So, if you are a user of FDM 3D printing, there is a great chance that you had probably dealt with warping. What most people don’t often say is that warping can also occur with Stereolithography (SLA), Selective Laser Sintering (SLS) or even Digital Light Processing (DLP).
Often described as “material shrinkage”, it is a situation that occurs when there is a great difference of temperature between layers of extruded plastic. When we look at the three other mentioned technologies, SLS has the most potential for warping.
Anyway, when warping occurs, the corners of the print lift and detach from the build plate. So, what are the contributing factors to this situation and how can we address it?
In FDM 3D printing
Most filaments used with FDM 3D printing are thermoplastics. The machine has to heat the filament so that its liquid form has to be extruded on a build plate. During this heating process, the material expands, shrinks, cools down before returning to a solid shape. This process often leads to some movement in extruded plastics which is the root of warping.
We usually hear “makers” highlight this warping issue but this situation can also occur in industrial production. It is not linked to the user profile or the manufacturing purpose. No matter what type of 3D printed part you produce, you might face warping. However, there is a great chance that warping occurs when printing larger parts or parts with a large surface area.
Furthermore, the type of filaments you use can also have its part to play in warping. Materials that require high printing temperature for instance – like ABS – are more likely to cause warping (when shrinking) because of the extreme temperature difference when cooling.
So how do you prevent it?
Amid the number of things, you can do to avoid warping, the first one should be to ensure that your 3D print adheres to the build plate of the 3D printer. If there is no bed adhesion, your print can detach from the build plate – especially at the corners as mentioned earlier. One solution to ensure this adherence consists in applying an adhesive to the glass plate when using a heated build plate. It’s important to check the material manual or guide as adhesion methods vary from one material to another. Also, by using small discs (also called mouse ears) that you 3D print under your model, you can enhance bed adhesion on corners. The discs should be placed in the slicer so that they barely touch each corner of the model.
Furthermore, with a heated build plate, the thermoplastic is kept at a temperature just below the point where it solidifies (the glass transition temperature). This can ensure that the part also stays connected to the build plate. Using the right temperature and controlling it is crucial when one uses a heated build plate, hence the importance of an enclosed print chamber. If your 3D printer does not have a built-in enclosed chamber, you can always adjust cooling fan speed settings or simply keep the temperature of your production environment as ambient as possible (for instance, you can prevent cold air from touching the 3D print by closing windows and doors. Be careful to 3D printer emissions though!).
Moreover, by adjusting your slicer’s settings, it is possible to prevent warping. It’s quite ironic but slowing the print speed can help ensure things run smoothly. The initial layer speed is critical in this case as it helps to hold the print in place on the bed.
In SLS or SLA 3D printing
There are only slight differences between the contributing factors of warping with FDM 3D printing and other technologies. External factors for example, like heat and humidity are also prevalent here. In addition to what has been mentioned above, it’s also recommended to consider weather or shipping conditions. A SLS 3D printed part that is shipped during a hot day of summer for example, can have a risk of warping if it is not well insulated.
As seen above, materials remain the challenge number 1 here. Some materials are more prone to warping than others. The team at Quickparts for instance explains that they use “a composite, high-temperature material (called HST) exclusively for SLS, as it’s easier to build a flat box with HST versus other materials. The presence of glass fibers in this material limits the shrinkage along the X-axis of the part (parallel to the machine’s roller movement) and, thus, helps to reduce the risk of distortion. In addition, the HST material is designed to handle higher temperatures.”
With SLS 3D printing for instance, one way to avoid warping is by printing the parts separately and then assembling them together later. Geometry, size, and design can also be contributing factors to warping. Both flat area (more than 6” – 152.4 mm) and thicker area are at risk of warping. Sometimes, if well handled, part orientation during the build can result in a desired product but it’s often difficult to achieve. Printing several pieces of a part (and then assembly them) is therefore a less risky option to ensure accuracy with respect to geometry.
Warping is definitely irritating but despite these warnings and tips, it’s important to note that the 3D printing experience remains a holistic one – therefore, it can be difficult to tell at 100% what will happen until the part is printed. Sometimes, the only choice you get is to print your part and see by yourself what happens.
Other sources utilized to write this piece include Ultimaker’s support guide. Remember, you can post job opportunities in the AM Industry on 3D ADEPT Media free of charge or look for a job via our job board. Make sure to follow us on our social networks and subscribe to our weekly newsletter : Facebook, Twitter, LinkedIn & Instagram ! If you want to be featured in the next issue of our digital magazine or if you hear a story that needs to be heard, make sure you send it to firstname.lastname@example.org