I thought it was time to try to print with PETG.

Since the arrival of the “3D printing era” most people have been using either ABS or PLA filament. ABS is known for its strength, notably impact resistance and toughness. PLA is well regarded for its ease of use. ABS requires a higher extrusion temperature and a heated bed. PLA can be used without a heated bed and is biodegradable.

Many new 3D printing filaments are becoming available. One new type of filament that is gaining a lot of attention is PETG, which is a modified form of the polymer used in polyester. PETG is said to be softer and more flexible than ABS and PLA. As far as printing temperatures go, less heat is needed for PETG than ABS, for both extrusion and heated bed. It is said to have higher heat resistance than PLA, and is also recyclable.

According to the chatter, PETG is being marketed as a replacement for ABS.

3D Print with PETG – My Early Experiences

As I construct my Mostly Printed CNC machine, everything so far has been printed with PLA. However, there were a few places that I wanted greater strength and particularly heat resistance. This is particularly for pieces that would hold a spindle or rotary tool. These electric devices will get hot under load, probably hot enough to deform or partially melt PLA.

So, I picked up a spool of orange PETG recently and gave it a try. Since everyone’s printer is a bit different, and most manufacturer’s filaments vary, trying a new filament requires some patient experimentation. The data sheets indicate to print with PETG you should use an extrusion temperature of 200-240 and a bed temperature of 75-85. In both cases, more than for PLA and less than for ABS.

I spent a whole day experimenting with various settings and here is what I ended up with to get good prints:

• Extrusion temperature of 240/235 degrees (240 for the first layer) with an extrusion multiplier of 0.92
• Increased retraction. PETG is very “runny”. Extra retraction helps with reducing mess if you are using supports, as shown above.
• Bed temperature of at least 75 degrees. Without this, corner lifting happened quickly.
• Kapton tape or glass bed, with some ABS slurry. I was never able to print well on blue masking tape; I could not get good first layer adhesion.

PETG appears to be very fussy and unforgiving with respect to temperatures, nozzle height and bed treatment. But in the end, I was able to print with PETG a few complicated parts with extensive support requirements – as shown above. PETG also has a much glossier finish. Indeed, my experience also showed a good combination of strength and flexibility.

Of special note, unlike PLA and ABS, PETG is quite flexible. In certain situations this may be an advantage, in others not. More on this later after I experiment.

Since temperature readings vary across machines, let me just say that my print temperatures for PETG are about 15 degrees warmer than I use with PLA, and about 15 degrees less than with ABS.