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My machinery 2021: Direct Granules Extruder

Waste plastic turned into raw material for 3D printing.

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For this year's Hackaday Prize I dive deeper into 3D printing. The aim is to reuse waste prints with a direct granules extruder. I got this working nicely during the past weeks and I also discovered a way to use industrial pellets as raw material, replacing the need for filament (on plastic spools). Another benefit of using granules as raw material is the capability of printing a wider range of materials that are otherwise too soft or to brittle to be processed as filament.

The extruder is meant to be a drop-in replacement for existing desktop filament extruders with no additional electronics needed, thus it is working with a relatively weak stepper motor and uses one normal heating cartridge. No extruder you can buy anywhere, yet!

With my machines I aim to give students a better understanding of how technology works and of course I'd like to drive innovation as well. "Keep things simple" is the mantra that I follow. Simple to build, out of parts that are simple to source and bring it to live with simply some lines of software code.

I am fighting common thoughts that complex machines like 3D printers must be composed of complex parts manufactured with complex machinery. I am replacing expensive tool chains with my brain ;-) That often means breaking with conventional ideas.

Done:

- Build a reliably working extruder prototype (V3).

- Create build instructions (including video), even so it is a prototype made following my intuition.

- Explain in detail how the extruder works and so why normal wood screws are better than anything else: In contrast to conventional extruders, the forwarding happens in the cold zone only.

- More details about how to print with household sugar and so using materials with essentially different properties than common FDM materials.

Done, but not explained in detail, yet:

- What to consider when preparing raw material

- How to feed the extruder with conventional, industrial pellets

- Find ways to convert waste prints into new raw material for the extruder

To do:

- More print tests with a larger variety of raw materials

- Build version 4 with series production in mind instead of the handmade version 3

Rocket.zip

openSCAD and stl files of the Rocket I have printed as a test run of the extruder.

Zip Archive - 311.58 kB - 11/07/2021 at 07:27

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Build-Instruction-Extruder-V3.pdf

Build instruction of Direct Granules Extruder V3. Keep in mind, that this handmade prototype was largely build using the rule of thumb.

Adobe Portable Document Format - 391.30 kB - 10/25/2021 at 08:40

Preview
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Extruder-V3.zip

3D files of the printed parts needed for Extruder V3 (STL and OpenSCAD)

Zip Archive - 3.95 MB - 10/25/2021 at 08:33

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warping.zip

Python scripts that generate G-code files to minimize warping of 3D prints. The scripts generate G-Code for a gear rack and a box.. Also included are stl files of such a gear rack and box.

Zip Archive - 709.24 kB - 09/03/2021 at 10:43

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RobotArm-v1_0.zip

The Python script (tested on Debian Linux) and Arduino sketch I have written for my robotic arm v1.0 You can control the robotic arm with your keyboard and store/replay movements.

Zip Archive - 5.97 kB - 08/19/2021 at 06:17

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  • 1 × Aluminum bar 16x16, 300mm length
  • 1 × Aluminum plate 3x65x130mm
  • 1 × 3mm threaded rod 1m
  • 1 × Glass block 25x25x8mm
  • 1 × Teflon tube 8mm inner diameter

View all 12 components

  • 3D printing Sugar in more detail

    Norbert Heinz11/10/2021 at 08:02 0 comments

    My lazy Sunday afternoon project of 3D printing sugar is followed by a more in depth view on what can be done with that exotic material and what can't be done:


    Sugar isn't plastics

    Due to a different chemical composition, the physical properties of sugar are totally different from that of common plastics used in FDM printing. A glass temperature exists, but only academically speaking. The transition from solid to liquid appears almost instantly. The viscosity is clearly lower than that of common plastics and the surface tension is higher. With that, sucrose, as used in my experiments, drips out of the extruder without forming strings.

    It works in general

    The very first try was a copy of the pinion on the stepper motor of my extruder. You can recognize it as being a gear, even the 3mm teeth can be seen, also the layering. The top surface is very rough. That's due to the low viscosity and the surface tension of molten sugar. At low print speeds, there is always a drop of sugar sticking to the tip of the nozzle and droplets form on the top layer.

    Print it fast to get rid of droplets on the surface:

    You need to print sugar with a higher print speed (30mm/s) to give the molten sugar not enough time to form droplets while cooling down.

    Print it slow to avoid cracking

    even when printed, sugar is still a very brittle material. With high print speeds, tensions build up in the material which can lead to cracks in thin walls. With a low print speed of just 10mm/s I could print 1.8mm walls without any problems.

    The more you know about a material, the better the results

    Part cooling and heated build chamber will make things better

    The diameter of the cone at the base is 100mm., the angle is 45degrees. The closer the print came to the tip, the less time there was for the sugar to solidify. That caused the forming of droplets and finally to an aborted print. Part cooling for small structures could be an improvement. Also a heated build chamber can help to avoid tensions in the material. There is more experimentation to be carried out, but not yet...

