While it may only seem like a cosmetic problem at first, a stringy bottom layer on the part you’re 3D printing is actually an issue that will most likely lead to the print failing completely, as it effectively means that your 3D printer wasn’t able to print the first layer, which will act as the foundation for the rest of the print, in a correct manner.
In this guide, we will go through the issues that can cause the bottom layer of your 3D-printed parts to turn out stringy and explain how you can fix this problem in the quickest way to get back to printing stringing-free initial layers once more.
Bottom Layer Stringy on 3D Printed Part – Causes & Fixes
As a stringy bottom layer can be the product of a few different possible culprits, ranging from temperature-related problems to a misconfigured Z offset value, it’s vital to rule each of them out one by one to ensure that we can resolve the issue in a clean manner and not have to experience it again.
Misconfigured Nozzle Gap (Z Offset / Z Probe Offset)
Printing with a nozzle gap that’s larger than optimal is the primary culprit that leads to a stringy bottom layer where the plastic does not stick to the build plate at all, as the extended distance between the nozzle and the surface will practically create a scenario where your 3D printer ends up printing in the air, which then turns into a stringy mess.
To find out whether there is an issue regarding the nozzle gap configuration, start by homing the axes of your 3D printer, whether it’s with the LCD controller or a G-code command, bring the printhead close to the center of the surface, and move the Z-axis up until there’s some distance between the nozzle and the build plate.
Next, slide a piece of paper under the nozzle, bring the Z-axis position to 0, and try to slide the piece of paper off the build plate without applying too much force to the paper, which will give you the information you need regarding whether the nozzle gap is correctly adjusted or not.
In the case where the paper slides off the build plate without any pressure from the nozzle at all, we can say that the gap between the build plate and the nozzle is too large, with your 3D printer effectively printing the first layer in the air instead of squishing it to the build surface for it to adhere as intended.
On the other hand, if you are unable to slide the paper off the build plate without the nozzle scratching or ripping it, this is also a problem (albeit a different one), as it indicates that the gap between the nozzle and the build plate is way too narrow for the filament to come out of the nozzle correctly.
To fix this problem, regardless of whether the nozzle gap is too large or too small, start by resetting the Z offset (or Z probe offset) value of your 3D printer to 0, home the axes, bring the Z-axis to a position where there is some distance between the nozzle and the build surface, and slide the paper under the nozzle again if you have removed it earlier.
Next, bring the Z-axis position to 0, try to slide the paper off the build plate, and increase or decrease the Z offset (or probe Z offset) value of your 3D printer based on your observations, with the paper getting stuck between the nozzle and the build surface meaning that an increase is necessary, and it being possible to freely pull the paper without feeling any pressure would require a decrease of the Z offset value.
Finally, keep repeating the process of adjusting the Z offset value and trying to slide the paper off the build plate until you reach a point where it becomes possible to get the paper out without the nozzle damaging it, but not without some pressure that you can feel when attempting to move the paper, as this would practically indicate that the nozzle is close enough to the build surface, but not so close that it leaves no space for the filament to come out.
Printing on Tilted Bed
Another commonly encountered problem that can lead to the bottom layer of your print turning into a stringy mess is the usage of a print bed that’s severely tilted, as this will lead to the distance between the nozzle and the surface becoming larger than optimal for parts of the print, which in turn will end up with your 3D printer extruding the filament in the air.
When it comes to finding out whether the print bed of your 3D printer is tilted, the method we recommend following is to print a bed leveling tester suitable for your 3D printer (such as this one for an Ender 3), and while there are many other techniques you can utilize to achieve the same effect, we have found this one to be the option that is the easiest to apply regardless of experience level while also producing reliable results.
In the case where your 3D printer’s bed is indeed tilted, signified by the fact that parts of the test print on the different corners (and the center) of the build surface look differently than each other, with some showing signs of the nozzle being too high (such as poor bed adhesion and gaps between lines on the first layer), and others showing signs of the nozzle being too low (such as uneven print lines and scarring), correctly leveling the bed will be the first order of business.
