This is a redesign/rethink of my previous attempt of an interlocking scrabble tile.
The previous "universal" design, was able to connect on all four sides - but for scrabble you really don't need more than two, all letters have to face the same direction.

Since there are clearly defined male and female connectors, it's easier to connect them - just slide the male under the female and it'll push it upwards and connect.

The downside is that the connection isn't as strong, and you probably can't pick up the whole plate without it crumbling.

Rotating the set still won't be a problem, though, and I think that is worth a lot.

Wanhao i3

Doesn't Matter

No

doesn't much matter :-)

dunno, a bit?

The tiles you see in the picture have been printed with a .6 nozzle and .3 layer height - I suppose a bit lower height might be better for smooth connecting, but so far (testing with 4 tiles) it works fine.

You may have noticed that I re-set this to WIP for a while.
I decided to slightly alter the connectors again.

Now the tip of the male is a tiny bit lower than the lip of the female, so it can be pushed under without having to lift the second tile. It will be pushed upwards later, of course.

Also, I made the male a bit longer, to have more grip on the female sides - that way it doesn't wobble so much.

There are two versions in here - the one with holes is so you can easily drop a fitting plate (15x15mm) on it and don't have to worry about the whole set getting too high.
The one without holes has about 1mm above the holes, so you can either cut down carefully, or simply glue on some letters.

https://tinkercad.com/things/jQrcp8uzYnI

Use this for easy duplicating/manipulating of the tile.