The circular economy in FFF 3D printing. Goal: zero waste

Circular economy, closely related to recycling, refers to a systemic approach aimed at optimizing the use of resources by minimizing waste generation and encouraging their reintegration into the production cycle, thus reducing energy consumption, raw materials, and waste production.

It is a production and consumption model designed to extend the lifespan of products, materials, and resources as much as possible, unlike the traditional linear model (extract–produce–use–dispose). The circular economy proposes to:

• Design for durability, reuse, repair, and recycling.
• Reduce the consumption of virgin raw materials.
• Optimize processes to minimize waste and emissions.
• Promote business models based on sharing, reuse, or service.

This approach aims to close the life cycle of products, creating regenerative systems that reduce environmental impact and increase resource efficiency.

In this context, 3D printing can play an important role. As an additive manufacturing process where only the material needed to make the part is used—thus producing no waste—unlike subtractive manufacturing, which removes material to obtain the desired part, generating waste.

Image 1: Additive vs subtractive manufacturing. Sources: Raise3D, Daniel Smyth.

But this is not entirely true, since FFF 3D printing also generates waste, although to a much lesser extent. Let’s look at a brief overview of what they are and how to prevent them:

Material used for supports or adhesion (like rafts, skirts, etc.): While this may vary greatly depending on the part and orientation, in some cases it is unavoidable depending on the model and material used, generating waste.

Image 2: Model with supports and raft. Source: Formlabs.

To prevent this, one should carefully consider the topology and orientation of the parts, reducing the use of support or adhesion materials. Configuration options such as using infill for purging, different support types, or even manually adjusting them can help reduce the amount of material used, saving both time and cost.

Image 3: The same model in different orientations can lead to significant savings. Source: Filament2Print.

Purge towers in multimaterial systems: Whether using a different support material or combining spools of various colors, this generates the well-known purge towers. The wasted material in such cases can far exceed the amount actually used in the part:

Image 4: In this example, 73% of the material used is wasted. Source: Filament2print.

Reducing this kind of waste can be challenging. Options such as purging into infill might have undesirable effects, like color mixing, or might not be viable depending on material combinations.

An alternative is the “Purge to object” option, using the purged material to print a different model where color or material mixing is not an issue.

Image 5: You can reuse purges to print other objects. Source: Reddit.

Spool leftovers: Even after optimizing to reduce all other waste, some material may still remain. This small amount is often insufficient for a new print and, despite filament end sensors, becomes difficult to reuse due to loading and purging processes.

Image 6: Spool leftovers. Source: Reddit.

While the use of dual extruder systems such as the one in the Raise3D Pro 3 HS, or multimaterial systems like the Bambu Lab AMS or the Prusa MMU3, makes it possible to perform what's known as “filament backup.” This means that when a spool runs out, printing continues with another loaded in the multimaterial system. This prevents ending up with leftovers on the spool, although it creates waste in another way, such as purges like those previously discussed.

This material waste, as well as inevitable aesthetic (and sometimes functional) defects resulting from the spool change, can be avoided. It’s very simple when using a tool like the Sunlu filament connector:

Image 7: Sunlu filament connector. Simple and reliable. Source: Sunlu.

Insert the ends of the filament into the tube, place it into the connector, close it, and... Done! A perfect joint, ready to print. Not to mention the interesting effect achieved if there's also a color change.

Image 8: Examples of printing with joined filaments of different colors. Source: Reddit.

Failed prints or those that have served their purpose: In addition to all the previous examples, there are cases where a part fails or no longer fulfills its purpose (templates, tools, prototypes), becoming waste material.

While using quality printers, accessories, and filaments can help prevent failed prints, it's nearly impossible to eliminate the risk entirely. And then there are those parts or tools we no longer need because they've served their purpose. In such cases, what can be done?

Image 9: Bucket with waste material. Source: Reddit.

Reuse and recycling of print waste

Once waste generation has been minimized, for the unavoidable waste, recycling is the next step. The circular economy, the economic model designed to minimize waste and maximize resource efficiency mentioned in the introduction, aligns perfectly with this practice. In this context, filament recycling becomes an essential component, transforming plastic waste into new resources, thus closing the material’s life cycle with nearly zero waste generation and minimal energy cost. We’ll focus on physical processing, meaning shredding, melting, and extruding thermoplastics for recycling and reuse.

Filament recycling in 3D printing is an innovative practice gaining traction in additive manufacturing. This process not only reduces plastic waste but also promotes sustainability by giving a second life to materials that would otherwise end up in landfills. Today, there are highly affordable machines that allow achieving near-zero waste.

Image 10: Recycling and reuse process. Source: MDPI.

