Replacement part for model railway wagon

[curious aardvark]

The other thing to remember about 3d printing is that you DO NOT HAVE TO copy the existing part exactly.

I can see a couple of ways you could change the end couplier so that you do not need to use supports.
Any part printed without needing supports will be better than a part where you have to cut and sand/file them away.

As long as the part does the same job - it does not need to be identical.

To do that you do need to see the part in use, but can't envisage why you could not get away with a part that did not need supports.

Also you can make the part in 2 non-support necessary sections and simply glue or clip them together.

I don't think in the last 7 years I have ever designed a part from the ground up that has ever needed supports.
Very occasionally if I am copying an existing and broken thing - there is no way round it. But for the vast majority of things - you should never need supports.

Don't get hung up on feeling you have to replicate an injection moulded part exactly.
You have the luxury of being able to make something new and often, better, to fit your production method. :-)

Also until you have worked out the particular quirks of your printer - you really have no idea what it will do and not do.
I did start designing stuff before i got my first printer.
None of it was practical.
3d printers are amazing machines, but you need to learn the capabilities and limitations before actually designing complex things.

So don't start from : 'I have this thing I need to duplicate exactly.'

Start from: 'I need a part to do this job, what can I actually make and how will my printer cope with my design.'

You coudl well end up with a better designed coupler that you can mass produce and sell to the model railway community :-)