Trying to modify a model from a STEP file

[sprior913]

I'm trying a make a minor modification to a 3D printer part which was provided as a STEP file here on github.  The modification is that I want to make the box a bit deeper, say 10mm but keeping the same holes for the screw on lid.  I was able to import the stp file into Fusion and then turn on design history.  My thought was that I'd create a sketch of the front surface and then simply extrude it out 10mm joining it to the existing body, then make the new enlarged side holes I need - sounded easy at the time.

One complication was that the edges of the front surface are rounded as supplied.  I tried to delete the fillet features, but Fusion gave me an error that it couldn't heal them.  So then I thought I'd simply extrude the front face back over the existing piece with a join operation to square them off, but now I'm getting the error displayed in the screen capture.

Attached is a Fusion export of the project with the imported body and the sketch I created.  Can someone tell me how to approach this?  Again all I want to do is to extend the depth of the box out 10mm while keeping the same mounting holes.

[etfrench · Accepted solution]

Here's one way to do it:

Note: You could also create a plane at the bottom edge of the top fillets and use that as the splitting tool.

[TrippyLighting]

Wihil4 @etfrenchS solution is probably  the fastest, when working with imported / dumb geometry turing on the timeline is exactly not the first thing to to.

That component can be completely de-featured in Direct Modeling mode, starting with the small fillet.

[sprior913]

That does look easy, thanks!

[sprior913]

Trippy, I don't understand what the difference between direct modeling mode and the mode with history turned on would be that would allow deleting the fillets in one but not the other.  Is that something you can explain a little?  My thinking was "OK, you've imported this model as a unit, now turn on history so that from now on whatever you do to it can be undone."

[TrippyLighting]

You can simply do some things in Direct Modeling that aren't possible in Timeline Mode.

The link is to a Auodesk Class Recording on Direct Modeling features and is well worth the watching.

[sprior913]

Last night I tried both the split body/extrude technique and watched the video about direct modeling.  I ended up going for the learning experience and defeaturing (a word I learned yesterday) the model which included completely removing the side holes and fillets, then I could do a push/pull for the 10mm and draw slightly enlarged side holes and recreate the fillets.  Then sent my creation to the 3D printer and this is the result - a usable part for that very same 3D printer (I will say that well lit pictures of 3D prints always make them look much worse than they do in person)

Thanks all for your help, I now have some new techniques I hadn't heard about.