  • Hackaday Prize finals video, discussing the "Rocket"

    Norbert Heinz11/07/2021 at 07:26 0 comments

    Hackaday Prize 2021 comes to an end today. My project was voted into the final round and as part of the competition, an up to 5 minutes video for the jury has to be recorded. Here is mine:

    For this video I have created a "Rocket" in openSCAD ((see files section):

    The printer settings were:

    Hotend temperature: 181°C

    Bed temperature: 65°C

    Layer height: 0.2mm

    Layer width: 0.5mm

    Infill: 0%

    Rocket dimensions: 100x100x150mm

    Lets have a closer look at the result, my extruder delivered:

    First thing you will notice is the tip of the rocket:

    This is definitely where a part cooling fan would be helpful. Even though there is one implemented in my Extruder design, I did not screw it in place. The reason is, that is blocks the view on the nozzle and this is why I rarely used it during my test runs. These tests were always about the extruding capabilities, rather than about the overall print quality of the whole printer. So forgive me not to have added the fan before starting the print...

    While talking about the extruding capabilities, a smooth surface is a result of constant extrusion and that is what a good extruder MUST deliver.

    The detailed look at the surface demonstrates, that the surface is a it should be. What seems to be a crack in the surface at a first look is in fact nothing else than a single grain of non red color that entered the extruder (I didn't clean the blender nor the hopper that carefully).

    Stringing is not addressed, yet:

    In the video about the construction details (see previous blog entry), I have demonstrated how it  works. The issue is that the screw squeezes out an extra portion of plastics when going intro reverse. That must be addressed in an additional parameter in the slicing software, but doesn't exist, yet. More on that in a coming video/blog entry.

    Ghosting can be seen on the right fin of the rocket. This is due to the weak printer mechanics, not due to inconsistent extrusion.

    The first layer looks good, which is also an indication of constant extrusion:

    All in all, the quality, this handmade prototype delivers, is better than anything I have seen from a direct pellet/granules extruder. It only can get better with a better printer mechanics, a part cooling fan and a more precise machined extruder following this design (that is under construction).

    More on the sugar print will follow, soon:

  • RepRap Ltd starts reproducing my extruder design

    Norbert Heinz11/02/2021 at 15:43 0 comments

    I got in contact with Adrian Bowyer and now he tries to make a "copy" of my design, publishing the process on twitter via the RepRap account. As experienced 3D expert, the copy is of course no 1:1 rebuild of my drawings. It is also ruled by the materials he has in stock (e.g. the Teflon tube has an inner diameter of 7mm, not 8mm as I recommend).

    RepRap via Twitter:

    Can't wait to see it working!

  • Feedback comes in!

    Norbert Heinz10/31/2021 at 12:55 0 comments

    With the steps forward, I made during the months of this year's Hackaday Prize and the deeper insight that I gave into my experimentations, lots of feedback comes in from people being highly interested in my extruder V3. I am proud that Adrian Bowyer, the father of the RepRap movement, which finally gave all tinkerers a 3D factory on their desk, is among those who gave feedbak via Twitter:

    TweetTo make my extruder replace filament printing, there is still a lot more to tell about what I have figured out. Previous attempts, using "classic" extruders have failed. I must explain in more detail, what my extruder is different in and why I used the design I am using. The knowledge about the working principles must become more mainstream. Open source doesn't end in publishing CAD files or drawings...

  • Video showing the history of my extruder development

    Norbert Heinz10/30/2021 at 19:17 0 comments

    In a video I am talking about the history of my extruder development. It was no  straight path to success:

    Analyzing material samples from the inside of the extruder enabled me to finally build a working prototype:

  • Revised build instruction, drawings added

    Norbert Heinz10/26/2021 at 09:17 1 comment

    Requests are coming in from people that are interested in making a copy of my extruder prototype. That's why I have revised the build instruction and also added drawings with more exact dimensions. I have built the extruder prototype more or less following my intuition, so I had to do a couple of measurements to give you some more numbers:

    CAD files will be available for the coming stage of my extruder evolution since this is meant to be created by machines...

  • 3D printing sugar

    Norbert Heinz10/24/2021 at 19:40 0 comments

    Have I found the sweat spot of my direct extruder?

    Printing PLA works fine. The raw material can be sourced from failed prints, pellets or waste plastics. Put it in a blender and sieve the grains - done. But what about using a raw material that is available in each hosehold? On a lazy Sunday afternoon,. sugar came to my mind. So let's check if that material melts at temperatures my extruder can reach. Yes, it does. So heat up the machine and put a couple of spoons full of sugar in the hopper. First thing I noticed was that sugar doesn't exit the extruder as a string, such as PLA does. Instead it is dripping out more like water:

    Well, now that there is sugar in, let's give it a test run anyway. Getting a first layer stick to the print bed worked in the third run. I swapped to a different wood screw to get a higher extrusion rate. The layer of glue stick grew thicker with each run. Finally the printer made it:

    While the print grew layer by layer, I have adjusted the flow rate. It was tricky to do so, because of the very different properties of the extruded sugar. Due to the more water like viscosity and the high surface tension, the top layer always looked a bit rough. Nevertheless the gear grew:

    The final result is far from being perfect, but keep in mind it was just a lazy Sunday afternoon project:

    There is more than just one kind of sugar available in a supermarket, maybe that there are better recipes for the "sweet spot". Sugar is too brittle to be turned into filament, so there is no way around a direct granule extruder if you want to print with a brittle material like that. It would be a great material for water soluble support structures.

