-
Posted October 16, 2007
Autodesk Inventor provides a powerful means for creating feature-based models. This building block approach works very well until you need to delete or modify a feature that has other features that are dependent upon its existence. When this happens, you will need to eliminate the dependency in such a way that preserves the parametric properties of the model. The good news is that it is fairly simple to restructure the dependencies on most features. This tutorial focuses on proven methods that will retain stability within the model.
Finding dependencies
In the example file, BD-100(ver 9-2008), select Hole1 and attempt to drag it upwards in the model browser tree. You will be unable to do so because Hole1 is dependent upon the existence and placement of Extrusion3. Likewise, Extrusion3 is dependent on the previous feature as well. You will find that every feature within this part is dependent upon the existence of a previous feature. See Figure 1.
Changing dependent relationships
Let's say that you want to change the location of Extrusion3 without altering the location of Hole1. You can do this simply by redefining the inputs for Hole1.
- In the model browser, RMB on Hole1 and select Edit Feature.
- Pick a selection arrow for Reference 1 and select the vertical edge of the Extrusion1 base feature. Then, pick the selection arrow for Reference 2 and pick a horizontal edge on the base feature.
- Change the dimensional values on both newly referenced edges to maintain the same location for the hole. As long as the selected face of Extrusion 3 exists, the start point for the hole will remain the same. See Figure 2.
Creating a new feature relationship
The key to creating a new feature relationship is to retain the parametric properties of the feature being reassigned. In the previous example, Hole1 is still dependent upon the face of Extrusion 3 for its existence. If you were to delete Extrusion 3, the hole feature would be deleted at the same time. If the length of Extrusion 3 is changed, the hole feature will adjust parametrically. If the hole will begin on a newly created face, then move the Hole feature below the new face in the Model browser, and Edit the Hole1 feature again to resect the new face.
References for feature dependencies
This tutorial features only one of the many approaches to creating and editing feature dependencies. By using careful planning when constructing a model, you may avoid many dependency issues. Developing a workflow that reduces the number of edits during construction is your end goal. By basing your dependencies upon origin features, you will be well on your way to improving productivity.
Dennis Jeffrey is an Autodesk Inventor Certified Expert, Autodesk Implementation Certified Expert, and a five-year instructor at Autodesk University. He is the author of Creative Design With Mechanical Desktop and Creative Design With Autodesk Inventor, and a new book is scheduled for Spring 2008. He is releasing an online version of Creative Design With Inventor 2008 later this year.
Comments
-
October 18, 2007 07:03 AM Tim Rumph
When I tried to do this, I could not select the work plane for the Face in the Hole dialog box. In fact, I could not select the work plane for a new hole. Tim
-
October 18, 2007 09:15 AM Johanes Keppler
every thing goes well until i try to pick the plane, I can't link it to the hole feature. What hapened?
-
October 18, 2007 09:33 AM Dennis Jeffrey
You are correct. While I did test this, it does not appear to be repeatable. This document will be corrected.
-
October 18, 2007 10:39 AM Mark Vorobik
-
October 18, 2007 10:42 AM Mark Vorobik
This gave our office its morning laugh. I wish AutoDesk would take a year off and just streamline Inventor, making sure that processes that are intuitively straight forward are bug free. We often find this not to be the case, and is cause for most of our inefficencies.
-
October 24, 2007 06:29 PM Leslie Wolfe
I agree with Mark. Autodesk has some work to do. This example does not behave at all as I would expect. When I change the reference 1 & 2 dimensions to be dependent on extrusion 1, everything works okay. But when I change the face to the back face of extrusion one, the dimensions jump to new values. What are the programmers thinking? I also was unable to select the hole in the graphics window. I had to pick the feature from the tree to edit it. Is there a setting I need to change to make feature selections from the graphics window?
-
November 8, 2007 08:37 AM BRAD MICHELL
I worked on this today and expereinced the same issues as everyone else. I've not received an update to this tutorial nor seen one in the community. Has Dennis updated the tutorial? Where do we find the update?
-
November 12, 2007 08:06 AM Dennis Jeffrey
An expanded, updated tutorial is in the works. Unfortunately, due to time constraints, it will not be available until sometime after AU 2007. In answer to Stephen's question, if the back face is selected as the hole location that dimensions change as the hole flips direction. This is correct, since a model is made up of numerous faces and each face normal points to the outside of the part.
You must be logged in to post a comment.