In 3D printing, keeping your print in one place during the printing process is critically important to the success of the print. If the print moves as the print process are ongoing, then future layers will be printed in the wrong position about the model, or even over thin air, leading to a bird’s nest of messy filament.
To prevent this sort of catastrophic failure, it’s important to ensure that your print adheres properly to the print bed. This adhesion holds the print in place during the print process and weakens once complete, allowing the print to pop off. The weakening is typically caused by the difference in thermal contraction amounts between the print and the heated print bed or by bending a flexible build plate.
Some prints are more stubborn than others, though, and much harder to get to stick to the print bed. Several filament types are particularly prone to warping during the printing process. One of the ways you can increase print adhesion and reduce the chance of warping is to use a raft.
What Is a Raft?
A raft is a disposable sheet of printed filament, typically a few layers thick. It expands the footprint on the build plate, and the actual print is constructed on top of it. By increasing the contact area with the print bed, the adhesion force is noticeably stronger, making the print more likely to stick. Additionally, even if the edges of your raft do warp, it doesn’t matter, as the raft is intended to be removed during post-processing.
For example, many character miniatures have very tiny feet. These would, of course, provide minimal surface area to stick to the build plate. By printing miniatures on top of a raft, they’re much more likely to adhere to the print bed. As an added advantage for miniatures, you don’t need to remove the raft afterward as it helps them to stand. However, in most cases, the raft is designed to be a temporary feature that you can remove during post-processing.
Rafts are a great tool to significantly increase the print contact area, increasing the chance of print bed adhesion. They do, unfortunately, come with a fairly heavy post-processing stage. You have to remove the raft from the print once it’s complete and sand down any artifacts. Most 3D modeling or slicing software suites offer functionality to add a raft to a model. You may, however, want to design a raft by hand for models where you intend to leave it in place.
If you’re struggling with print bed adhesion, a raft may be the answer you need. If you’ve got any tips to do with rafts, feel free to share them down below.