In this guide we deal with Skirt Brim and Raft, we will try to explain what they are and in what situation it is better to use one rather than the other. The advantages and disadvantages of using these 3 techniques Skirt Brim and Raft. Which are very different but which are equally indispensable.
We will go into them one by one, with instructions on how to use, how to set it and how to get rid of it. Lets start with Skirt Brim and Raft!
Skirt Brim and Raft: SKIRT
We can start with the simple Skirt, a contour that surrounds the entire model. It is not in contact and does not affect the press in any way. The purpose of this function is to trigger the filament and make sure that the material comes out at the beginning of the print. If you do not have any particular adhesion problems, this option should always be active.
Observing the skirt materialize on the printing plate you can also realize problems of leveling, following the thickness of this line become thin if too flat and that does not adhere to the plate if there is too much breath.
Setting 2 or 3 lines of skirt will also have the time to some correction in the race and in extreme cases we could stop the press even before its start.
Skirt line number – indicates how many laps of skirts we want to do. Obviously 1 full lap is enough to trigger the filament but if we want to try some correction in race 2 or 3 passages will give us enough information to do so.
Offset Skirt – Indicates at what distance from the model should be deposited the Skirt, preset about 1 centimeter.
Although it is not connected to the model and therefore not a problem for the success of the printing, I would still like to tell you my method to remove the skirt from the plate.
I use a “soft” spatula to which I have sharpened the upper edge. A little pressure is enough and even the most stubborn skirt comes off easily.
Skirt Brim and Raft: BRIM
The Brim is nothing more than a skirt attached to the edges of the model. We use this setting to help the adhesion, when we want to decrease the possibilities of warping and when we are in the presence of a model that touches the plate with little surface. The Brim is a middle ground between the Skirt and the Raft, to be used when additional help is required to the adhesion without entering in extreme cases, for which the Raft is more indicayo. In essence, the Brim increases the size of the amount of the first layer decided, increasing the adhesion and moving away from the model the possibility of warping, which normally affects the edges of the model.
Brim line numbers – The settings of this option are very simple, it is simply a matter of deciding how many lines (or what thickness) to make of Brim. Normally 1 cm of Brim is more than enough for any application, but it can be decreased or increased if necessary.
Brim Esternal/Internal – This option determines whether we want the Brim only outside or also inside, in the case of hollow/empty objects.
The Brim at the end of printing is only one layer attached to the base of the model. It is rather brittle and can be easily removed with a little traction. It can happen that some small pieces remain anchored to the model. Just follow the profile of the model with a cutter and you will no longer have a trace of the Brim!
Skirt Brim and Raft: RAFT
We close our review with the Raft, which is a horizontal grid 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) to promote adherence to the bed. It can also be used to give stability to all those models that have very few parts resting on the plate. It is also particularly recommended to strengthen the supports that are “born” directly from the plate. By building this wide base, combined with the greater plastic-plastic adhesion, we can have the security of a better stability of the model in print. Precisely because of this property of adjuvant adhesion, the Raft must be deposited at lower speeds than the subsequent layers, and possibly at a higher temperature.
The additional material that we will have to compute to finish the model will be little compared to the problems that this option solves us. Let’s say that the raft is a very powerful weapon, and like all weapons of a certain power should be used only when necessary.
Top Layers: The number of layers on which the model will rest, we recommend at least 3/4 layers to ensure a smooth surface.
Base Layers – Number of layers in contact with the plate. These layers are printed lightly and over extruded to ensure a strong bond with the printing plate.
Offset from model – How much larger the raft will be than the model, specifically the value indicates how many millimeters the raft will be protruding from the model.
Separation distance – This is an important setting as it determines how close the raft will be to the model and thus the level of stability and how easily it can be removed. Typically, a space of 0.1 mm can keep the model firmly in place, while still allowing for easy separation once printing is complete.
Raft print speed: as mentioned above, it is advisable to decrease the normal printing speed by a good percentage. Obviously it must be evaluated case by case. If we are using raft to increase the adhesion of a material that detaches from the plate we must decrease the speed by at least half. If, on the contrary, we are using the raft simply to increase the contact points of a model, we are free not to change the speed with respect to normal printing.
If the separation distance setting is properly adjusted or we are in the case of a few points of contact it is likely that the raft will come off with a simple pull. If this is not possible, with all the attention of the case, 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 tin welder and the removal will become very simple.
Obviously the detachment operations, no matter how precisely they are carried out, leave marks on the model, colour variations or small growths.
The model can be sanded with a very fine-grained sandpaper in water. This work, however much it may polish the surface, will lead to a change in the colour of the part concerned, which can be hidden by painting it, or if the natural colour is to be maintained by means of specific smoothing agents.
ABS is smoothed with pure acetone, while PLA requires a special smoother or ipossidic resin.