Thursday, 2 August 2012

Look No Hands! - Formula Free Positive and Negative Offset

The following video outlines a method for achieving positive and negative offset, using a blank(ish) nested Generic Model family. The offset value of this family, once it is nested, can then be through-linked to a parameter in the host family and under certain conditions, can then control geometry

The first part of the video demonstrates the creation of the blank 'plane' family. Essentially, the steps are follows:

  • Create a new family from the 'Metric Generic Model' template (or its imperial equivalent)
  • Under 'Family Category and Parameter's, ensure only 'Work-Plane Based' is checked
  • In an elevation view, set the reference plane running along the level line to 'Strong Reference'
  • In the plan view, put in two model lines along the reference planes and lock off. Set to 'Not a Reference'. These lines are provided purely for visual reference once the family is nested
  • Under the family parameters, add a new yes/no instance parameter 'Lines Visible'
  • Select the model lines and link their visibilty parameter to this. This will allow visibilty control of the lines once nested
This now completes the 'plane' family.

In order to use this, create a new family and load this in. This can then be placed on any workplane (ie named reference planes and levels) and the offset from workplane controlled from a parameter in the family by linking the two together. 

Above I stated that this is subject to certain conditions. Essentially, you can only control the geometry by locking the sketch work of the solid, not the solid itself. For instance, if you place an extrusion and use the solid's drag handles, as opposed to the sketch line for that edge, it won't work. The same is true for sweeps, you must lock the path sketch line itself, not the solid. The video goes on to demonstrate this behaviour in action.

Hope this helps and enjoy!

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