Guides

Guide: How to Print with PETG

After the novelty of making Benchys and Marvins in PLA has worn off, you may start to consider more practical applications for your 3D Printer. Each material has its own share of pros and cons, where ABS for example is durable, easy to print and can even be vapor smoothed, yet this plastic emits toxic fumes when melted. PETG in comparison is both strong and flexible while also being completely safe to print. It is widely used in the manufacturing industry for functional components, where it can be injection molded, vacuum formed and even 3D printed. If that isn’t enough to convince you, it also comes FDA Approved, making it great for anything from food containers to medical devices.

We are going to look at the most important differences to be aware of when moving from PLA to PETG. Small adjustments will make a world of difference, often those which are overlooked or lack general explanation. Once your settings are tweaked and configured correctly, PETG can print just as well or better than the traditional choices.

PETG Vase
PETG Vase

PETG Brands

I’ve used several options available on Amazon with mixed results. Although I found Hatchbox to be the easiest to print, the surface quality was somewhat mediocre and often had a rather bland finish. Inland was an improvement but seemed to string and ooze the most, requiring some additional work to remove the excess plastic. My personal preference is the eSUN brand when it comes to PETG, where the Semi Transparent line of filament produces gorgeous results and has the least issues with stringing during print.

For first timers however, I would advise starting with the absolute cheapest (reputable) option available. You may very well go through several rolls before you have the settings tuned as desired. In my case, I wasted an entire spool when creating a set of functional parts, only to later find they were as brittle as potato chips, splitting into pieces under very little pressure.

Bed Leveling

Since PLA is often the first material every new maker uses, most will be familiar with using a sheet of notebook paper to space the nozzle from the bed. PLA essentially needs to be smushed into the build plate, where a very small gap is required for optimal extrusion.

PETG on the other hand works best with a distance between the nozzle and bed, where the extrusion lays down much like squeezing toothpaste. If the nozzle is too close to the bed, it won’t extrude properly and may cause the filament feed gear to jam. Spaced too far and the filament won’t properly adhere to the build plate. Using the same approach for leveling as PLA, substitute the thin notebook paper with a thicker sheet such as an index card or your ex’s wedding invitation.

Print Temperatures

PETG has a higher melting point than traditional filaments such as PLA, where it flows best between 240-260C and sticks to a heated bed at 75-95C. Every spool of filament is different to some degree, but it will include the Manufacturer’s optimal working temperatures listed on the side. I would suggest printing a Temperature Tower first, where this will give you an idea how it looks, feels and prints at incremental temperatures. If the nozzle is too cold, PETG parts will have weak structure and delaminate with ease. If the nozzle is too hot, it will cause excessive stringing, oozing  and blobbing.

Nozzle Temperature: 240C – 260C
Bed Temperature: 75C – 95C

Note: Perform a PID Tune on your extruder when switching to PETG. This will prevent heat fluctuations and keep the nozzle as close to the desired temperature as possible.

As a word of caution, many 3D Printers do have a white PTFE tube liner inside of the nozzle. This plastic is not designed for excessive temperatures, where it will begin to degrade at 245C and becomes toxic at 260C. While you can still print PETG at the lower end of the recommended spectrum, this will greatly accelerate the wear of the PTFE liner. Although cheap and easy to replace, long term printing will be better served by using an aftermarket solution. The Micro Swiss All-Metal Hotend and E3D V6 are both popular choices, designed to eliminate the plastic PTFE tubing and facilitate printing with higher temperatures and abrasive materials.

 

Cooling Fans

Most articles and discussions concerning PETG makes extremely different claims as to what works best in terms of cooling. Among the top search results on Google, one adamantly states a cooling fan is needed, while the next says no cooling fan should be used at all. This vast range of opinions does nothing more than impose even more confusion on which one is correct.

The truth of the matter is PETG will print anywhere from 0-100% fan speed depending on your intended goal. The amount of cooling should be chosen based on the purpose of the part.

PETG Temperature Tower w/ 0% Fan Speed

Low Fan Speed: The less cooling used, the stronger the part will ultimately become. The molten plastic essentially melts into the previous layers, providing exceptional adhesion to one another. The downside is that this can lower the aesthetic quality by a considerable amount in exchange for stronger parts.

As can be seen in the image, bridges and overhangs will suffer without proper cooling. To address this problem, it is recommended to use the Bridging Fan Speed Override setting in Simplify3D or a similar feature within your desired slicer software.

Temperature Tower Comparison

High Fan Speed: The faster the part is cooled, the better it will look when finished. This is often the best choice for vanity prints such as masks, vases and other aesthetically pleasing designs. It will not offer the same level of durability as prints that set at room temperature, however the overall surface finish will be a drastic improvement.

The temperate tower on the left was printed at 100% fan with a 50mm blower fan and the Dii Cooler, where the tower on the right was printed using the low powered stock fan. The higher powered fan causes the plastic to set quickly, which prevents the bridges from sagging and overhangs from warping at the edges.

