You Must Adapt...

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  You Must Adapt...
  August 20, 2008, 02:43 PM Jay Tedeschi

  Adaptivity is one of the pieces of core Inventor functionality that sets it apart from almost every other design system sold today, however it is also one of the least understood. Today I want to show you a little exercise in adaptivity, and in the process show you a perfect example of where it is best employed… for part level geometry changes based on assembly relationships. Consider the following example… a microphone attenuator.

  

  I want to get a really tight fit between this and the microphone that it encloses, ideally a bit of an interference fit. So I am going to start by sketching the ID of the barrel and then adding a dimension to control it.

  

  Once the dimension is added I need to highlight it and change it to a Driven Dimension. This has a couple of purposes, not the least of which is the ability to create documentation as early in the design process as possible. This driven dimension is also required for adaptive changes to the sketch diameter, which a fixed dimension would prevent. Once the extruded cylindrical feature is defined, I need to edit the properties for the extrusion.

  

  Under the adaptive category I need only select “Sketch” as this is the only property of this feature that I will need to change adaptively. If I planned on changing both the extruded distance as well as the sketched diameter I would need to select “Parameters” here as well. For wholesale adaptivity changes I don’t really need to use the properties dialog box, I can simply select the feature from the browser, right click and set adaptivity.

  Now I am going to move over to the assembly and add the Attenuator component I just created. It will need to be constrained to the microphone, which is already grounded. The first thing I have to do to allow for adaptive geometry changes is to flag the part as being adaptive. This may seem counterintuitive, especially after the steps I took when modeling the part, however this one feature is what sets adaptivity apart from pure parametric geometry changes, and ultimately makes it arguably a much more useful tool… it can be turned on and off.

  

  I will select the part from the browser, right click and then select “Adaptive”.   That’s it and now I am ready to size my part.

  

  From the Place Constraint dialog, with a Mate constraint active, I select the inside diameter of the Attenuator… it will initially select the cylindrical axis which is not what I need to change. Pause for a second and allow the “Select Other” indicator to pop up… pick once to cycle through the options and the interior cylindrical face will be highlighted.

  

  I will select this and the exterior cylindrical face of the microphone, and then set the desired offset distance between these two faces to negative .001. This changes the inside diameter of the Attenuator to be one thousandth of an inch smaller than the outside diameter of the microphone, which should give me the interference fit I am looking for.

  

  A brief query with the Interference Detection tool verifies this and we are good to go. Once this geometric relationship is established, adaptivity can be toggled on and off via the assembly browser. 
  This type of modification is exactly what adaptivity was initially envisioned for, and is significantly more straightforward than any other method of assembly level, relational geometric changes. Try it the next time you are about to use a skeletal part or global parameter file.

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