3D-printable postcards: Because paper is so last millennium (Part I)

I love sending physical post to my friends - postcards from my travels, little greetings to those I don't get to see often - it always cheers people up when they get mail! And because I have a 3D printer, I thought, “could postcards be 3D-printed and would they actually be delivered?” The short answer is: Yes, totally! And my friends love them!

The postcards are designed in PrusaSlicer and, although they're multicolor, they can be printed on a single-extruder printer. My inspiration comes from the Creative uses of PrusaSlicer article. Here you find a description of how to create your own postcards and some interesting postcard ideas.

It arrives! 📫

To prove my point, gaze upon this postcard that I sent to our office! It arrived within days. It works best with the sticker postal stamp, but even the old-timey lickable one sticks to it well. I sent some postcard to my friends in various parts of the country and also to my family in the USA. I'm obviously not going to show you those (data privacy, you know), but it happened.

The idea 💡

The postcard works just like any old paper postcard - there is a field for the address, a field for the message, and there are pictures on the other side. It is created purely in PrusaSlicer, using Text and SVG modifiers.

It is designed to be printed in two or three different colors on any 3D printer - you don't need any multicolor or multi-material properties. The color change will be done manually, by you. Therefore, I'd also limit to a maximum of three colors because more colors means more color changes and it gets annoying.
The color and even the materials are up to you. I would just always stick to keeping the side with the address light colored, so that if the post needs to print something on it, it will be visible.

See for example this “wooden” postcard - printed in Prusament Woodfill Linden Light and Woodfill Chocolate brown:

Of course, you could just edit the design uploaded on Printables (Editable, fully-3D-printed postcard). But I'd like to invite you to read the detailed guide below and get creative!

How-to guide 🪛

The easy way: Edit the postcard.3mf

When you open the file, you find this:

Printer: Prusa MK4S HF0.4 nozzle
3 extruders, all with PLA of different colors
😮

The file is set to having three virtual extruders - meaning three different colors. Everything is set up for you, just change the contents and keep the settings.

Changing the pictures

In the object list (right menu) find the SVG modifiers
Right click → Edit SVG → opens the SVG menu on the left side
In the SVG menu, click on the little triangle under the picture → choose Change file…
Select an SVG from your computer. Adjust size if needed, but leave the Depth at 0.4 mm.

Changing the text
In the object list (right menu) find the text modifiers
Right click → Edit text → opens the Emboss menu on the left side
In the Emboss menu, change the text
Adjust the size and font if needed, but leave the Depth at 0.4 mm.

Slice now! Then, check the layers - it must look like this:

You could change the colors in PrusaSlicer, but in the end, it's up to you, which filament color you load into the printer - you are the multi-material unit here.

How the printing works

When you're happy with the result, send it to your printer. At the points of the color changes, the printer will pause, unload the filament and wait for you to load another one. It will wait infinitely, but it's better to wait around and change the filament right away. The “Sliced Info” tells you the estimated printing time and the number of filament changes.

Mind that this is a bit of a hacky way for multicolor printing - therefore the printer is a little confused.

When you start the print, it will tell you that the loaded material is the wrong type - you can ignore that.
Then, it will do one filament change after printing the purge line - but you want to keep the “paper” color (white).
You start with the “paper” (white), then change the filament in the following order: paper (white) → pictures color (blue) → paper (white) → text color (black) → paper (white)
You can also just use two colors - the printer doesn't care.

The file is prepared for the Prusa MK4S HF0.4 nozzle. If you change the printer, make sure to TRANSFER all the preset changes - and I mean ALL of them.

Why do I emphasize that? Because by default, Slicer does NOT transfer the Custom G-code (as you can see above). But this is the little trick that makes the manual color changes possible! Without it, the printer will print everything in one color. So, make sure to check that checkmark and then you're ready to go.

Neat trick: A secret message

In the same way as described above, you can create a postcard with a hidden secret message! Use the postcard_secret_message.3mf.

On the outside, it looks like an empty postcard:

But, if you look against the light! There is a message for Sherlock Holmes!

The model here is printed using a Vanilla White filament for the hidden text and Pristine White for the postcard body (Prusaments). It is important to use a color that is lighter than the white “paper”. If you choose a color that is too dark, your message will not be hidden at all. In the picture below, the text inside is black, just like the address:

The hidden text is just in the middle layer (important!). Here, it is also important to have it assigned to a different virtual extruder than the address, otherwise the printer will not make a filament change between those two.

If you ever wrote secret messages using lemon juice and a candle, this is basically the same trick, just 3D-printed. Also, Lady Worrington must have been pretty high-tech for the 19th century.

The creative way: Create from scratch

Generally, this is just a few PrusaSlicer tricks combined for a cool result. You are very much invited to use it for your own ideas! Because this article is getting long, I will give you detailed instructions on how to set this up in PrusaSlicer in the follow-up article: 3D-printable postcards: Because paper is so last millennium (Part II)