Ender 3 (V2/Pro) Under Extrusion: Common Issues & Solution

The Ender 3 V2 and Ender 3 Pro are popular, low-cost, and reliable machines.

For the budget, they’re hard to pass by. But they’re not without issues, a big one being filament feed issues.

This article will take you through a range of settings and fault-finding scenarios that will allow you to manage your printer better. We’ll show you where the Ender 3 under extrusion faults usually lie and how to diagnose and fix them. We’ll also explain how not to be distracted from the chain of evidence, but optimize your machine and make reliable builds.

How To Fix Under Extrusion In Ender 3 (V2/Pro)

Printing 3D parts is a complex process and a lot of functionality must operate right, for the pyramid to have a fine point. Learning to diagnose the issues of each layer of the pyramid ensures your outcomes are good.

These are often straightforward, and the symptoms point towards issues. At times, though, a build failure has several potential triggers, so experience in diagnostics and a systematic approach to analysis is a plus. 

Below, we will work through the well-known causes for the amount of filament coming from the extruder being too little to build a quality model — apparently random under extrusion.

Some of these are simple, demanding simple corrections. Others are considerably more demanding.

The video below shows one of the simplest ways to fix an Ender 3 Pro printer under extrusion:

Increase The Extrusion Multiplier

This is a simple change to make in software, but you might be compensating for and ignoring another fault. That’s not a bad thing, necessarily, as what matters is whether print good or not good.

It’s a good idea to perform a full calibration for the machine at regular intervals, and this will include extrusion multiplier settings for each filament you use, because it should be varied according to material, diameter, and your own print requirements.

The extrusion multiplier, or FLOW variable in Cura Slicer, sets the speed of the extruder. Cura performs a calculation based on the volume of build material required, to set a motor speed to ensure supply is sufficient.

All machines default to 100%, but for finesse in setup, you’ll find that materials generally require settings between 90 and 110%.

It’s your machine, so you need to try stuff, but as a rule, if your extrusion seems to require 120%, then you may be covering up another issue.

Correct The Filament Diameter

Misconfiguration of the filament diameter will definitely cause supply issues.

If the software is setting the filament flow rate for a 0.5mm filament but you have 0.4mm installed, that will result in a 20% undersupply — enough to seriously disrupt the layering and make a very ‘gappy’ print.

Increase Temperature And Decrease Speed

To every user who has watched a print proceed, it is clear that the filament must arrive at the fusion point on the model at a sufficiently high temperature to fuse to the already printed layers — without distorting them by overheating.

Without that fusion, there is no model, just a roughly shaped pile of loosely-joined threads. But the temperature at the nozzle also affects flowrate — a hotter extruder flows more easily, reducing resistance to the filament feed, and increasing material supply.

As usual, avoid making big-step changes to settings. We suggest adjusting the flow rate by 5% and evaluating the effect on build quality before making any more alterations.

When you want to adjust the temperature, steps of 3°C should be safe, moving things towards the desired result.

But once again, be cautious — if you’re adjusting more than 10°C from a previously good setting, you’re likely covering up some other, more fundamental issue.

Cleaning And Adjusting The Nozzle

Cleaning the nozzle can be a real hassle and there are missteps you can make in disassembly and reassembly that can create new problems.

However, it’s not always necessary. A process that’s commonly called ‘cold pull’ can be a quick fix that solves nozzle problems. But only try this with a tough filament, because breaking off a chunk inside the nozzle is annoying.

Regular cold pulls will result in the nozzle never showing signs of clogging. But be careful of damage and potential injury when it releases and your hand flies out!

Here are the steps in cleaning and adjusting the printer’s nozzle:

1. First, you’ll need to remove the Bowden or guide tube from the extruder.
2. Power up the hot tip to the temperature of the filament you’re using to clear the head. We suggest nylon, but any tough filament will do the job.
3. Push the cold pull filament into the nozzle until you see some melt at the tip.
4. Switch off the hot end, but keep light pressure on the filament with your fingers to keep the nozzle full.
5. With the hot end below 60°C, the filament in the nozzle will have solidified and the detritus will be stuck firmly to it.
6. Reheat the hot end and pull on the filament with a steady force – use a pull tool or a pair of pliers, to make this part easier. Remember to pull hard enough to extract when not fully melted, but not hard enough to snap the filament in the head. You may need to practice this to get this right.
7. Repeat until the pulled filament comes out clean.

The next ‘easy fix’ is cleaning the outside of the nozzle and heat block, and it pays to do this regularly, as it’s a great preventative measure.

If you have a silicone boot over the assembly, you can peel it off first, then heat the extruder to a moderately high temperature and when it’s hot, brush it clean with a brass wire brush.

