Inconsistent Extrusion In 3D Printing: 7 Solutions That Work

For your 3D-printed object to look flawless or work as it should, the machine must extrude filament in a very consistent flow. 

Inconsistent extrusion refers to a flow that is not consistent. Under-extrusion and over-extrusion are two of the most common inconsistent extrusion issues, but the printer might also mix them due to bad settings or other issues. This could result in missed layers, zits and blobs, ridges, and other defects.

If you’re struggling to get calibration right and achieve a consistent flow, these tips might help you get rid of extrusion inconsistencies.

How To Fix Repeated Inconsistent Extrusion

Inconsistent extrusion can happen for a variety of reasons. Identifying the culprit can help you fix the problem quickly.

However, if you don’t know where to start, these steps can help you.

1. Keep The Nozzle Clean

A dirty or clogged nozzle is often the cause of extrusion inconsistencies. Filament residues that are not cleaned after each print can build up inside the hot end and form partial clogs. You might not notice them at first, but as the clog gets bigger, so will the extrusion issues.

Clogged nozzles can lead to both under and over-extrusion. Signs include missing lines – total or partial – oozing, stringing, and blobbing.

There are various ways to clean the nozzle, depending on how large the clog is. If it’s only a small clog, scrubbing it with a wire brush and removing the residues with a needle should do. 

If you’re dealing with a larger or stubborn clog, you could clean the nozzle with solvents, use a jewelry cleaner, melt the clog with a heat gun, and so on. If the nozzle is too damaged or too dirty to clean, you should replace it completely.

2. Check Extruder Gears

Extruder gears are mechanisms 3D printers use to push the filament through the hot end. If these gears are dirty or worn out, they might not grip properly onto the filament.

In printers with a Bowden tube setup, the same could happen due to loose spring tension.

Whether it’s grime, age, or a loose component, if the gears can’t feed the filament properly, it results in repeated under-extrusion.

The easiest way to prevent this problem is by performing proper maintenance.

Check the extruder gears regularly and clean them as often as necessary. Inspect for wear and tear and replace when needed. If you notice any loose springs or bolts, tighten them to ensure adequate spinning and grip on the filament. 

3. Store Filament Properly

The next most important variable to the success of your printing project is the type of filament you’re using and how you’ve stored it.

Poor quality filament is notorious for twisting and knotting. Yet, the same can happen to a high-quality filament that has not been stored properly. 

To avoid issues, always wind the filament back onto the spool when you’re removing it from the printer and store it in a filament box. Filament boxes are built in such a way to prevent unwinding and knotting while the filament is not in use.

If you don’t have a filament box and don’t want to buy one, place each spool in an individual sealable plastic bag. Make sure to add a few packs of silica gel into each bag if you’re using hygroscopic filament such as PETG.

4. Dry Filament Before Use 

No matter where you store the filament, certain filament types have the capacity to absorb moisture from the air in just minutes. And, if you didn’t know it, printing with wet filament is a recipe for disaster. 

Beyond extrusion inconsistencies, printing with wet filament can lead to stringing. Air bubbles can also get trapped inside the filament as the moisture evaporates during extrusion, leading to unsightly defects on your items.

If these defects are purely aesthetic in visual pieces, they could compromise the structure and function of functional parts.

The best method to dry filament before use is with a filament dryer. These machines work like convection ovens, but they have settings for various filament types.

More advanced models can even detect the moisture level in your filament and let you know when the spool is ready to use. 

If you don’t have a filament dryer, the two most common methods involve the kitchen oven and food dehydrator. These appliances can dry the filament in about six to twelve hours when set at around 149°F (65°C). 

Depending on the filament, you can also employ other methods, such as drying in a vacuum chamber or directly on the heated printer bed.

5. Avoid Heat Creeps 

Heat creep happens when the heat travels up the hot end and melts the filament before it reaches the melt zone. The problem can manifest either mid-print or during cooling, even though the former circumstance is more common.

Heat creeps can cause a whole array of extrusion inconsistencies, from extrusion stopping mid-print to layers that look fuzzy or filament extruded with air bubbles in it.

Keeping the room temperature constant and the printer outside of an enclosure is an easy way to avoid heat creep.

However, heat creep can also happen when the hot end temperature is too high for the filament you’re using or when you’re not using a cooling fan.

Incorrect retraction settings or a too fast printing speed are other potential culprits for heat creep.

If the room temperature is constant and around 77°C and you’re sure the hot end temp is right, it might be worth checking the fan settings and calibrating your printer.

