Hi all,
what I'm trying to do is the same cam you can see in this youtube video.
I have the motion law I want to assign to the rotation of the tower in function of the rotation of the cam.
In Mechanism environment, I've made the trace curves of some points of the roller that I've used to cut the cam with surfaces or variable section sweep.
For now, I've tried only one roller cut (three in total).
The cut was decent but there were points where I have interpenetration between cam and roller; especially at the start and the end of the cut.
So I've thinked that I had to rotate the plane of the roller where I've put the points for the trace curves. The situation was better but the motion law I've assigned to the roller was random: a sinusoidal law, as the main one, that at the half reverses the direction (otherwise the cut plane too on itself).
But, which is the right motion law to assign to the cut plane of the roller?
How would you have done?
Would you know tell me where can I find more detailed informations about this kind of 3D modeling?
I searched on the web, but I've not found nothing if not videos like what I've attached where, however, you can't see HOW to do it.
Thanks.
Bye
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Giulio, the process of making graphs with an arithmatic equation is not too difficult but certainly not direct. You can project an equation curve into a sketch. You can save the sketch as a .sec file. You can then insert (get data) the section file into the graph.
Here is a comparison; top is the graph driven sweep, and the bottom is a cosine equation datum curve.
Attached is the source section file.
Another way to get a points file is to pattern points along an equation datum curve. When you export this, you can easily extract the point locations to manipulate in excel or elsewhere and bring it back into the mechanism table driven servo. Be careful with this, however, since the time steps for patterning is not always as accurate as you would want. this is why I prefer writing the equation in the servo definition itself.
As for splines... yikes! Yes, they need help in the user interface. One issue is locating that intermediate point. You cannot move it once it is placed. This means that the ratio along the spline is fixed. And it affects every other action form then on. If you are "certain" the midpoint is exactly 50% along the curve at creation, it will stay there and you can work with it. But if it is arbitrary, all hope is lost. However, you can control radius of curvature and tangent angle directly from the spline... or you can use the controlled polygon mode. Either way, you want to know exactly where any of the points between the ends are located with respect to ratio along the curve. There is one way to manage the points along the curve using a local coordinate system. But even that has implications. It is not as simple as saying, for instance, "1/2 way along the curve".
Hi,
I've made it with an internal software we have at work.
The type of the law is a sinusoid, like the type you can find in proE
In other way, I write the law in MathCad, and I export it as points' curve into a text file.
Here is a very straight forward sinusoidal sweep with defined dwell times for a servo motor.
the math gets a little tedious as you have to keep track of "t" within the process, but it is fairly easy to edit and watch the updated graph. If the sequence suddenly changes, it will warn you and show you the results.
This one dwells for 3 seconds at 0 degrees; "-1*" inverses the cosine; "(t-3)" resets t to 0; "/4" account for 4 seconds for a 1/2 cosine sweep making t range 0 to 1; "*180" makes the sweep 1/2 cycle; *30 set amplitude (1/2 of overall since the cosine function returns -1 to 1); the "+30" manages the offset to start at the last known position... in this case, 0. Followed by another 3 seconds of dwell, holding at position at 60 degrees. In angle terms... you could divide the time segment into 360 steps and you time would equal 1 degree per value of "t".
Be sure the domains remain continuous.
...and as an aside, you can change the curve somewhat using power functions on the Cos statement.
Here you have a hard start and a soft stop by brining the statement up to the power of 4. You can play with both sin offsets and cosine to tweak the profile you prefer. I don't know why you'd do that, but it can be done.
I didn't know graphs did this during playback 
(the red tracking line in from the measure graph)
No matter how often I do it, I can never get use to capturing graph data into a file that can be imported as a curve.
However, each time I do it, I seem to learn something new.
I defined a motor profile using a cosine function.
The preview graph only used 0.2 second intervals. I couldn't find a way to change that.
However, when I define the analysis, I could set the step size. In my test case it was set to 0.1 seconds.
I can then use the mechanism Measure to get the axis rotation based on the analysis and it returns ever step of the analysis.
I can save that measure graph to a text file.
I edit the text file to replace the header (1st 4 lines)
Open Arclength
Begin section
Begin curve
...and rename the .txt to .ibl
Next, you can read the .ibl file to a "Curve from File" ...which for some extra-ordinarily silly reason, is not in the ribbon. When you use the command search just type curve and it shows up.
Select a coordinate system and then select you .ibl file.
The thing I learned today is that the .ibl file does not need a Z value! This is huge as you do not need to do this in Excel.
Now you can make the section by projecting the curve into the section...
Then you can save the section...
Then you can import the section into the graph... and add the coordinate system it wants... and lock the remaining applicable dimensions. Be careful not to let the imported section get distorted.
See, simple !!! 
...and importing iges files into datum graphs works too. This eliminates the interim section generation.
Have a look at these videos... it is a pretty simple thing to wrap your head around...
And this thread...
Hope that helps...
...need to find the video to show that SolidWorks does this already 
Funny how advanced Pro/E is......yet for this you still have to use almost the exact same technique I had to use in the early '90's as a boolean operation in AutoCAD to do a barrel cam.....
A little more information. 1st of all, you can get all kinds of point files including cylindrical and spherical output. However, I question the accuracy level. I have the accuracy set to default (relative .0012) and this is the return of the trace curve set to spherical. I get 100 points and the trace point is exactly 1" away from the CSYS. That means that R should always be 1.00000000000. Judge for yourself if this level of accuracy matters to you. Changing the accuracy to absolute at .00005 did -not- change these values! I don't know if this error level is the result of the trace curve or the precision used for the analysis. I suspect the ladder. 100 points for a 360 degree element seems a little sparse to me.
That's why I didn't say anything till now 
I'm very impressed with all the modelling in this thread, wouldn't want to have missed it!
