Every 3D printer user at least once experiences failed or ugly first layers. However, curling can happen due to various reasons, and it’s sometimes hard to solve. The first layer may curl due to uncalibrated machines or temperature-related pressures. This article is a comprehensive guide on solving the 3D print first layer curling issue. Note that some of the suggestions may seem more evident though they should be done with extra caution.
Why does First Layer Curling happen?
When the first strings of molten filament come out of the nozzle and contact the printing surface, it’s exposed to severe temperature differences. In hot environments, materials tend to expand (or contract in a few cases). So, when the solid filament goes into the nozzle, it gets hot and expands.
The hot filament that can be as hot as 250oC depending on its type becomes squished on a heated bed (approx. 90oC). This temperature gradient induces a severe filament contraction on the surface and causes the first layer to curl. This phenomenon may fail the print from the start or show itself after several layers. The temperature difference between the heated bed and the filament is the first cause.
Note that the print bed isn’t the only relatively cold substance contacting with the hot filament. The ambient air usually has a way lower temperature than the filament. Industrial 3D printers have a heating chamber to eliminate these effects, and domestic 3D printers can also benefit from enclosures. Still, open frame ones are exposed to ambient.
Thus, any air draft could improve heat transfer, make a significant temperature gradient, and induce first layer curling. The air draft’s primary source can be an open window, air conditioner, crowded corridor, or the printer’s cooling fans.
Since now, We learned there would be an internal tension that wants to pull the bed’s first layer. Adhesion between filament and print surface or two-layer are the only forces that confront curling. Melted filament usually has more significant interlayer adhesion than the bed. However, there are some ways to improve it.
We can mainly increase filament and print surface adhesion by two methods. The first option is to squish the hot string to the print surface by adjusting the z offset and leveling the bed. Another way is to use proper adhesives or change the print surface. These options will be discussed in the following.
How To Solve The First Layer Curling Issue?
Level The Print Surface
An unleveled bed is the first and most common cause of first layer curling. Imagine a warped print that a 3D printer nozzle is putting filament strings on it. As the nozzle moves, The small gap between the nozzle tip and the bed increases. This way, The filament won’t squish and stick to the surface, so the adhesion won’t be strong enough to resist warping pressures.
In general, every 3D printer uses a different leveling mechanism. Some have four or more knobs under their print surface, which can change one corner’s height. Also, there may be other knobs for adjusting the whole bed’s size at the same time.
On the other hand, various bed-level sensors automatically level the bed and find if it has warped. However, you can always upgrade your 3D printer with a professional bed-level sensor like Bltouch if your 3D printer already hasn’t one. Using the BLtouch is worth it, but doing it manually can be easy.
Manual leveling usually starts with bringing the nozzle to one corner of the print bed. The next step is to adjust the surface’s height to the point that a standard paper can barely pass through the gap. You can use the paper though some people prefer to have their calibration tools like business cards. After finishing one corner, you should go for the remainings and repeat the whole process two or three more times.
Another factor that ensures an even first layer is z-offset. It is the distance between the Z-axis home position and the nozzle’s tip. In theory, this parameter is equal to the gap between the print surface and the hot end. Practical errors like faulty microswitch non perfectly leveled bed and homing probes make it different. Hence the first action to have a good z-offset is to do the leveling correctly. Having a suitable z-offset and a leveled bed is the key to a perfect first layer.
It’s good to know the ability to adjust this parameter can open new doors. By learning the process, you can directly print on top of another object or pause the print and embed something into it. There are mainly two methods for adjusting the z-offset, and learning each one has its unique benefits. You can either use slicers or changing the output G-code.
To change the offset using G-cod, you need first to send the nozzle home. The relative G-code command is “G28 Z0”. After doing so, it’s time to adjust the z-offset, and its code is like “G92 Z0.3”. In this case, the nozzle will start printing 0.3 millimeters lower, so the gap decreases.
Using the z-offset parameter in your slicer is much more comfortable. It’s more than enough when it comes to solving the first layer curling problem. This parameter’s exact location varies from slicer to slicer, but it’s typically easy to find. However, you need to know that this parameter works in the opposite direction of the G-code command. Hence a z-offset value in a slicer increases the gap.
Regulate Nozzle And Heated Bed Temperatures
As we mentioned before, the temperature difference between the hot filament and the print surface makes the first filament layers curl. Thus, decreasing this difference can weaken curling. This is why a heated bed is necessary for 3D printing some exotic plastics. Since the filament is hotter than the bed, you need to increase the heated bed temperature and reduce the nozzle temperature as low as possible.
However, there are some limits on printing temperature, and significant changes can induce new problems. For example, hot filaments naturally have more liquidity and adhesion, so lowering the temperature negatively affects adhesion and increases the chance of nozzle clogging.
In general, the best way to fine-tune the temperatures is to print a test object several times in a wide temperature range. This way, you can find the best value that drastically improves the print quality. The below table is a good testing start point though the best value changes from filament brand to brand. Even two different filament spools from one company may slightly vary in properties.
|Filament Material||Nozzle Temperature (C)||Heated Bed Temperature (C)|
|PLA||190 – 220||70|
|ABS||240 – 270||110|
|PETG||230 – 250||75|
Increasing the heated bed temperature can also reduce the chance of first-layer curling. In theory, the hotter printing surface improves layer adhesion and eliminates temperature gradients. Still, there are some limitations, especially if your 3D printer has a magnetic bed. Increasing the heated bed temperature over 80oC can destroy magnetic beds and affect their poles.
