kinds of combined motion. So, during sweep, cam profile will change with follower’s displacement line graph. Sweep was pided into four parts (360°in total); the precise cam model could be built, as shown in Figure 3(b).
The relation’s details of rectangle section were shown in follow:
if(tui==1)
sd7=rb/2+evalgraph("Graph1",trajpar* dtat)
endif
……
In the same way, input the other section relations. Then follower, fixture, and so on, were parametrically modelled in sequence. It is necessary to think carefully their assembly relations about design place, shape and size, and to establish beforehand datum point and axis.
Fig.3.(a)Assemble (b)connection Fig. 4 (a)Trajectory; (b) cam;
4. Virtual assembly of cam mechanism
New-built a assembly as follow: firstly, to insert the fixture using the default method, secondly, to insert the follow by pin connected method which the fixture’s role axis aligned follower’s and pre-created datum point aligned each other, as shown in Fig.4 (a).
5. Cam mechanism’s motion simulation
After connections’ definitions were completed, designer can add corresponding drive to them by the mechanical module. Designers choose “Application Program”-“Mechanism”, enter the mechanism module, as shown in Fig.4 (b).
To click “Drag" button, open dialog box, move follower’s height position and make its matching surface near cam’s matching surface, drag and rotate cam’s starting location which touched with follower, cam and follower’s location was adjusted.