In this article you will find how to proceed if you are experiencing stringing/oozing
Note: This is an advanced article. You'll have to tweak a lot of settings in BCN3D Cura, if you don't see some of the settings listed here, update it to it's latest version, go to Settings/Configure settings visibility and click on the "Check all" box.
When 3D printing, it's possible that you have seen your parts with strings at certain points. This is a printing issue that can be solved easily by tweaking the BCN3D Cura Settings or drying the filament.
What is Stringing and why it happens
Stringing, also known as oozing, is easily noticeable, as you'll see fine strings left around on the print, those fine strings look like cobwebs or strands of hair. This normally is due to the filament oozing out from the print head while this is travelling.
As the print head travels across the build volume, some filament may ooze out in small quantities, this will solidify and stick to the printed parts. Normally stringing shouldn't happen, however, it will sometimes happen depending on the filament you are using. PET-G is notorious for stringing, and hygroscopic materials such as TPU or Nylon may have stringing issues if they are not well conditioned.
Note: Before digging into this article, make sure your filaments are dry and in good conditions, check out this article first:
There are many ways to fix this issue, luckily, it's easy to solve. Let's look at all the points that can influence stringing.
How to fix it
Note: Our printers are open filament, this means you can print with whatever filament you like. However, every brand uses different additives on their filaments, this can cause some differences in the printing properties of a certain material. We recommend using BCN3D filaments with our 3D printers. The default BCN3D Cura profiles for BCN3D filaments are tailored by our Lab to deliver the best quality and reliability on your prints.
Enabling retraction is key to solve stringing. Retraction is a feature that is enabled in BCN3D Cura by default. This particular setting will make the extruder motor pull the filament back before any movement, preventing it to ooze while the head is travelling. If you still experiencing stringing issues with the retraction enabled you'll need to tweak the retraction settings. These are located at the Custom configuration mode, in the Material menu.
1. Retraction Distance: It is the setting that most affects the printing quality, it is the distance which the filament is pulled back. If you increase it's value, it will reduce stringing, but if you increase it too much, your print will have gaps on its walls. Try to find the sweet spot by performing printing tests. This model can help you, it is quick to print and doesn't consume much filament: Basic Retraction test by Stefan_Alberts_
2. Retraction speed: The speed in which the filament is pulled out of the nozzle also affects on stringing. If it's too slow, the material will have a lot of time to ooze out while retracting, if it's too fast, the extruder motor gears can grind the filament and cause underextrusion to happen. You'll also need to run some tests to find the sweet spot. In PET-G, it is the opposite, you should lower the retraction speed as it is a very viscous filament, and if pulled out quickly, it will make even more stringing.
3. Prime speed: The opposite of retraction is priming. This movement pushes the filament back in the nozzle exit so it can continue extruding. If you lower this speed, the filament will have a more controlled extrusion. If it's too fast, oozing will also occur at the start of the extrusion path, leaving behind a blob of filament.
Set the right temperature
As the temperature increases, the filament becomes more viscous and runny, which means it will be easier for it to ooze and cause stringing even after tweaking the retraction settings. A lower temperature will leave less room for stringing, however, if you set it too low, underextrusion will appear.
Once you notice stringing happening, you can decrease the temperature while the printjob is running by going to Settings/Temperatures and lowering the extruder temperature in 5ºC steps until you find it won't string anymore. You can run print tests to find the right temperature for a particular filament. Write it down so you can apply it on your next prints.
The travel speed can also affect stringing, if the print head takes too long to go from one point to the other, stringing will be more likely to happen, as the molten plastic will have more time to ooze. A travel speed of 150mm/s is ideal for most of the filaments.
Keep your hotend clean
Remember to clean the hotend regularly, specially when loading different materials in it. Also clean the nozzle with a brass or copper brush before printing to prevent any residue to stick on your printed part.
Still having issues? Check out our forum community for more solutions.
It's important to keep your printer in good shape to make the most out of it. In this chart you can find a list of the extruder maintenace procedures and how frequently these should be done.
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