19 Replies Latest reply on Mar 2, 2017 8:47 AM by John Stoltzfus

# How do i mate this?

Hi all,

How do I mate these two rollers together so they are always in contact with each other but don't go through each other when i rotate them.

Thanks,

Joseph

p.s I have tried coincident points at the center but this doesn't stop the bodies intersecting, nor is it accurate as when they role the middle points won't always be coincident.

• ###### Re: How do i mate this?

You might try a Tangent mate between those two cylindrical surfaces to see if that will do what you need.  And welcome to the forum.

• ###### Re: How do i mate this?

Are the two rollers parallel to each other?

If they are, can you use a tangent mate?

Maybe even a plane that lies tangent to the non moving roller (at the assembly level), and then mate the other roller to the plane with a tangent mate.

If they are not round, then another option is to use sketch geometry to map out the curve that a point on the edge of the roller travels along.  Do this for each roller, then make the two sketch curves tangent.

• ###### Re: How do i mate this?

I cannot test this right now but is a "Cam-Mate" possible?

• ###### Re: How do i mate this?

Thank you all for your help so far - the tangent mate didn't seem to do it. I will try the other suggestions (thanks ed and dan) but at the moment still getting this intersection.

• ###### Re: How do i mate this?

I would use a sketch curve from one assembly and a sketch point from the other assembly and mate them coincident, then add a parallel mate for the vertical alignment...

edit - added picture - Mate Point (red circle) to Arc (blue line) + plus add a tangent mate and if you need to control the over travel then a distance mate or an angle mate...

• ###### Re: How do i mate this?

Looking at John's sketch are the two 'arms' fixed or do the 'roller halves' roll to accommodate a positional change of the arms? If so the radius of the roller halves would have to be the same as half the distance between the two pins that the roller halves are mounted on. But understand that this is just an observation from the picture provided. The roller halve radius does not appear to be correct (it's much larger) from my observation.

• ###### Re: How do i mate this?

Showing the connecting linkage would give us a better idea, however the point I wanted to make was to utilize sketches and sketch points for mates.  Also, if any of the ends aren't controlled by additional linkage then I would create a surface dome and use a sketch point for a tangent mate, this type of mate keeps the sketch point within the moment of travel or within the dome and won't jump across form positive to negative like a distant mate.

• ###### Re: How do i mate this?

It looks to me (in your first image) that the blue pads are not uniform thickness on the rollers.

Is this true or is it just the image projection that is off?

John's answer seems like it would work if the thickness is uniform and the parts are parallel.

Bernie's answer made me think of something.  Be sure that the 2 parts are not both fixed.

At least one of the sub-assemblies must be floating

• ###### Re: How do i mate this?

Thanks all for all your help - i really do appreciate it.

I am still having trouble as I have tried johns suggestion but unfortunately no success (could be my poor solidwork skills!).

If it helps, i want to effectively mimic this

The connecting arms need to be fixed and all that is moving is the rollers.

• ###### Re: How do i mate this?

Joseph,

This is my observation looking at what you have and what you want to achieve(Knee rotation).

Depending on your approch the variable you have are the 2 tangent surfaces,  then you have the surfaces themselves never interfering with each other. You also have a pivot point on radial pieces where they attach to the arms themselves.

This is a lot of control to capture.

Are the radial pieces allowed free pivot on the arms?

Is the lower one going to be fully constrained and the upper flex around it?

John Stoltzfus sketch is the initial approach I would take. I would also utilize a plane at the intersection of the ends of the radius on my fixed radial piece. In my sketch on my rotatating piece I would utilize end of radius sketch points and set up limit distant mates to create a max an min function of movement. If you join the 2 pieces at the apex of the radii this would give you rocking motion with no interference issues.

• ###### Re: How do i mate this?

Paul Risley    -  Perfectly explained - thanks for picking up my slack - been a busy morning...

• ###### Re: How do i mate this?

Thank you paul for your detailed response I will try and give this a go!

In response - the upper is going to be fully constrained and lower flex around it. The radial pieces are also allowed free pivot on the arms.

Thanks again john and paul.

Kind regards,

Joseph

• ###### Re: How do i mate this?

Hi all,

I have tried the distance mates and coincident point mates but that doesn't give the rocking motion required.

constraints. Upper body is fully constrained and lower flex around it. Needs to rock like a knee joint. surfaces need to touch at all times but not intersect each other.

sorry for going on, but help is appreciated.

• ###### Re: How do i mate this?

What version do you have - would it be possible for you to upload your assembly model?  In the picture you show the two pins holding the rocker, are the upper arms pivoting there or could you show the side view of the assembly of only those parts?

• ###### Re: How do i mate this?

Admittedly there's a lot of guessing going on, can you upload the models and the assembly? Realizing there may be some IP you would like to protect perhaps you can 'cut off' some of the parts or assembly before uploading. Maybe upload what we already see in the picture?

• ###### Re: How do i mate this?

This assembly just needs some additional modeling work prior to mating properly...

You only uploaded the pivoting components, however in the pictures you also show the linkage.  The radius's of the cartilage are split instead of one radius, delete the mirror features so you have one continuous radius and that would make everything a lot easier.  Also the spacing between the pivot points swing radius and the radius of the cartilage is a lot of difference, so for this to work something has to move vertically or radially to keep surface contact all the way.

• ###### Re: How do i mate this?

Thanks a lot for your help John. I have redone the model using your advice. If you could help with mating the two now that will be greatly appreciated,

I only need these two parts to rock with each other, (I have successful been able to mate the linkages okay now, so sorry for the confusion there)

• ###### Re: How do i mate this?

If you have the parts corrected then do a tangent mate and if that would want to flip or go outside the travel zone, then follow the instructions that Paul Risley mentions above..