To fully leverage 3D printing waste, it is crucial to consider every aspect of the process:

Material separation: Not all thermoplastics are recyclable, and even among those that are, some may require a specific percentage of virgin (non-recycled) material to maintain properties. Given the varying physical and chemical properties of different thermoplastics, proper separation is essential.

This table shows some examples of different thermoplastics and their recycling requirements:

Other thermoplastics can technically be recycled, but they present greater challenges due to their composition, reinforcements, or thermal degradation.

It is essential to keep different types of materials separated to properly process the material and obtain an optimal result, given the varying properties of each thermoplastic. PLA, ABS, PETG, ASA... should be stored independently to avoid undesirable outcomes such as clogs, impurities, or gas generation. Special mention goes to additives. For example, if PLA and PLA-CF (PLA with carbon fiber) are processed together, the carbon fiber will be present in the final output.

Waste processing (shredding): Once the discarded material is separated, it needs to be processed for reuse. For this, a shredder such as the 3devo GP20 can be used. Thanks to its hopper and automatic speed control, it prevents clogs, reduces the material to the appropriate fragment size using its built-in filter, and keeps the temperature controlled to avoid melting.

There are other alternatives, such as the Felfil shredder, with a simpler design geared toward workshops or test labs, which also enables this processing task.

Image 11: Plastic processed in the 3devo GP20. Source: 3Devo.

It is important to note that shredding is more important than it may seem at first glance, as oversized fragments could result in pellets that are not fully extruded or cause clogs, and undersized ones or those processed at too high a temperature could degrade the plastic and its properties.

Extrusion and Spooling:

Now that the material has been separated and converted into manageable granules, the next step is extrusion, either to create new filament on a spooling machine or directly in a pellet extruder. In both cases, it is important to achieve a proper mix between the recycled material and the virgin material or additives to ensure consistency and the desired properties in the final product.

To create new spools, there are two main approaches: Using an extruder such as the Felfil Evo, which melts both recycled and virgin material using a heated extrusion screw, then feeds it into a spooling machine like the Felfil Spool+, which monitors the diameter of the resulting filament and winds it onto a new roll.

Image 12: Recycling process using separate shredder, extruder, and spooler. Source: Felfil.

This approach has some advantages, such as the educational value of seeing the entire process in separate stages, which is especially useful in classrooms and labs, or the reduced cost when replacing or upgrading just one part of the setup.

Alternatively, there are 2-in-1 solutions: extruder/spoolers in a single device that simplify the process, such as the Filament Maker TWO by 3devo. This machine has a container at the top where the material is placed (remember: recycled and virgin mix) along with any additives like colorants or fibers. Then, using the side display interface, the user configures the desired working parameters (temperature, speed, diameter…), and the machine does the rest. All that's left is to attach the filament start to the spool.

Image 13: Filament Maker TWO. Source: 3Devo.

To conclude, there are “all-in-one” solutions such as the Protocycler v3 by Redetec. It manually shreds, extrudes, and spools the material in a single device. It is ideal as a cost-effective and compact recycling solution.

Another approach, perhaps more tangential, is to use the material directly in a pellet-extruding printer or for injection molding. This eliminates the need for extruders or spoolers, allowing the recycled material to be used directly in prints and projects.

Image 14: Pellet-head printer and injection molding machine. Source: Piocreat, RobotFactory.

This video shows the full recycling process, in this case using filament spools, and the possibilities it offers in terms of experimentation and customization.

Video 1: Recycling spools to create filament. Source: Made with Layers.

Summary:

We’ve seen how waste generated in filament-based additive manufacturing can be both reduced and reused. But what are the advantages? Many and varied:

Benefits for the professional sector:

In addition to the clear environmental and sustainability advantages—since the material can be reused almost indefinitely with minimal energy cost—this also represents cost savings through material reuse.

It helps meet sustainability targets, which are increasingly required in tenders, regulations, or international standards, and adds a layer of innovation and differentiation through the use of circular materials or certified ecological processes.

It also creates business opportunities. Once the goal of zero 3D printing waste is achieved, the same infrastructure can be applied to materials such as plastic bottles, disposable cups, etc.

Benefits for the research, education, and maker sectors:

In addition to all the previously mentioned advantages, this process allows experimentation with material combinations in various proportions to create custom compounds, for example through the use of additives and virgin material pellets.

Moreover, the resulting parts from recycled materials will have unique characteristics.

Image 15: Objects printed with recycled material. Source: 3devo.

All this shows that circular economy in filament 3D printing not only reduces environmental impact but also provides economic and strategic benefits, aligning with the shift toward more responsible and efficient additive manufacturing. These processes can contribute to a more sustainable system in line with circular economy principles and help promote a greener and more responsible future. Very few processes can be refined to this level of reuse and zero waste.