Mating vex bearings

So I have been using solidworks for a year now ( never work on a vex bot) and I am trying to mate a bearing to the metal and doesn’t like it when I mate the little prongs on the back. I will be able to mate one then when I mate the other to the other side it will " yell " at me .I have watch videos of other software that look really easy. Is it a solidworks thing or a me thing?

That’s because they don’t have perfect width to vex holes; there is tolerance between the widths of each, so this problem would happen with any CAD software. Here is a still easy but better process to mate bearings to c channels:

  1. Mate the flat back face of the bearing to the c channel
  2. Choose one aligner (prong, etc.) that you’re going to use to keep the bearing in place and mate one face of it to the edge of the hole, then mate the other face of that aligner to the other perpendicular edge inside the c channel’s hole. This will not align it perfectly (though you can introduce an offset to center the bearing properly) but is the easiest and fastest way to do so in my opinion, and alignment really doesn’t matter too much.

An alternative way is to tangent mate the circular hole of the bearing to the faces of the hole.

Side note: This is the wrong place, this should be in VRC CAD Discussion.


there’s a vex library for solidworks which makes mating easier by enscribing a circle within the square holes for every part. You can then mate by concentric mating the bearing.
this is the library that I use
Alternatively you can linear sketch pattern the circles yourself

Here’s the issue, molded plastic parts like bearings have a slight taper on all sides (called “draft”) which is designed into the part so it can be released from the injection mold during manufacture. After mating the main “flat surface” of the bearing to the vex metal, select only the edge of the bearing (it will be a line) rather than the side surface of the bearing. That line can then be mated to planer surfaces without the errors you’re encountering. If you don’t want to use the modified standard vex parts in the library, then the bearings can be aligned precisely centered over the holes using a “width mate” which you’ll find in the advanced mates. Select two opposite “square hole” sides as the “width selections” and select the round hole of the bearing as the “tab selection”, and the round hole will center itself on the vex metal. Repeat for the other direction. If you download my V5 clawbot CAD from grabcad, you can see example of this technique.

One more thing I’ll point out: on shafts (in the library for sure, and I think also on the original vex .step files–I can’t remember if I added it for the library or it came that way), the corners are “rounded” with a circular radius about the central axis. This means that you can mate shaft to a circular feature (like the bearing hole) with a simple concentric mate. If you’re using the library with my “circular features” on all the square holes, you can concentric mate the rounded corner of a shaft to the circular feature on the hole. When prototyping, this speeds up the process because you can position shafts and vex metal for full motion, then add hardware and bearings later.

Are there any good video tutorials that walk through this process with some part of a vex robot?

No specific vex parts videos that I know of, but there are articles about width mates:.

I need to get our U-Team to make some videos.

Thanks for the link.
That would be really helpful!