3D Printer Over-Extrusion: 3 Easy Fixes


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3D Printing over extrusion in red pla filament from a 3D Benchy test print

Key Takeaways

3D printer over-extrusion is when your machine extrudes more filament than intended.

Over-extrusion presents itself as drooping layers, stringing, oozing, zits, and blobs.

You can fix over-extrusion issues by setting the right filament diameter and lowering the print speed and flow rate.

Over-extrusion occurs when a 3D printer extrudes more filament than intended, resulting in issues such as drooping layers, stringing, oozing, zits, and blobs. 3D print defects caused by over-extrusion can affect the final appearance of your printed objects.

But don’t worry.

We’ll cover three easy fixes to eliminate over-extrusion that’ll quickly improve your print quality. 

What is Over-Extrusion?

3d print over extrusion causing zits and blobs on two cubes
(Source: u/donnysaysvacuum via Reddit)

Over-extrusion in 3D printing occurs when your printer extrudes more filament than intended.

When over-extrusion occurs, more filament is deposited onto your print than is required. The extra filament creates print defects like drooping, oozing, stringing, blobs, and dimensional inaccuracy.

If you notice any of these print defects in your models, it might indicate that your printer is over-extruding filament.

Several factors can cause over-extrusion, such as dimensional inaccuracies in the filament, high flow rates, high print temperatures, and incorrect filament diameter settings.

An over-extrusion issue ruins your 3D print and can lead to jams inside the hot end and nozzle. These jams often require disassembling the print head to fix, which can be time-consuming and frustrating.

Now that you know what causes over-extrusion, let’s dive into the three easy fixes to eliminate it from your printing.

How to Fix 3D Printer Over-Extrusion

Over-extrusion in 3D printing can negatively affect the quality of your prints. In this section, you’ll find ways to fix over-extrusion by focusing on three main aspects: adjusting the filament diameter, decreasing the print temperature, and lowering the extrusion multiplier. 

Decrease Print Temperature

A 3D printed temperature tower printed in color changing pla filament
(Source: Hiroloquy via Thingiverse)

Lowering the print temperature is one of the easiest ways to solve over-extrusion. When your printing temperature is too high, the over-melted filament uncontrollably flows through your printer’s hot end.

Start by decreasing your printing temperature in 5-10 degree increments. Run a test print after each adjustment and take note of print quality.

You should see a noticeable improvement as you lower the temperature of your printer’s hot end.

Pro Tip

You can save time by printing a temperature tower. The temperature tower test print creates a stack of bridges at varying hot end temperatures.

The temperature tower allows you to test several printing temperatures at once, quickly determining the best printing temperature for your filament type.

Remember that each material type may have a different optimal printing temperature. It’s a good idea to read the manufactures recommended printing temperature as a starting point and adjust as necessary.

Lower the Extrusion Multiplier

Checking the flow rate using a test print and digital caliper
(Source: petrzmax via Thingiverse)

The extrusion multiplier, also known as the flow rate, determines the amount of filament that your printer extrudes during the printing process. Lowering the extrusion multiplier setting reduces the amount of material deposited on each layer which fixes over-extrusion issues.

Most slicer software sets the default flow rate value to 1 (or 100%).

I recommend reducing the extrusion multiplier in 0.025 (or 2.5%) increments.

Take a look at our tutorial on calibrating your 3D printer e-steps for an in-depth guide to determining the perfect flow rate.

After each adjustment, run a test print to check how your changes affect your printing. If lowering the flow rate doesn’t fix or reduce the amount of excess filament, try lowering the printing temperature and checking your filament diameter setting.

Adjust the Filament Diameter

Close up of a test print of an owl in white pla filament

One common mistake is setting the wrong filament diameter in your slicer settings. 3D printing filaments commonly come in 1.75 mm, 2.85 mm, and 3 mm diameters.

If you set the filament diameter to a thinner value than you’re using, your printer will extrude filament at a higher rate.

You can find the filament diameter on the side of the filament spool, on the filament’s box, or by using a caliper to check the measurement manually.

Once you determine the diameter, update your slicing software to the correct value.

It’s also possible that inconsistencies in the filament can cause over-extrusion.

Inconsistencies are less common now, as manufacturers have improved the manufacturing of 3D printing materials.

However, if you’re printing with a cheap filament, it’s a good idea to use calipers at several points along the spool of the filament to check the thickness. You’ll definitely want to avoid using filaments with wide inconsistencies. The best 3D printing filaments have a dimensional accuracy of +/- 0.05 mm or less.

Marcello De Lio
Marcello De Lio

Marcello co-founded 3D Print Mentor to share his love of 3D printing. Marcello used to own an online 3D printing company, where he sold unique designs and customized novelty gifts. After closing the business, Marcello’s new passion is 3D printing replica movie props and cosplay items.

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