How do you constrain a cam roller (cylinder) on a bell or drum cam?
The "cam" constraint only works with simple disc cams.... a priori!
came.jpg
came.jpg
I'm not going to help you much except that I remember a similar question has already been asked on this forum.
It's a bit old and I remember that there wasn't an obvious answer.
If I find 2 minutes, I try to look.
Hello @JFCLEMENT
Can you post your ASM (with the pack and Go function)
Cams are a real mess if you don't respect strict conditions whose first thing is to have a continuous sketch (in one piece) and also to have a contact surface of the cam path strictly square to the central axis
The other thing concerns whether or not to use the toolbox to create the cam.
Kind regards
Thank you for your interest!
The assembly is attached.....
What do you mean Zozo by "the use or not of the toolbox to create the cam."?
Franck Ceroux, that's what it's all about! On the other hand, the "Cylinder / surface" constraint????
The cam function does not work in this case....
I also tried a 3D sketch showing the external path of the constrained traj. / cylinder surface = > doesn't work either...
came.zip
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Hello @JFCLEMENT
Here's what it can look like (watch the video made with your model)
For this to work, your cam path must be made with a spline, so you don't have any interruptions between each part of the cam path.
Kind regards
PS; Thanks @ franck.ceroux for his trick with the tangency with a sphere (instead of the cylinder) because everyone knows that otherwise it doesn't work.
chemin_de_cam_2020-09-29_20h12_27.mp4
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Hello @Zozo_mp,
Great, that sounds ok!
Would it be possible to send me your assembly so that I can "dissect" the way to make the cam?!
Thank you in advance and THANK YOU for taking your time.
Sincerely,
Hello @JFCLEMENT
Here is the cam brought into line with your model (unlike the demo video). You will notice that now your cam path is smooth and you don't see any interruption anymore because the spline is continuous. (see the attachment for the comparison between the two methods, you have an explanation in this image)
Allow me a piece of advice!
For the sketch of your winding function, your sketch must be centered in relation to the origin, whereas here it is currently wedged on one end. The logic of the winding function is to start from the center and wind to the right and left simultaneously.
Otherwise, either you will get an error message, or depending on the shape you will have construction defects.
Kind regards
chemin_de_came_discontinue_pour_les_contacts_-_2020-09-30_09_53_40-window.jpg
Hello @JFCLEMENT
Look at the attached image to understand the subterfuge used for the contact between the roller and the cam track. Be careful the sphere must have the same diameter as your pebble ;-)
Kind regards
escamotage_axial_guide_from_zz.zip
Zozo_mp,
GREAT thank you!
I'm looking at it more closely....
And I take with pleasure and humility your advice on the winding function....
Kind regards.
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Zozo_mp,
I admit to having "shortcomings" concerning splines, and therefore being a little allergic to them because I don't know how to control IT!!!
To understand after having "recalibrated" my cam profile in the center as mentioned above, you used my "so-called perfect" curve made up of line and arc of a circle to trace your spline on it and then erase my "perfect" curve?
Is it possible to obtain a spline precisely using a "perfect" curve made of line segment and arc of a circle without having an approximate curve?
Kind regards.
I have just "finally read up on Splines and associated tools, and I understood that you had used the "Fitted" spline function which creates a spline on a guide curve, this same guide curve passes in construction lines.
Many thanks Zozo_mp.
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Hello @JFCLEMENT
You ask the following question:
(((( Is it possible to obtain a spline precisely reproducing a "perfect" curve made of a straight line segment and an arc of a circle without having an approximate curve? ))).
The answer to this question is in the affirmative for several reasons.
I suggest you read the attached PDF document and in particular the point that answers your question but also others ;-).
In the SW example I gave you, I turned your model into a construction line and then gripped the spline on this path. (and not the other way around)
maitriser_les_splines_version_sauvegardee_2020.pdf
Hello
In fact I did "exactly" the same manipulation, that is to say to de-emboss the cam from a "ADJUSTED" spline centered ...
I say "adjusted" because I don't want an approximate shape.
If my plan goes in fab and therefore taken up in CAD/CAM...
And it doesn't work!!! CANNOT perform the debossing!!
So back to square one... Even simplifying the shape of the cam, it is impossible to relay the function of degassed winding with the spline....
I don't understand!
Kind regards.
Hello@JFCLEMENT
There is no reason not to carry out the de-gauffing. On the other hand, in my opinion, the right angles are not justified for your cam since your roller is cylindrical. That's why I didn't put a right angle in the template that I submitted to you as an example.
You have to respect certain rules such as having the same dimension as the perimeter for the projected sketch (see 0.05 mm or 1 to 2 mm less! sometimes SW makes us whims).
Try to generate the CNC file from the file I sent you, it should be good normally
Kind regards
PS: a nice little remark ;-) ;-)
With a normal spline but constrained correctly (here from the sketch with rigorous dimensions) and.or using the method I propose in the attached PDF you will have a perfect shape if I use the common sense in mechanics.
In addition, for a cam and especially the movement you want to make, there are only two positions, or even only one (generally the high or low position) which requires an accuracy of around 0.05 mm without taking into account the stops.