PETG filament for 3D printers
August 6, 2020
Posted by: Grilon3 NTH
Durable and easy to print, PETG filament is likely to become the most widely used filament over time. This guide provides in-depth tips and tricks on how to get started and embrace the fantastic properties of this material.
Durable and easy to print, PETG filament is likely to become the most widely used filament over time. This guide provides in-depth tips and tricks on how to get started and embrace the fantastic properties of this material.
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PETG is an abbreviation for Polyethylene Terephthalate (with a glycol modification) which is one of the most widely used polymers today. It is used to make water bottles, food containers, and countless common plastic items. As a 3D printing filament, PETG plastic has proven its worth as a durable material that is easy to use. Figuratively speaking, it combines the most useful characteristics of ABS filament (the rigidity and mechanical properties of functional parts) with the ease of printing that PLA filament provides, offering “ the best of both worlds ”.
What is PETG?
It is common to see references to PETG in one or more of the following forms: PET, PETE, PETP, PET-P, PETG, GPET, PETT, and others. These can be confusing for someone trying to understand the differences between them and the effect any of the suffixes (if any) would have on their 3D printing experience.
PETG is the most common form of PET used for 3D printing filaments. The G stands for glycol-modified, and this makes the resulting resin lighter and less brittle than raw PET. Raw PET is not normally used for 3D printing. PETE, PETP, PETT, and PET-P are modified versions of PET (called copolyesters), but by far the most common material used in 3D printing is PETG.
For the purpose of this article, we will use PETG as a general term to describe the different variations of 3D printable filament.
Quality PETG 3D Printing Filament
To achieve quality prints it is vital to have quality PETG filament in principle.
It is also very important to know that if the material is not dry enough, it will not print correctly, causing problems and wasted time.
PETG is hygroscopic, which means that it will actively absorb moisture from the air. For this reason, PETG plastic should be stored in a cool, dry place, and dry out if exposed to humid air for too long. The “too long” depends on the relative humidity in the air, but when it comes to 3D printer filament, it is better to go wrong by making the filament “too dry” rather than leaving it a little “wet”.
Wet PETG printing can lead to hydrolysis that will permanently alter the filament at the molecular level, making it significantly weaker than it would be if it were printed dry.
Vacuum sealed bags and desiccant packages ensure that the filament is exposed to as little moisture as possible. Sometimes a bag can get punctured and lose its vacuum seal, but as long as everything is packaged and with its desiccant, the material can be kept in good condition, at least until unpacked.
Using the correct 3D printer
All printers are not created equal. Some have features that others do not, and there are some specific requirements for printing PETG.
To print PETG, your printer must be equipped with an extruder ( hotend ) that can reach a temperature of at least 235 ° C, although the ideal would be 250 ° C.
It should be noted that each spool is unique and may require a temperature slightly higher or lower.
Filament printing with PETG
The PETG Grilon3 (and most PETG) flows and correctly printed between 230 and 240, being simpler print below 220 above 240. The filaments of lower purity or quality usually require higher temperature, and the best and purest filaments, less.
Getting the correct first coat
As with printing any type of filament, getting a good first coat is essential for a successful print. Without a good first coat, the part will likely need to be reprinted, so it is imperative that you know what it takes to start a successful print so that it can fully develop.
We experimented with different types of beds and bonding methods, and the best practices we found are listed below.
Printing on Blue Painter’s Tape Blue painter’s
tape, with or without heat, is the best surface for printing on PETG plastic. The finish on the bottom is quite smooth, although without reaching the results of glass.
Printing on glass
The glass is very smooth, which gives a shiny surface on the printed part. Printing on this surface requires the use of a heated bed (60 ° — 70 °). If lacquer is used, it works best on bare glass.
Other print bed
surfaces The BuildTak print surface works well with PETG filament. It is a universal bed surface, so it will also work with PLA and ABS without the need to change plates or surfaces. It wears out over time, but prints stick very well.
