Mechanical Cam Mate

[FusiveR]

I have modeled a cam, and a cam follower, yet when I attempt to mate these 2 models using a mechanical cam mate I get the following error message.

"The selected faces do not form a closed and continuous cam extruded from a single profile."

I am running solidworks 2008. The cam was modeled using the toolbox cam option. I'm surely doing something wrong if a proprietary feature is spitting out an error.

Link for the necessary files (remove all ~ characters): ~http~://~ww~w.filefactory.c~om~/mupc/af17aad/

If you would be so kind as to point out the error and/or send me a proper assembly file I will be thankful.

http://s5.tinypic.com/28sye6q.jpg



PS. I'm new to the forums, so "Hello World."

[shift1313]

welcome aboard.

Im not at work yet so i dont have SW in front of me but take a look at this thread.

http://www.cadtutor.net/forum/showthread.php?t=31599

I was trying to answer a question for someone on motion analysis and used the cam/rocker setup.

Looking at your image, what does the cam lobe rotate about? Where is the rest of the assembly? What motion are you trying to get?

i put some quick marks on your drawing. are these the two faces you are selecting?

[FusiveR]

Looking at your image, what does the cam lobe rotate about? Where is the rest of the assembly? What motion are you trying to get?

i put some quick marks on your drawing. are these the two faces you are selecting?

Sorry, just have a few minutes here so I will partially reply to your response. Rest assured that the rest of the components are in fact present and that it is a full assembly. I have created a similar setup with a semi-circular cam and witnessed good results. The cam lobe mates with a square motor cam (Hence, the cam lobe rotates about the center of its extruded cut square. I am trying to get motion whereby rotation of the cam lobe will cause linear translation of the follower arm.

Yes, those are exactly the faces I am selecting. In fact, when I select the faces on the cam lobe, I select them by right clicking a face and clicking Select Open Tangent, and ensure that all faces have been selected.

I will post a complete response later this evening as I must be on my way. Thanks for your time.

[FusiveR]

So here is what I am trying to achieve.

http://s5.tinypic.com/nwd4sz.jpg

As can be seen, a motor drives a cam lobe, which causes linear translation of an arm. This assembly is mated properly, such that rotation of the cam lobe does in fact cause linear translation of the arm, as depicted above.

I am seeking the same effect, except with a differently shaped cam lobe. The new cam lobe was modeled using the toolbox cam option compared to the cam lobe shown above which was modeled by me. I modeled the lobe above simply using 2 circles with tangent edges, and then extruded.

I believe that the new cam lobe is causing an issue because of the continuity of its profile. If one were to zoom in on this profile, they'd notice that the overall shape is actually created by a series of straight lines (or arcs depending on the option selected in toolbox) as shown below.

http://s5.tinypic.com/2nvuhs2.jpg

I believe that this series of lines/arcs is causing an issue.

[shift1313]

i tried to download your file but i wasnt able to. Do you have any other way to host it or zip a file here. I think your post count has to be 10 before it will let you attach a file to the post.

ill try and play with the cam lobes toolbox when i can. Right now i have an analysis running so i cant use SW.

[FusiveR]

i tried to download your file but i wasnt able to. Do you have any other way to host it or zip a file here. I think your post count has to be 10 before it will let you attach a file to the post.


Here is a link to the file hosted by another host (remove all * chars): ht*tp://drop.io/aab*aa22

If this doesn't work, please email me at (remove all * chars) fusive*resonance*@*hot*mail.c*om

[shift1313]

sure thing. ill give it a shot tomorrow morning at work

[shift1313]

alright i played with it when i got to work this morning and didnt have any issues with mates. I had to make a few components to the assembly was actually constrained so i could animate it. I added two links, some pins and a torsion spring to the top link to keep some downward force on the follower. i was only able to upload a zip file of 2seconds of the ani because of size issues.

[shift1313]

Just so you know. i put all my coincidnet and concentric mates in the model space, but i did the cam/follow, spring and motor stuff in the motion study. Are you using the mate button in model space and the Mechanical Mates tab? or were you doing it in the motion study as well? When i try to use the mech mates in model space i get the error.

[cedar]

Toolbox has a cam program? Where? I can’t find it.

I’m pretty sure the segmented profile is the problem.
SW has a special CAM Mate.
I drew a cam assy using a Spline for the profile. It works.

[shift1313]

mine is under toolbox up top.

[shift1313]

when you created the original cam using the cam toolbox, did you select the arc check box?

[FusiveR]

Just so you know. i put all my coincidnet and concentric mates in the model space, but i did the cam/follow, spring and motor stuff in the motion study. Are you using the mate button in model space and the Mechanical Mates tab? or were you doing it in the motion study as well? When i try to use the mech mates in model space i get the error.

