[MakerSpace] wanted to 3D print an RFID card holder. On one side is a slot for a card and on the other side has recesses for the RFID antenna. They used these to control access to machines and were milling them out using a CNC machine. Since there were no flat surfaces, he had to turn on supports in the slicer, right? No. He does use supports, but not in the way you might imagine.

Inspired by creating cast iron using sand casting, he decided to first 3D print a reusable “core” using PETG. This core will support future prints that use PLA. When printing the actual item, the printer lays down the first few layers and pauses. This allows you to stick the core in and resume the print. After the print completes, you can remove the core, and the results look great, as you can see in the video below.

While the PLA doesn’t stick well to the PETG, it can stick a little, but using a glue coating as a release agent solved that problem. This is one of those ideas that once you see it, it seems obvious, but it probably isn’t something you’ve thought about doing until you see it at least once.

There are a few other tricks in the video. For example, the core is a little larger than necessary, so there is a tab that sticks out. This makes it easy to tape down to the bed and also helps when you try to remove it from the PLA print. The results are great, and it makes us want to revisit our abandoned badge holder project from years ago.

Some people never print flat. Others do very specific support structures at key points. It seems there’s always multiple ways to print the seemingly unprintable.