That said, considering that the process of leveling the bed will be different for each 3D printer, with some featuring physical knobs under the bed for leveling (such as the Ender 3) and others making it possible to perform the entire leveling process through the LCD controller, our recommendation to ensure that your 3D printer’s bed is correctly level would be to refer to the manual, which should show the exact steps you should take for the process.
Once you level the bed as instructed by the manufacturer, you can re-print the bed leveling tester again, and in the case where the stringiness doesn’t seem to appear on the test print, you can move forward with an actual print, which, hopefully, should be stringing-free this time.
High Initial Layer Print Speed
Provided that there are no issues regarding the distance between the nozzle and the build surface as your 3D printer is putting the first layer down, the usage of an initial layer print speed value that’s way too high comes to mind as a possible culprit behind the stringy bottom layer problem you’re experiencing, as extruding the filament too quickly will prevent the plastic from having enough time to adhere strongly enough to the build plate.
The most straightforward way to find out whether this is the problem is to reduce the initial layer print speed to a safe value where it’s practically impossible to cause a problem, such as 20 mm/s, and run a test print, which will allow you to rule this possibility out in a quick and easy manner.
In the case where the initial layer print speed was indeed the problem, our following recommendation would be to keep testing while increasing the initial print speed value from 20 mm/s in 5 mm/s increments until you reach the point where issues start appearing again, as this process will allow you to push the initial layer print speed as high as possible (and hence reduce print times) without introducing problems.
High Initial Layer Hotend Temperature
Another print setting that can contribute to the occurrence of a stringy bottom layer is the initial layer hotend temperature, where using values that are higher than optimal can lead to the problem you’re experiencing as a result of the filament getting way too melty and oozing out of the nozzle uncontrollably (over-extrusion) as the printhead moves around.
Similar to the initial layer print speed, the quickest way to find out whether the usage of a too-high initial layer hotend temperature is creating the issue in your case is to reduce the temperature value to a safe level where it cannot lead to the stringing issue you’re experiencing (such as 5-10 degrees higher than the lowest recommended temperature for the filament you’re using) and run a test print, as this will allow you to directly see whether this is where the problem resides or not.
In the case where the initial layer hotend temperature was indeed the factor creating the stringy bottom layer issue for you, we can practically say that you won’t have to perform any further optimizations, as you can keep using the initial layer hotend temperature you have used for the initial test provided that it isn’t causing other problems, such as poor bed adhesion due to it being too low, in which case we would recommend increasing it in 5-degree increments and continuing the testing process.
Dirty Print Surface
Last but not least, the usage of a dirty print surface can be the reason behind the first layer stringiness problem you’re experiencing, as printing on a surface contaminated with dust, dirt, and grease will considerably reduce the strength of adhesion between the plastic and the build surface, which in turn will lead to your first layer turning into a stringy mess that comes off the print bed.
As the best way to rule this possibility out is to clean the print surface, start by combining some plain dish soap with warm water as the cleaning agent you will be using, which should work perfectly regardless of the type of build surface you have.
Next, remove the build surface from your 3D printer and wipe it thoroughly with a towel you dipped in the soap-water mixture until you get all the dust, dirt, and residue off the build surface.
Finally, rinse the build surface with water to remove all the soap residue, dry it with a fresh towel, and place it back on your 3D printer while refraining from touching the surface with your bare hands to avoid contaminating it again, which will ensure that your 3D printer is printing on a surface that won’t create any issues in the adhesion department.
Conclusion
As the bottom layer being stringy will, in most cases, mean that your 3D printer won’t be able to build on top of this layer correctly, you will need to cancel your print and resolve the problem you’re experiencing before you can move forward with a print again.
While this particular problem can be a bit tricky to solve, as there are a fair few factors that can contribute to the occurrence of this problem, going through each of the possible culprits should allow you to put everything back into order eventually, at which point the issue will hopefully be a thing of the past.
As a software developer by profession, David has been particularly interested in how 3D printing works even before he picked up his first 3D printer, and completely fell in love with the hobby once he got his hands on a Prusa i3 MK2 for the first time back in 2017. Due to him enjoying both the functional and the non-functional sides of 3D printing equally, you’ll rarely see David’s 3D printer in an idle state.