solidworks add relation tutorial for begineers

When you are sketching in solidworks your sketch objects are in one the following states:

  • Under defined (blue objects) : needs to get fixed in its position
  • Fully defined (black objects): good job. Everything is ok
  • Over defined (yellow objects): you did more than necessary. Remove some relations

When you start the drawing of an object it is under defined (blue) certainly then you can make it a fully defined object (black)using:

  • Dimensions
  • Add relation

But if you apply unnecessary relations then they conflict with each other and the object becomes over defined. In order to have an accurate sketch all of the sketch objects must be in fully defined state (a complete black sketch). here is an example:

Draw an ellipse like this:

22 solidworks add relation tutorial 1

As you can see the sketch is blue which means it is under defined and we need to fix it. first add theses dimensions. 

22 solidworks add relation tutorial 2

Despite the added dimensions the ellipse is still under defined because it can move freely in the working area. try it yourself. Left click on ellipse and hold the mouse button then drag the sketch around:

22 solidworks add relation tutorial 3

So we need to fix the position of the ellipse. We use “add relation” for this purpose.navigate to the sketch toolbar and click on the tiny triangle under the “display/delete relations” then choose “add relation”. Now add relation window is open on the property manager and we just need to select the objects.

22 solidworks add relation tutorial 4

We want to merge the ellipse center on the origin point so click on the ellipse center and origin point respectively then select “coincident” and finally click ok for applying the relation. 

22 solidworks add relation tutorial 5

The sketch is still under defined. Why? Because the ellipse can rotate around the origin point so it is not fixed yet. We need to add another relation to prevent the rotation of the ellipse so select these two points and apply a vertical relation between them:

22 solidworks add relation tutorial 6

By clicking on the ok button the ellipse becomes black which means it is fully defined now. Now if I add another unnecessary dimension to the sketch then it becomes over defined and it is not good:

22 solidworks add relation tutorial 7

 

 

 

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