How to Make Your Own 3D Printer Filament
Melting plastic is easy. Turning it into filament that holds the same diameter along an entire spool and prints reliably is a different matter, and that is what decides whether home-made filament is any good.
This guide walks through the process from sorted scrap to finished spool, shows which steps depend on each other, and gives an honest view of who it pays off for. For what you can do with scraps in general, including without your own machines, see recycling filament scraps.
The process at a glance
Scrap becomes filament again in several steps:
- sort the material
- clean it
- shred it
- dry it
- extrude
- cool
- measure the diameter
- control tension and speed
- spool
The first four steps prepare the material; the last five happen at the same time on one line. Mistakes made during preparation are hard to fix later: contaminated or damp regrind will not make good filament, however good the machine.
Sorting the material
Only process known polymers together: PLA with PLA, PETG with PETG, ABS with ABS. Different plastics melt in different ranges and do not combine into a uniform material. Even small amounts of a foreign polymer can cause inclusions, weak spots and uneven flow.
Scrap you cannot identify with certainty stays out of the batch. The same goes for carbon- and glass-fibre composites: they are not mixed with unfilled material, and the fibres can wear the screw and nozzle much faster. Whether a machine is designed for filled materials is for its manufacturer to say.
Cleaning
Before shredding, remove everything that is not the plastic itself:
- metal such as screws, nuts or inserts
- paper, labels and tape
- adhesive residue, for example from the print bed
- dust and dirt
- other polymers, such as soluble support or parts printed in a different filament
Metal is not just a quality problem: it can damage the shredder and the extruder.
Shredding
Failed prints and supports have to be shredded into regrind so the extruder can feed them evenly. The more uniform the particles, the more even the feed.
Pieces of very different sizes, or long thin strands, can bridge in the hopper or make the feed stall. That goes straight into the flow and from there into the filament diameter. Many users therefore sieve their regrind or shred it in more than one pass.
Drying
Regrind has far more surface area than a spool of filament and absorbs moisture correspondingly faster. Damp material can form bubbles during extrusion, cause diameter swings and degrade the polymer further as it melts.
How long and at what temperature to dry depends on the polymer; the machine and material manufacturers give guidance. The basics are in drying filament. Keep dried regrind sealed until you process it.
Extrusion
In the extruder, a screw carries the regrind through heated zones, melts it and pushes it through a nozzle. The right settings depend on many factors:
- the polymer and its exact formulation
- the temperature of each heating zone
- screw speed
- nozzle geometry
- material throughput
- cooling after the nozzle
That is why there is no universal “recycling temperature” for PLA, PETG or any other material. Start from the machine manufacturer's recommendations for the material and tune from there on your actual regrind. A new batch may mean starting that tuning again.
Diameter: the critical point
Filament with a nominal 1.75 mm diameter is only usable if it actually holds that diameter consistently. What counts is not a single measurement but how little the diameter varies along the whole spool. The printer assumes a fixed cross-section and feeds accordingly; if the filament deviates, the amount of plastic is wrong.
Too much variation leads to:
- over-extrusion where the filament is thick
- under-extrusion where it is thin
- uneven flow and visible banding
- poor dimensional accuracy
- in extreme cases, filament jamming in the hotend or the filament path
So the diameter is measured continuously during production and the line is adjusted based on that measurement. Filament that is only right in places is no good for consistent prints.
Cooling and spooling
Straight out of the nozzle, the strand is still soft. How fast it is pulled away determines how much it stretches, and therefore its diameter. Cooling fixes the moment its shape stops changing. Pull too fast and the filament gets thinner; too slowly and it gets thicker.
Extrusion, cooling and spooling are therefore tightly coupled. If throughput changes, say because the feed stalls briefly, the puller has to follow, or a thin or thick section appears immediately. A good line adjusts the pull speed from the measured diameter.
Finally, the filament is wound evenly onto the spool, since a messy winding can tangle during printing. A test print shows whether the new spool works in practice.
Blending recycled and virgin material
Repeated melting can change a plastic, for example its strength, toughness or flow. Filament made from 100 % recycled material is therefore not automatically equal to virgin material.
Depending on the process, virgin pellets are blended into the regrind to stabilise properties and processability. There is no fixed percentage that suits every material and every machine. The ratio depends on the input material, how often it has already been processed, and what the finished part has to withstand. Test home-made filament before using it for loaded or dimensionally critical parts.
Is it worth doing at home?
For the occasional failed print, your own recycling line is more of a maker project than a way to save money. Shredder, extruder, drying and spooling are an investment, setting them up takes time, and dialling in the process produces waste of its own. If you only have a small amount of scrap, handing it on sorted is usually the better option.
Making filament becomes more interesting where large amounts of single-material scrap build up regularly, or where the process itself is the point:
- maker spaces and FabLabs running many printers
- schools and universities that teach the process
- businesses with a high volume of waste from a known material
- research and material development, for example into recycled content or new blends
Safety
Shredders and extruders work with sharp cutting tools, high forces and hot zones. A shredder does not tell plastic from fingers, and nozzles and heating zones can cause serious burns.
Use machines whose guarding is designed for the job, and follow the manufacturer's operating manual. Covers, emergency stops and interlocks are part of the machine and must not be removed or bypassed. This guide deliberately contains no build instructions for home-made shredders or extruders: designing such machines safely takes expertise that an overview cannot replace.
Also make sure there is good ventilation when melting plastic, and follow the safety information for the specific material.
Frequently asked questions
Can I make new filament from failed prints?
Yes, with a shredder, an extruder and a controlled spooler. The scrap has to be single-material, clean and dry. The real challenge is a consistent diameter along the whole spool.
At what temperature is recycled filament extruded?
There is no universal temperature. It depends on the polymer, the formulation, the machine, the screw speed and the throughput. Start from the machine manufacturer's settings for the material.
Why does the diameter matter so much?
The printer assumes a fixed filament cross-section. If the diameter varies, too much plastic comes out at thick sections and too little at thin ones, giving uneven surfaces and poor dimensional accuracy.
Will making my own filament save me money?
With occasional failed prints, usually not. The machines, the setup time and the waste while dialling in outweigh the material saved. It becomes more economical with large volumes of single-material scrap, for example in maker spaces or businesses.
Is home-made filament as good as bought filament?
Not automatically. Repeated melting can change the material, and without good control the diameter is less consistent. Test home-made filament before using it for important parts.
Can I process different plastics together?
No. Different polymers melt in different ranges and do not combine into a uniform material. Unknown plastics and composites do not belong in a single-material batch.
Build a part with Vuolti: Go to the 3D generators