I’m working on adding a small powered speaker to a fischertechnik model and decided the simplest first pass would be an insert for the standard cassette that many of the older sets shipped with. I’d like to not alter the original part, so ideally, this will be a simple press-fit part which works very similarly to the stock cover. The first goal was to get a simple flat lid working.

While iteratively designing and test fitting, I found that having a version with an empty space in the middle helped in terms of print time and material usage.

I used OpenSCAD and shared the files on Thingiverse in the hopes that this may help others who are tackling similar problems.