6. Calibrate Your Printer 

Calibration issues can result in much more than heat creep. A wrong layer width, for instance, can result in squishing of the print, elephant foot problems, and oozing. Oozing can obviously turn into the inconsistent extrusion. 

Retraction settings, feed rate, print speed, and hot end temperature can all affect the quality of your print. 

For this reason, it is crucial to learn the settings of the material you’re working with and calibrate the printer before each use. For the best results, it is recommended to slice the object after you’ve run the calibration.

7. Perform Regular Printer Maintenance 

Lastly, extrusion inconsistencies can happen due to issues like Z-wobble or play in the other axles. These are caused by loose screws or worn-out parts. 

While there is nothing you can do to stop aging, you can keep the printer in good condition for longer by performing regular maintenance. 

Calibrate the axes regularly and check for any loose fasteners. Tighten the screws and springs whenever needed and replace them if the threads are worn-out.

Make sure to perform all maintenance recommended in your printer’s manual regularly, as instructed by the manufacturer.

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Type of Filament and Its Contribution to Inconsistent Extrusion

Using the wrong settings for the type of filament you’re printing with can result in inconsistent extrusion, even if everything else is working perfectly.

Here’s how to fix these issues for specific filament types.

PETG

PETG is one of the most popular filament types, but it comes with issues beginners may be unaware of.

The first is that PETG is a highly hygroscopic material that absorbs moisture from the air like a sponge. It needs constant drying before use, even if you’ve set the spool aside for less than a day. 

PETG is also different from other materials in that it doesn’t need any initial squishing. A low initial layer height can cause over-extrusion for the first layer and result in other problems for the rest of the print. 

The initial layer height for this material should be around 0.28mm.

Other settings include: 

• Nozzle temperature: 210°C to 250°C
• Bed temperature: 50°C to 70°C
• Fan speed: 100%
• Retraction distance: 0.5 to 2 mm
• Print speed: 30 to 50 mm/second

TPU

Like PETG, TPU absorbs a lot of water which could lead to bubbling and uneven extrusion. However, the material requires lower printing speeds and also less retraction than PETG.

This material is one of the most challenging to print with for beginners, but you could avoid issues with the following settings: 

• Nozzle temperature: 210°C to 235°C
• Bed temperature: 25°C to 60°C
• Fan speed: 0 to 40%
• Retraction distance: 0.5 to 2 mm
• Print speed: 15 to 40 mm/second

PLA

PLA is a common choice among users who want to print with an environmentally friendly and sustainable material.

It is also one of the best filaments for beginners, as it doesn’t require a heated bed or too high nozzle temperatures, and it is overall easy to work with. 

However, this material is more likely to cling to the nozzle and clog it. As explained, clogging can lead to extrusion problems.

For the best results with PLA and to avoid inconsistent extrusion, use the following parameters: 

• Nozzle temperature: 180°C to 220°C
• Bed temperature: Room temperature to 60°C
• Fan speed: 0 to 100%
• Retraction distance: 0.5 to 1 mm
• Print speed: 50 to 100 mm/second

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Voron, Prusa MK3, and Ender 3 Not Extruding Consistently

Inconsistent extrusion can happen on all printers, but the issue is more common among entry and mid-level models like Voron, Prusa MK3, and Ender 3. 

Voron

Voron printers used to be affected by a famous issue #6, an error code referring to inconsistent extrusion.

The primary cause is the printer’s poor stacking tolerance, which basically refers to its ability to output a consistent stream of material despite the filament diameter or shape varying slightly from one section to another.

This often results in ridging, bumping, and other defects visible on the prints in a regular or random pattern. 

The only way to fix this issue is by compensating for these filament variations with a Bowden tube or another similar element. 

Prusa MK3

Similar to Voron, the Prusa MK3 also has staking tolerance problems. The error code is #602 and refers to changes in extrusion amounts along the X and Y axes. 

Proper calibration before each print often helps avoid these issues. If the problem persists, you might have to replace the Bowden tube. 

Ender 3

Luckily for Ender 3 users, this printer type rarely has inconsistent extrusion issues due to staking tolerance.

Instead, the filament mounts and gears might not get a proper grip on the filament, resulting in insufficient force for pulling the filament out.

These can lead to inconsistent extrusion, as explained above, and the issue is easy to fix by replacing the filament mount with a higher-quality one.

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Conclusion

Inconsistent extrusion can lead to a variety of printing defects, including zits and blobs, bubbling, stringing, and more. The issue is often caused by incorrect settings or calibration, a clogged nozzle, or faulty extruder gears. Other factors can also cause this issue, including the type of printer. Inconsistent extrusion is more common on the Voron, Prusa MK3, and Ender 3 printers.