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Under-Extrusion

· 9 min read
Pranav G.
Pranav G.

Under extrusion​

What Is It?​

Under extrusion is caused when there's an interruption in your filament flow. Gaps in your layers, irregular layer lines, or webbed layers in your 3D model indicate an inadequate filament flow to the nozzle. It's one of the most common printing issues and is prevalent with Bowden drive extruders due to the long path of the filament.

Things to check​

  1. Print Temperature
  2. Print Speed
  3. Bed level
  4. Extruder gears and body
  5. Nozzle and Hot end
  6. Filament flow rate

How to Fix it?​

Increase Print Temperature​

If the filament material cannot melt adequately, it won't flow properly, and you will face extrusion issues in your prints. You can try to increase the printing temperature by 5° at a time until you get a smooth filament flow.

Many filament manufacturers mention the melting range for their filament materials. You can try to print at the higher end of this range and ensure that the hot end temperature is high enough to melt the filament correctly.

Decrease Print Speed​

Along with a high printing temperature, your filament needs to have enough time to be able to melt properly. If you're printing at a high speed, your material doesn't get to spend much time in the hot end and, as a result, it will not melt adequately to ensure a smooth flow.

You can decrease the print speed by 10 mm/s from your previous settings while simultaneously increasing the printing temperature slightly. Adjusting both these parameters should result in a smooth and uninterrupted filament flow and solve your under extrusion issues.

This parameter is solely applicable if you're experiencing a rough/under-extruded first layer. Under extrusion in first layers occurs due to less gap between the nozzle and the printing bed surface. The filament does not have sufficient space to flow out of the nozzle, thereby causing an uneven first layer.

Check the Extruder arm and gears​

The gear teeth on low-quality, budget extruder gears can easily get worn out due to the constant grinding with the filament material. Moreover, as many of these cheap extruders use plastic for low costs, the high-spring pressure will eventually crack the extruder arm.

If this happens, the gears will not grip the filament properly, as there's no pressure on the filament. It will cause the filament to slip between the gears, resulting in an inadequate flow.

You need to check the extruder gears for any flat spots or wear signs. You need to also ensure that the extruder body itself has no cracks. If you notice any of these issues, the best option is to replace the extruder completely with an all-metal extruder. It'll be slightly expensive but a worthwhile investment for the long run.

You can resolve this issue by printing a bed level test or using thick paper to ensure an even gap between the nozzle and the print bed. You can also try printing additional skirt lines around the model, and adjust your print bed by evaluating the quality of the skirt lines; however, this is tricky to execute, and not recommended for beginners.

Clean the nozzle​

Often, a speck of dirt or impurities might block the nozzle's orifice and obstruct the filament's flow. It would be best if you unscrew the nozzle, dip it in an acetone/IPA solution and clean it using a brass brush or a nozzle cleaning needle.

If you merely use a cleaning needle, while the nozzle is still in its place, the dirt will get displaced for a moment, but might clog the nozzle again when the filament starts to flow.

Cleaning with IPA/acetone ensures that the impurity is wholly removed and the nozzle's pathway is clear.

Ensure zero gap between nozzle and hot end​

In most 3D printer hot ends, the PTFE tube goes all the way inside the hot end and sits right above the nozzle. If there's any gap between the PTFE tube and nozzle, the molten filament will flow out and fill in this gap, obstructing the filament flow.

Once you've cleaned the nozzle, ensure there's no gap between the PTFE tube and the nozzle sits completely flush with the tube.

Adjust Filament Flow Rate​

If your printing temperature and speed are set correctly, the issue might lie in your extrusion flow rate. This setting controls the volumetric flow of your filament that leaves the nozzle and is dependent on your filament diameter and extruder's calibration. If it's set too low, less filament will come out of the nozzle, thus, resulting in under extrusion.

Adjusting the filament flow rate is a simple procedure, and you can refer to this guide that'll walk you through the steps to set your extrusion rate perfectly. Additionally, check the filament diameter in your slicer settings too.

First Layer Issues​

What Is It?​

First layer issues reduce the chances of a successful print and are often the cause behind several failed 3D prints. Some of the significant and most common first layer problems are - prints not sticking to the bed surface, the first layer too rough, the nozzle not extruding filament or holes and lines in the bottom of your prints.

These problems can either affect the quality of your prints or cause them to fail, leading to loss of filament and printing times. Therefore, it's crucial to eliminate these issues and ensure a smooth and even initial layer.

Things to check​

  1. Print Bed level
  2. Nozzle-Bed Distance
  3. Printing Speed
  4. Printing Temperature
  5. Cooling Settings
  6. Layer Height
  7. Print bed surface

How to Fix it?​

Level the Print Bed​

An incorrectly leveled print bed is the top reason behind a failed first layer. Leveling the print bed ensures that the nozzle and the bed surface are at an equal distance at all points on the print surface.

If the hot end is too close to the print bed, it will squish the filament on the surface. In contrast, if the nozzle's too far away, the filament will not stick to the bed leading to a failed print. Billie Ruben has created a helpful infographic poster using which you can understand the side effects of an incorrectly leveled bed.

If your printer has a manual bed leveling system, you can adjust the bed level by inserting a business card between the nozzle and the bed. You need to adjust the bed screws until the card slightly drags between the hot end and the bed, and repeat this procedure on all four corners of the print bed.

Alternatively, with automatic bed leveling, you'll need to adjust the z-offset setting of your 3D printer. This setting is available in the printer's configuration, or you can configure it within your slicer software.

You can refer to this first layer calibration guide by Michael from Teaching Tech to iron out your first layer. It goes into detail over both the methods and you can use the Gcode generator to create a test print for verifying your bed leveling.

Decrease Initial Layer Print Speed​

A slow initial layer print speed will allow sufficient time for the filament to stick to the print bed properly. It ensures that your first layer's delicate outlines and intricate details (if any) are laid down slowly on the bed surface and stick well to it.

Usually, you can set the first layer print speed to be around 20% of the overall printing speed for your model. In terms of actual units, an ideal first-layer speed can be anywhere between 15 -25 mm/s. This range should give you a good balance between print quality and time and ensure that your first layer sticks well to the surface.

If the print peels off due to high printing speed, and it's left unattended for a while, the subsequent layers will form a spaghetti-like structure and ruin the printing process. You can Obico (formerly Spaghetti Detective) to automatically detect the failed print, and stop the printing. It will help you save on the precious filament material and save some printing time.

Increase First Layer Print Temperature​

It would help if you kept the initial layer temperature 10-15 °C higher than the normal print temperature. It allows the filament to melt neatly, resulting in a smooth flow for the first layer. It also helps the filament to stick well to the print bed and form a strong bond with the printing surface.

Additionally, you can use a heated bed to create a warm ambient temperature, reducing the chances of warping or curling the filament on the first layer.

Shut off the Part Cooling Fan​

The part cooling fan will induce a cool air stream onto the hot first layer. This temperature difference will cause the first layer to curl up from the edges leading to warping or filament not sticking to the bed.

Shutting off the cooling fan for the initial two layers will let these layers stick correctly to the print bed and increase the chances of your print's success. This setting is available in every slicer, and you can configure the layer numbers for which you need to shut off the cooling fan.

Prime the Nozzle​

Priming the nozzle before the printing starts ensures there's sufficient filament in the hot end to lay down a smooth first layer. Otherwise, the initial points of your first layer might not have adequate material leading to an uneven or rough layer.

You can prime the nozzle by adding skirts or brims to your prints from the slicer settings or add a priming Gcode to start your print. Alternatively, you can manually push the filament out of the hot end to ensure adequate material before the print begins.