  • Video shows details of the construction of Extruder V3

    Norbert Heinz10/23/2021 at 11:15 0 comments

    The video also explains why I did some things the way I did them and you can see a quick speed test at the end:

  • First test print with a 0.6mm nozzle

    Norbert Heinz10/22/2021 at 18:49 0 comments

    If you want to hide the weak points of your printer, print something big in vase mode ;-)

    I don't want to hide the weak points, which is why I have made a test print of a tiny object. It is the link of a chain with the dimensions  27x25x12mm. The object cooling fan is still not mounted on the extruder and closing the nozzle to avoid stringing doesn't work as it should (yet). Stringing will be a subject in a coming video. I have used a 0.6mm nozzle for the print. Layer height is 0.2mm, extrusion width 0.5mm.

    The 2mm walls are straight, which is an indication that V3 can handle constant extrusion:

  • I have printed a spare part with my extruder for my extruder

    Norbert Heinz10/21/2021 at 18:43 0 comments

    The main gear of my extruder drives the wood screw I am using as auger. During lots of experimentation, especially when failed designs lead to clogging of the extruder, there was a bit more wear on the shaft than it could handle. With a trick (placing an additional nut on top of the screw head) I could use that gear for a last print:

    I have printed a copy of the failed gear to get my needed spare part.

    Even though the result isn't perfect (I should have squared the weak printer mechanics before starting the print), the replacement part works fine:

View all 15 project logs

  • 1
    Why there is no step by step build instruction for Direct Extruder V3, but of course an instruction exists

    Direct Granules Extruder V3 is a prototype you can build from cheap, commonly available materials with low tech tools. It is not for beginners in 3D printing, but advanced tinkerers should be able to make a copy. Since not being intended for beginners, I don't provide a step by step build instruction. Instead you get drawings and pictures in the "files" section that should enable you to create your own extruder.

    Another issue is, that this design is based on other physical principles than existing extruders. It is essential to get a deeper understanding of those principles that I have described in the logs of this projects that also include videos.

    Leave a comment if you still have questions about the build process of the direct extruder.

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Discussions

benjjyman wrote 11/07/2021 at 11:51 point

1 can we vote for you?

2 one problem with design is ptfe tube for use with recycled ABS, or Nylon or anything above 260 degrees celcius , other than that this brilliant

3 could you please explain warping python script ?

  Are you sure? yes | no

Norbert Heinz wrote 11/07/2021 at 14:43 point

(1) You can like my project (on top of this page), but votes are up to the Hackaday Price jury.
(2) Yes, in a future design, the PTFE tube will no longer reach into the hot zone.
(3) What explanation is needed? It was just a proof of concept, not yet meant to be an implementation in a slicing software.

  Are you sure? yes | no

heinz wrote 10/23/2021 at 04:05 point

Nice, I'm a fan of your design style. 

How is the screw located in the whole assembly? Does the screw end where the teflon tube ends and the 1.5mm rod continues to go into the heater block?

  Are you sure? yes | no

Norbert Heinz wrote 10/23/2021 at 11:17 point

Thanks! Right now I have added a log entry with a video, that will hopefully answer your question: https://youtu.be/oH-e_poDeYE

  Are you sure? yes | no

heinz wrote 10/23/2021 at 14:07 point

Ah okay, screw ends on the cold side or a little bit beneath. Didn't realize the 1.5mm is rod is for sealing the nozzle on retraction, thought it had some stirring function.

  Are you sure? yes | no

nodemcu12ecanada wrote 08/23/2021 at 14:24 point

Very inexpensive 6 degrees of freedom robot arms are readily available.

You have to get a power supply and do the controls yourself. I used a $4 NodeMCU.

https://hackaday.io/project/177278-robot-arm-with-web-page-hmi

  Are you sure? yes | no

Norbert Heinz wrote 08/23/2021 at 15:03 point

I never said, my robot arm was the first and only one. ;-)

Countless arms using RC hobby servos exist, I also have built one before:

https://homofaciens.de/technics-machines-robot-arm-v0-1_en.htm
These are all interesting devices to learn basics about robotics. Add some new design details to the army of DIY robots is why I created mine from wood.

  Are you sure? yes | no

Jason wrote 08/18/2021 at 21:35 point

Super cool!  I'd love to see some details and files that I could use to put together kits for local schools!

  Are you sure? yes | no

Norbert Heinz wrote 08/19/2021 at 06:24 point

Thanks! Sorry, I had forgotten to upload the file. The package is now available on Hackaday.
I have also added a link to my pages in the project log

  Are you sure? yes | no

duda.sertorio wrote 08/18/2021 at 17:09 point

FANTASTIC ! FANTASTICO [pt_BR] !! CONGRATULATIONS ! PARABENS [pt_BR] !!

  Are you sure? yes | no

Norbert Heinz wrote 08/18/2021 at 18:45 point

Thanks!

  Are you sure? yes | no

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