I first want to be sure that everyone understands what I mean by "Top Down Design". When you have an assembly, containing one or more components, and you need to design a new component that needs to match another component, in some fashion, that is top down design. For example, if I need to design a plate that will bolt to the top of the blue component of my assembly, I do not want to have to measure the hole spacing for the tapped holes, I want to design in directly on top of the component and graphically pick up the hole centers.
In my last article I showed you two methods of creating an assembly by either using "Linked" or "Contained" components. In this article I want to show you how to design this top plate in both environments. With either method, the top plate will be "adaptive" which means if the hole locations, in the blue component, move the tapped holes in the top plate will automatically update their position to match. Of course at any time you can break this "adaptive" link and the hole locations in the top plate will become static.
My first video will be of the top down design of the top plate in a "Contained" assembly. If you did not read the previous article, this is an assembly which contains all of the components internally.
My second video will be of the top down design of the same plate in a "Linked" assembly. If you did not read the previous article, this is an assembly which contains components that are only linked, as separate component files, to the assembly.
If you watched both methods you have probably noticed that creation of a top down design component is easiest in a "Contained" assembly but if the link needs to be broken, the process is a lot harder than in a "Linked" assembly.
You also have the ability to created a top down designed "Contained" component in a "Linked" assembly and visa versa if you would like but don't get yourself too confused.
There are two basic methods of creating an assembly. You can model each component separately and then use the "Insert into Current Design" command to create your assembly with "linked" components or you can create your "contained" components directly in the assembly file. I want to compare each method and allow you to make your own decision. In order to refer to each method quickly, I will refer to the one method as "Linked" and the other "Contained".
Linked
In this method you create all components separately as individual files and then using the data panel "Insert into Current Design", or you can left-click drag, the component into the assembly.
Using this method creates a link to the external file which has two distinct advantages. First, the component can be used in an number of assemblies simply by repeating the above steps. Second, if the component is changed, it will semi-automatically update in all the assemblies that it has been linked to. This process occurs after the changes to the component have been saved and the assembly, in which it is linked is opened. The reason I say semi-automatic is because you must click the "Out of Date" icon in the assembly.
The link to the component file can always be broken by either right-clicking on the component in the timeline or the browser and selecting "Break Link" from the context menu. This does not alter the component or assembly placement, only breaks the update link to the master component.
Contained
Using this method all the components are created inside the assembly. The assembly is normally the active component but if one of the included components needs to be edited, it is first assign the active status by left clicking on the small circle at the end of the component or assembly name in the browser . Once it is active, a dot appears in the circle as indicated by the red arrow.
This action directs all editing functions to the active component and the timeline will change to reflect all the past editing done to the component.
If the component needs to be shared with another assembly, it can easily be copied in the original assembly and then using the "Paste New" command be placed into a new assembly. It is very important to remember that this is only a copy and WILL NOT update when the original component is edited.
Now you know the two methods of adding components to an assembly, which one is right for your design. Some will say keeping all components in separate files and linking them to the assembly is too much work but others will say this is the most efficient way to use components in multiple designs. I want to say I am biased because of my many years of working with Autodesk Inventor which is based on the linked components method.
By the way, top down design is easily done using either method, especially since the new "Insert Derive" command has been introduced. I will try and cover this topic in a future article. Both methods work as well with associated drawings so that should not be a determining factor. So the choice is yours or maybe you will decide to use a little of both methods in your next assembly, this has some unique advantages also and both methods work well together, just keep them straight!
