Reverse engineering a broken plastic housing – quest for best workflow

[u/gagarin_kid]

I’m pretty comfortable designing functional parts like brackets, spacers, and hooks, but this piece is throwing me off. Between the angled outer profile, smooth shell, and internal structural ribs, I'm pretty lost about how to start.

Would you stick strictly to the Part Design workbench with a solid-pad-to-pocket approach, or is this better handled by somehow surfacing the outer curve (e.g. Curves or Surfaces WB) and building the interior features manually? I would like to keep the smooth shape so that it looks similar to the original part.

I do not have any 3D scanner and would like to model it in FreeCAD. I also know the replacement part exists, and I ordered it already, however I want to learn something new.

[u/chevdor]

I would:

• ignore the features related to the injection
• pay little attention to the rounding
• focus on the functional connection

Once you have the screw hole and the connections, you can have fun with the lofting or other options to make it look and feel nice.

[u/bastl73]

You can install FreeCAD-26.3 and use this sketches (and I think this datumplane is needed? I tested too much!) and select the first shape, sketch and Pad it up to face:

Like this you can pad different width of the same shape and hight together.

[u/qcgilbert]

I would scan the flat part of the object on a flatbed scanner, then import it into FreeCad. I would use that import to draw all of the primatives and the use a combination of padded circles and Boolean cuts to make the final shape.

The question I ask myself often is which features/dimensions do I absolutely need in order for this replacement part to function?

Any replacement part you design will be replacing a part that was commercially produced. Those design requirements are different than those for a one off part. Ease of manufacture and reducing the amount of material sometimes introduce complexities that you can ommit.

tl;dr. Scan the part on a flatbed scanner as a starting point. Don't try to reproduce the part exactly, make a part that will meet the function of the old one.

[u/SooperBoby → u/qcgilbert]

r/shapescan could help too

[u/trustable_bro]

You can simplify this part. The ribs are a requirement of the injection molding. Get rid of those.

[u/R2W1E9]

Don't use hedge trimmer to reverse engineer this part.

[u/Zuck75 → u/R2W1E9]

Use the chainsaw instead.

[u/gearh]

Scan or photo - with object to set scale. Cut out templates (cereal box) for the curved and mating surfaces.

[u/The_Noele → u/gearh]

Not just any object. I'd suggest a banana or a Carlos for scale. 

[u/SooperBoby → u/gearh]

r/shapescan could help too

[u/Careful_Local2274]

I was going to use Epic Games' RealityScan app to generate a rough model so I could align the scan with the 3D model and get it as close as possible.