How to mate a bracket to an extrusion

julien_vanier

I want to mate 2 types of brackets to an extrusion with a slider mate so I can later position the brackets when I add this sub-assembly to my main assembly. Here's the document with this assembly https://cad.onshape.com/documents/bdc4c00fc12953de70d92344/w/c536a3bfb15c5f16eaba63a4/e/ead3a5788c9d9ab4ae0224d6

My main issue with the slider mate is that it slides only with the Z axis so it makes the .

For the 90 degree angle bracket, I get the desired motion by mating the middle of the lower edge of the back face to one corner at the end of the extrusion, with an offset of 1mm in X since there is a fillet between the back and bottom faces of the bracket, and an offset of 2.1mm in Y to center the bracket to the slot on the extrusion.

For the flat bracket, I can't make it work since the back edge has a draft angle.

If I could make the slider mate slide across the X axis, I'd mate one of the holes at the bottom of the bracket to a corner of the top surface of the extrusion, but since I can't change the sliding axis, with this mate the motion is away from the extrusion instead of along it.

Can someone suggest a better way to mate these brackets to the extrusion so I can get a sliding motion along the extrusion? Thank you.

Matt_Shields

The draft angle is 5 degrees. So you could add a Mate Connector with a 5 degree rotation.

Matt_Shields

The draft angle is 5 degrees. So you could add a Mate Connector with a 5 degree rotation.

S1mon

It might be better to add a mate connector to the flat face and then use the move option to rotate it 90 degrees. Unless you are in control of the draft on the bracket, adding 5 degrees in the mate connector definition is dangerous if the draft changes.

eric_pesty

I was going to say you should practice with editing the mate connector themselves, using re-align and offsets (instead of just using offset in the mate feature itself).
For these I just use the hole in the center as the reference on the profile side (and offset by 1/2 the profile width).
You could also define an explicit mate connector on the bracket that is 1/2 the profile width away to save time (only really helps if you don't use the bracket on different size channels).

There's an example here:
https://forum.onshape.com/discussion/comment/87424#Comment_87424

julien_vanier

Thanks for the suggestions. So in summary, it's best to define explicit mate connectors and leave the mate features without any offset because if the parts change, the mate connector will change with them but the offsets won't.

eric_pesty

https://forum.onshape.com/discussion/comment/107505#Comment_107505

Hard to have a "universal" rule.

For a bracket like this that you are going to (presumably) user multiple times, the explicit mate connector makes sense as it will save time every time.

However putting the profile 1/2 width as an offset in the mate itself is valid approach too (especially if you are going to use the bracket in other places with different size tubes, etc) so not all offsets are "bad".

If you use an implicit mate connector, it's definitely better to pick a "stable" reference like the flat face that mates along the tube and adjust the mate connector itself (using a "re-align") rather than the drafted edge and adding a 5deg angle adjustment.

julien_vanier

For a bracket like this that you are going to (presumably) user multiple times, the explicit mate connector makes sense as it will save time every time.

That makes sense. Since the bracket comes from another document that I don't control, how would you recommend that I add the explicit mate connectors to ease reuse?

I was thinking of creating an "Off the shelf parts" Part Studio and use Derived to add the parts from the other document and add the mate connectors there so I can reuse the parts in multiple assemblies.

eric_pesty

https://forum.onshape.com/discussion/comment/107515#Comment_107515

Yeah if you don't have control over the doc where the part comes from then you have to either copy it or use a derive to create your own "version" of it unfortunately.