A lot of 3D printer users have issues with getting the first layer right. The layer does not stick, is uneven, has poor finish or, if they are printing with materials like ABS, then warping fails the print.
All of these problems are quite demotivating but they can be avoided if not eliminated with a simple fix. A 3D printing raft is a horizontal mesh of filament deposited directly on the build platform. Upon this layer, the first layer of the print is deposited. This is a handy way to get the first layer right and also keep the print grounded to the build platform.
Rafts are generally used while working with ABS filament as it has high chances of warping. 3D printing rafts are not only important for avoiding warping but also to increase bed adhesion.
In the above image, the raft can be seen in blue.
Although a raft can be used for many different reasons, the following three are the most important:
Like every technique, a 3D printing raft also has a few pros and cons.
Note: Take precaution while removing the raft as it can cause injuries while dealing with tough rafts.
It’s important to note of any observations when experimenting with slicer settings. Subtle changes in settings, whether increasing or decreasing values, should be done incrementally. This will help you check the progress (or regression) in a gradual way, allowing you to easily fine tune your ideal settings.
These settings are dependent on the 3D printers used, the filament used, the ambient temperature and even the build platform. One setting may not suit all purposes. A trial and error process has to be followed to find the ideal setting.
The separation distance is the height of the space between the raft and the first layer of the print. Or simply the distance between the mating layers of the raft and the model. This is undoubtedly the most important setting for a raft.
A tighter separation distance will make it hard to separate the raft and the model. In the above image, we can see the distance between the raft (blue colored patch) and the first layer of the model.
For starters, try a separation distance equal to half of your nozzle diameter. If you have a nozzle diameter of 0.4 mm, try printing a raft with 0.2 mm of separation distance. The results will help you understand the necessary modifications you need to make to the settings.
According to a number of experienced users, the ideal separation distance is 0.1 mm. If the distance is increased then the print is easier to remove from the raft but the first layer of the print has a poor surface finish
This is the very first layer deposited on the build platform. Therefore it’s recommended that it be kept thick and printed at a slow speed. This will help to achieve greater bed adhesion. You obviously don’t want a raft with poor bed adhesion, so be generous and keep a thick layer. According to a number of experienced users, the ideal raft bottom layer thickness is 3 mm. If the thickness is increased then it gets difficult to separate the raft and the print and it also wastes material.
The top layer of the raft will mate with the first layer of the print. Since this layer will determine the surface finish of the bottom layer of the print it is recommended that you should use at least two to three layers to achieve a smooth surface.
Some slicers have a setting that determines the distance the raft will extend to outside the edges of the print. Keep it slightly outside the print but not too extended.
Rafts are only used in FDM 3D printing. A 3D printing raft has significant power to impact any print, but only with careful control. A regularly failing print can be successfully printed by accurately adjusting the settings.
3D printers with a single extruder will of course 3D print rafts with the same material as the print, but a dual extruder printer can be programmed to 3D print a raft in a different material.
Common support materials like HIPS and PVA, if used for rafts, can be extremely beneficial. For example, printing ABS with HIPS or PLA with PVA is common practice.
HIPS and PVA are soluble in D-limonene and water, respectively. As such, if rafts are printed with these either of these support materials, they can be easily dissolved in the appropriate solution, eliminating the need to remove material. This can also help when working with a tighter separation distance.
License: The text of "3D Printing Raft – When Should You Use It" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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