Thursday, May 26, 2011

Using Isolate Before Creating Assembly Feature Cutouts Saves Time and Effort

When you create assembly level features to make cutouts in stock parts, you often find yourself having to remove participants from the features. Because the components that you are removing from the assembly feature participation are complex, Inventor takes a long time to cut them when the assembly feature is initially created and then takes a long time to calculate when removing them from the feature participation as well. You'd like to know if there's a better way to handle this, so that you don't have to wait on Inventor twice to  cut, and then uncut complex parts that you don't want to cut in the first place.

If you isolate just the component (or components) to be involved in the assembly level cut feature before creating the feature, Inventor will only consider it in the feature participation. This will keep the calculation times short and eliminate the need to remove components from the feature participation that you didn't want to include to start with.

Let's review the standard procedure for creating assembly features first, and then we'll have a look using Isolate to make this more efficient.

Here I have an enclosure modeled with a circuit card inserted into it. The connectors and switch used on the circuit card are currently sticking through and interfering with the top plate of the enclosure. Because I use the same top plate for many enclosures, I stock it as a standard part, with no cutouts included. Then I create cutouts in this stock part as needed for specific designs. I want these cutouts to exist at the assembly level only, so they don't impact my standard top plate, so I use an assembly level feature cutout rather than creating the cutout in the actual part file.

Here you can clearly see the circuit card and switch part files that I want to create cutouts for. Note that the circuit card is really an assembly of many small complex parts, but because it is provided to me as a single part number it is contained as a single part file here.

The first thing I'll do is create a sketch on the top plate. Again, it's important that I do this from the assembly level and not at the part level. So in the assembly, I go to the Model tab and click Create 2D Sketch and then select the face of the top plate.

I'll then use the Project Geometry tool to pull in reference edges of the circuit card connectors and the switch, in order to precisely locate and size my cutouts.

Here the sketch has been completed. Notice where the sketch resides in the assembly browser.

I'll use the Extrude tool to make the cutout feature from the sketch. Recall that assembly level features can only remove material, therefore the Join, Intersect, and New Solid options are not available. 

In this case I'm using the All extents option. Doing so allows me to change the thickness of the top plate later if needed, without having to come back and adjust this extrude feature. Keep in mind that even if I set the extents to a distance equal to the top plate thickness, the circuit card and switch would get cut by that much.

The assembly feature is created as Extrusion 1 and placed in the Assembly browser, as shown. You'll notice there are three participants involved in the Extrusion 1 cut and listed in the browser. It took a bit of time to calculate this cut because the circuit card file (01-0322-06 Rev 1) has a lot of complex geometry.

Here the top plate has been removed so you can see that Extrusion 1 has cut through the circuit card and switch as well as the top plate.

To remedy this, I'll select the parts I don't want to be included in the cutout feature and then right-click and choose Remove Participants, as shown:

This removes the other files from the assembly level feature so that only the top plate is being cut. Removing the participants takes a while to calculate again because of the complex geometry involved in the circuit card model. But in the end I get the result I'm after: cutouts in the top plate, that only exist in the assembly file.

A better way, using the Isolate option

So let's look at a better way. I'll step back in time to the point at which I'd just finished creating my sketch at the assembly level. So now I'm ready to create the cutout. But this time I will select only the part (or parts) that I want to create the cutout in, and then right-click and choose Isolate. In this case I only want the cutout in the top plate part.

The result of using Isolate is that the visibility setting of all of the parts not selected (in this case, everything but the top plate) is toggled off.
Now I can create the Extrude cut, this time only involving the part I intend to be cut and no other parts.

The browser shows that Extrusion 1 is only cutting the part named 10-0312-12 Rev 1 (the top plate). So there is no need to remove any unwanted participants from this feature, and no need to wait for Inventor to calculate the inclusion of parts I don't intend to cut.

To turn all of the other components back on, I'll simply right-click and choose Undo Isolate. This will toggle the visibility setting of all the components that are off, back on.

One thing to know about using Isolate and Undo Isolate is that if you manually toggle the visibility of a component after you use Isolate, but before you use Undo Isolate, you can upset the Isolate selection set, and will likely have to manually toggle the rest of the components back on. So don't mess with the visibility of components during the use of Isolate.

Once Undo Isolate is used I'm done:

If you happen to forget to include a component in your selection before isolating, and then realize this after the the assembly feature has been created, you can just right-click the feature (Extrusion 1 in this case) and choose Add Participant. Then just click the component to add in the browser and it will be listed under the assembly feature, and any material in that component that intersects the cut feature will be removed.

So don't forget to use Isolate to narrow the scope of your assembly level features.