3D Printing Under-Extrusion: Causes and Fixes

Under-extrusion is one of the most common issues in FDM 3D printing, and it results in missing layers or obvious gaps and holes on the print surface. If you're experiencing this problem, it's important to understand that it's typically caused by hardware and incorrect print settings. However, it's not a problem that cannot be solved and there's no need to feel frustrated about it. Let's take action and dive right in. This tutorial focuses on the causes of under-extrusion and how to resolve it.

Why Is My 3D Printer Under Extruding?

3D Printing Under-Extrusion

Under-extrusion in 3D printing is the opposite problem of over-extrusion and occurs when too little material is extruded during printing, leading to negatively impact the print's aesthetics and weaken its overall structure. This issue is closely tied to the condition of your machine's hardware, print settings in the slicer, and even the materials you're using. You can troubleshoot the hardware first, such as the nozzle and extruder, and then check the software settings like print temperature and extruder flow rate. Finally, ensuring proper storage conditions for the filament should not be overlooked. Below are common causes of under-extrusion:

  • Filament is degraded or has an incorrect diameter.
  • 3D printer nozzle is clogged.
  • Print temperature is not enough to melt the filament.
  • Extruder tension is inappropriate.

How to Fix 3D Printer Under-Extrusion

1. Seal and Store Your Filament

Vacuum-Packaging Filament

To properly store 3D printer filaments like PLA, ABS, PETG, ASA, and so on, it's essential to keep them dry and free from dust. When filaments are exposed to the air, they can absorb moisture, which can lead to reduced print quality and issues such as under-extrusion, bad layer adhesion, and 3D print stringing. Therefore, when selecting filaments, it's crucial to choose a reliable brand known for good quality and packaging.

Anycubic, a global 3D printer manufacturer, offers filament with a 1.75mm diameter that is compatible with most printers on the market. These filaments are shipped with double packaging, providing an extra layer of protection. They come in vacuum-sealed packaging with sturdy cardboard boxes.

Moreover, it's important to store filament in a low-humidity environment after each use. It's recommended to place them in sealed bags or containers along with desiccant packs, and vacuum-sealing is the best practice for long-term storage. If you encounter wet filament issues, it's not irreversible; you can dry them by using an oven, a food dehydrator, or a filament dryer box.

2. Maintain 3D Printer Nozzle

Clogged Nozzle

(Image source: Anycubic official user group)

Nozzle clogging is one of the most common issues in FDM printing, and it often occurs due to nozzle or room temperature fluctuations and an unmaintained nozzle. Nozzles are consumables, and with use over time, cleaning and replacing them in a timely manner is common practice. A blocked nozzle's tip can become smaller, and the amount of molten filament coming out is less than the expected amount. In this case, under-extrusion may occur. Thus, it's necessary to clean and remove residual material from the nozzle using a needle or brush after each print. For more information, I recommend checking out this article on how to clean a clogged nozzle.

3. Increase Print Temperature

3D Printing Under-Extrusion

Different materials require different printing temperatures; for example, PLA filament typically needs a nozzle temperature range of 180 to 220°C, while ABS filament usually requires temperatures between 230 and 250°C. If the hot-end temperature is too low, the material will melt more slowly than expected, resulting in your 3D printer under extruding. You can perform small test prints with slight temperature decreases of 5-10°C to observe the effects and fine-tune the settings. Additionally, consulting the filament manufacturer for their recommended optimal print temperature is an effective and direct way.

4. Adjust Extruder Tension and Flow Rate

Filament gets stuck in extruder

If no problem here with your filament, nozzle, and temperature settings, and you still encounter under-extrusion issues, you can check your machine's extruder. Incorrect extruder tension can easily lead to filament grinding, slipping or jamming inside the extruder, resulting in debris buildup. As this debris accumulates, it reduces the extrusion rate, and 3D printing under-extruding happens. You should start by cleaning your extruder, and then calibrating the extrusion tension. Another reason for under-extrusion issues can be an insufficient flow rate from the extruder. It can often be resolved by adjusting this parameter in the slicer, and increasing it by 5% until it gets better.

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