How can we prevent warping? In this short article, I will explain why warping occurs and how to prevent it. Based on the material used, and the external environment, we can have different warping issues. Warping does not only change the shape of the final object but can lead to prints unsticking from the bed due to the deformation. Obviously, this issue can also derive from an incorrect calibration, for example, an inaccurate bed leveling can trigger some warping or even an incorrect bed temperature.
Why do 3D prints warp
FDM printers usually use thermoplastics as material. PLA, ABS, and PETG change properties with different temperatures. When the material heats and becomes liquid it also expands in volume. This is lead in a quick cooling process, right after the extrusion, which means a fast shrinkage in volume. The print behaves like the sum of the retractions of the individual layers.
How to prevent warping in 3D printing
So practically the effect we observe is nothing more than the sum of the deformation of the various layers which, cooling at different steps, also drag the underlying layers into a contraction movement.
As we already concluded the main problem here is the temperature, or more exactly the difference of temperature. When we use a heated bed we reduce drastically the difference of temperature between the extruded material and the outer environment. This is why when using ABS it is necessary to use a temperature of around 100°C to have a good bed adhesion, the first layers will simply unstick after 10 seconds without proper bed temperature.
Another thing to take into consideration is cooling,. It is recommended to avoid using cooling fans for some materials as they are very susceptible to this phenomenon. This is why by default all slicer software disables cooling for the first layer, to prevent warping and to increase adhesion.
Some materials, like ABS, other than needing a high bed temperature to prevent warping it also requires an enclosed chamber, this way the heat from the bed gets trapped inside the chamber and the print doesn’t wrap on the higher parts. This is the only way to prevent ABS delamination, this phenomenon occurs when we print very fast or when the temperature of the environment is to low causing splits on the printed object.
One last tip is to use the room temperature in your own favor.
Surely, even with the perfect environment, errors can occur, that’s why slicing software have some options that come in help. All slicers can create special structures to deal with warping. The setting is located under the build plate adhesion section. There are three options for this setting: Skirt, Brim, and Raft.
If you want to learn more about Cura build plate Adhesion check my article here!
Build Plate Adhesion to prevent warping
Skirt is the default option in Cura. It is a line around the print on the first layer that only helps trigger the filament in the extruder. This makes it come out before starting the print. So it is not useful for our purpose
The settings that interest us are Brim and Raft.
Brim increases the base of the model. It’s an additional edge of a single layer, which increases the contact area of the model with the build plate and strengthens it. Brim helps to prevent warping in the most exposed parts to this problem, the corners. The positive side is the easy removal once the printing is finished. It doesn’t leave any marks and does its purpose.
Raft is an additional structure that is printed below the model. This is a pretty extreme solution. It is generally used on parts that barely touch the build plate and with materials that suffer warping, it should be used only when it is strictly necessary. It is essentially a thick grid construction between the model and the plate that helps adhesion by printing the model directly on this plastic “raft”, and also reduces uneven heat distribution from the bed to prevent warping. The bad side is that generally, it is hard to find the correct Raft Air Gap which is essentially the distance between the raft and the first layer of the model. If the value is to low this will make the model fuse with the raft, and if the value is too big, it will result in bad adhesion and an ugly first layer. Usually, with a 0.4 nozzle and a layer height of 0.2 mm I use a Raft air Gap distance of 0.2/0.3 mm.
Sometimes the limitation of our machine is not the printing speed but the material we use. Some materials need a slow printing speed to avoid a quick cooling process that can lead to delamination and warping. Generally, when printing big objects it is much easier to have some warping. Even with PLA, that doesn’t really suffer this issue, we see some warping. This problem generally is due to high printing speed. Try using a lower speed and check for changes, I find that the 35mm/s generally works great with every material except TPU where I use 25 mm/s
Thicker first layer
A thicker first layer makes adhesion easier. You can make the first layer thicker by changing the Initial Layer Height setting. This is a setting that can be set in any slicer.
If you have problems with ventilation, you should set a procedure to activate it very gradually. Via the setting called Fan speed adjust at height, which turns on the fan gradually, from 0 for the first level to maximum power at the specific height.
Slower speeds at the first layer contribute to better adhesion. Given the fact that it will cool in more time.
3D printer build plate adhesives
Generally taking care of these parameters will result in no warping and a good build plate adhesion, but with time build plates ruin and the adhesion properties diminish. That’s why generally it is a good reason to use a glass build plate as it lasts for a longer time. To avoid this problem, we can use adhesives to guarantee that the first layers will stick considerably to limit warping.
Hairspray for 3D printing
If you use a glass build plate the best solution is hair spray! Adding a thick layer on the glass and heating it gradually will produce this sticky layer that will help adhesion. Be aware that PETG tends to stick a lot to the glass so avoid using any product.
For ABS the best answer is some ABS juice which is basically ABS dissolved in acetone. Putting a thin layer on the bed and heating it will create a plastic coating that will considerably increase adhesion.
Blue tape and glue stick
Work excellent with every material and it is easy to use and to remove. The preparation takes a long time but it gives the desired effect.
If you want to reduce warping the best thing to do is to optimize the first few layers. Having an excellent bed adhesion in the first layers will guarantee us that there will be no warping. If we encounter delamination, that is a side effect of warping, we have to optimize ambient temperature and printing speed avoiding a quick cooling process.