What is filament?

3D printing filament is the thermoplastic feedstock for fused deposition modeling 3D printers – essential “3D ink”.

FFF 3D printing process

The need for recycled filament

Globally, we are producing and consuming more than 300 million tonnes of plastic per annum. 3D printing is now widespread in many industries; applications include creating prototypes, augment manufacturing processes and producing finished products. Research by Gartner suggests that over the next four years, the number of units shipped in 2020 will total more than 6.7 million. However, because FDM/FFF 3D printer use plastic as feedstock, the technology will exacerbate the plastic problem. Assuming each of these printers uses 20 kg of filament per annum, this will means that 134,000,000 kg of plastic will be needed annually to support market growth. It is therefore clear that as 3D printing becomes more popular, plastic production and consumption will increase, causing many environmental impacts.


What is quality?

The term quality can be vague, so how can we make it more tangible when it comes to 3D printer filament?

The first quality parameter is diameter tolerance; the gold standard across the industry for filament tolerance is +/- 0.05mm. In a real world situation, this means that filament advertised as 1.75mm [+/- 0.05mm] will have an average measurement between 1.66mm and 1.84mm.

The second parameter when it comes to quality is roundness. Unlike diameter tolerance, academic research on roundness is limited, however, going by technical datasheets from various sellers, it seems that ≥ 95% is an acceptable, quantifiable value.

Determining factors

As with any manufactured product, the quality is a only as good as the feedstock it is produced from. The concern with recycled 3D printer filament is that “there may be issues related to getting clean and good quality waste and “ensuring an ongoing, clean and high quality supply of plastic is also a significant challenge”. Foreign debris and/or contaminants in waste streams could cause print failures and extruder blockages. There could even be potential health and environmental risks when the plastics are heated.

The software controlling your 3D printer tells it how much plastic should pushed out of the nozzle (flow rate). The 3D printer then does this by turning the extruder wheel and pushing a certain length of filament down the hot end. If the filament has an irregular diameter (outside +/- 0.05mm) the volume of extruded plastic will be irregular and the software won’t be able to adjust the extrusion length to compensate – leading to inconsistency when printing.

You should ensure filament is consistently round because filament that is more oval-shaped can cause problems, such as extruder failure. In all honesty, filament will always suffer some compression due to the extruder wheel gripping the plastic, however filament roundness consistency is very important overall in ensuring your printer runs smoothly.

The consequences of bad filament

If filament is inconsistent across its either its’ diameter or length , this will change the rate of material extrusion resulting in poor quality 3D prints. If you’re printing for pleasure this is disappointing in itself, but if you’re printing for business – such as a 3D Hub – this could be detrimental in terms of refunds and client loyalty.

The most serious consequence of bad filament is damage to hardware – usually extruder failure. If your filament suddenly becomes too thin for the tensioning mechanism, this leads to insufficient pressure gripping the filament. On the other hand, if the filament’s diameter is suddenly too wide, the extruder motor is not strong enough to push it through or it does not fit into the hot end opening.

In a nutshell, bad quality filament can cause anything from bad quality prints, to breaking the 3D printer itself.

Ensuring quality

So we have explored the challenges of producing recycled filament and how that can produce ‘bad quality’. However, that does not have to be the case; recycled content and quality do not have to be mutually exclusive.

The first step is careful selection of waste streams. All feedstock used is meticulously checked to ensure homogeneity – making sure there are no contaminants or foreign debris.

The next step is to guarantee +/- 0.05mm diameter tolerance and ≥ 95% roundness. This is achieved by using state-of-the-art machinery, adhering to strict strict ISO guidelines. During extrusion, filament is measured by lasers from 2-axes, with an alarm bell sounding if the diameter falls outside our high standards.

Even after the filament is extruded, the quality ensurance continues. Technicians visually inspected each spool to find any imperfections. A sample from each batch produced undergoes a rigorous 3D printing test; if we’re not happy with the print quality then it won’t leave the factory, simple as.

It is true that the quality of polymer can degrade after repeated extrusion cycles, resulting in poor mechanical properties. However, polymer engineers found that recycled filament for 3D printing is possible with minimal loss of strength. With this in mind, we ensure that all filament sold undergoes no more than two extrusion cycles, which ensures that mechanical properties are not affected.


Overall, it is clear than bad filament can have a detrimental impact on 3D printing. Previous research into recycled filament has focussed on technical feasibility only (proof of concept) rather than market viability (is this filament high quality enough for use?). However, recycled filament is only bad quality if the waste stream is not homogenous, the diameter tolerance and roundness is inconsistent, and there is a general disregard for quality control and assurance.


Filamentive specialise in sustainable 3D printing filament – including recycled filament. The catalyst for starting Filamentive was the realisation that the high quality filament in the market was not sustainable, and the recycled filament options were not up to standard

There is also a clear market demand for recycled 3D printer filament:

  • 98% of 3D printer users believe recycling is important
  • 93% would buy recycled filament
  • Two-thirds of those are motivated by environmental reasons
  • Most 3DP consumers would pay at or above the market price for typical filament

Our market reception has been incredibly positive. (just search Filamentive on YouTube to see what the experts have had to say). In regards to our current customers, 94% have said that Filamentive is either a very high quality or high quality filament.

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