Tuesday 23 December 2014

No more filament? - Quest for a Universal Pellet Extruder for 3D Printing

Pellets - Let's shake things up!

A few months back I asked the question on G+, Would anyone like to discuss Pellet / Granular extruders? I ask because I have been working on various designs for quite some time with success and also plenty of failures , it's not easy, it needs collaboration and I would like to see it stay open-source and accessible to all at a very low (no) cost. 

Directly using pellets or granules of many different types will be another very big game-changer in 3D printing.

Using all sorts of different materials for 3D printing is good news, it helps people find more uses for the technology and further's the progress of design, manufacturing and innovation.

Since designing various Universal Paste Extruders, it's been a real pleasure to see so many people use, re-design and further extend paste and food printing in so many different ways.

Using pellets and other granular materials for 3D printing are a next evolutionary step in both simplicity and flexibility.

It has plenty of challenges...

I have been working on and off for a while to design and test other types of extruders for granular materials for 3D printing, my focus was initially using Sugar with great success but this year I have also moved onto plastic pellets (resin's) that are normally used for injection molding or to make the 'standard' filament's we already use in home 3D printers.

This whole area needs more development and a focus from the open-source RepRap community, makers and developers to refine a system to use all sorts of different granules and materials for 3D printing.

This Blog post is an introduction / development update of where I'm at, and at least a way to form some prior art statements about ideas and directions for this sort of extruder development in 3D printing.

The point of this blog post it launch this as an open-source community project. The files have been uploaded to Youmagine here, if enough people take an interest and can assist with further development it could be a good idea to have a section on the RepRap Forum or Google+ Group for Pellet extrusion development.

I started out with a focus on sugar - the main idea being to use it as a support material as it can be washed away. PLA sticks really well to sugar (and sugar like materials)

Isomalt is a really nice sugar often used for sugar-craft and as a sugar substitute, it has a nice advantage of being less likely to burn or go brown than normal cane sugar.

It worked surprisingly well when you get a good temperature (around ~155 Degrees C) you can get a flow of Isomalt sugar from the nozzle.

- First, lets get back to building one for yourself. - 

Lots of info below, or if you like, you can watch my video about the project here first - 

It's also in HD over on YouTube.

If you have been with me for a while, you know I like to use as many off-the-shelf parts as possible, so it's as easy for people all around the world to build and enjoy 3D printing. Without the need for custom machining, or expensive equipment.

That does not mean you should not make refined custom / machined versions of my work, I know may people do exactly that, and make a successful business out of them. That's great ! - just remember me when you become rich and famous :) and please do try to contribute back into Open-Source developments and Open-Innovation in whatever way you can. * end of philosophical rant  *

Because I decided to use a 'standard' J-Head Hot-end for experiments with this project, I had to base the dimensions around the 6.35mm hole normally used for a PTFE liner

J-heads now come from a LOT of different sources, for reference all the ones here are from the original designer (Reifsnyder Precision Works) over on hotends.com

I tried a number of different 200mm long x 6mm wood Auger bits from DeWalt and Black & Decker, most were almost identical and operated the same.

A 6mm wood Auger bit fitted perfectly and with only a slight modification I had the basic outline of a granular extruder without using any custom parts other than being 3D printed.

A little bit of cutting and polish and you have a granular feed system.

I found it better to cut off the end of the drill, but position in the J-head does need to be quite specific, you will need to experiment for the best melt and flow.

I drilled out the end nozzle to be 0.65mm. No other modifications to the J-head are required.

J-head MK3 - with Aluminium tape to help with cooling.

Different J-head's can work, I experimented with both MK4 and MK3 - The MK3 worked better.

While experimenting with different materials and plastic pellets I designed two different Motor drive systems - One (Above) using a normal NEMA17 motor and Herringbone gear system - just like a 'normal' extruder.

The second design used a NEMA17 with a Planetary gear box fitted. This can generate a lot more force but requires a very large number of motor steps (20,000/mm) so bear that in mind.

