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Constraints in assemblies

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Message 1 of 3
newcomer
313 Views, 2 Replies

Constraints in assemblies

I'm getting a bit better at assemblies, but am far from basic proficiency.  The problem I just hit is typical of the kinds of problems I have had to work around in the past, but none of my workarounds seems to solve the problem I have.

 

As you can see in the .iam file, I'm combining three other drawings into an image of a bearing (the idea is that I am modeling the parts I have bought for my project).  I have two issues here.

 

I had constrained the mate of the bearing edges to be half the difference between the ball diameters and the ball-holder thickness.  Worked fine.  But after a few more adventures (to be described below), although this mating constraint appears to be active, in fact, I can drag the outside layers to any distance from the bearing.  This should not be possible.

 

I was trying to come up with a way to guarantee the three componenets are concentric.  Everything I tried failed; the most recent failure was when I tried to create an axis along the centers of the three sketch circles.  It created a skewed line that bound all three components together, so moving any one of them moved all of them, but now they were as skewed as they had been before.  So I deleted the axis, and after that the mating distance constraint no longer held.

 

I was unable to create a plane tangent to one of the circles (or, more correctly, the extruded surface of one of the sketch circles); it insisted on trying to create a work plane parralel to the circle.  My intent was to create a work plane tangent to one of the parts, then make the other parts also be tangent.  Do this with two work planes normal to each other, and I've constrained them to being aligned.

 

What I miss is the inability to say things like "coincident constraint" for the centers of the circles.  Exploring possibilities of constrain did not reveal anything that worked.

 

So how can I force these to be concentric?  (There will be a rod through these, whose end is machined to the ID of the bearing, and which is going to have a force normal to the surface of the bearing [an axial force downwards through the center], and I want to be able to insert this part in the drawing of the final project, and quite possibly even simulate the forces.  But that's a battle for a different day.

 

Thank you for your patience with a new user.

     joe

 

2 REPLIES 2
Message 2 of 3
WHolzwarth
in reply to: newcomer

Perhaps like that?

Walter

Walter Holzwarth

EESignature

Message 3 of 3
graemev
in reply to: newcomer

The parts look ok, but the assembly is a bit of a mess.  Toss it and try this:

 

1.  On the ball cage, define an axis in one of the ball holes.  Yep, just one.

2.  Insert the ball cage, grounded at the origin if you so choose.

3.  Insert one ball, constraining its origin point to the ball cage's mid-plane and to the axis generated in Step 1.

4.  Make a circular pattern of the ball using the origin axis of the ball cage.

5.  Place each bearing plate and constrain each as follows:

6.  Mate the origin axis to the origin axis of the ball cage.

7.  Tangent mate the bearing surface to the ball surface, running clearance/interference as desired.

8.  Sit back and have a refreshing drink for a job well done.

 

Your bearing is now complete and constrainable either by origin centerpoint mate or bearing face insert.

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