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Globoidal Cam Design Wedge Rib

B

bimbo666

New member
Hi guys,


Continiung with the globoidal cam design problem, I made a report about all the issues that I found when I tried to design it, below I`ll find the report copy,



I have another problem continuing with the Roller Gear Cam Design, well I found the way to achieve the complex curves through the globoidal surface, -in the Figure 1.0 you can look the dummy model, -just for the first curve trials- , but now I have a problem to make the sweep cut out, because is not a commonly sweep, remember that the section needs to rotate, when the turret will be index
 
Dear Pablo,


After replying to your PM, I have been trying it myself and have synthesied the cam curve thru the trace curve function. But this is not yet good enough for manufacturing hence am not posting it here. Possible method to get the cut is described below. I have not tried this method my self but then that is how I see myself going.


Now to addtess your problem of the slot being normal to the roller axis, use a VARIABLE SECTION SWEEP.


First define Three points on the roller, ONE at each end on the circumference of the roller and the third at the center. Derive Three trace curves. The central curve for VSS cut and the two other curves to determine the NORMAL direction.


This again will not be good enough for manufacturing because you need to ensure shock free entry of the next roller into the cam and to define the DWELL period, I am working on a methodology, which I shll post in the form of a hand sketch.


Trust I have been of help.
 
Instead of making the cut in one go, create only a surface that represents the median surface of the slot. Then make offset surfaces to either side of that. That plus a few extends, boundary blends... and a buncha merges will get you what you need. See the part I provided in your other post. or here.

Edit: Updated link to correct it.




Edited by: gkbeer
 
I tried to create a cam by using the median surface and offseting it. I find that this results in a cam that has an interference at the begining and end of the sweep. If you make a cut offseting the center of the cam you make a cut using apaper thin cutter that is all ways normal to the path thru the part. In reality when you move a round cutter thru the path given, the resulting cut spreads out a bit.
 
Dear Pablo,


After fiddling around the following are my observations:


CAM:


Trace curve is the only way to get the curve that would satisfy the acceleration / deceleration requirement.


To generate the trace curve, the cam should operate for 3 cycles. One for Entry, TWO the work cycle; THREE for the Exit.


If the servo motor (say servomotor 1) time is 10 secs (which will be a CONSTANT VELOCITY profile, operate the analysis for 30 seconds


ENSURE that the initial cam size ENCOMPASSES the POINT on the INDEXER.


You can Trim the CAM after getting the Trace curve.


Indexer:


Create a point on the center of the roller, about to enter the cam.


Define THREE MOTORS (Servomotors 2,3 & 4); All the three will be a copy of the other. To define the profile, consider the dwell time as a portion of the total time. Since our analysis is going to be of 30 secs, our cycle time will be 10 secs. If the dwell time is 40% of cycle time, the indexing time is 6 secs. For say 6 indexes on the indexer, the angle of index is 60 deg. hence the amplitude is 60 deg in 6 secs.


Create THREE snapshots, for Three positions viz. Entry, Work cycle and Exit.


For the analysis:


The time for the analysis will be 30 secs (THREE cycles)


Servo 1 will run from START to END


Servo 2 from Start to 6 secs (time 6 to 10 will be the DWELL TIME)


Servo 3 from 10 to 16 secs


Servo 4 from 20 to 26 secs (26 to 30 will be the dwell time


Servo 2, 3 & 4 shall run from snapshots 1, 2 & 3 resp.


Create the analysis from Snapshot 1. Run the trace curve.


----------------------


Now I am Stuck. to get the cut somebody had mentioned that you can use a solid to sweep along a profile. You cannot use a section in this case as the points of tangency along the cut will differ. Ideally if you have Promill you can simulate the cutter (I presume)


I shall come back to you on this.
 
Ok, Here is a part that properly creates the slotted cam.

(WF 2 - STUDENT EDITION PART)

cam2.png



edit 12-9-11: Updated link.




Edited by: gkbeer
 
Keep in mind that "All motion is relative".

To under stand the above it's helpful that "All motion is relative" and then look at the problem like this:

The grooved part is stationary and the roller part is spinning about it's axis, while also moving in an arc around the axis of the grooved wheel. The result is a simple ruled surface.

The transparent mid-surface you see is a vss with only one trajectory curve, and one sketch that is modified with an evalgraph("graph",trajpar) relation in the sketch that is swept. The model is constructed entirely of merged surfaces then solidified.
 
Dear Srini,<?:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" />

After a few trials, I can make the wedge cut rib, with a little modifications on your method and are the following:

Indexer
I just made one servo motor through the User Defined Profile, that contains all the movements that I want through the domain
 
Hi all!


I am a new member from Czech Republic. I am doing a project related to design globoidal cam in ProE. Could you help me to get some materials about that cam and teach me how to model it by using ProE?


Thank you very much!
 
bimbo666 said:
After makes that, I followed the procedure that you suggest me, and cut the wedge (VSS) in a single one time, but when tried to run a collision kinematic analysis, I found a few volume collisions detected yet, so maybe I
Click to expand...
 
I've built one of these globoidal cams by using a VSS and a spinal bend. The VSS is along a straight line and represents the centerline of the follower gear arm, and the angle of the follower cam is driven in the sketch by a graph, then using evalgraph and trajpar. That VSS is then wrapped around a circular profile curve (the spinal bend), and then i created offset surfaces to represent the width of the follower cam arm. Then the surfaces are all merged with a surface for the cam, and there you go. Pretty straighforward, especially when you know the spinal bend trick.





The problem I have now is that my graph is a spline with control points through specific points that are dimensioned, and do not exactly represent the true profile of the follower. I do however have an equation that gives the profile of the follower for the full range of the cam.


Pablo, i'd like to know how you created the graph that you posted above. Is that just within mechanism (servo motor), or does that drive your geometry? My equation is similar to that in that the movement is defined in increments, but i can't figure out how to get my equation in to my evalgraph. I haven't tried cylindrical coordinates yet.


Thanks,


Matt
 
Dear mjl3720


Tha graph that I posted above was made with an equationservo motor, to then extract the path that my VSS would follow, then make an offset to the surfaces-both sides-and make the cut.


If you need more inf, you can reach me at:


[email protected]


Regards


Pablo Ulloa
 
dear all cam designer

can anyone send me pro/e asm file with mechanisam constrain

i am student and i need this file for my project purpose

please help me

best regards
nishant
Edited by: nishant789
 
Dear gkbeer

which link is updated and i need some help to create 3D curve from graph and equation of globoidal indienxg cam plz share some detail information about this , my emial :[email protected]


regards
nishant
 
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