Print Settings

Printing PETG successfully is all about finding the right balance of settings. While it can be a bit more complex at first, it is a considerably better choice for most applications. There is no getting around the need to experiment, however the following should work as guidelines when building your own PETG configurations.

Print Speed: Use a slow speed for the first layer to ensure proper adhesion to the build plate. This should generally be around 20-25% of your normal print speed. Start with 30 mm/s for your PETG prints as the base speed and increase this gradually until you find the perfect speed for your printer.

Print Speed (Layer 1): 10 mm/s
Print Speed (Layer 2+): 30 mm/s

Retraction: PETG is notorious for creating strings and blobs, where finding the correct retraction values will help to minimize this. Start with these settings and tune as needed, increasing the distance if excessive stringing is present, or decreasing if you experience clogs.

Retraction Distance: 1.0 mm
Retraction Speed: 30 mm/s

Temperature: The heat applied to PETG can cause a wide range of results to both the look and strength of the material. The recommend temperatures below are middle values, where you can tweak these as needed. More heat to the extruder will increase the flow of plastic (and increase stringing), where 245C is a good starting point.

Extruder Temperature: 245C
Bed Temperature: 85C

Fan Speed: The cooling fan speed is described in depth above but make sure the first layer is set to 0% to ensure proper adhesion. For the remaining layers, choose the fan speed based on the purpose of the part. Lower fan speeds for strength and higher fan speeds for aesthetic items. The “Bridge Fan Speed Override” is essential for good bridges regardless of your other settings.

Fan Speed (Layer 1): 0%
Fan Speed (Layer 2+): See Details Above
Bridging Fan Speed Override: 100%

First Layer Height: 90%
First Layer Width: 100%

Use Skirt: Enabled (Clears the nozzle of any excess residue)
Skirt Outlines: 2

6 thoughts on “Guide: How to Print with PETG

  1. PETG has been a difficult filament for me… and your post is the first that covers a lot of in-depth content. I have applied all your suggestions, especially speed. I look forward to printing better with PETG

    1. I’m glad to hear that it helped, appreciate the feedback as well. Definitely let me know how it goes for you, PETG is amazing to use once you get it printing correctly!

  2. I have had issues with PETG as well.
    My findings: You need to add around 0.1mm extra distance compared to PLA. I do this in the preamble GCODE.

    Have yet to find optimal printing surface. Now I use glass with water/PVA glue mix. Does not stick hard. And I do get warping sometimes. Will have to put the sides/top on the printer to try again. Some say an enclosure helps. Or use brim/raft. I often use both got ABS (which I like a lot). Working on my enclosure, since I have seen splits mid-part on my HIPS prints.

    Had lots of stringing issues. Even where head does not move.
    Using an extrusion test from thingiverse, I am down to around 80% extrusion. This combined with the 0.1mm extra bed distance has removed much of the random stringing (which is caused by the nozzle going into the plastic, which sticks to the side of the nozzle, and causing stringing that way). Still get retract/move stringing. Coast would likely be an option here (stop extruding shortly before retract).

  3. I had heeeeaps of trouble swapping to petg last week.
    Here’s what I did to get it working.

    1- start with abs profile and work from there
    2- bed 50deg, nozzle 238-245
    3- no fan on first layer, then full fan
    4- adhesion , I just use a glue stick and it’s good
    5- first layer 0.25mm, following layers 0.2mm
    6- first layer nice and slow to start with. Start at 15mm/sec, then work up.
    7- CHECK THE FILAMENT DIAMETER. under extrusion stops the print from sticking.
    8- put lots of lines on the skirt to get the shit off the nozzle, and give time to tune before the print starts. until you’re tuned enough to start clean. A messy nozzle will wreck your print.
    9- slow it all down to start. Like 20-30mm/second, then work up.
    10- retraction 5 to 7mm, speed 45mm/sec
    11- nice quick travels. Like 100mm/second

    I’m getting pretty good prints with the above. Still working on it, but I was ready to throw the petg in the bin until I got to this point.
    Now, I’m a convert. Strong prints that can be put into service as mechanical parts. Not just visual prototypes.

    Also I’m printing on a genuine prusa with no enclosure. Just room temperature.

    Stick with it, petg isn’t a scam like I thought. It is as good as they say, just a tricky to tune.

    Oh also if you’re using the current version of cura, 3.1, uninstall it and get 3.04.
    3.1 has a bug that sets all nozzle temps in the g-code to 210 regardless of your settings.

    1. I have no problem with Cura 3.1. It sets the temps I ask for every time. I’m slowly tuning my PETG. Finding I can use very little fan if I want a strong part. Currently printing at 230 and 3% fan. Much more fan and the surface is very matt and the parts have little strength.

      1. PETG printed with low/no fan will be exceptionally strong. I have printed PETG temperature towers that were impossible to break by hand. I believe the matte color however comes more from the temperature you are using though. The parts I printed at 230C were a matte color and very brittle, but the parts done at 245C were translucent and nearly indestructible (both at 100% fan). I have found that 25-50% fan offers a good balance of strength/aesthetic quality, but you can go 0% for high durability or 100% fan for visual pieces.

Leave a Reply