Using Mate Connectors

tim_proby

I'm so frustrated with mate connectors. I find the tutorials and explanations that I've found completely counter intuitive and overly simply. I feel like mate connectors are totally predicated on having all your parts in one design studio. Is this correct? If so - I guess I will just model everything in one partstudio which I find hard to organize and overly complex. 

I am trying to mate a concrete footing to the ground and center it over my deck beam. I want the footing to be related to both the ground and centered over the main deck beam. Usually I would use coincident mate to align to the ground and a center plane to align with the center of the deck beam.

If there is a way to mate these together without one part studio I would like to know how I should approach.

https://cad.onshape.com/documents/ca6790362fc53c7971e108fb/w/855c164f03d0136dd0f97358/e/d55ad60546c660fe71ee307d

tim_hess427

Hi @tim_proby - If you're coming from certain other CAD packages, the way mates work in Onshape can be fundamentally different (but I think work pretty darn well).

A few points that may not come through in most tutorials that just show you where to click (my apologies if you already know this stuff):

1. "mates" and "mate connectors" are two different things.
   
2. A "mate connector" is really just a local coordinate system attached to part. You can define a mate connector in a part studio or in an assembly.
   
3. A "mate" brings two different mate connectors together and defines how many degrees of freedom they have to move relative to each other. So, a "fixed" mate brings two mate connectors together and there are zero degrees of freedom for the parts to move relative to each other. Likewise, a "revolute" mate brings two mate connectors together, but allows the parts to rotate with respect to each other around a single axis. 
   
4. Usually, you won't need to explicitly create mate connectors, you can just create them while you're creating a mate.
   

Bringing all this together means that typically, for two rigidly connected components, you only need to bring both components into an assembly, add a "fasten mate", and select the feature will walk you through creating "implicit" mate connectors on both objects. The components will then come together and not be able to move relative to one another.

All of this is in contrast to other systems where you would have to build up multiple constraints between two components (such as aligning two circular holes and then making the faces coincident). In Onshape, those steps would be combined into one mate.

Is this what you're going for? It looks like the doubled-up red beams are too wide for the channel in the block, but its mounted up against the beams and centered on the red beam.

Theo_R

For intermediate users, look into "Offset" both Mate Connectors and Mates (thinking specifically of fastened) include an offset capability. So if it is not centered, or placed as desired you can manually adjust the placement.

michael_mcclain

If you really have trouble and cannot find the right mate type, I find that using several parallel or planar mates can help me limit degrees of freedom one by one and is most similar to other CAD program's mates.

I usually use mates like fasten, slider, cylindrical, etc... but sometimes I find that 2 or 3 planar mates are what I need instead. It all depends on your understanding of the concepts and what the particular situation calls for.

Mr_GK

@tim_proby


I got your point.

If you want to use a specific location on assemblies, you can create a Mate connector on your own. Catia has something like that, called publications. For some companies, they only can create engineering connections (mates) using publications (mate connectors), this option can be enabled on system options.

For Onshape, Mate connector creation and usage is optional.

You can see below that I created two mate connectors on this part studio. They are associated with my skeleton sketches.



These components are grouped in a subassembly. I'm not using these mate connectors here



I used these mate connector in a different assembly. It helped me to create only one mate for fixing this subassembly on Base assembly. I created a fixed mate and connected two "connectors".





I hope that these images and this model can help you to get more ideas on mate connectors usage.

https://cad.onshape.com/documents/d20824155b8ae7dbb812ade7/w/c8841e86e9c39ce881824ce8/e/396d6539555b3b1a5514dee0

Some colleagues here mentioned that you can combine multiple mates types. It works nicely for some applications, but I wish I could provide you more explanations about Mate connectors feature.

Regards,

Mr_GK

I copied your design and applied my own methods on that.

First of all, It is needed a sketch that contains a point



A new Mate connector is associated to this sketch point and an edge as a reference.



Observe that the main axis (blue) is up and will be aligned to the concrete part on assembly.



As the fine step, we are able to create a fastened mated using two mate connectors.





https://cad.onshape.com/documents/03e1e0c548d038d92f787ef7/w/3c674ea3acacb9592f0bcb09/e/14ce9408c474d146713b8d4e