Some people like to approach non-disassembly cleaning from the other end — or both — using a clearance wire (often called a needle) to push the acreted stuff upwards, to help in its removal:

1. Heat the hot end to the melt temperature for the filament (or the clearance filament you’re going to cold pull).
2. Push the needle into the nozzle and push against the filament, to get it backing up out of the top. You may want to do this a few times, pushing the filament in to refill the nozzle each time.
3. Extrude some filament to flush further residues and make sure the flow looks right.
4. Repeat until clean extrusion at the right flowrate is re-established.

These are the first go-to methods for clearing obstructions. But sometimes, you just have to get up close and personal to work it out, and there’s no substitute for removing the hot end so you can see what’s going on.

If this is the first time you’ve removed the print head, relax, it’s not that hard to do.

There is one rule that will help you avoid later troubles and costs. Make sure you preheat the hot end before removing it. It needs to be positioned hot, as it changes size when heated and you want it right when it’s in use.

When you refit, you can attach it cold but don’t tighten the screws until after you’ve heated it up. Getting this wrong can result in damage to the hot tip, which can render it useless.

With the hot end off of the machine, you can see inside and judge how well your cleaning is doing:

1. Put the hot end into an appropriate solvent bath for the material you most use. Some options are ethyl acetate for PLA and Acetone for ABS. Follow H&S recommendations for ventilation, fire risk, and use of a filter mask.
2. After an hour or two in the right solvent, the residues will have softened sufficiently to be removed with the clearing needle and tweezers/snipe nose pliers. A big advantage of removing the head is you can look through and see your work’s effect.
3. Refit the hot end to the machine, but remember not to tighten those mounting screws until you heat it again.

You cleaned everything out, but if you’ve still got filament feed issues, it’s conclusively not a blocked nozzle issue!

Replacing The PTFE Tube

The stock Bowden tube is made of nylon. It’s a great material: strong, abrasion resistant, and ‘self-lubricating’. But despite all that, it will wear, which can add drag to the feed, degrading the feeder performance. This will eventually influence builds.

The good news is there’s a low-cost upgrade available: switching to PTFE, which has all the same properties as nylon but is better. And it’s easy to fit.

Here’s how to replace the printer’s tube:

1. With the extruder hot, pull back the filament at the spool, so the Bowden tube is empty.
2. At the hot end, push down the ring around the neck of the tube. It retracts the claws that grip the tube.
3. At the spool end, repeat the tube removal procedure.
4. Cut off or backfeed the old tube through any ties or attachments and remove it from the machine.
5. Reverse the process with the new tube, ensuring that the length and lay of the tube is as it was for the old one. Fit only the spool (outer end). If you cut the tube to length, try to make sure the ends are square cut and not crushed.
6. Feed the filament off the spool and when it appears at the far end of the Bowden tube, fit it into the back of the (still hot) extruder.
7. Push the new tube’s outer end into the retainer and run some extrusion to check that all is well.

A worn tube is unlikely to be the only cause of filament feed issue, but consider this a preventative maintenance issue for any heavily used machine.

Replacing The Stock Extruder

While the Ender 3 is a capable machine, its budget shows in a few places — the extruder being one. There are upgrades available for this. For example; double pulley all metal construction; or stock.

These options will make the machine more tolerant of wear and dirt.

Repairing The Hot End

There are several failure/trouble modes associated with hot end faults that lend themselves to quick and low-cost fixes — not every fault requires new parts.

First off, thermal runaway error messages are generally the result of one of three failure modes:

1. The thermistor is not properly pushed into the hot block or in poor contact because the screw is loose (be very careful not to overtighten it and break the thermistor) — removing it and applying some thermal contact paste before refitting can help.
2. The thermistor wires are broken. These can be repaired by soldering or the use of a screw connector (though this can be quite clumsy. If the break is close to the thermistor itself, some fine heat shrink tube will help avoid shorting it out.
3. The thermistor can, on rare occasions, fail. It’s a low-cost part, so buy a spare when you’re ordering parts, it’s a big time-saver.

Next, underheating is as much of an issue, and it has four causes, of which three can be addressed by maintenance at no cost:

1. Excess cooling can cause apparent heater issues. Make sure you have a thermal boot on the hot end and ensure the cool end fan is not robbing heat where it’s needed.
2. Check the condition of the heater cartridge wiring and check the grub screw retaining the cartridge is tight. But not too tight.
3. Dirt can reduce the heat transfer from the heater module to the extruder, so cleaning and application of thermal contact paste will improve heat transfer.
4. Just sometimes, the heater module itself fails – and this is another low-cost item.

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Diagnose Ender 3 Under Extruding Problems

Like all diagnosis problems, the extruder undersupplying filament has various underlying causes.

More than one of these can be at play, so you need to be open to the evidence that the machine and the print are showing you, to analyze and repair quickly.

