I was looking into DIY filament extruders but I find the tolerance varies too much: diameter 1.75 ± 0.2, with perfect parameters ± 0.1, it’s not reliable and it might cause problems in the printers. Also, without a real extruding screw (people use drill bits) you have problems with bubles. If someone will produce local filament for local distribution and reuse those empty spools, it’s gotta be decent quality.
Skip to main content
I would like to find a decent machine, no too big, no too expensive, and to crowdfund it with local Makers who would benefit from local and more affordable materials and contribute to better recycling practices. In the Lab where I’m operating (Making), if I have no time to do it, there are members willing to take over tasks like pulling and extruding filaments.
You know, that PLA and ABS as well as the spools (most times PC => Polycarbonate) are polymers ?
Hi pomaer! we tried the idea of using pellets in a printer instead of filament few years ago in our lab. It was a monster DIY printer intended to be the next home appliance… We quickly realized that moving a hopper and all the weight around was not an option. We also realized that pellets bring problems with air and filament is still the best way to go. It’s light and the print head can muve faster, and the printer will endure less stress from the head changing direction, and it’s consistant. Then we decided to put a hopper and an extruder in the top back side of the printer and the filament produced would be uneven and cause many problems, and that it had to be dried before we feed into the printing head. Our conclusion was that instead of trying to build a do-it-all thing that does nothing right, it’s better to do things with specific jobs as good as possible. Often times, keeping things simple and sturdy is your best option. It’s still possible to have a crusher and an extruder dirrctly integrated into a home appliance sized 3D printer. It would look something like a stove. But there are so many parameters to watch out for… Unless it’s a super reliable closed loop feedback system that monitorizes and decides for best parameter by it self, most users are not Makers and will lose patience… now for the heating of the shredder blades, I think it’s better to freeze the plastic before you mash it, it becomes more brittle and snaps easyer when it’s frosen hard. I think heating it up even a bit will just make it bendy-er
Freezing could have a quite positive effect on the crushing of parts. Did your pellet extruder contain a filter and did you use an extruderscrew or just an auger one? One of the most important features that DIY pellet extruders are missing is a real extruder screw that compresses the pellets by getting smaller (the space where the pellets are gets smaller). I thought about a design for a printer, that doesn’t move the printhead, I’ll explain that later. -Marius
This is all interesting stuff. I think that there are many challenges here and it’s best to separate out the issues. Firstly, I think we need to decouple shredding from extruding.
Shredding has its advantages, which are mainly environmental, rather than financial. Realistically, I think a semi-centralised shredding function is most practical.
Extruding is financially very attractive. As Marius says, granulated plastic is cheaper than filament, except that the actual difference in cost is enormous. I heard that the World market for filament is less than 100 Tonnes. The market for granulated plastic is in the Millions of Tonnes per year so the potential difference is very high - think 1-2 Cents per kilo for granulated plastic. Now THAT concentrates the mind!
There are one or two granule-fed print heads surfacing. TBH, I think it’s only a matter of time before the technical challenges are met. Perhaps it’s been done already.
cheers,
AndyL
Pot8oSh3D
most of those machines don’t have a closed loop control of the filament… What they all lack mostly are a sensor that measures the filament width and then adjusts according to that.
Modular Filament Extruder by diegotrap - Thingiverse is close to cheap and good enough, all its missing is this one Filament Width Sensor - Prototype 2 by flipper - Thingiverse
and then you simply adjust the speed of the puller so the diameter matches… it will take a bit for the width to be stable, but once you reach that stage you simple cut the filament and the first bit you can cut in small bits and melt them again
going to build it over and after summer…
You’re right, we used a drill bit for the proof of concept and we should have tried with a real screw. We thought the best way would be twin screws heated by induction to keep the temp stable. There are some neatly designed twin screws that take care of air bubbles, evenly mix in pigments and other stuff like carbon microfiber or nanotubes, etc… But then again, extruding the plastic is not enough. Pulling, stretching and cooling is a fine balance of parameters for best results with each plastic. That’s for filament usung 3D printers, I can’t wait to see your design… Cheers!
@Pot8oSh3D @BDan I thought about anot extruder design somewhat similar to the STACKER 3d printer. You can change the stacker-hotends depending on the material that you want. There would be three heat zones in the extruder which is will explain soon. Sadly I wasn’t at the PC since todays morning morning. -Marius
Here is the explanation. I hope everything is readable.
The following is the text on the picture on the left side:
(1) Sliders for extruder
(2) ramaining panel for mounting the extruder
(1) “feed”-area where pellets get inserted into the screw; Temp -> 25°C (no heatsource in this area)
(2)“compression”-area where the pellets get heated to glass transision temperature and get compressed to form an air-free paste, the screw’s geometry is made for this; Temp -> 60-100°C (depending on material)
(3) “extrusion area” selfexplaining; Temp -> 180-300°C (depending on material)
//The small brown connectors between the bigger blocks that determin (1) to (3) are heatbreaks just like in nearly every hotend to ensure, that the possible 300°C from the hotend do not get up to the “feed” area. The screw is obviously out of metal and therefore conducts heat very good.
-Marius
yes i do i meant that use the polymer to make the spool into the Abs or Pla filament print with it