So for the past two weeks we worked on extruding PLA and ABS with our very own Filabot extruder. For those of you who haven’t heard of the Filabot; it’s a machine that grinds small plastic pellets and extrudes them into your very own filament. So far results were good for ABS but for PLA we weren’t able to extrude the right diameter.
This week we tested extruding Polypropylene, or in short PP. This is the really cool part since PP is nowadays hardly used for 3D printing. PP is one of the most used plastics in everyday life so if we manage to extrude and print PP we could be opening up a whole new world of possibilities. Imagine printing new Marvins from your old plastic bags!
As a first step we decided to extrude and print with new PP pellets. We ordered the pellets through Ebay and used very normal pellets that are more commonly used to fill stuffed animals.
This went a lot better than expected and we actually managed to produce rather consistent spools of filament for extruding at 160, 165, 170 and 175 degrees Celsius. The only problem was that the diameter was on average 2,0 mm instead of 1,75mm which meant we couldn’t use the filament on our Leapfrog.
Luckily we found a part that was thinner which we pushed through the feeding tube using a normal piece of filament which we placed behind it. The filament could definitely be extruded but so far we haven’t had any succes with actually printing an object.
Some learnings to take from the printing so far:
Extrusion temperature: We started at 220C which is definitely high enough. We then tried 160C which also extruded the filament so next time we will see if we can lower the temperature even further.
Warping: The warping is a serious problem which we haven’t tackled yet. We’ve tried setting the heated bed to 90C but this hasn’t solved our issues yet.
So far we must conclude that we haven’t had any successful results yet but we are confident that with a little tweaking of the settings we will be able to provide some best practices in addition to these worst practices soon!
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Cool! Love this filabot-series! 
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Luuk
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@Emre_1 Hey Tyler, any tips on how to get the right diameter on extruded strings of filament? We considered maybe drilling our own nozzle, with a smaller diameter hole. Any less radical solution maybe?
Thanks!
Your experiments are so fun!
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I think professional extrusion machines, whether its for filaments or sheets control the pulling of the extrusion to get it to the right diameter/thickness. That means that you have to have a winding spool whose speed is controlled and a little faster than the extrusion speed. Some machines even have a laser thickness gauge to have a closed loop control with the winding spool, to have very tight dimensional control. There’s a video a filament maker made showing this, but I can’t find it for the life of me.
Awesome test! We have been playing around with PS (Polystyrene) from Ben and Jerry’s Spoons.
For the filament being oversized that is from die swell. It is the change of pressure from the extruding process. There are a few variables that can be changed to help with the swelling. Extrusion temperature as you noted in your post can change the size, a hotter extrusion temperature can reduce die swell, lower temperature more die swell. With our Filabot extruder we ship two nozzle a 1.75mm and 3mm nozzle, in actuality the nozzles are drilled smaller to compensate for die swell. The 1.75mm is drilled at 1.35mm and the 3mm is drilled at 2.85mm.
To solve the issues of oversized filament I would suggest getting a new un-drilled nozzle and drilling it smaller. The new nozzle should have a hole size of about 1mm or 1.1mm
Thanks and we look forward to seeing more testing
I’ve made an extruder myself, running only PLA. I have to say it’s a real struggle to get the diameter just right! I’m planning for a closed loop system where I measure the error in extruded diameter and compensate in the pulling speed.
Russ (#15 ~Russ's Filament Extruder: Digital Caliper Filament Measuring Device Finished. - YouTube) is using a digital caliper, and it’s possible to link those measurements to your system to control the thickness…
But I will go for a CCD (something like Filip Mulier designed).
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@bramhallo Keep up the good work! Can’t wait to see what else you’ll find out.
Very interesting to see. Thanks for the link! Will be rather difficult to make such a setup here in the office 
But I can definitely try to see what we can do here.
Cool thanks for the info! Have you been able to produce good results with Polystyreen?
I will definitely try some temperature changes again to see if maybe this has some results after all. However I think we’ll be trying to indeed drill our own nozzles as well. Will keep you posted on our progress!
Thanks! Although I expect this to be rather difficult we are going to see if this is something we can do here!
Mik3D
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You should buy PP tape and apply this to your printbed. The print will stick to the tape and the tape prevents it from warping.
You can print on PP plate (for example a cuttingboard) as well, the stiffness of the plate prevents the warping. You’ll be having troubles getting the print off though.
Nice experiments by the way!
P.s. GermanReprap sells build plates for PP. https://shop.germanreprap.com/en/printing-plate-pp-230x230x2mm I don’t know if this works, haven’t used it.
You need a cooling tank and a puller to “draw down” the resin and maintain tension on the filament as it comes out. The gap between the exit of the extruder and the entry of the cooling tank (water bath) is critical as is the temperature of the water. The proper cooling rate is essential too, as the filament cools from the outside circumferance inward to the center which may cause a void in the center. I have designed extrusion die for 15 years an am very familiar with the extrusion process.
Hi guys! Good to see some experimenting going on! It’s only a matter of time before 3D printing moves to fully recycled filaments. We from the Perpetual Plastic Project dis some test last year with different plastics as well. PP is a hard one to extrude indeed but is has some really nice printing qualities. Check our blog post for the other plastics and our findings as well: http://www.perpetualplasticproject.com/blog/2014/5/30/plastics-recycled-for-3dprinting
I’ve had a conversation with a manufacturer of PLA granulates on this topic. He said it’s really bad to have the extruded PLA filament to run through water, because it will absorb the water and make steam while extruding on the printer…
Ward, this goes for extruding PP, NYLON, PE, HDPE, ABS, PVC etc. Have not extruded PLA before, but am pretty sure you would extrude PLA like any other plastic. This is how “industry” extrudes plastics. Yes, extruding plastics you need proper ventilation or you will be inhaling “polymer vapor” which is toxic. I work for a company who has been extruding plastics since the 70’s. Extruding filaments is fairly easy with the proper equipment, check out this book: http://www.rauwendaal.com/pubs_books.htm if you want to learn polymer extrusion.
I’m pretty sure PLA will lose quality with watercooling. PLA granulates are shipped in aluminum like bags to preserve them from absorbing moisture from contact with air… so I think running it through a cooling tank won’t be good.
http://www.conairgroup.com/assets/Knowledge-Center/Whitepapers/General/Handling-Drying-and-Reclaim-Considerations-for-PLA-0810.pdf
From the conclusion of the article: “excessive moisture and heat represent a serious threat to the quality of PLA products.”
So I avoid contact with water at any case while extruding my filament 
Is there an inherent advantage to fillament and spools over icosahedronal feed stock for a 3D printer in general?
The print head would melt these units as they are extruded to form a continuous stream.
