The 3d FDM printing, so at the disposal of molten material may in some cases, may experience problems of deformation in the prints. With this technology, plastic reels are brought from room temperature to 200/300 degrees in a few seconds and then cooled again in the single possible time. These thermal stresses can lead the model, especially when the dimensions are considerable, not to behave as it should. One thing is that we don’t always see any deformation in our prints. In fact, it is a problem with well-defined variables.
In general, we can say that the deformations that the printed models may undergo have already been specifically treated in the articles concerning delamination and warping.
This article is intended to be a trait-d’union between the two problems that, even if they are distinct, have many of the factors that cause them in common. By dealing with them together we will be able to eliminate them more easily.
Deformation in 3D prints: what are these variables to be taken into account?
In essence, the variables that interest us and to keep in mind when we start a print are the type and quality of the material used to print and the size of the model that we want to create.
If you follow this blog for some time you will be familiar with the materials for the 3d press, all described in this article, and also the various problems that we may encounter. So you probably know that the characteristics of some materials make them more suitable for certain applications and more sensitive to certain conditions.
We can start by saying that no material is immune to it, even if the studies on the materials go towards an increasingly lower thermal expansion. We then move on to a probabilistic percentage of delamination and detachment from the printing surface influenced by:
- Environmental conditions
- Type of material
- Material quality.
That too is a crucial variable. The bigger a model is, the more important the thermal shrinkage forces (as it cools down) will become. Just as the train tracks move a few inches between day and night on summer days, our press will want to move while cooling. Our problem, however, is that 3D printing has no margins. Movements even of an order of less than a millimeter can cause the printing to fail.
We can give up and divide a large print into small pieces, to be joined later. This method is only valid if we then carry out a painting, or in any case a rather high post-production once the model has been glued. So will we only print small objects? No, we’re not giving up!
Here are some small tips to follow to eliminate, or at least contain as much as possible the deformation in 3D prints due to temperature.
Let’s start by saying that we will have to act simultaneously both on the software and hardware side (with small physical devices).
Obviously it will be up to us and our experience to give a proportionate response to the danger of delamination and warping. It will be excessive to insert an important Raft for the printing of a 2×2 cube even if in ABS. Just as it will be too optimistic a simple Brim by half a centimeter on a 20×20 print. Experience is the only good counselor.
Software: Preparing the model
Using the most appropriate print settings for the situation is the crux of the matter.
There are a few simple rules but they must be followed to the letter.
Deformation reduction: Nozzle Temperature
The nozzle temperature, especially when printing a large model, must be kept 10°/20° higher than the recommended temperature. If we are printing a large model before the nozzle passes through the same spot, it will take a long time. This time will allow the extruded plastic to cool down well, whatever the extrusion temperature. Extrusion that is warmer than necessary will help to join the various layers more firmly.
Deformation reduction: Bed Temperature
Also in this case the temperature of the top should be kept as warm as possible, or at least until you notice the phenomena of “Elephant foot”. Normally this phenomenon can be noticed with plates at more than 70° printing PLA and derivatives, and at more than 110° with other materials. A temperature of just over 100° constant could be the trump card.
Deformation reduction: Filling
A good idea, in some ways against intuitive is to minimize the material used. The tensile forces that lead to deformation are the stronger the more material they affect, a less dense model is also easier to “hold in place”. This also applies to walls, of course. But in this case, let’s remember that the walls also retain the structural strength of our model, so they must be proportionate to the size. However, it is always recommended to set walls larger than one millimeter and a multiple value of the size of the nozzle.
Deformation reduction: Brim e Raft
We can use Brim and Raft to help lift the edges of the print. If you want to know everything about it, you can read the article, which describes its properties and how to use them.
However, it is enough to know that if you have evaluated the danger of very low warping (eg. printing PLA with cold plate) you just need to use a brim by half a centimeter, going to increase its width as the danger increases. If the danger warping begins to become high you will have to switch to use the Raft, increasing the offset of the latter up to 3/5 cm for the most desperate cases.
Deformation reduction: Ventilation
All materials sensitive to delamination and warping require the total absence of eddy currents, and therefore also ventilation on the model. This means that the layer fan is completely switched off. Rather, if the print (maybe the final part with some tips: eg ears, crest, spire) is too small to cool from one layer to another then I suggest you set the minimum time on the slicer for layer greater than 20/30 sec. If you think this could ruin the model because of the loss of a little ‘of filament then you can proceed with 2 identical prints and when it is not’ possible then just a tower side by side of the same height.
Now let’s move on to the small manual adjustments and tricks we can take before and after printing to ensure its integrity.
A well leveled surface is the key to good adhesion to the printing plate, but also to the adhesion from floor to floor. When hanging, it can form material accumulations at a given point and insufficient pressure at the opposite point, which leads to detachment between layers. Here you will find a guide to the process of levelling the plate.
Increase adhesion to the bed
This operation is feasible in many different ways. The most common method of increasing adhesion to any printing surface is through the use of an extra strong hairspray. This method is the preferred by most makers because in addition to ensuring excellent adhesion we can remove the old lacquer after printing even through water. The rise of 3D printing has also contributed to the rise of the lacquer Splend’or. Previously used only by grandmothers, now it has become, thanks to its economy and hold, one of the favorite lacquers of the Makers.
A stick adhesive can be used. With these methods I recommend glass above the printing surface. It can be removed and washed in the kitchen, or even in a dishwasher. You can also cover the top with bluetape or Kapton tape. In addition to these and other archaic methods to increase adhesion, the technology can also help us with specially designed platforms. These are: Ultrabase, Buildtak and PEI.
Checking how the surface heats up
It is quite common among 3d printers that there are in the same plane as the hottest spots and others colder. These hot and cold spots can compromise many of your prints before you know it.
The practice to detect them is quite simple, just get an infrared thermometer and build a grid on the plate, to measure the temperature at various points. Maybe repeat the analysis after a few hours to verify the accuracy of your data. You can make a diagram like the following, and once confirmed you can remedy it.
If you don’t want to intervene on the hardware you just need to know the cold spot and you will know that you can’t place corners of the prints in that point or you will be liable to warping. Or you can also decide to raise the temperature by 10 degrees to bring your cold spot to the right temperature.
Transforming the printer into a closed machine
A closed printer that is not moved by air and is able to store the print at a certain temperature is practically essential. And you should think about closing your own if you are printing sensitive material. Even having the micro-particles emitted during printing dammed in a closed place is not bad. This part depends a lot on the size of your printer. If you have a normal 20×20 you will most likely be able to close it with an Ikea Lack, a super cheap table that forms the basis for the closure. To which you can add bulkheads in cardboard, plywood, plexiglass, depending on the budget available. Larger models require more customised solutions.
The closure not only contains the micro particles and also contains the noise, but also helps to maintain a constant temperature between the various layers of the model. It reduces heat loss as you move upwards, which is typical of open printers. If you have just finished printing a large model of ABS with the 100° plate, avoid making it suffer thermal shocks and remove it only one hour after the end of printing. Or at least when you are sure it has cooled down evenly.