What Causes Stringing In 3D Printing?

Stringing, oozing, whiskers, or hairy prints, is an infuriating issue affecting 3D printers. This is caused by plastic coming out of the nozzle at the wrong moment, creating untidy 3D prints that can ruin the overall appearance of the model.

Stringing happens when threads are left on the printed model and can be prevented by altering printer settings

But what causes stringing and how can it be avoided? We have put together this quick guide to help keep 3D printing projects ship shape and shiny.

What Is Stringing?

Stringing is the name given to the small threads of printing material that are left when the project has finished printing. They can be very fine and can make your final project look hairy.

Stringing is caused by plastic dripping out of the printer nozzle when it is moving to another place on the project.

This means that strands of plastic will be falling out of the nozzle when it is not meant to, creating an unwanted fibrous texture to the model and potentially ruining the finish.

There are, however, some fairly basic precautions that can be taken to help prevent stringing. Hopefully, this will guarantee your projects are hair-free!

Precautions Against Stringing

Speed of retraction: If the nozzle is moving too quickly, otherwise known as a quick retraction speed, the filament can separate from the hot plastic inside the printer nozzle and drip out the end which creates the stringy appearance.

If, however, the retraction speed is too slow, the plastic can ooze out of the tip of the nozzle when it is moving to its next printing location.

To prevent stringing, all you need to do is find the perfect speed for your printing medium. This is usually between 1200-6000 mm per minute. Fortunately, most printers will come with some printing settings for some printing materials that are pre-configured.

This means that you just select the correct options and go – no need to fiddle around yourself. You can of course experiment to find what works best for your preferences, but these set modalities are a great benchmark to find the best results.

Distance Of Retraction

This is possibly the most important setting for a 3D printer as it controls how much plastic is pushed out of the end of the nozzle.

As a general rule, the greater the volume of plastic that is retracted from the printer nozzle, the less chance there is of premature dripping. It is this premature dripping that needs to be avoided to get a string-free finish on your project.

To achieve this, try increasing the distance by 1mm at a time and trying to print something again. Hopefully, the printer will produce better results with the increased distance. Most 3D printers have a retraction distance somewhere between 0.5mm to over 2.0mm so there are some wide margins for success.

Speed of movement

Simply put, the slower your nozzle moves, the more chance it has to drip unwanted plastic. By increasing the speed at which the nozzle moves, you will limit the time available for drips to form in the retractor which will reduce the stringing effect.

Most 3D printers will have a ‘speed’ setting that you can view to make sure you are using the best options for the printing medium. Speed is usually displayed as an X/Y Axis Movement unit, representing the speed that the nozzle travels from one side to the other.

Try increasing the speed to limit stringing, but exercise caution. Only increase the speed to a tempo that your machine will be able to tolerate.

Moving over open spaces: If possible, limit the duration of movements that the nozzle makes as it is printing. Short motions often do not allow enough time for the plastic to leak out, which will prevent stringing.

What is stringing

Newer 3D printers come with software that can adjust printing routes so they are the most efficient. This tends to result in the nozzle not traveling a great distance over open areas of the printed design, building up from already printed areas without crossing over the outline to open sections as much as possible.

This alone is often enough to stop stringing as there is nowhere for the strings to develop because the printer is always pushing plastic out of the nozzle.

Temperature: Perhaps the most obvious issue that can cause stringing is a temperature that is too high for the printing medium to work properly.

If the temperature is too high, the plastic will melt too much, becoming excessively viscous, and is able to leak out easily. If this is the issue, decrease the temperature settings a little and try again.

Be sure not to turn down the temperature too much as this will mean the plastic does not melt enough, meaning it will remain a little too solid to be easily pushed out of the nozzle. This is likely to strain your machine.

With this in mind, try reducing the temperature in 5-10°C increments – most printers available use Celsius as a unit for temperature but if yours uses Fahrenheit, aim to change the temperature by 5-7%.

This temperature difference is enough to cool the plastic enough so it stops dripping, but not too much that it will affect the printer’s performance.

Printing Material

Some printing plastics are more flexible than others, and are therefore prone to more stringing. Opt for printing materials that are as inflexible as possible, but not so rigid that they are brittle and impossible to move.

How Do I Stop 3D Printer Stringing?

Stringing is the term used to describe the hairs or fibers that are on your finished printing project. They are caused by drips of melted plastic from the nozzle being dragged through the air as it moves, this cools the drips and forms string-like threads.

The threads can vary in thickness depending on the settings of the printer, but can easily be gotten rid of with some simple setting adjustments.

To stop your 3D printer stringing, you need to experiment with your printer’s settings. Try increasing the retraction speed, reducing the retraction distance, and limiting printing outside the outline of the printed model.

You can also easily reduce the temperature of your printer to prevent the plastic from getting too liquid, and increase the speed that the nozzle moves as it prints.

If none of these work, try changing the printing medium to something with less flexibility. If you are unsure of changing any of the printer’s settings, do check with the manufacturer for more information.

Conclusion

Stringing in 3D printing is an extremely common issue. While it is not necessarily normal and is generally an undesirable quality to your printed model, it is easily fixed with some minor experimentation.

Michael Moore
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