Avoid Stringing

The Main 3D Printer Settings to Help Reduce Stringing

What is stringing, why does it happen, and how to get rid of unwanted stringing? Stringing is generally referred to as the strings, hairs, or goop that appears between walls and in gaps during 3D printing.

This happens when the liquid filament oozes out of the nozzle during non-printing moves of the nozzle.

A string usually starts where the nozzle leaves one printed section and can connect all the way to the nozzle starts printing the next section.

On some occasions, the stringing can start in the middle of the gap and there you will see small pillars of globs of filament and strings connecting to your print.

There are a few ways to limit the stringing of your prints, retraction settings, temperature control, speed control, and material selection can all affect the stringing of your parts.

Materials like PETG and Nylon are more likely to string but adjusting these print settings can help reduce stringing regardless of material choice. Retraction, temperature, and movement for FMD or FFF prints. SLA, DLP, binder jetting, and the like should not have stringing issues.

If you have an FDM or FFF 3D printer and are having issues with stringing please continue reading to get an understanding of why it happens and how best to troubleshoot your issues.

 

Retraction

 

Retraction is the most important setting to adjust when trying to troubleshoot stringing in your prints.

Retraction settings include whether to enable retraction, retraction distance, retraction speed, retraction priming speed, retraction priming distance, and extra retraction priming volume.

Below you will see two examples of a part that is likely to have stringing where one has retraction enabled and one with retraction not enabled.

We will also go through the relevant Ultimaker Cura slicer software settings and explain what each setting does and when to adjust each setting. Even if you are not using Cura your slicer should have similar options.

The first part example was printed at 205° C with 65° C bed temperature and all retraction settings turned off.

You can clearly see the stringing between each of the posts and the globs of filament that catches in the middle. These strings or hairs are unsightly and can ruin the fit, form, and function of your parts as well as how they look.

The next example shows the same part with retraction settings enabled. The settings used are pictured below in the Ulimaker Cura description.

You can see that there much fewer strings attached to the two towers and the surface finish is much better directly off the printer.

Below you will see the settings in the Ultimaker Cura slicer software that can be adjusted to fine tune your retraction.

Enable: Turns on and off retraction

Retract at Layer Change: Will retract and prime at each layer change

Retraction Speed: Adjusts the speed at which the extrusion motor will pull the filament back into the extruder.

The speed of retraction should be quick if you see an improvement with stringing but it isn’t perfect then increase this speed until it goes away or your extruder can’t move any faster.

Retraction Extra Prime Amount: This is the amount of additional filament that you extruder will compensate with after pushing the filament back to the nozzle.

If you are seeing under extruded sections after travels you might not have your prime amount high enough. If you are seeing large globs of filament after travel moves you might have this too high.

Retraction Minimum Travel: Minimum length of travel for the extruder to retract filament. Any travel less than this amount will not make the extruder retract.

Nozzle Switch…: This affects the retraction when you have addition nozzles when you have a printer with additional nozzles.

 

Temperature

 

Another setting that can affect your stringing is the temperature at which you are printing. If you are still not getting perfect prints after fine tuning your retraction settings it can help to adjust your temperature settings as well.

Since temperature is one of the most important settings to getting ideal prints you should be careful and document your changes so that you can go back if your prints get worse.

Another thing to consider is that different brands and even different colors can behave best at different temperatures so your settings might need to be adjusted for each different spool you use.

Below you will see 3 different prints of the two towers at 195, 200, and 205° C. Each print has retraction turned off to show the differences with each temperature.

Temperature affects the stringing because it affects how viscous the filament is at the end of the nozzle.

The higher the temperature the easier the filament will flow through the nozzle and the less force it takes to pull it through resulting in more string starts and globs during travels.

The other side of this is that if your temperature is too low your extruder won’t be able to push the filament through the nozzle because it isn’t melted completely.

This can be fixed by slowing down your printing speeds which we go over in the next section.

 

Speed

 

Speed it the last adjustment you should make to fix your stringing issues. There are two different speeds that you can adjust for your printing, the printing speed, and the travel speed.

Printing speed won’t affect your stringing but the travel speed can have an affect.

The faster your travel speed the less stringing your are going to have. But the same warnings apply to speed as they do to temperature, faster speeds can result in a reduction in print quality because they can cause vibrations in your printer and overshooting the destination.

 

Questions

 

So you have your printer tuned to the best possible outcome for stringing but you are still getting a few strings or hairs on your prints. The best way to get rid of these is with some post processing of your prints.

You can take a small knife or scalpel, sandpaper, or just rub them away. Below I show the result of removing the strings from the 205° print with a scalpel and rubbing off any excess stringing.

Sometimes stringing can be the desired affect. Take the lion shown in the link below where the mane is made from purposeful stringing.

[Lion stringing link]

 

Final Words

 

If you are having trouble with stringing the first setting to work through and enable is your retraction settings.

Make sure that your retraction is enabled, your retraction speed is high enough, and that your prime amount is at the correct level for resuming printing.

Second, make sure your temperatures are low enough to not let the filament ooze out but high enough that your extruder isn’t slipping.

Lastly, increase your travel speeds to reduce the amount of time that stringing has to occur.