Shift1313: I have added all my mates in model space. I didn't know you could add mates in motion study. I'm still not sure I'm doing it right.

Here's what i did.

- I rebuilt the cam, this time checking the "arcs" option.
- I created all necessary mates in model space (ie. coincident etc)
- I attempted to use the cam mate in model space. This gave me the same error as outlined in my original post.
- I hit the motion study tab and attempted to use the came mate. This too gives me the same error. Is this what you mean by creating a mate in motion study?

Would you be so kind as to upload all the files you used to create that 2 second animation?

[shift1313]

i would but it said my version was newere than yours so im affraid they would do you no good. im using SW09.

when you go into a motion analysis there is a box on the left side with a drop down arrow. There is Animation, Basic Motion, Motion Analysis(in SW09). I think 08 might have advanced motion. you need to make sure you select the bottom one(motion analysis or advanced or whichever you have). All the mates that allow your assembly to move should already be in place and the only one needed in here is the 3d contact constraint. The icon is a cam/follower. It prompts you for components, you should just select your cam and your follower wheel. From there if you like you can specify material, friction etc.

Since i didnt have the rest of your model i created a square to fill in your square drive. and added a hole through this for a shaft. carried that shaft into a plate which i kept Fixed, all other components are allowed to float.


The issue with your cam is the facets. Look at the image i uploaded. When setting up the mecanical mates in model space you will need to select every facet of your cam face, then under the cam follower selection just your roller. this should work but its very time consuming. if i get time i will try this to see if it works

[shift1313]

i did it real quick, 182 faces and no it doesnt work that way.

[FusiveR]

Nope. Not working for me. Im selecting the contact constraint and selecting the faces you mention above.

When I apply a motor to spin the cam lobe, I have 2 issues: 1) Cam follower does not translate up/down. 2)The cam lobe slows down during a certain portion of the stroke. Upon further analysis it is obvious why this happens due to the cam profile shape, yet I am seeking theoretical assembly motion with a constant torque motor. The problem here is: I'm forced to perform the above steps with "Physical simulation" selected vs "Assembly motion"

Ah well, guess I won't be using the toolbox cam option for motion simulations. Thanks a lot for your help though.

[shift1313]

i still have yet to create a cam using the toolbox option. but i cant imagine that it would create a cam thats not usable. ive drawn simple cams in a sketch and they work fine with the mechanical made in the model. Maybe tomorrow ill get a chance to work it out some more. if you figure it out be sure to let us know:)

[FusiveR]

Thats exactly why I started this thread shift1313. This is my first time creating a cam using the toolbox option and I believe that it'd be silly if I wasn't able to use a mechanical mate on this cam. Seeing as how I had trouble with this, I decided to consult the experts.

The cams that I've modelled myself are working fine. With exception to one cam I made using splines, which spits out the same error.

[shift1313]

are you hoping to do this in model space just so you can rotate things around and modify the profile of the cam?

ill keep working on this when i have time, but i dont think there are many Sw members on here let alone ones that use it for this application so the responses may be limited:(

[cedar]

Whats the problem?

[cedar]

Haha, I cheated.
I traced a spline around the profile and extruded a surface to mate against.

I don’t have that cam program for some reason so I can’t analyze it. Shift said SW wouldn’t make a cam program if it doesn’t work… I’m not so sure. I think SW does release half baked functions. If the sketch in the cam that Fusive posted is the output of the cam program… then I think it was not intended to be used for the finished cam. There are no constraints, no adjustments, why all the little segments if a single arc would work? I tried to put tangent constraints on the sketch segments and it went wacky. Even when I fixed the sketch so all the arcs were tangent… cam mate wouldn’t work. Maybe your cam is too complicated for the cam generator to calculate.

All I know for sure is that a single spline works great for cams. And that cam generated sketch can be traced with a spline almost perfect.

[shift1313]

well the cam generator worked in a motion study so you can analyze the profile by tracing it and analyze forces etc. Cedar, in the cam generator you can create a very detailed cam. you give it radius, degrees of motion, type of motion etc. The program is very Picky as to what it will let out.

Fusive, did you have a spec sheet for what cam values you inputed? how did you determine your cam values?

[kelven]

Hi, everyone.

I have a problem to use the cam mate? pls teach me how to use it.
my problem have attach with a photo.

Thanks

[shift1313]

It looks like either you havent selected all the faces of your path OR you dont have tangency everywhere. When you are selecting the path just right click on one of the faces and "select tangency" and it should select all the faces. If it doesnt you may need to alter the part