Following on from the previous post on how to dimension a sketch we can look into sketch relations. These are also used to define sketches in SolidWorks, and although are not always necessary as everything could be done using dimensions alone, they do help simplify the sketch. There are a couple of main relations that you will likely use as you start working with SolidWorks, these include:
- Horizontal – Fixes the particular line to be on the horizontal axis
- Vertical – Fixes the particular line to be on the vertical axis
- Colinear – Two lines are on the same axis
- Parallel – Two lines are parallel to each other
- Perpendicular – Two lines are at 90 degrees to each other.
- Equal – The length of selected lines are equal
During normal sketching SolidWorks will automatically define some relations which are obvious, this just makes it slightly easier to sketch without having to define every single thing. An example of this would be the rectangle in the Previous Post where the vertical and horizontal relations were done automatically. If this was not done you would need to define each of the angles of the rectangle with reference to a specific point. These relations can be seen in the image as the small green boxes with a black symbol representing the type of relation.
The same sketch could be simplified by reducing the number of dimensions and increasing the number of relations. This can be seen below.
As you can see, the two positioning dimensions have been removed and replaced with a vertical and horizontal relation. These new relations specify that the middle of each line is vertical/horizontal with the origin point. This does the same thing and also allow the sketch to be even more flexible as if either length is changed the rectangle will remain centred about the origin point. This can be done with dimensions, however, will require the use of equations which we will cover at a later date.
To create a relation all you need to do is click on a particular line, this will bring up a toolbar with all of the available relation which can be applied to this line. If you are selecting multiple lines, for instance two lines you wish to be parallel, you simply select them both whilst holding the control (Ctrl) button on your keyboard. Once again a toolbar will appear with the available relations.
With that we have covered most of the fundamentals of sketching in SolidWorks, you should now feel confident enough to create a fully defined sketch. Next up we will look at manipulating the sketch to do more complex shapes and designs.