Printing the bottom layer of a 3D printed model as successfully as possible is one of the most vital factors for a printing process with satisfactory results, especially considering that this layer acts as the bridge between the build plate and the rest of the model.
On the other hand, as we can consider the printing process of the first layer to be different than the rest of it to an extent due to the first layer’s connection to the build plate, optimizing the first layer is usually a unique process that requires specific configuration of its own parameters.
Today, our topic will be the issue of the bottom layer becoming stringy on a 3D printed model, which is a problem that prevents the bottom layer from acting as a reliable foundation for the rest of the model.
So, what causes a stringy bottom layer on 3D printed models?
- A print bed that is not level
- A Z-offset value that is higher than optimal
- First layer height value that is higher than optimal
- First layer width value that is lower than optimal
- Clogged hotend
- Wrong filament diameter value
Next up, we will take a deeper look into the factors that can cause a 3D printed model to have a stringy bottom layer and find out how to prevent and fix the issue of stringy bottom layers as efficiently as possible.
What Causes Stringy Bottom (First) Layer on 3D Printed Models?
As the appearance of a stringy bottom layer on a 3D printed model can be a product of many factors, going into each of them will be the best way to find out which particular one is causing the issue in your case.
Print Bed Not Level
A print bed that is not level is the primary culprit behind the appearance of a stringy bottom layer on a 3D printed model.
When the print bed is not level, the inconsistency of the extrusion can cause the first layer to appear stringy on the areas where the distance between the nozzle and the build plate is too great.
Aside from the stringy bottom layer issue, you can observe problems related to bed adhesion, inconsistencies in print lines, clogging of the hotend, and gaps and holes on the first layer due to a print bed that is not level.
Z-Offset Value Too High
Another common culprit behind a stringy bottom layer on a 3D printed model is a too high Z-offset value.
When the Z-offset value is too high, the long distance between the nozzle and the build plate will cause the bottom layer of the 3D printed model to appear stringy due to the extruder printing in the air.
Alongside a stringy bottom layer, a too high Z-offset value can cause weak bed adhesion, as the plastic won’t be able to adhere too firmly to the build plate when the distance between the build plate and the nozzle is too great.
First Layer Height Value Too High
A too high first layer height value creates a similar effect to a Z-offset value that is too high, which could also be the reason behind a stringy bottom layer.
When the first layer height value is too high, the extruder will end up printing in the air, essentially dropping the print lines on the bed. In this case, the lack of pressure can cause the bottom layer to appear stringy.
A first layer height value that is too high will cause similar signs to a too high Z-offset value, with weak bed adhesion being the primary symptom.
First Layer Width Value Too Low
Slightly different than the factors we have talked about earlier, a first layer width that is too low can cause a stringy bottom layer on your 3D printed model.
When the first layer width value is too low, the print lines being way too thin will create a stringy look on the bottom layer as there won’t be enough plastic to create a uniform bottom layer.
Alongside bottom layer stringing, a first layer width value that is too low can also bed adhesion problems and roughness of the first layer.
A physical factor that can cause a stringy bottom layer on a 3D printed model is a clogged hotend, which may be pretty challenging to notice.
When the hotend is clogged, the print lines becoming inconsistent and thin can cause the issue of a stringy bottom layer, as the extruder won’t be able to push the entirety of the filament through the nozzle in this case.
A clogged hotend will also create the common signs of under-extrusion, such as inconsistent print lines, missing parts on the print, weak bed adhesion, and curling of the filament.
Misconfigured Filament Diameter
Last but not least, a misconfigured filament diameter value can be the culprit behind your issue of a stringy bottom layer.
When the filament diameter setting in the slicer is larger than the actual diameter of the filament, the printer will end up under-extruding the filament, causing the bottom layer to become stringy due to the lack of plastic.
You can also observe signs such as poor surface quality, clogging of the extruder, and dimensional inaccuracies on the model if a misconfigured filament diameter is the problem.
How to Fix Stringy Bottom (First) Layer on 3D Printed Models?
As fixing the issue of a stringy bottom layer on a 3D printed model is usually pretty straightforward when you know the reason behind it, the main difficulty is successfully finding the cause.
If you have not been able to find the reason behind what’s causing the issue for you, here is a step-by-step checklist we recommend following in order, which should cover the fixes for most of the common culprits behind this issue:
- Level the print bed. Ensuring that the print bed is level is paramount for a successful printing process. While manually leveling the bed is possible with enough effort and time, we highly recommend investing in an auto bed leveling sensor, such as BLTouch, to eliminate the problem of a build plate that is not level once and for all.
- Decrease the Z-offset value. In an optimal scenario, the distance between the nozzle and the build plate should be large enough to accommodate a piece of paper. We recommend decreasing the Z-offset value until this is the case, eliminating any Z-offset-related problems.
- Reduce the first layer height value. While a slightly higher first layer height value helps strengthen the bed adhesion, a too high value is problematic. We recommend using a number that uses the formula nozzle size * 0.75.
- Increase the first layer width. Slightly increasing the first layer width compared to the rest of the model (such as using a 0.48 mm first layer width for a 0.4mm line width) can become quite handy to print a better bottom layer.
- Clean the hotend to ensure that it’s not clogged. Since it’s not possible to see whether the hotend is clogged or not from the outside, a thorough cleaning now and then is something we highly recommend.
- Re-configure the filament diameter value. Measuring the diameter of your filament with calipers and ensuring that the number matches the value in your slicer settings is paramount to avoid under-extrusion.
We highly recommend running a test print after each step to check whether you have solved the problem or not, which will both save you from having to perform all the steps and give you more insight into what caused the problem.
As there are a fair few factors that can cause the stringy bottom layer issue on a 3D printed model, finding the culprit that is causing the problem can, without a doubt, take a decent amount of effort and time.
To quickly recap, here are some of the factors that can cause a 3D printed model to have a stringy bottom layer:
- The print bed is not level
- Z-offset value is too high
- The first layer height is too high
- The first layer width is too high
- Hotend is clogged
- The filament diameter value is wrong
In most cases, going through all of these factors and ensuring that everything is in order should fix your issue of bottom layer stringing and allow you to print satisfactory first layers once again.
Mike started his 3D printing journey with the Anet A8 when it first came out back in 2017, and has been obsessed with 3D printers ever since. Nowadays, he primarily uses his Ender 3 to print functional parts that make his life more convenient whenever possible.