HDPE plastic bottles recycling for 3D printing

What any newbie in 3D printing thinks when seeing plastic recycling, is milk jugs, water bottles and similar cheap and available plastics, might imagine it's easy to create tones of 3D filament and start printing iron man suits, a quick google search will reveal comments from expert users who will say : don't bother trying, HDPE has bad proprieties that are incompatible with 3D printing, it is impossible to print with, and it's unusable...Yeah, I'm gonna have to go ahead and sort of disagree with you there.

 

HDPE ? Umm Yeah...

First, I tried to extrude HDPE pellets using Filastruder, but some kind of blobby chewing-gum like material came out of the nozzle so I quickly forgot about doing raw material and moved to recycling.

Having no grinder or other way to cut,  I took some Head & shoulders bottles because they are soft easy to cut by hand I mean by scissors, spent weeks to gather a few grams as cutting 5mm pieces is like counting sand grains.

 

1- HDPE filament Extrusion :

HDPE 3mm filament and test prints

Using Filastruder at 150 degrees / 3mm nozzle the extrusion went really well, without any noticeable problems except the extrusion speed that was super slow due to no pressure from the plastic chunks, so it took me a few hours to extrude like 5 meters of HDPE filament (would have taken an eternity if I used the 1.75mm nozzle), enough to print that famous gerbil sorry I mean the owl. 

 

2- 3D Printing with HDPE : 

First try, my HDPE filament didn't stick on the print platform, so I used Pattex glue and it worked, for the print settings, I printed at 150 degrees C, no cooling fan, 0 degree C hotbed temp, print speed between 40mm/s and 60mm/s.

2.1- Testing 3D print with 0% infill:

I wanted to try first a quick print with 0% infill to see for the first time how this material is going to behave :

• Bed adhesion: is horrible and the print warps very quickly. 

• The layer to layer: adhesion was acceptable to perfect on some areas.

• HDPE won't travel and won't do overhangs.

• Some details were printed really well (body/middle part of the owl) which is very good news here, I also noticed the raft was printed well too, the more material you put the more it sticks well, so I went through a 100% infill test.

Quality of the HDPE 3D Prints - 0% infill

Notice body/middle part of the big owl

2.2- Testing 3D print with 100% infill:

Better results with 100% infill

Better results with 100% infill, the warp is always there but not too much, layer to layer adhesion is perfect like if you are 3D printing with any other gentle 3D filament I mean like ABS or PLA, the print here is a U shaped piece with holes on the sides,  it's a strong and flexible print that looks like a mold injected thing, I believe for direct Z extrusion prints with no supports or overhangs this materials is more than able to do it, and all hoaxes you read online about HDPE are just to keep you away from this strong, cheap and durable plastic, so if you are wondering about the suitability of recycled HDPE for making filament and 3d printing you have the answer in pictures (not in graphs and numbers).

Conclusion:

I consider both prints (at 0% or 100% infill) as a success, compared to other materials like ABS or other plastics recycled at home like Polypropylene, we are dealing with the same problems except this is a free material available on any corner.

I believe the warp can be dealt with, I may experiment more with this material, may be try bigger print nozzle up to 1mm, increase the layer height to the max possible and play a bit with the flow rate, and the most important thing is to try a blend with other plastics?, as I'm not sure whether these head and shoulders bottles are 100% pure HDPE or a cocktail plastic.

I couldn't do more tests because I have no more filament, and the smell of shampoo is very horrible, during extrusion and during print (same odor when you use hair dryer after you shower with head and shoulders), I guess I should switch to Clear shampoo bottles -but I can't bear both odors-