Mid-Print

If the model shows signs of underfeeding of filament mid-print — a sudden or gradual deterioration in model print quality for example — then it’s less likely to be a steady wear problem, as most of these issues are not sudden onset. 

First, check that you’re not out of filament. Though it’s obvious, missing the simple answers is a common feature of diagnostic processes.

These are the main faults to look for:

• Overworked filament in the feeder drive gear. If the feed stops, then a common cause is that the filament got so rubbed/worn at one spot that the feeder has no grip. This is less common with tougher filaments, but can happen with any material.
• Out of filament. One obvious reason for undersupply is that the machine has run out of filament. It’s surprising how easy it is to overlook the maddeningly obvious.
• The extruder is clogged. all the causes for this are discussed above. This is usually not a sudden onset problem, but if the build has degraded progressively then it might be the key.
• Filament feed motor overheats. This motor has to work hard, as there’s a lot of resistance to the movement of the filament in a clean, well-adjusted machine. Expect to see a transition from good to not over a single layer, maybe two. Reducing the clamping force on the filament, freeing up the movement by cleaning, reducing excessive print speeds, etc will all affect this — but if it doesn’t go away, you may need a new extruder (or just the motor).

First Layer

Putting down the first layer exactly right is the most important feature of a successful print. Common causes of failure in this first layer are;

• Table adhesion is too poor, so the build material is being wiped around.
• Try an alternative table material, such as a layer of builders tape, or a pre-conditioning of the table with one of the proprietary adhesives sold for the purpose.
• Use a table overlay, there are many types available, so read some reviews before trying them.
• The extruder is running too close to the table, causing the same symptoms – try increasing the gap in steps to test for improvement.

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8 Tips For A Smooth 3D Printing Experience

1. Maintenance Is Key

Keep your printer clean and check critical parts regularly. It’s a small price for peace of mind about the build you’re about to start.

2. Make Sure The Bed Is Level And Flat

It’s tedious to manually set, but if the bed isn’t level and flat, print quality will suffer.

The best approach to manual leveling is through the following steps:

1. Go through the settings to disable steppers.
2. Lower the adjusters for the bed in two turns.
3. Adjust X and Y manually so the nozzle is right over one corner adjuster and, with a piece of paper on the bed, wind Z down until the nozzle just touches the paper, then back off 5 steps (you’ll feel the click of the stepper 5 times).
4. Slowly adjust the table corner upwards while sliding the paper, until you feel a slight drag. 
5. Repeat for three more corners of the plate, but make sure you These are the main faults to look for: the Z height. When you move to the next corner, if the hot tip pushes into the paper, lower that next corner a little and start again.
6. When all 4 corners are set, go back and check again.
7. You’re ready to print.

There are G-code scripts to make this easier – but you’ll learn a lot about your machine by doing this manually at least once

3. Monitor Nozzle Temperature

The Ender 3 has only one nozzle, so getting the temperature right isn’t such a big task. Too high and you’ll get stringing and potentially serious distortion/slump on taller models; too low and you’ll get insufficient feed.

Start at the middle of the filament supplier’s recommended range and adjust in small steps, 5°C maximum.

Solutions you can include to help obviate temperature issues range from making test pieces to validate that you’re close, to including walls and touch point column parts outside your build, and breaking up the layers and allowing some nozzle cooling.

This is a setting you’ll need to practice tuning; nothing substitutes for experience.

4. Speed Is Also Important

Don’t try to print too fast. Slower prints are generally better prints — other than the time taken!

If you need fast printing, consider switching to a bigger nozzle/filament and setting a larger layer thickness. Compromises are required.

Good, quick, and cheap. The world is mean; you can generally only have two of these, so plan accordingly.

5. Wall Thickness/Infill

Remember that solid prints take a lot longer and add little real value, so use infill settings to suit the part — you’ll build faster without compromising quality.

6. Accelerate!

Be considerate of your printer in setting acceleration and travel speeds.

Let the machine wind up more slowly and it will skip fewer motor steps, build cleaner models and wear your equipment out less. Yes, it can mean building a little more slowly.

Good, quick, and cheap. Machine wear is a hidden cost that must be paid by every model.

7. Be Supportive — Just Not Too Much

Supports cost build time, cleanup time, and material, so use them sparingly.

Experience will teach you where the line between sufficient and slump lies, but it is a good line to learn (and pull back from).

8. Keep Your Filament Warm and Dry

Many filaments are moisture sensitive — and the water content absorbed from atmospheric exposure is enough to badly influence builds.

Read here about which filaments need which conditions, how to recover filaments, and when to give up and buy new ones.

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Wrapping Up

Ender 3 inconsistent extrusion is a chronic problem with many causes. By learning from the experience of others and by taking a systematic approach to a fault and system diagnosis, you can become the master of the tricky art of depositing the right amount of plastic exactly where you need it!