5 Ways How to Fix Stringing and Oozing in Your 3D Prints

Stringing, oozing, whiskers, hairy prints. These are all the same thing and are a common issue when using a 3D printer.

It occurs when melted plastic does not lie properly in your design. This results in extra strings or spills of melted plastic which can ruin the overall aesthetic of your 3D print.

Luckily, there are many easy fixes for this problem. Gone are the days where your projects are ruined by excess plastic, or you have to spend hours sanding off the filaments.

Follow our tips to make stringing and oozing a thing of the past.

What causes stringing and oozing?

Stringing and oozing is primarily caused by the printing nozzle having to move across large open spaces to get to the next point where printing is required.

As the nozzle moves across the printing area, the nozzle will continue to force out melted plastic. This will result in thin strings of plastic between the printed layers.

The main reasons for this occurring are to do with the retraction settings. They are either not being used, the speed is too low, or the distance is too short.

Other causes of stringing and oozing include the printing temperature being too high, the filament absorbing too much liquid, or the printing nozzle being jammed.

Use Your Retraction Settings

The retraction of your machine is very important when trying to produce a clean and polished final product. This is when the filament recoils to stop the plastic from dripping as it moves. The retraction settings being engaged means that there is less chance of your 3D print becoming oozy or stringy.

This means that the half solid plastic in the nozzle will be pulled back from the nozzle as it moves. This puts less pressure on the plastic and means that it will drip less.

The default for these settings is to be activated, but we advise checking them if you notice any issues with your printing. The plastic filament should be getting drawn back whenever the nozzle passes over an open area in your project.

Start with a retraction speed of 50 mm/s. You should make adjustments of 5-10mm/s at a time. The retraction distance should be set at 3 mm, but make adjustments at the rate of 1 mm at a time.

There should also be a setting on your 3D printer that is called combing mode. This means that the nozzle will only travel over paths that have already been printed. This should reduce the stringing problems.

A good way to check your retraction settings is to download a retraction test from Thingiverse. This will allow you to check the precision of your retraction settings.

Check Your Printing Temperature

The higher your printing temperature, the more likely it is that you will see stringing and oozing in your finished print. This is because the plastic will be more melted and will run out of the nozzle more. This will then result in thin strings of plastic being created as the heat makes the filament more liquid and viscous.

Reduce the temperature of the machine and check for improvements as you do so. You should check the packaging of your filament for the temperature range that is best suited. Ensure you have set the temperature of the printer to within this range.

It is a good idea to use a filament such as PLA (polylactic acid or polylactide). This is because it melts more efficiently at lower temperatures.

As you drop the printing temperature, you may find that you need to play around with the extrusion speed too. This is because the filament will take longer to melt at cooler temperatures and cannot be extruded as fast.

We recommend printing some smaller objects as you are playing around with the settings. This will allow you to find the sweet spot of temperature and extrusion speed for the specific filament you are using.

Varying plastic types will perform differently at different temperatures. Experiment with the printing temperatures, varying them by 5-10 degrees at a time.

Some people choose to print their first layer at a temperature that is about 50 degrees Fahrenheit higher than the rest of the product.

They will then drop the temperature to complete the product. This will mean that the layers adhere to one another better, resulting in a more polished final product.

Check Your Printing Speed

This is an important factor to adjust, particularly following a change in printing temperature.

If you have dropped the temperature, you should also drop the printing speed. This is because your plastic filament will take longer to melt and print as the viscosity will be lower.

If your printing speed and temperature settings are both high, this can also lead to stringing and oozing on your 3D print. A slower printing speed will reduce the chances of stringing as less plastic will leak from the nozzle.

A good speed to start at is between 40 and 60 mm/s. Your travel speed setting should be in the range of 150 to 200 mm/s. This will vary according to the material that you are printing with, as all materials will melt at different speeds.

Reduce the speed at the start of your printing process to allow you to test your printing. Speeds that are too high and too low can both cause issues.

Try a range of speeds to find the optimal one for each material you use.

Look at the Filament

Moisture is one of the biggest issues that can happen to filaments in your 3D printer.

They are susceptible to absorbing moisture from the air surrounding them if they are stored incorrectly. This moisture then turns into bubbles when the material is heated up, which can cause real issues with your 3D print.

These bubbles are likely to burst which is the main factor in the creation of stringing and oozing in your print. The moisture trapped inside the filament can become steam when exposed to heat. This will impact the filament and will cause the plastic to drip more. This in turn will cause more issues with stringing and oozing.

Nylon and HIPS (high-impact polystyrenes) are much more problematic in this respect. To reduce the chances of this happening, you can choose a filament that absorbs less moisture.

You should store all of your filaments in an airtight container. To further reduce the moisture they absorb, store them with a desiccant such as silica gel. This will absorb ambient moisture and will prevent it from entering the filament.

If you notice that there is moisture within your filament, you can attempt to dry it out before using it in your 3D printer. This can be done using an oven set to a very low temperature.

Check the Nozzle

The printing nozzle is often the source of issues with your finalized prints. Some plastic particles from your last print are likely to remain stuck in the nozzle which can impact your print quality.

This is particularly prevalent when you switch between filaments with varying print temperatures. For example, this could be during the transition period between a high-temperature ABS material to a lower temperature filament such as PLA.

To prevent this from happening, you should clean your nozzle thoroughly before you start a new printing project. This will also clean off any residue or settled dust from the print nozzle. To do this, use a brush containing metal bristles. This will be more effective at removing plastic residue than softer bristles.

You should clean the nozzle after every use of the 3D printer. It is easier to do when the printer is still warm as the plastic residue will slide off with less force required. If you have allowed plastic residue to cool onto and stick to the printing nozzle, you may need to use acetone to help remove the plastic.

It is absolutely essential to clean the printing nozzle when you are switching the filament material.

How to Clean and Maintain the Print Nozzle

You should use different nozzles for each filament material that you work with. This is because each will have different properties and melting temperatures. Using a separate nozzle for each will reduce the chances of imperfections within your finished 3D print.

You should change materials while your print heads are still warm. This will prevent the filament material from cooling too much and causing problems later down the line.

When inserting the new filament into your print head, do not force it too hard. This will mean that materials can get dislodged and stuck within the print head. This can then cause filament buildup inside your print nozzle which will impact the quality of your final product.

When cleaning the print nozzle using the wire brush, you should use a linear motion. Try to regularly alter the angle at which you are brushing from. This will ensure that the filament is cleaned from all angles and is likely to stay in better condition for longer.

It is vital to use a metal brush as there is a higher level of friction which is important to dislodge melted or burnt plastic. You should check the manufacturer’s instructions for the cleaning of the print nozzle before using a wire brush on it. Some print nozzles can be damaged by the metal fibers.

If this does not solve your issues, there may be cold plastic residue stuck to the inside of the print nozzle. This will prevent any fresh filament from being extruded and block up your printer.

To fix this, you should heat the extruder to soften any plastic residue. This can be done through your printer or by using a hot air gun. Use a needle to then push this out.

If you are still experiencing problems, use the acetone method. Take the print nozzle off of the print head and submerge it into acetone. Leave it sat there for a few hours to allow the acetone time to absorb into the plastic residue. This will melt the plastic slightly, and then you can use your trusty needle once more to push the residue out with ease. 

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