Daily contact lens holder

Inspiration

My wife recently started using daily contact lenses instead of monthlies. Each contact lens comes in an oddly shaped, sealed package. She wanted to be able to carry a spare pair of contact lenses just in case something happened to at least one of the ones that she was wearing. But, she didn't want the sealed packages to get damaged rattling around in her purse.

So, this is what I had to work with (cat head for scale because I didn't have any bananas):

Design

I grabbed my calipers and between them shutting off because I needed to change the battery, I took some measurements to come up with this highly detailed (?) dimensional drawing:

Using this I proceeded to create my masterpiece in FreeCAD, though after printing my first iteration I discovered that 29mm measurement should really have been 29.5mm, as you can see in the following sketch:

The actual dimensioned shape for the contact case is drawn in the light-blue construction lines, and then the green lines for the actual recess shape are stood off by 0.25mm as the clearance distance. If you want to print this and the recess for the contacts are a little tight because your printer needs more clearance, simply adjust the “PartClearance” parameter in the spreadsheet of the FreeCAD file and the orange dimension should adjust. There are a couple other editable dimensions in the spreadsheet if you want to adjust things like the wall/lid thickness, the recess depth, and the size of the lip for the sliding lid. The blue reference dimensions in this recess sketch are also referenced by other sketches, so edit the red dimensions in this drawing to change the geometry to fit your own daily contact lens packages.

Printing

I've printed this in both PLA and PETG and both plastics work well. I didn't need to use any supports when the base is oriented as in the .3mf (and .gcode). As long as your printer is able to bridge up to at least 18.059mm, you shouldn't need supports either. I did discover, however, that Polyalchemy Elixir doesn't have strong enough z-layer strength as I was able to snap the base into parts fairly easily. The lid does take some effort to fit the first time, but after a couple of cycles it loosens up to slide easily. Time will tell if it slides too easily and needs either a modeled in bump or embedded magnets. I also discovered that Hilbert Curve top layer fill creates a nice “grippy” texture in addition to the shallow recess in the lid around the view holes to help get purchase when opening and closing.

See the pictures for the as-designed look. The holes are to allow you to see inside the box so you can see if there are any contacts, but the hole as designed is a little small to easily see inside (see the 4th picture).

Customizing

The holes in the lid being small is intentional. I was actually planning on using negative volume objects in PrusaSlicer to make custom shaped holes without having to draft them myself. The holes not only provide a base for the shallow chamfer to help grip the lid, but also as alignment targets for what ever negative volume objects one wants to use for the view holes.

My wife likes unicorns, so a little searching and I found a suitable unicorn head shape in this model here on Printables for Unicorn Crocs Charms. I loaded the unicornstl.stl file as a negative volume and scaled down by 50% before putting them over the modeled holes. I also used modifier cubes, scaled and moved to the sides of the base, to add fuzzy skin to help grip the sides of the box. Here is what the settings look like in PrusaSlicer:

Results

After printing in Prusament Galaxy Purple PLA and GreenGate3D Purple Reign rPETG, here are some more pictures. (Not included in the main pictures because the models files won't directly give these results.)

Cat head (and tennis ball) for scale:

And some closeups:

I hope this is useful for others, and enjoy!