These .STL files are solid 3D objects. To make the trays you must use "spiralize" setting in Cura or "Vase mode" in other slicers.
These are very thin, easily breakable trays useful for lots of stuff. They take awhile to make but use very little material.
When my printer is not otherwise busy I will make another one of these. I use them on my shelves to sort & store all my 3D printed stuff & to keep a few memorable failures. I may not be very good at this stuff but my printer has been very busy since I got it in Feb 2018. I also use them to sort small parts for assembly, etc. I even use them for non-3D print related stuff!
All of mine are done with .2mm layers. 3 layers on the bottom for a .6mm bottom.
Maybe it would be fine at .3mm layers? I don't know. Probably. I found something that works for me & I'm sticking to it.
I use a .4mm nozzle. If I ever get a larger size maybe they would be more durable with thicker walls?
They are stackable.
You can easily scale up the Z to make a taller/deeper tray
more ADDED 1-8-19
Spiralize square tray 140x140x30
Spiralize square tray 140x60x20
Spiralize square tray 140x60x40
Spiralize flower tray 140x140x30
an early spiralize experiment made with Tinkercad "flower" shape. 15 flowers stacked & grouped into one object. not so useful for storage but still kinda neat.
more ADDED 1-13-19
Spiralize square tray 175x40x40 vcut edge
Spiralize square tray 175x40x30 vcut edge
Spiralize square tray 175x40x20 vcut edge
these are turned at a 45 degree angle to fit on my 140x140 build plate
4-8-19 added by request
Spiralize square tray 200x40x20 vcut edge
for taller trays just scale the Z
i hope it works. this is too big for my printer.
They also work great in TPU
but you must turn off the fan after printing the bottom or the wind from the fan will cause the thin wall to move around while printing, resulting in a bad print.
.8mm bottom (4 layers)