Often it can happen that at the end of the work we find ourselves with real holes in the press, on the walls of the model. This problem can be very annoying because it compromises the aesthetics of printing.
To be able to address this problem first we need to examine the model and determine whether the holes are present on the horizontal or vertical faces.
This small difference leads to completely different solutions.
Holes in the print: vertical face
If we find holes in the vertical faces, we know that they are due to a physical limit of the printer. We have to know and keep in mind that the printer has an interchangeable but fixed nozzle, i.e. it cannot vary the width of the line with a software as it is done for the height.
This means that you need particular care in some cases.
The case par excellence is the construction of a figure with very thin perimeter walls. When determining the parameters on the slicer, we must bear in mind that the line width parameter cannot be modified. So, for example, using a 0.4 mm nozzle, we will have to set the values of the perimeter “walls” to multiples, then 0.8 mm – 1.2 mm – 1.6 mm, etc..
This small step will avoid us problems because the insertion of a parameter in half, for example 1 mm will cause the slicer to create a line of 0.4 mm, 0.2 mm of vacuum and another line of 0.4 mm. In essence it will form 2 faces of 0.4 mm, much more fragile than a single face of 0.8 mm, and if one of the faces has an imperfection or a small lack will be perceived as a real hole.
In the case where for design reasons the contour must have a particular size. According to the example of first 1mm, to get a good result we can also proceed to change the nozzle and install a 0.5 mm one. So as to form our cohesive perimeter of 1mm with 2 passes.
Only it is necessary to remember to communicate the change to the slicer before preparing the model.
Holes in the print: horizontal face
If instead we find holes on the horizontal faces of the model we can behave and implement the remedies already described for pillowing. They are formally two different problems (because the pillowing occurs in the middle of the face of the hole near the perimeter walls or at least near vertical faces) but we are practically dealing with the same problem.
The hole in the horizontal part of the model, near vertical faces, can also be due to a perimeter face that is too thin, to which the horizontal layers cannot cling. Perhaps the most common cause of the presence of holes, however, is the too small size of the totally solid layer of closure, to be sure to close a model well we should make sure to set at least 6 layers of material and using the thickness 0.2 mm, go to 8 for layers of 0.1 mm and at least 10 for the thickness of 0.05 mm. As specified in the article on pillowing.
Fundamental step to eliminate holes: Adjusting the infill
Many times, however, the filling is the only support to which the upper layer of closure can cling. Missing that and not using the small tricks explained in the article on bridges and scaffolding, we can find ourselves with a result not really satisfactory, leaving real holes on a face that we would expect completely smooth.
In order to solve this problem we will have to increase the percentage of infills, or change the plot. Let’s choose the type of filling with the thickest weft. This will provide more support points to the extruded material and will make it easier for the printer to print horizontally.
Filling is generally printed much faster than contours. However, if it is printed too fast. It will not have enough time to bind to the perimeter and will not build a strong enough support net. In this case we can try to reduce the printing speed of the infill, trying to reduce it by at least 20%.
If we do not want or cannot change the shape or parameters of the infill, we can use ventilation.
The ventilation of the freshly extruded filament is essential when the nozzle has to travel great distances without supports. In fact, if the newly extruded filament is well ventilated, it solidifies immediately and remains in the suspended position in which we want it.
If the efforts made do not give the desired effects, only one possible cause remains. The underextrusion!