First...Solidworks is not a drafting Software it is a Solid Modeling program. Yes you can add to or subtract from a step part but you do not have the original features to modify. All you have is an imported solid.

Jim

Actually, it's not a silly question. It's a question with a very complex answer.

The STEP file format allows for virtually every, feature, part, assembly and drafting entity to be exported from the source system, depending on the robustness of the source export software and the selections of the operator generating the STEP file.

What you get for import into Solidworks is dependent on that and and the robustness of the importing conversion software, not to mention the selection of options made during the import process.

In a nutshell, you don't "modify the STEP file". You import it into your CAD system and then modify models, drawings, etc. Then, if necessary, you re-export the data to a STEP file.

STEP is nothing more than a convenient standardized CAD file format for transporting data between proprietary CAD systems. There are always some system specific proprietary features that will not transfer at all, as the vendor has not or will not release their specifications to the spec authority.

FWIW, I have imported some very complex 3D models into my Inventor system from STEP files generated from a Solidworks system. It does help, though, when both of us understand the transfer process, as I have also gotten a lot of junk from people who don't have a clue.

It's not a trivial process.

Hooker

Typically STEP files are used to transfer a model from one platform to another (e. g. Solidworks to Fluent, or Pro-E to SolidWorks). The problem that arises is because the original design intent is lost when saving as a STEP file. Sure a feature can be measured in the model space, but the relationships between the features (perpendicularity, parallelism, and distance) are lost in the translation. It basically becomes a 3D picture of your model.

STEP files are used to move a model from one platform into another. You absolutely can modify the file by adding details/features to it, but you are prevented from modifying the existing features that were there when the file was converted into a STEP file.

Here's a really simple example. Say your co-worker sends you a drawing of a 4 inch diameter Schedule 40 pipe with BSP straight threads on both ends that you want to run a fluid flow and stress analysis upon. You have to get the file into a program (unless you have Cosmos Flow Works) like Fluent to mesh the pipe and flow field for the computer to run the stresses and flow analyses, respectively. If you find that the threads should have been tapered pipe threads, or the pipe should have been Sch 80 instead of 40, you are prevented from changing the features of the imported STEP model. It must likely be redrawn. Now if you determine that you want to add a threaded hole (using the Hole Wizard) half way down the pipe, you can do that to the STEP model, but you can not change the imported STEP features.

Hope this helps.

Don

That's why I said "robust" in my previous note.

Inventor has a non-advertised add-on called, I think, "feature finder". It runs during or after file conversions like STEP and IGES. It will automagically find stuff like holes, extrusions, etc, or you can manually pick stuff that you want if you don't need it to try to "featurize" the entire model/assembly.

Works pretty good for an unsupported feature.

Hooker

Lot of Thanks for all replies. They're all truly helpful information !

Once again, Big Thanks to Jim, Hooker and Tucson Don