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Symmetrical constraints

Symmetrical constraints

I'd like the ability to create symmetrical constraints, so I'm not required to work around this via other methods. 
It would allow me to work faster and with more assurance.   Also, I'd like the option to select symmetry based on various points, lines, planes. Etc.

14 Comments
smithar
Autodesk
Status changed to: Under Review
 
jletcher
Advisor

Again this is already posted but why?

 

 

Offset constraints is a big no no . Use a sketch instead trust me.....

Mark_Wigan
Collaborator

as i read this, the key word is symmetry, not offset.

 

ie the o.p. would for example (in one case) be contraint locking mid plane of one object to midplane of the other object. in inventor we have to use workplanes etc for this. other products allow symetrical (along with various other) methods of symetrical contraining, even if there was no mid plane or symetrical origin plane to use, we could pick various object attributes on the fly to allow us to place our contrainsts in a quick and efficient manner. mechanical desktop was a fine example of this excellent functionality.

 

"sketch instead" is a pretty vague statement. if this refers to using sketeton geometry and parts being located according to their position relative to a master sketch or skeleton then yes this is alaso a great method. sometimes the environment that we work in dictates one method over the other.

 

having the new idea would not diminish the operation of those who prefer other methods or have to work one way or another.

 

it took inventor quite some years before some functionality of MDT came through. i am surprised that this has still not yet been given the green light.

tmoxam
Advocate

this is easy people. create your parts assemblies using the origin planes. Begin the sketch of each component relative (symmetrical) to the origin if that is your intent.  when you place the component the insertion point of the model IS the origin on the first sketch and when all your parts are created in the same way the same origin planes in each part can be constrained together to maintain position independent of the size of either part.

Basically, each time you start a part you must consider the datum in the original sketch and position the sketch accordingly.

jletcher
Advisor

Mark_Wigan,

 

  No sketeton geometry is not what I mean but can be used.

Also in order for somthing to be symetrical would it not be an offset? if you have a mid plane or the orgin and you want a part to be symetrical from the one plane would this not be an offset constraint from that plane?

 

tmoxam,

 

 No you do not have tho think or consider the datum in what I am saying.

 

To explain:

 

 I have two parts part "A" and part "B".

Now Part "A" is grounded and I want Part "B" to be located 1" from the edge of Part "A".

So what I would do is double click part "A" start a sketch on the face make a construction line and dimension it from the edge 1". Finish edit and constrain part "B" to the line.

 

No sketeton geometry is needed unless that is the way you wish to do it.

 

But the one thing I want to make clear is an offset constaint is not good for many reasons....

JimSteinmeyer
Advocate

jletcher,

If I read this correctly you have two components in an assembly. You ground, or otherwise constrain part A, you then create an assembly sketch of a line with one end constrained to part A. Next you exit the sketch and finally constrain a surface on part B to the other end of the line? I would be open to learning the logic of this method. To me it looks like you are doubling your work and leaving part B able to rotate with respect to part A rather than constrained with parallel faces.

I know you want to make it clear that offset constraints are not good, but I have not found any reasons for this. Again I am open to learning what they are.

 

Jim

jletcher
Advisor

@ JimSteinmeyer

 

   No you don't use a assembly sketch.

 

Lets say you have two parts part A and part B.

 

Now when you start an assembly and insert part A this part would be grounded.

 

Now you insert part B now lets say part B is mated to part A flush at the top mate to the face now part B has to be set back from the front edge about 2 inches. Most would us a offset constraint this 80% of the time will make your assembly explode out of the blue and you don't know why.

 

Now instead of an offset constraint open part A put a sketch on the face part B is mated to on the sketch draw a line and dimension it 2" from the edge you want part B to be offset from. Finish sketch.

 

Go back into the assembly and take part B and put a mate on the face of part B to the sketch of part A.

 

Now most the time I will name the sketch in part A so I know it controls the location of part B.

 

No offset constraints and never ever had issue with exploding assemblies or issues when I go and make it adaptive.

 

If this does not clear it up I could do a small video and upload it to you tube for you..

dan_szymanski
Autodesk
Status changed to: Accepted
Accepted idea [US5155]. Thanks!
dan_szymanski
Autodesk
Status changed to: Implemented
This idea has been implemented in Autodesk Inventor 2014.
Quickcola
Enthusiast

This sayes "Implemented" but it doesn't work right. Up to this year I was working on SW, thier symmetrical constraints work great and I am very used to using them alot. This year I changed jobs and ended up working on Inventor 2014. So early was I disappointed from this feature in Inventor that it was during my initial Inventor training. I questioned the Inventor Trainer about what could I be doing wrong for it to not fonction properly. I was told by my Trainer that Inventor added the feature so they could say that they did but that it was baisicly useless.

DRoam
Mentor

A big issue with the Symmetry constraint is we can't symmetrically constrain between two faces on the same part, or between instances of a pattern.

 

It seems the Symmetry constraint was created only with the intent of driving the location of the left and right components, not the center component. And therefore if the left and right components are already fully defined, the Symmetry constraint either won't accept them as inputs or will cause broken assemblies. But what if we want to drive (i.e. center) the location of the CENTER component?

 

The Symmetry constraint really needs to be smarter and simply keep the the left-to-center and right-to-center distances equal--that's it. Even if two of the selections are on the same part or members of the same pattern.

 

A much better solution, though, would be doing away with the Symmetry constraint and replacing it with this functionality: Constrain with midplane between existing faces. Using the functionality described in that Idea, we could not only do what the Symmetry constraint should be able to do, but we could also constrain the midplane of two pairs of faces. In other words, we could center two features together without having to create part-level midplanes for those features first.

 

At the very least though, the Symmetric constraint needs to be fixed.

 

asiu
Advocate

This (the existing Symmetry constraint) is really an incomplete implementation, where one has to create additional geometry to be able to use it properly.

 

[Unless there is a patent involved, SW has it working a lot easier. This is not to get you aggravated, but just to point you to an existing implementation.]

 

You can evolve the existing constraint to make it work on pair of parallel faces or in between parallel faces and a cylinder, cone. The symmetry plane has to be calculated but not actually created as an entity in the browser.

 

Thanks.

NicoletDesign
Participant

What is described above by Quickcola, DRoam and asiu should be an obvious, necessary assembly functionality.

 

I've been going nuts trying to make the Inventor symmetry constraint work.

 

I believe SolidWorks has had it for more than 15 years.

AlexZW28B
Advocate

Having just started to use Inventor recently, this is a HUGE frustration, especially when aligning components with holes and slots. I want to align the component concentric to a hole, and then the slot feature I want to mate symmetric to the corresponding hole on the other part - but as symmetrical between the slot size feature. This is not an easy task to do currently - and super frustrating. 

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