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Rack and Pinion mate causing parts to "jump" out of alignment

dave_franchinodave_franchino Member Posts: 52 ✭✭
in General
Hey kind folks, 

I'm trying to implement a rack and pinion mate which should be pretty easy - but when I select the slider and the rotational mate my slider part is "jumping" around 40mm causing the initial aligment to be off.  When I select the slider mate it is bringing up a linear dimension from some origin but editing that also appears to mess up my rotational mate. I can't find any documentation on these additional dimensions. Any clue on what i'm doing wrong?  

Before:



After I select the slider and the rotational mate


Comments

  • eric_pestyeric_pesty Member Posts: 1,885 PRO
    The key thing is that the relation mates use always start from the "zero" position of each mate. In order to fix this, you have to edit the mate connector on the worm gear and change it's rotation until the teeth mesh properly with the mate at it's "zero" position.
  • dave_franchinodave_franchino Member Posts: 52 ✭✭
    Eric, I will try this but I'm not certain I understand what a "zero" position is on a slider mate... isn't a slider mate unconstrained in the linear axis by definition?  I've selected two cylindrical surfaces for my slider - are you saying that the origin of the Z-axis on each selected cylinder needs to be identical even though I'm selecting cylinders??  

  • eric_pestyeric_pesty Member Posts: 1,885 PRO
    dave_franchino said:
    Eric, I will try this but I'm not certain I understand what a "zero" position is on a slider mate... isn't a slider mate unconstrained in the linear axis by definition?  I've selected two cylindrical surfaces for my slider - are you saying that the origin of the Z-axis on each selected cylinder needs to be identical even though I'm selecting cylinders??  

    The zero position is when the two mate connectors are coincident (or at the specified offset in the mate). If you select the mate in the feature tree and drag the parts it will show the current "position" in the 3D viewport. It's also what is used when setting "limits" to the mate: setting the max and min to zero will fix the part in the zero position.

    What you need to do is right click on the mate and select "reset", it will return the parts to their zero position, and from here you need to edit the mate connectors so the teeth mesh properly.

  • Ste_WilsonSte_Wilson Member Posts: 342 EDU
    https://forum.onshape.com/discussion/22163/gears-thooth-coliding-on-gear-relation#latest
    This thread might help explain it. I think that it's the same problem
    https://hwh.stephenteacher.com/txtbook.html
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