On the other hand, 3D printers have limited power for heating the surface. It usually takes much longer to reach higher temperatures.
In conclusion, It would be best to heat the surface as long as it doesn’t damage the 3D printer. After setting the temperature, it takes around five minutes to reach the setpoint. The temperature profile also becomes more even.
Turn Off Cooling Fans
Cold air flows over the hot string of filament can strengthen temperature difference and thermal pressures inside the plastic. Cooling fans are mainly used to eliminate low surface quality and avoid stringing. Simultaneously, they create unwanted airflows, so it’s highly recommended to turn off cooling fans for the first layers. The exact way to tune the cooling fan operation varies between slicers though it’s a simple task.
Clean 3D printer’s bed
It’s a good habit to clean the 3D printer’s bed once in a while. Because each time you use it, some filament leftovers will remain on the surface. Even a thin layer of dust or dirt can drastically reduce filament adhesion.
There are various cleaners and alcohols available in the market which you can choose for cleaning the surface. For example, using isopropyl alcohol with a piece of soft cloth can be used after each print.
Still, it’s necessary to monthly remove the print surface from your 3D printer and wash it with soap and warm water. This way, it becomes immaculate. After cleaning, please don’t touch it while you’re inserting it back.
Most 3D printer users try different adhesives for their projects. While there are so many products on the market and each one promises the best results, some options are more common among the community.
Blue painter and Kapton are two beginner-friendly options. To use them, you need to put an even layer on your print surface. You can also set a thin layer of glue stick on the top to increase adhesion.
Another option is to use hairspay on the bed directly. While this method is sufficient most of the time, it should be cleaned after each print. Of course, there are other commercials like nano polymers and PVA glue sticks which you can choose.
If the first layer curling at first doesn’t show itself, but as the print goes on, it becomes an issue, this section can be handy for you.
The geometry of the print can change adhesion and filament’s temperature profile. For example, adding a brim gives the model a wider bottom area to grip much better to the surface. A Brim is one or more extra layers of the model’s outlines, as shown in the picture below.
Another option is to add a raft. This way, your model’s base becomes bigger, and the brim creates a bigger grip for the 3D printed object. A raft is separate from the printed item, and you can quickly chop off the print from it.
Another creative way is to add thin discs in your design’s foundation called mouse ears. They are small discs with a few millimeters height that you can put under the model and enhance adhesion under corners. You can put them everywhere though it’s more common to use mouse ears on sharp corners, where warpage is maximum.
Removing mouse ears from the print bed is easy. After removing your print from the surface, you can break and remove the discs by hand. You can also use a small torch to erase its effects on the corners so that the quality won’t drop.
If you’re using an STL print from others, you can import the model to a free CAD program like TinkerCAD then add some ear mouses to the base object.
Maybe you’re doing everything you can, but the first layers still curl. In this case, it’s time to check for open windows, AC units, etc.
Use An Enclosure
Imagine a 3D printer starts to print the first layer. In this stage, the hot and melted filament is first in contact with the hot end, then spread on the heated bed. The first layers will keep their temperature around the temperature of the heated bed until the process finishes. However, this situation changes a little for the second and upper layers.
As the nozzle goes up, the upper layers go away from the heated bed. Now, a hot nozzle is the source of heat for the layers. So they are cooler than the first layers and the highest layers. This situation can create temperature contours causing internal stress and tensions. Internal pressure is the number one cause of warps and even cracks between the first layers.
Materials like ABS and Nylon with higher printing temperatures have more tendency to induce internal stresses. Fortunately, there are some ways to reduce the first-layer warpage. As mentioned above, you can use strong adhesives to make them stick and Increase the heated bed temperatures to eliminate warpage at some levels.
On the other hand, An enclosure can also reduce warpage. It can keep the object warm by saving the generated heat in the chamber and avoid air drafts. Hence, using it while printing can improve the overall quality by reducing base warpage. Enclosure even becomes a necessity for big objects with thick parts.
You can either Buy an enclosure or create one.
A 3D printer can be as simple as cardboard or a box, but you should consider some tips while creating one. The primary purpose of an enclosure is to make the temperature around the heated bed more homogeneous. Other factors like safety, accessibility, dust protection, aesthetics, cost, reducing toxic fumes, and noise reduction may be your secondary concerns.
Putting the whole components of the 3d printer may cause excess heat to the mainboard and electronic components. Hence, it would be best to separate these parts if you can rewire them.
High temperature can degrade PLA filament or the printed part, so it’s a good idea to make a vent or window for the enclosure. You can seal it while using ABS.
FDM 3d printers use hot nozzles and heating elements. It can cause a fire if left in a room. An enclosure made of non-flammable materials (for example, metal and glass) can eliminate this issue. In contrast, plastics and cartons can be the fuel of the fire.