Rotational speed and torque are both important, so I would recommend starting and experimenting with the Non-Planetary version first.

3D Print the parts - I printed all of them in ABS. (and also experimented with metal coatings - more on that later)

Most of the fittings are M4, they should be easy to understand from the models and images here, but you need to assemble in the correct sequence for everything to be tightly clamped together.

Bearings are standard 606 style for the Gear and Drill bit.

M3 fixings for the motor and gears.

The mounting method uses my standard universal quick-fit carriage mount.

Quick-Fit carriage - Many versions available for different machines - allows the use of many different extruder types - all my designs use this method.

Auger should be fixed firmly and be straight down the middle of the j-head - make sure your bearings are fitted tightly - they should be a tight fit and may require some pressure and slight heating of the plastic to get a firm fit.

You will need to experiment with the placement of the Auger depending on the style / type of your J-head.

Make sure to secure the J-head well and remember you will need to cool the J-head body with a fan just in the same way you would when using PLA filament.

Important bit - The design of this pellet/granular trap (shown above) is really important for good operation. I experimented with many different versions / designs and I'm sure it can still be greatly improved.

You should end up with something like the above that you can experiment with. Note all the different colour parts, I had quite a few versions of the design before this one.

Then you need some pellets or granular materials to melt. is a typical selection above and below. Some are round, some sharp shards and most are in cut round pellet form.

I finally managed to source a lot of different materials, but at the start I cut up normal filament into small pellets - crazy I know, but at least it allowed some testing as I could not find many places last year that would sell me small batches of different plastic pellets.

Top shows Woodfill pellets and right shows PET

A friend kindly send me a large selection of recycled material for testing, but as can be seen above (left) they are quite large and irregular sized shards, so as much as I want to use recycled plastic, for this extruder it's not going to be possible because of the screw size. I will be using them for other interesting things - more on that soon :)

By far the easiest way is to now buy pellets from ColorFabb here. I purchased a selection.

And if you look closely at the above image you will see 1.75mm and 2.85mm pellets, so I'm reasonably sure these are actually from filament cut up - maybe a good way to recycle any out of tolerance spools, but regardless it's good to know they are small pellets - ideal for this type of extruder.

The ColorFabb PLA pellets are not the same, they are 'pearls', and unfortunately don't quite work in this size of extruder. I bought a lot of these not knowing the size, so check before buying pellets from wherever you manage to source them. - I will find use for them :)

You can even get Woodfill - but, have not tested it yet.

Fill hopper, make sure you have a fan on constantly cooling the thermal break on the J-head and lower half of the extruder body. Experiment with temperature and speed of stepper motor drive.

You can use the standard extruder retraction to stop or limit the flow ! but you may need to slow it down to under 15mm/sec.

Experiment and play, and please let me know how you get on.

One really important thing - Make sure you run the Auger motor in reverse! - that's anti-clockwise as you want to push down the pellets into the hot-end and not drill them out.

I ran out of time with this project in the summer (2014) due to other projects and shows, so the files being released still need work and refinement to get to a working solution that can process many different types of material in pellet form. I have still yet to try the Colorfabb Woodfill pellets as I didn't want to block the second extruder after already blocking the first one with 'A-PET' material.

This is a very exciting project, do let me know what you think about it, all and any feedback is good. And if you decide to make one or want to evolve the design, please feel free and spread the word.

Thanks for reading, have fun, experiment and play. Also please do let me know how you get on.

Until next time, and have a Happy Christmas / New-Year Holiday / Seasons greetings.


- A little notice - 
My 3D Printing work (and video's) are released under Creative Commons CC-BY-SA License.

But - All my images, photographs and words published anywhere are covered under International Copyright law, so please do ask me for permission and remember to state where they came from - me, Richard Horne. - (AKA RichRap)

Sorry to have to put this up, but I see a lot of my images and words being used without my permission for commercial activity, by people who want to make money, that's fine but do ask my permission first and be open about what you want to do with them. I'm cool about most things.

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