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Posted September 15, 2008
Replace Parts Without Losing Constraints!
Designing a product or a machine is an ongoing process of evolution. Components that are present in the opening stages may change or be replaced in the later stages of a project. These changes can be driven by scope changes, sizing requirements, or even aesthetics.
In a machine, components can be assembled in a multitude of ways. Components have relationships with the surrounding parts and assemblies within the design. As parts are replaced during the design process, the relationships between the various components are affected.
Autodesk® Inventor® Assemblies describe component relationships using constraints. These constraints are affected as components are replaced just as the real-world relationships are affected in the physical assembly. New components may be slightly different, or they may be vastly different. In some of these cases, replacing parts results in lost constraints. This forces the designer to recreate them. This paper sets forth to describe a workflow to prevent the loss of these constraints.
The Setup
Imagine that you are working on the design of a large blower assembly. The design of the Blower Assembly, the Motor Mount, the Drive System and the Support Structure are complete. The Output Duct has been mounted in the correct location using constraints. During a design meeting, it is determined that this design would be improved by using a different output duct. The new output duct was designed in conjunction with an earlier project. It has the same mounting interface as the one currently mounted to the new blower. It is your job to replace the output duct.
This replacement can be accomplished very easily without jeopardizing the constraints that are currently in place. Let’s take a look at how this can be done.
1. With your assembly open, the first step is to place the new part. It does not matter where you place it.
2. The next step is to defer updates on the assembly. This setting is found in the Application options. Simply check the Defer Updates setting and click OK.
3. To make things easier to see, switch to Wireframe Display mode
. This will make it possible for you to see through parts while working with constraints.
4. If you expand the part to be replaced in the browser, you gain access to the constraints which locate the part within the assembly.
5. The next step is to edit the constraints one by one, replacing the original part references with similar references on the new part. With the first constraint open for editing, you will be able to determine the location of the constraint and which reference belongs to the part in question. Simply assign this half of the constraint to a similar location on the new part.
6. Continue replacing the constraint references with selections on the new part until there are no constraints left associated with the original part in the browser.
7. The next step is to delete the original part. Performing the delete removes the original part and forces an update of the assembly. The update operation moves the new part into a position that honors the constraints. This completes the replacement.
The Conclusion
Leveraging this workflow permits the replacement of components quickly and easy. Constraints are maintained – even with the most complex components and constraint relationships.
By using this method you will be able to replace complex components without concern for constraints or the need to re-create them. This can save you a great deal of time, allowing you to dedicate your valuable resources to completing you product design.
Comments
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September 17, 2008 05:45 PM carlos lopes
very good tip you for
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September 30, 2008 08:52 AM Kirk Arthur
Maybe I am missing the point. Why not just delete the original component, then place the new component and reassign the constraints? That seems quicker than trying to figure out where the original constraints were assigned.
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September 30, 2008 09:06 AM Richard Sore
Me too. It does seem a lot of work, and much more complicated than just deleting and adding the new part and re- constraining.
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September 30, 2008 09:32 AM Guillaume Massart
It is just to avoid missing a constrain somewhere during the replacement. Could be interesting when the new part is between two other parts (link). For example replace a quick model part by the final assembly
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September 30, 2008 09:32 AM Joan Lipovetz
Good tip. I use this procedure often but I never thought about using Defer Updates to keep the assembly from updating. That will be very helpful. Thanks!
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September 30, 2008 09:34 AM J Harcomb
Just deleting and adding the new part is simple if you have 3 constraints. This method helps if you have numerous constraints and all at set distances not just zero offset. I often replace parts this way if the normal replace fails.
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September 30, 2008 10:42 AM Bill Fane
If this is going to be a regular process, for example if you have a number of different ducts and a number of different blower casings that you mix-and-match, then I would suggest using iMates. Now all you need to do is to replace the existing component with the new one and all the constraints will automatically be carried over.
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September 30, 2008 10:44 AM Dave Hoder
I use this quite a bit but a bit differently: I isolate the components using 'constrained to' selection then use the move tool to move the original part away slightly. I find this easier to determine which constraint is which.
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September 30, 2008 11:18 AM eddie allen
Why not just use replace component? If the shape is basically the same it doesn't even loose the constraints, plus it does it for you. In this case it would have worked perfectly. I use this command all the time.
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October 13, 2008 10:44 AM Richard Porqueddu
This is a useful tip, turning off the defer updates is a great idea, to bad it is so difficult to navate to.
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October 16, 2008 09:16 AM Dave Smith
When replacing components with a large number of constraints, I will load the component into the assembly and start editing constraints. When I have trouble identifying the constraint or the newly loaded component obscures the constraints, I turn off the visibility on the component being replaced. Both parts of a constraint will highlight and I can easily tell which part of the constraints to edit. Watching the newly loaded component move into position is also helpful.
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