PET (Also called PETG and T-Glase/T-Glass) is an incresignly popular print material. It combines the ease of use of PLA along with the extra strength of ABS without the warping. It's more flexible than both, so thin walled parts will bend easily, but parts with thick shells and more solid infills will be stiff and rigid. It's my favorite material to print with, and with these tips you'll be falling in love as well!
Recomended Settings
For printing on Flashforge machines, using Flashprint, standard PLA settings with only temperatures changed produced great results. This means for a layer height of 0.2 mm a base print speed of 60 mm/s was used with temperatures of 235 on the extruder, and 85 on a bed with Flashforge blue bed tape. Printing to cold Flashforge blue bed tape was possible with an Inventor 2!
On a Prusa i3 MK2 using Slic3r a base speed of 40 mm/s was used for layer heights up to 0.3 mm. With a larger nozzle and layer heights up to 0.6 mm up to 80 mm/s was printing successfully. An extruder temp of 230 rising to 240 after the first layer was used, with a bed temp starting at 85 rising to 90 for printing to a PEI surface.
Bed Adhesion
PET prefers a heated bed in the 80 – 90 degree range, and a hotend temp of 230 – 250, but we’ve had success on a cold bed. PET adheres well to most things, glass bed and glue stick, blue painters tape, Flashforge Blue Bed Tape and BuildTak all work very well, Flashforges Blue Bed Tape even works cold. PEI can work too well, and a layer of glue-stick or hairspraiy is recommended to not rip holes in your bed. When printing to PEI removing the part was easiest around 60 degrees, and very difficult when cold.
First Layer
A good first layer in PET looks like one in PLA, not overly crushed. If the material balls up on the nozzle then you're too close, if it drags along behind the model, too high. As PETs are usually translucent the first layer can be pretty difficult to see.
During the Print
PET carbonises and burns quite easily, as well as being quite stringy. Retraction may need to be increased and temperatures dropped to help stop both things, keep an eye on the print as black debris can be easily transferred from the nozzle to the print if not kept nice and clean. PET can be cooled for nicer finished parts, but can be printed without cooling for better layer adhesion and stronger parts. If your prints shell isn't as transperant as you'd like then try upping the print speed in 10mm/s steps until you're getting the results you want, or the print starts to fail.
PETG compared to other filaments
As PET is cooled very happily is bridges and overhangs almost as well as PLA.
PETG is stronger than most filaments, and flexible; but a note on that. It can be sensitive to layer seperation in thin walls under pressure if you did not get your settings perfect.
Support structures with PETG
It does support structre well too, but you may need to increase the gap between the top of your support and the bottom of the part for it to be easily removable.
Why choose PETG
PETG is the plastic that your softdrink bottles are made of and supplies strength with flexibility. You might need it if your part is going to contact chemicals that would dissolve PLA or ABS (ABS is the most sensitive to chemicals in general). It’s great for components with snap fits as it is less susceptible to fatigue.
Customer examples
Parts within a swimming pool. We have a customer who prints parts fitted to pool cleaning equipment who reports that PETG has the best resistence to pool chemicals of any 3d printer plastic he has tried
Model car fuel tanks – we a surprising high number of customers experimenting with PETG for model car/plane/boat fuel tanks. We are not sure that is a good idea, and exactly how PETG will deal with petrol over time; we await their results
Snap Fit parts – The pictured wiring harness has enough flex to provide an excellent snap fit to square section, and thanks to PETGs strong bridging ability was fully printable without supports
Drone Parts – PETG is a popular choice for protective parts on drones like landing struts and propeller cages. Its tensile strength is key here, as it will deform instead of shatter on impact
What not to print with PETG
PETG is partly UV stable, so parts for heavy outdoor use would need to be treated, or treated in a more resistant material such as ASA or Polycarbonate.
For applications where temperatures are going to exceed 85 degrees then ABS, Nylon of Polycarbonates would be a better choice.
About Commercial food storage/contact applications in australia
It is a common myth that PETG filament meets food safety regulations in Australia as it has in other countries. To the best of our knowledge no filament has beed certified for food contact applications in Australia; however some of our clients have certified their products for decrotive applications in Australia using both ColourFab XT and PETG. Colourfabb XT (https://www.bilby3d.com.au/DispProd.asp?CatID=&SubCatID=110&ProdID=FIL175XTNat) is FDA approved for this purpose and is a PET blend. We note that colour additives may change the 'food grade' status.
Where to get PETG
We are unloading a shipment of PETG as this post goes up, so jump online and order some today for shipment tomorrow:
Find PETG
Sydney - Kingsgrove, NSW
Melbourne - Clayton, VIC
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