One of the most useful options of slicer programs is the automatic creation of supports, where you need it, without any specifications.
By setting the pattern, the filling percentage, the distance from the model for all the axes (even if the fundamental is Z) the program will create for us a support base for the suspended points of the model. In some slicers we can also indicate if we want these supports only inside, only outside or in the whole area of the model.
It’s not all gold that glitters, the settings of the supports are not easy to adjust and can ruin the surface of the model itself that they support.
Supports: Here are some settings tricks
First of all, having a double extruder at your disposal, you could think of printing in 2 different materials, one for the object and one, more easily soluble, for the supports.
There are many cases, in fact we can use ABS for the object and HIPS for the supports. HIPS, acronym for High Impact PolyStyrene (more commonly polystyrene) is soluble in Limonene, an acid that comes from lemons. However, under current legislation, Limonene, once it ceases to be a resource and becomes a waste, is classified as hazardous waste and must be disposed of in special collection centres at the cost of being identified and fined as polluters. It is a hydrocarbon for which it is highly flammable and can cause skin reactions. As far as we are concerned, we do not recommend the use of HIPS as a soluble material for the amateur press, we consider it too dangerous to use and keep for an amateur.
Another way, also not without doubts, is to print the object with ABS and the supports with PLA.
PLA as known dissolves in caustic soda brought to about 80 °, but if leaving the nozzle to soak for a night or bring it to a boil to eliminate the residues of PLA from the nozzle, which is very small may involve a few decilitres of caustic soda, the same process applied to a large print and involving many liters of caustic soda may make the process dangerous, especially if it is performed in a domestic environment with all the problems and uncertainties related to it. As a positive note we can indicate that caustic soda has always been used as a pipe stura-tubature so if we use the PLA as a meltable support we will avoid clogging in the household drains.
Best material for supports
Surely instead of playing the little chemist we recommend, if we want to print the media with a soluble material, the PVA (Polyvinyl Alcohol).
Even if it is not as cheap as HIPS or PLA, PVA (sold at 40 $/Kg) is soluble in water! Simply fill a bowl of water to remove the substrates effortlessly. Being soluble in water it is very hygroscopic, absorbs all atmospheric moisture, so it has a short life and should be stored in dry places.
Supports: The perfect setting
If we don’t have a double extruder, we’ll have to work on finding the perfect adjustment of the supports.
We can start by saying that the best possible support is the one that doesn’t exist.
As an indication, you should follow the 55° rule. Up to this angle from the platter there is no need for supports and the plastic supports itself. Then we can use a little trick to increase our chances! Reduce the height of the layers. A thinner layer means multiple layers forming the same object. So a more gradual ascent can ensure the seal even with more overhang.
As an indication we can say that if a layer 0,2 mm can be printed without supports up to 45°, with layer 0,1mm we can push ourselves to 65° and using the very thin 0,05mm we can dare even 80°. These values are valid for ABS, obviously in the case of PLA if all this is assisted by a fan on a plate at maximum speed we can consider 5 ° more.
Now let’s get to the heart of the matter: Supports
Just as in the case of Pillowing, already discussed in this article set a plot of support little dense may not support properly the press and leave holes in the face that must be supported. It is always recommended to use media infill values higher than 30%/40%, so that the object really has a support.
An equally important step is to determine the number of layers to be left between media and model: normally 1/2 layers are sufficient, provide good support together with the ability to be easily removed. Not leaving a gap would create a too strong link between supports and object and the separation would become a difficult task.
Unfortunately, beyond the distance and the composition, the supports still leave the sign of their presence. To free us from them, we must proceed with sanding, by hand with sandpaper, or with sanders, or with Dremel, or the like.
The importance of experience
Then there are some characteristics of the supports that we will have to verify and adjust. More than with specific data with experience and common sense, one of them is the relationship between base and height. A support with a very small base and very high is very likely to collapse with the movement of the plate before supporting the model. It will be advisable to increase the base with the slicer program, and where it is not possible to replace the slicer that you are using. (There are a lot of slicers on the market, even free of charge, you can find in the appropriate section a review of the main ones and the links where to download them, knowing how to use 2/3 slicers according to your needs can be a good idea)
In some cases, where we are facing specific problems and the work of the slicer does not satisfy us, we can build our own supports. Through a 3D drawing program (here you can find the reviews of the most famous and the links where to download them) and just erect geometric figures, based on the needs of parallelepipeds, cylinders or cones, and go to support the points that in our opinion deserve special attention.