Test Drive articles provide a 'sneak-peek' at upcoming filaments, 3D printing accessories, and helpful software.
The fine people at Push Plastic were recently offering samples of their new PETG filament. I had never used PETG before, so I figured it would be a good idea to grab some and experiment with it a bit.
PETG offers the printing ease of PLA (no warping or odor), with greater tensile and elongation strength than ABS! Also, PETG prints can be used in higher temperature situations, as it begins to soften around 80° C (176° F), compared to PLA's 60° C (140° F).
Geek Sidebar: This "softening" temperature is called the "glass transition temperature"
PETG is still a relatively new filament on the market, so prices aren't as low as they could be, and color selection is pretty limited. You probably won't find "Neon Chartreuse" from your favorite supplier. Still, for basic colors and some very cool translucent ones, PETG definitely deserves an investigation.
The first thing you notice is that this filament has a rough texture. It isn't smooth like the PLA or ABS you might be used to. I've read on various blogs and from suppliers that this texture was implemented to give the extruder drive gear better grip, preventing the filament from slipping while extruding. Hey, that sounds plausible!
When I get new filament, I'll take a couple diameter measurements, just for a sanity check. Of course, this doesn't guarantee there won't be something horribly wrong further down the line, but it puts the mind at ease for a little while.
Since this was a brand new filament type to me, I mostly printed hollow cubes and towers with my sample. Pretty boring stuff, especially for pictures, but it's the best place to start. I am using a direct-drive style extruder with an E3D V6 hotend and .6mm nozzle, and a GeckoTek HT plate on top of Borosilicate glass for the bed surface.
When it comes to surface quality, recommendations from various blog and forum posts were to play with the extrusion multiplier and slow down the print speed, compared to PLA. I didn't really have enough sample material to fully verify those claims, but here's what seemed to work well for me at the start:
Nozzle Diameter: .6 mm
Extrusion Width: .65 mm
Layer Height: .4 mm
Extruder Temperature: 240 °C
Bed Temperature: 60 °C (w/ GeckoTek Plate)
Print Speed: 35 mm/s
I didn't have a chance to fully investigate proper retraction settings, so I just used what I usually do for PLA.
I had no bed adhesion issues at all with the GeckoTek plate -- parts held in place very well and released easily once the bed had cooled.
The strength of printed parts is overall much more "solid" compared to PLA. I don't have any data to back that claim up quite yet, but eventually I hope to have a test in place to quantify various properties.
A single wall cylinder flexed, but did not snap, while a double wall cylinder was amazingly much stronger. Here, in an entirely un-scientific fashion, you can see the difference. I held a 500g weight on a cylinder that was placed on its side.
The single wall cylinder has much more deflection. I was very impressed that just adding a 2nd wall made the cylinder that much stronger!
I noticed that the temperature really impacts surface quality and clarity. Higher temperature makes the surface very cloudy. Layer-to-layer adhesion seemed very good as well, but again, I'm hoping to develop a test to quantify this in the future.
Additionally, I've also just started to play with some Natural PETG from eSUN and one surprising discovery was that fast retractions cause the surface to become more pitted. If I turned retraction off, nearly all the pitting went away. I'm guessing maybe air gets into the nozzle or the material material itself on a retraction somehow, which then shows up in the print. I spent quite a bit of time trying to get Push Plastic's Amber to have a perfectly clear & smooth finish, but ran out of material before I made my discovery about retractions.
After printing a bunch of test models, I had just enough filament left for one final model --better make it cool, right? In order to showcase the strength and flexibility of PETG, I decided to print this very cool carabiner model.
The whole print feels extremely strong, although I did not want to destroy it by testing its maximum weight capacity, so I can't give a number for that. The 'give' of PETG works well for the flexible latch part of the model, giving it some nice springiness. It snaps right back into place, even after many repetitions.
Overall, I'm very pleased with how this material prints. I am going to continue to investigate the properties of PETG, as it seems like a very promising material to work with. It should be more impact resistant and tougher than PLA, which makes it a good choice for more technical applications.
PETG from Push Plastic is currently available in Natural and Translucent Blue, in 1.75mm and 2.85mm diameters. Cost is $29 for 750 grams.
Please leave your comments or questions!