In this guide, I will discuss the 3 fundamental Cura build plate adhesions which are Skirt, Brim, and Raft. I will demonstrate how they work and what are the differences between these three techniques that have distinctive purposes.
We will deepen this discussion by treating them one by one, indicating which use case is the most adequate and how to optimize them to avoid problems.
Cura Skirt adhesion type
We will start with a simple Skirt, which is a contour that surrounds the entire model. Note that the skirt does not come in connection with the model and does not produce a better adhesion in any way. The purpose of this function is to trigger the filament and be sure that the material comes out at the start point of the print. This is more a default option to check if the bed is properly leveled and to extrude some material before it actually starts the print.
By observing the Skirt materializing on the printing plate, you can also inspect leveling problems, check the thickness of this line, when it becomes thick, or if it’s too flattened can result in build plate adhesions problems and bad layers.
By setting 2 or 3 skirt lines we will also have time for some corrections in the race and in extreme cases, we could stop printing before problems start to arise.
Cura Skirt settings
Cura Skirt line number
Indicates how many “turns” of skirt we want to do. Obviously, 1 full turn is enough to trigger the filament but if we want to try some bed leveling correction on the go 2 or 3 turns will give us enough time to do it.
Cura Skirt Distance
Indicates how far from the model the Skirt should be printed, using a bigger value will give a better insight into the overall bed leveling.
Cura Skirt minimum length
You can choose the minimum length of the skirt, if the overall length is not reached with the chosen number of lines, it will continue to extrude.
Cura Brim adhesion type
Brim is nothing but a Skirt attached to the edges of the model. This setting is used to help adhesion and to decrease the chances of warping. It is also useful when we have a model that touches the build plate with a very small print surface to ensure proper adhesion. The brim is a middle ground between Skirt and Raft, it is advised to be used when additional help with print support is required without going into extreme cases. In essence, Brim increases the area of the first layer decreasing the chances of warping and bad adhesion.
Cura Brim settings
Cura Brim width / Brim line count
The settings of this option are very simple, it is simply a matter of deciding how many lines (or what width) the brim should be made of. Normally 1 cm of Brim is more than enough for any application, but it can be decreased or increased if necessary.
Cura Brim Only On Outside
This option determines whether we want the Brim only externally or also internally, in the case of hollow/empty objects.
How to Remove the Brim
At the end of the print, the brim should seem fragile, it is a single layer attached to the base of the model and can be easily removed with a small pull. Some small pieces may remain anchored to the model. Just follow the profile of the model with this tool and you will no longer have a trace of the Brim!
Cura Raft adhesion type
We will close our guide with Raft which is a horizontal network of filaments that will be formed under our model. Basically, the model will rest on this printed part instead of directly on the printing surface. These rafts are mainly used with warping sensitive materials (ABS / Nylon/special bicomponent filaments) to improve adhesion to the bed. It can also be used to give stability to all those models that have small parts printed on the plate and also to strengthen small supports that arise directly from the plate. By building this wide base, combined with the greater plastic-plastic adhesion, we can be sure of better adhesion of the model printed. The raft must be printed at lower speeds than the subsequent layers, and possibly at a higher temperature.
The additional material that we will have to dispose of will be little compared to the problems that this option solves for us.
Cura Raft settings
Raft Top Layers
The number of layers on which the model will rest, at least 3/4 layers are recommended to ensure a smooth surface.
Raft Base Layers
The number of layers in contact with the plate. These layers are printed slowly and slightly over extruded to ensure a strong bond with the printing plate.
Raft extra margin
How much the raft will be larger than the model, specifically the value indicates how many millimeters the raft will protrude from the model.
Raft Air Gap
This is an important setting since it determines how closely the raft will adhere to the model and therefore the level of stability and how easily it can be removed. Typically, a space of 0.2mm manages to keep the model firmly in place, while still allowing for easy separation once printing is complete.
Raft print speed
As previously mentioned, it is recommended to decrease the normal print speed by a good percentage. Obviously, it must be assessed case by case. If we are using a raft to increase the adhesion of a material that detaches from the plate we will have to decrease the speed by at least half. If, on the contrary, we are using raft simply to increase the contact points of a model, we are free not to vary the speed compared to normal printing.
How to Remove raft
If the Raft air gap distance setting is properly regulated or we have a few contact points, the raft is likely to detach with a simple pull. If this is not possible, we can proceed to detach it with a cutter and where possible with shears. The activity of cleaning the model from the raft does not differ much from the removal of the supports. In extreme cases we could help by heating the cutter with a flame, or by connecting a blade to the soldering iron and the removal will become very simple.
This is not advised at all, and I strongly advise to tune the raft air gap until the model separates with just a pull
The most advisable thing is to have a proper build plate and to avoid using build plate adhesion, but in some cases, it is impossible not using any kind of help, in this case, it is important that we optimize our settings properly to avoid damaging our model.
Even with the perfect build plate support, it is impossible to avoid marks on the model, color variations, or small zits.
The model can be sanded with a very fine grain abrasive paper in water. This helps to avoid color changes from the heat. Another alternative is to use a special tool to remove leftover plastic from the supports.
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