Stringing

Stringing happens when small strings of filament are left behind on a 3D printed object.

This is typically due to filament dripping out of the nozzle while the extruder is moving to another location. However, this can be solved by changing a couple of settings in Simplify3D.

Retraction settings

The first setting to check is Retraction. This controls the filament to be pulled back into the nozzle when the extruder is done printing one part of the object. Once the extruder moves to the next location the printing process continues – the filament is pushed back out and it starts extruding from the nozzle again. To ensure retraction is enabled, click “Edit Process Settings” and click on the Extruder tab. Ensure that the retraction option is enabled.

1.1 Retraction distance

The most important setting is the retraction distance. This determines how much filament is retracted from the nozzle. In general, the more filament that is retracted from the nozzle, the less likely the nozzle is to drip while moving. If you encounter stringing with the object, try increasing the retraction distance by 0,2mm and test again to see if the performance improves. Our entire line up of printers is supplied with a stock profile. Please do not exceed the stock retraction distance +1mm before contacting Tractus3D support. If the retraction distance is set too high you can experience filament jams and clogged nozzles.

Retraction speed

The next setting that needs to be check is the retraction speed. This determines how fast the filament is retracted from the nozzle. If the retraction is too slow, the filament will slowly drip down through the nozzle. This way it may start leaking before the extruder is done moving to its new destination. If the retract is too quick, the filament may separate from the hot filament inside the nozzle, or the quick movement of the drive gear may even grind away pieces of your filament. There is usually a best option in between 1200-6000 mm/min (20-100 mm/s) where retraction performs best. Simplify3D has already provided many pre-configured profiles, but the ideal value can vary depending on the material that you are using. Therefore, you need to experiment to find out if different speeds decrease the amount of stringing. If the retraction speed is set too high, you will hear the extruder motor skipping steps, if so please reduce the speed again.

Temperature not right

The next most common cause for excessive stringing is the extruder temperature. If the temperature is too high, the filament inside the nozzle will become more liquid and will leak out of the nozzle easily. But if the temperature is too low, the filament will still be too solid and difficult to extrude from the nozzle.
Try decreasing the extruder temperature by 5 degrees. This can have a remarkable impact on the final print quality. You can adjust these settings by clicking “Edit Process Settings” and selecting the Temperature tab. Select the extruder from the list on the left, and then double-click on the temperature setpoint you wish to edit.

Travel movement

As mentioned before, stringing occurs when the extruder is moving between two different locations, and during that move, filament starts to drip out of the nozzle. The length of this movement can have a huge impact on the behavior of the dripping. Short moves may be quick enough in order for the filament not to drip at all. So long movements are much more likely to create strings. Simplify3D includes a useful feature that can help minimize the length of these movements.

The software can automatically adjust the travel path to make sure that nozzle has a very short distance to travel over an open space. In fact, in many cases, the software may be able to find a travel path that avoids crossing an open space all together! This means the nozzle is always on top of solid underground and will never travel outside the part. So there is no possibility to create a string. To use this feature, click on the Advanced tab and enable the “Avoid crossing outline for travel movement” option.