What Causes Under Extrusion in 3D Printing? How to Fix It?

Additive manufacturing is a revolutionary technology both at an industrial scale and in our homes. This technology is synonymous with limitless possibilities when it comes to design creativity and style. 3D printing is associated with cost-effectiveness, higher productivity, and easy customization. Nonetheless, this new age manufacturing technique is not without flaws. Without fixing them when you experience them, such conveniences may still be out of reach. Under extrusion is one such 3D printing problem that many experiences. However, it is one of the easily solvable ones for that matter.

What is Under Extrusion?

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3D Printing Under Extrusion (source)

Just as the expression states, under extrusion is a situation in which your printer cannot supply enough material through the nozzle. Often, it leads to a compromise in structural and dimensional integrity of the final 3D print. Under extrusion can lead to layers not sticking, layers warping or the whole assembly breaking down.

There are so many causes for under extrusion, and it is highly improbable that you will ever pinpoint the primary reason. The telltale signs of under extrusion include missing layers during and after 3D printing. Other symptoms to look out for are excessively thin layers, or layers decorated with cracks, holes, and dots.

This post examines the possible causes of this glitch and strategies for solving it. This is an all-encompassing problem from the settings to the filament spool and the nozzle.

Main Causes of Under Extrusion

Stuck filament spools

Filaments can get stuck if they are improperly wound. The blockage can also happen when the threads are not correctly rolled off by the 3D-Printer. When the filament spool gets stuck, it causes friction that often causes the motor to lose grip of the material when feeding it into the printer. That ultimately causes the reduced flow of the materials and by extension under extrusion.

Warped Teflon tubes

Many FDM 3D-Printers employ Teflon tubes to unroll the filament and direct the thread into the print head. If in any way these tubes are bent or distorted, they will cause a lot of friction on the filament material. The extra friction imparts additional pressure on the feeder motors consequently leading to under extrusion. What causes warping and distortion in Teflon tubes include overheating of the whole setup (FDM printers emit much heat), lack of regular maintenance and over usage.

Too little pressure on the filament feeder

Most FDM printers have allowed for adjusting the pressure settings for the filament feeder. This pressure controls the force that the motor exerts on the filament for a firm grip of the material. When this pressure dips, the motor loses grip on printing materials leading to the case of under extrusion.

You can quickly check the filament pressure by hand. When printing, hold down the filament while the motor is rotating. If you feel the filament slipping the pressure needs to be increased. It is also important to adjust the feeder pressure every time you change the filament – each manufacturer has their diameters.

Clogged extruder

If there are stuck objects in the extruder head such as filament remains, the new thread fed through it will experience additional friction when passing through to the nozzle. That extra friction slows down the printing material from reaching the nozzle thus causing under extrusion. The clogging could also be in the feeder motor. Check to ensure that feeder motor cog which pushes the materials through the nozzle is not contaminated with pieces of leftover filament.

Blocked nozzle

Your 3D printer nozzle needs cleaning from time to time. The residue and remnants of materials passing through it can build up and block the passage hole, thereby becoming a stumbling between you and your three-dimensional dreams. A clogged nozzle is the surest cause of under extrusion, but to be certain you can carry out a little test.

Detach the extruder lever and manually push the filament material through by hand. If it passes through with little resistance, your nozzle is clean, but if you feel some resistance in the processor if the filament or doesn’t come out at all, the nozzle is clogged and needs cleaning.

Low printing temperature

How hot is your printing temperature? The common cause of under extrusion is a low nozzle temperature. If you are printing at speed, the flow rate of the filament through the nozzle is increased. However, if the nozzle is not hot enough, the filament will not properly melt in a rate that matches the fresh material feeding into the nozzle. That will negatively impact the filament flow and lead to under extrusion.

Too high 3D-Printing speed

High print speeds could be the reason why you experience under intrusion with your 3D printer. In the extrusion process, you will have to make sure that the flow rate matches your print speed. If the later exceed the former, then there will not be enough material passing through to the nozzle, and that causes under extrusion. In light of that, it is advisable to change the print speed so that it is in sync with the flaw rate. Try decreasing your print speed by 20 mm/s and observe the result.

How to Fix Under Extrusion?

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How to Fix Under Extrusion? (source)

Unwind and rewind the spools

To ensure that filament rolls into the printer seamlessly, roll up the spools such the filament can get unwound without overlapping. The filament threads should not fall loose from the spools. To achieve flawlessness, unwind and rewind the spools this time making sure to smooth out all knots that can cause the material to get stuck. Coil it tightly to prevent overlapping. Disentangling the filament helps you materialize your 3D designs fast and without setbacks.

Replace the overused Teflon tubes

To prevent the filament from getting stuck due to warped Teflon tubes, replace the tube switch new ones. That is a corrective measure. Preventive measures include posing during your 3D printing project to allow the whole set up to cool down and conducting regular maintenance. It might require a great effort on your part or even interfere with your printing schedules, but it’s a step towards stellar print results.

Increase the pressure on your filament

Increasing pressure on the filament is a surefire way to achieve good quality prints. If the filament is pressed too lightly on the feeder gear, it might slide out of grip. Also, if it is too tight, it will crush under pressure, leading to deformation.

To adjust the feeder gear pressure, you need a screwdriver and wrench. For a printer with a single extruder, start by changing the bearing position on the right of the extruder. To achieve that, tighten or loosen the screws on top of the bearing mount. Run the printing to see if the under extrusion has stopped.

To increase the pressure on a dual extruder printer, you will need to adjust the whole stepper motor assembly. You will only need to change the single screw for the motors to increase the pressure. Tighten both screws and test the printer to check the rate of extrusion.

Clean the extruder and the feeder motor cog

To clean the extruder to set to the maximum temperature (that will help to melt away all shredded filament parts stuck within the walls) and feed fresh filament to it. You can also manually clear out contaminants in the feeder motor cog to help firm its grip on the filament materials.
Clean clogged nozzles

Usually, clogged nozzles are caused by particles or dirty filament plugging the hole. You always need to be cautious not to set the nozzle height too close to the print bed. Experts also recommend that you do not leave your printer unused with a hot nozzle.

However, there is nothing that regular cleaning and maintenance cannot fix. Spruce up the nozzle by brushing with a brass wire brush. That will help you dust off the whole surface and get rid of debris that could cause clogging.

The next step is powering up the printer and letting it warm up, then insert a hypodermic needle through the nozzle to unclog it. Equally, you can achieve fantastic results through cold pulling, a method that often involves pulling a filament thread through the nose to remove the stuck residue and particles. Another foolproof way of unclogging a nozzle is detaching it from the printer and washing it in a chemical solvent such as acetone.

Increase the print temperature

The hotter the nozzle gets, the faster the thermoplastics passing through it can melt. The result is a more rapid flow rate and increased extrusion. Increasing the print temperature should be a stepwise process until you find the right setting for your material. Adjust the temperature in the environments and print a test. It is, however, important to note that with materials like PLA, pushing up the extruder temperature can cause it to degrade and lose its definitive properties. That can lead to another critical clog that this time round might not be easy to clear. The recommended printing temperature for PLA is about 220 degrees Celsius.

Under extrusion can significantly interfere with the success of your 3D project. Use the above techniques to get the printer running smoothly.

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