Recycling PLA Filament from 3D Printing – A Complete Guide

3D printing is an innovative manufacturing process that is revolutionizing product design and development. One of the most common materials used in 3D printing is polylactic acid (PLA). PLA has become ubiquitous in 3D printing due to its low cost, ease of printing, and biodegradable nature. However, with the rapid growth of 3D printing, there are increasing concerns about PLA waste and recyclability. This guide provides an in-depth look at why and how to recycle PLA filament from 3D printing.

The Need for PLA Recycling

PLA is marketed as a sustainable, environmentally-friendly material made from renewable sources like cornstarch or sugarcane. However, PLA still takes decades to fully biodegrade in most environments. And like most plastics, PLA releases greenhouse gases when incinerated.

With more PLA being used in 3D printing, recycling efforts are essential to reducing its environmental impact. Recycling PLA decreases waste, greenhouse gas emissions, and saves on future PLA purchases. Most importantly, a circular recycling system helps make 3D printing and PLA use indefinitely sustainable.

How to Recycle 3D Printing PLA Filament

While commercial PLA recycling systems are still limited, 3D printing enthusiasts can recycle their own PLA waste through various methods:

Step 1: Collect and Clean the PLA Scrap

Gather together all leftover spools, snippets, scraps, and failed 3D prints made of PLA. PLA waste should be kept dry to avoid degradation.

Once collected, clean the PLA thoroughly by removing any dirt, adhesives, or other bonded materials. Most experts recommend soaking prints in warm soapy water to dissolve adhesives.

Step 2: Shred and Pelletize the PLA

A common DIY approach is to shred the clean, dry PLA into small pieces using a plastic shredder or heavy-duty bladed mixer. These flakes or pellets can then be fed directly into a filament extruder.

Alternatively, many desktop filament makers like the Filabot can grind and pelletize PLA in a single step. These systems create uniform PLA pellets optimized for re-melting and extrusion.

Step 3: Re-Extrude the PLA Pellets into Filament

Desktop filament extruders allow reprocessing of PLA pellets into usable 1.75mm or 3mm filament. The extrusion method, temperature profile, and cooling rate impact the quality and diameter of the filament produced.

PLA filament quality tends to degrade over multiple processing cycles as polymers shorten. But with careful extrusion control, reprocessed PLA can be strong enough for lower-stress prints.

Step 4: Use Recycled PLA Just Like New Filament

Once spooled, recycled PLA filament may be a little discolored but can print just like new material. The ideal prints to use recycled PLA for are concept models, prototypes, or decorative pieces with low structural demands.

Recycled PLA Properties & Performance

Recycled PLA filament can have slightly differing properties versus new filament, depending on reprocessing and quality control. Potential differences include:

• Color – Recycled PLA will be darker and possibly multi-hued from varied source materials. Dyes can be added to create specific colors.
• Strength – PLA can lose structural strength after multiple re-extrusions due to polymer chain degradation. But stratifying print orientation can still produce robust parts.
• Diameter Tolerance – Extrusion process precision impacts diameter consistency. Good diameter control ensures print reliability.
• Viscosity – More recycled PLA extrusion cycles could potentially increase melt viscosity slightly. Print temperatures may need to be adjusted higher.
• Contaminants – Improper sorting or cleaning before recycling can introduce foreign substances and clog the nozzle.

With testing and tweaking, recycled PLA can deliver excellent performance for the right applications. The filament is also far cheaper than virgin PLA.

Advanced PLA Recycling Methods

Makers have pioneered accessible PLA recycling systems for the 3D printing community. But commercial and industrial solutions are ramping up as well:

Chemical Recycling

Chemical processes like glycolysis, hydrolysis, and pyrolysis can break down PLA into reusable lactic acid or basic polymer building blocks. The materials can then be purified and re-polymerized into high-quality filament.

Industrial PLA Granulation

Specialized equipment like large-scale grinders and polymer extruders can efficiently process PLA into fine powders or pellets for remanufacturing. This closed-loop recycling stream maintains the purity and integrity of the PLA.

Filament Reconditioning

Some companies offer commercial PLA filament recycling services. Used filament is reconditioned to filter impurities and create uniform, high-tolerance filament optimized for printing performance.

The Future of PLA Recycling

Recycling initiatives are essential for scaling 3D printing sustainably and reducing the environmental impact of materials like PLA.

As PLA use increases, developing closed-loop recycling systems and biorefining capabilities will allow the 3D printing community to continue utilizing this versatile, renewable plastic. More widespread commercial recycling services would also make participating easier for the average user.

With growing interest and advancing technology, recycled filament from PLA and other plastics may one day become as commonplace as recycled paper. The future looks bright for a truly circular 3D printing ecosystem.