After my previous series of 3 Talk posts, that were an introduction to local recycling:
- Part 1: Introduction to 3D printing recycling
- Part 2: How does local recycling work
- Part 3: Which shredding and extruding machines are available
I would like to take that knowledge and apply it to a practical situation: “How to make your own filament from recycling old prints”. In the first post of this new series I will focus on my research setup. The second post will be all about the results and what we can learn from it.
Sneak peek of fully recycled filament
How to get the best recycled filament from your old 3D prints?
It is important to have material that is clean and separated so the plastic is only ABS or PLA. Also our guess is that material that is more similar in size, shape and chemical composition will yield better results. However so far no evidence of this assumption has been found. In my previous talk post I shared some general info on the recycling process and what is expected to work well. Now I’d like to go into more detail on my learnings and what my research setup looked like.
How to shred your old prints
You can basically use any machine that pulverizes your pellets into small pieces. For the Filabot my guess is that the maximum size the pieces should be is about 0,7cm in diameter. I used a Filamaker shredder that is specifically designed for shredding old prints. This post describes the setup for shredding that worked really well for me.
How to set up the filament extruder
The most important thing for sure when setting up the extruder is that the filament experiences a constant pull when coming out of the extruder. In more professional setups the filament is spooled using a spooling system that measures the diameter of the filament and adjusts the pull in order to keep the diameter constant.
In a more simple setup however this is not feasible and we should look at how we can keep the pull as constant as possible. I tried to do this by placing the Filabot on a table and letting the filament drop to the ground. You can then let the filament curl op in circles on the ground. What worked for me though was pushing the filament gently to one side once it had hit the ground. After trying out many different setups I found that the one shown in the picture below worked really well for me. The nozzle of the Filabot is at 120cm from the ground and as you can see the Filabot is placed horizontally.
How to finetune your recycling machine
Once you have chosen a setup that works well it is time to finetune the process in order to get the best results. I chose three different things to adjust:
- Nozzle size.
- Extruding temperature.
- Power and distance of the fan.
This is by far the most ‘rough’ adjustment you can make. PLA has a tendency to stretch quite a lot once it is extruded. I aimed at extruding at 1.75mm diameter and therefore used a 1.95mm nozzle. ABS on the other hand expands quite a lot after it is extruded and for this a 1.55mm nozzle was more appropriate.
The temperature at which you extrude is easy to adjust. Both for ABS and PLA it takes some experimenting to figure out what works best. In general if the Filament is extruded too slowly the temperature needs to be increased and if the filament stretches out too much or curls up right as it comes out of the nozzle the temperature needs to be decreased. I used the following settings primarily:
- ABS: 185C
- PLA: 155C
One of the things I noticed when extruding ABS however was that when the ratio of recycled material in the mix increased to 50% or more, the extruding temperature needed to be increased as well. Without this increase in temperature the Filabot would simply jam. I ended up extruding at 205C which in turn caused the ABS to stretch a lot more as well. To cope with this increased stretching instead of using a 1.55mm nozzle I used a 1.95mm nozzle.
As you can see the finetuning process is a constant struggle to combine and perfect all three settings.
Power and distance of the fan
The final parameter to control is the cooling of the filament. This decreases the extent to which the filament is stretched out. So more cooling in general means a larger filament diameter. There is a limit however because you don’t want to blow the filament away too much as it comes out of the nozzle.
I used the most basic fan I could find at my local home depot (called Praxis here in A’dam ;)). The fan produced 30W power and I used it for PLA at half power. I placed it at 30-100cm from the Filabot and aimed at the filament 10-30 cm below the nozzle. The more recycled material I used in the input mix the closer I had to place the fan because the filament stretched more.
My advice would be to first choose a nozzle size, then change the temperature and finally for the last bit of finetuning include a fan and adjust its position.
Next post will be about the precise details of my setup and the exact results I was able to get.
This post is part of the second series of 5 on recycling for 3D printing.
- Series 1 | Introduction to 3d printing recycling (Post 1, 2, 3)
- Series 2 | How to make your own filament by recycling old 3D prints
- Series 3 | 3D Printing with recycled filament
- Series 4 | The promise of 3D printing with recycled household waste
- Series 5 | Can Polypropylene (PP) plastic be the next big thing in 3D Printing