Sometimes it's hard to get a printed part to stick to the bed, and a raft can be the perfect solution. A raft is a large flat surface that is printed under your part and helps hold it down. Most materials stick better to themselves than to a naked print bed, and when you have small or intricate parts, a raft can help them stay attached when normal bed adhesion just won't cut it.
Here’s how to use a raft:
In MatterControl, the Raft settings can be found in the Settings tab under “Skirt and Raft”:
There are really only 2 settings for a raft – the size and the gap between the raft and the part.
“Distance Around Object” determines the size of the raft.
Here is a 3D visualization of a simple calibration box with no raft:
Here is the same part with a 3mm Raft:
Here's what a 10mm raft would look like:
The other setting for Rafts is the Air Gap. This is the setting that determines how much the part sticks the raft.
The smaller the air gap, the more difficult it is to remove the raft. The larger the gap, the easier it is to remove. Too big of a gap and the part won’t stick well to the raft. Too small of a gap and you won’t be able to remove the raft after printing.
A good starting point is ½ of your nozzle diameter. For example, a printer with a 0.5mm nozzle should probably start with a .25mm Air Gap.
Here is the calibration box printed in PLA with a 3mm raft and a .22mm Air Gap (.4mm nozzle)
With these settings, the raft easily peeled off:
Every filament is a little different with the Air Gap. Generally, materials that have very good interlayer adhesion require a larger air gap in order to easily remove the raft. We recommend printing a few test pieces with different Air Gap settings in order to achieve your desired result. Start at ½ your nozzle diameter, and increase or decrease in .02mm increments.
Using a Raft is an easy and effective way to print parts with lots of small contact points on the bed or parts that require a lot of support material. So the next time you are struggling with getting a print to stick the bed, give Rafts a try.