Wednesday, March 23, 2011

Detailing Frame Generator Weldment Members Individually While Still Maintaining Assembly Features

You have a Weldment Frame Assembly with assembly level features (cuts or holes in the parts made in the assembly rather than the parts themselves) and you want to detail each member of the frame individually and have it show the various assembly level features you've created. The problem is, the features do not exist in the part files. Is there a solution to this?

There are actually a couple of solutions to this. The first one is the proper way to get the results you're after, but it's often overlooked. Even in a standard assembly weldment, many Inventor users overlook this functionality, and I’ve seen others go so far as to say it can’t be done (it can, of course). But when you add a fame generator sub-assembly into the mix,  fewer Inventor users connect the dots to get this all to come together. So I’ll go through the correct process here, but I'll also offer a workaround in case you're reading this after having already started out on a different path.

First off let’s make sure we understand how to detail members of a standard weldment assembly individually so that the preparation cuts and holes created in the assembly can be detailed too.

Here I have a weldment assembly made of two instances of the same block, Block100:

Because these blocks are the same stock part, if I need to create the hole in them I need to do it at the assembly level. If I tried creating this hole at the part level in each instance, I would end up with 2 holes in both instances (as well as all of the instances of this part I used in every other assembly). So this is a bad idea. Another approach is to save off a copy and start making “renditions” of this part (also generally a bad idea if it’s intended to be the same stock part number). 

So, to detail each part individually using the proper technique, I first create the hole as a weldment preparation feature. Then I create a drawing view of the weldment assembly, and go to the Model State tab of the weldment view and choose which member to detail. This is kind of like using a Level of Detail, but it's all set up for you automatically as a function of the weldment tools:

When you choose Block100:1 only that part is included in the view. Here is a drawing of the same weldment assembly file. Each view uses a different model state of the weldment preparations. You'll notice the browser displays which part(s) is shown:

Click to Enlarge
So that's the basics of detailing parts individually from a weldment assembly There is an entire chapter dedicated to Weldments in the Mastering Inventor books (hint, hint). It's because of this added ability to filter for just one part at a time, that I recommend converting Frame Generator sub-assemblies to weldments even if they are not truly going to be welded. Then you can create your assembly features in the Preparations folder and take advantage of the weldment drawing tools. But you have to do this in the Frame Generator sub-assembly NOT the top level assembly. To understand the issue more completely, let's first take a look at the anatomy of a Frame Generator assembly. 

When you created your first frame member you were prompted for a New Frame File Name and a New Skeleton File Name:

Here is a simple Frame browser structure:

CW-0323-01.iam = Top Level Assembly
Frame_Skeleton_CW-0323-01 = The user created part the frame is based on
Sub_CW-0323-01 = The subassembly that Inventor creates with Frame Generator. This is where the frame members reside (Sub_CW-0323-01.iam).
Frame Reference Model = The reference part that Inventor creates with the Frame Generator. This is where the copied reference edges used in the member placement reside (CW-0323-01_Skeleton.ipt)

Here is the same simple frame with assembly features created in the top level assembly (in this case it's been converted to a weldment).

This is not the preferred place to create these features, because we can't detail the individual members with the assembly level cut features if they are placed in the top level. Instead, assembly level features should be created at the frame subassembly level. 

In this next image the frame sub-assembly has been edited, converted to a weldment, and then assembly level features were created. The results are the same as before, but the features reside in the sub-assembly, which is required in order to use the Model State tab in the drawing views correctly.

When the features are created in the sub-assembly, you can simply create a detail drawing of the frame subassembly weldment (not the top level assembly) and then use the Model State tab to set the weldment Preparation option to look at each member of the weldment individually, just as you can do with any weldment assembly. Here is the frame sub-assembly in a drawing:

Here the Model State tab is being used to filter for just one part is to be used in the drawing view:

Here the individual frame member is being detailed, showing the preparation cut on the left. You'll notice the machining features (the circular cut and the chamfer of its edges) are not included, because those features are post weld features and are not part of the piece parts, but instead applied to the weldment as a whole.

That's all there is to it. As long as you convert the frame sub-assembly to a weldment, and then place your assembly features in that sub-assembly (and not the top level assembly), this works fine.

The Work Around
But what if you've already created your features in the top level assembly? 

If you've already created the features at the top level assembly, rather than the frame sub-assembly, you really should just take the time to recreate those features at the right assembly level. But if that would entail a great deal of work, you can use Level Of Details to suppress all of the parts you don't want in a view and then detail it using the Level of Detail in the view. (as with any workaround you might find flaws in it).

To do this first set the selection filter to Select Part Priority, so that you can reach down into the frame sub-assembly and select individual parts:

Next create a new Level of Detail:

 And suppress the parts you don't want to see:

Then suppress the welds if needed:

 Create a drawing view of the top level assembly, and use the Level of Detail:

There you have it. It would be ideal if you could just select the assembly features and demote them into the frame sub-assembly. But currently you can't do that.

As mentioned before, I recommend converting Frame Generator sub-assemblies to weldments even if they are not truly going to be welded. Then you can create your assembly features in the Preparations folder and take advantage of the weldment drawing tools.

Suggested Improvement (hint for Autodesk)

I think that this process could easily be improved by Autodesk if they were to make all Frame Generator sub-assembly files automatically have the same ability to "filter" for a single part file in the drawing view Model State tab, that weldments currently have.

If you'd like to suggest this to Autodesk also  you can use this form:
Feature Request For Inventor