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Mate : impact of the order of mate connector selection

MathMath Member Posts: 7

I'am currently following the learning Pathway "Onshape Assemblies". I am now at the exercice "Creating Mate Connectors". And I've had difficulties with step 14.
Initially, I strictly follow the steps of the text : select explicit mate connector of the arm, select explicit mate connector of the base, check the alignement of the mate and then entering the limits.
And the motion of the two parts wasn't as expected (see following picture).

After one hour of exploring what could be wrong, I realized that on the picture of this Slide, the mate connector of base is select first and then mate connector of the arm. So I edit my mate to this order of selection.
And now, the motion of the two parts was as expected (see following picture).

So it seems that when mating two parts, the order of selection of the mate connectors has an impact on limits of the motion.

But I see nothing about this in the leaning pathway, the following technical briefing or the Onshape help :

So, there is someone could explain what happens in my case if I select the 2 mates connector in one order or the other ?

Thanks a lot !


Best Answer


  • frank_crutchfieldfrank_crutchfield Member Posts: 1
    This exercise was the most difficult so far. Math's observations helped me solve this. I still had to realign the secondary axis on the explicit mate connector. The overall effect reversed the direction of the limits on the revolute mate. IE: the -100 degree limit switched from being closest to the plunger to the -15 degree limit being closest to the plunger. I guess I came here hoping to understand where the heck zero degrees is located. Or just to understand what defines zero. Is it defined by an axis, a plane or a relationship?

    One other point of confusion in the description of the revolute mate, the first mate connector selected serves as the rotational point and the second mate connector selected serves as the stationary point. It seems to me the base would be the stationary point but to make this work you have to select the base first making it the rotational point.

     I am new to CAD not just OnShape so please forgive my ignorance.

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