The surface and methods for printing PETG are 100% compatible with all methods that work on PLA (even PEI beds).
What is effective as an adherent for PLA will also be effective for PETG, for example strong hair fixative.
Getting the temperature right
Keep an eye on how much filament doesn’t end where it is supposed to. PETG plastic is prone to threading and oozing, so you need to be on the lookout for filaments that end up sticking to the nozzle. Sometimes PETG filament droplets stick to the nozzle and then settle on another part of the print where it shouldn’t be.
If this happens, it will cool and harden, which can be dangerous for the nozzle the next time it moves into that space. The result is usually a layer change, which can be detrimental to printing.
Filament change
For PETG
When changing the filament from another material to PETG you must heat the extruder (hotend) to the required temperature.
Once the PETG filament is flowing well and the remaining remnants of the old filament are no longer chipping or flowing out of the nozzle, you are ready to print PETG.
From PETG
When changing from PETG filament to another filament, heat the extruder (hotend) to at least the melting temperature of PETG or slightly warmer. Once you feed the new filament, you can adjust the extruder temperature to match the melting temperature of that filament.
Part Design for PETG
One of the hidden powers of PETG plastic is that the flexing of the material lends itself to being used for press fit. When properly designed, PETG can have a very strong fit for zippers or functional zippers.
PETG has a shrinkage ratio (or shrinkage rate) of less than 0.004 in. / in, so large-area printing is not a problem as long as it is done on a well-leveled surface.
The use of brackets can be easily accomplished when using PETG plastic, but a larger air gap may be required for easy removal of the main body.
TROUBLESHOOTING
Here is an overview of some of the most common problems with PETG filament printing and the steps you can take to correct them:
First layer will not adhere to bed.
If the PETG filament swells at the nozzle and creeps instead of sticking to the bed:
- Make sure you have the proper bed surface for PETG as well as your adhesion method.
- Make sure you are printing at the correct temperature and that your bed is at the correct temperature. Extrusion temperature 230–240 ° C Bed temperature 60–70 ° C
- Make sure the print bed is level.
- Make sure the extruder is at the correct height, and if not: 1) adjust the Z-offset for the extruder or 2) adjust the limit switch of the printer.
- Check the ambient temperature. If it’s too cold, your printing may be adversely affected.
The printed part has bad fill and top surfaces:
When the infill or surfaces have poor finish or defects:
Make sure the extrusion temperature is not too cold. If you are closer to the lower end of PETG’s printable range (230–240 ° C), increase the temperature five degrees at a time until the extruded filament flows smoothly out of the nozzle and remains where it is extruded.
Reduce the print speed by 10–20%, either with or without increasing the temperature. Speed and temperature are directly related to obtaining correct flow.
Check the tension of the filament.
Clean the filament drive gear if necessary.
The outer edges of my PETG prints have a lot of small bumps:
Edges on the outside of printed parts can occur for a number of reasons.
If your printer stutters when connected to a computer:
Make sure the computer is not too busy to feed printer commands. Running applications other than the printer control software at the same time as printing can cause interruptions in the flow of information from the computer.
Print from SD card. This often helps the printer have enough data to run smoothly.
If the filament “bursts” as it exits the nozzle:
Dry the filament. Wet filament will hydrolyze as it melts and will be significantly weaker than dry printed filament.
The quality of the filament has a great impact on the quality of the final part, however, a good configuration and patience are also necessary to obtain the best result.
Tall sections of prints are melted or squashed and warped:
Turn on the layer fan for that section of the print.
Lower the temperature and speed.
Print more than one piece to cool the layers as the nozzle moves back and forth between them.
Use a small fan. If your printer does not have a built-in fan, you can use a small desktop fan making sure the fan does not cool the extruder (hotend).
The printed part is curving off the bed:
While it does not occur with PETG as much as it does with some other filaments (such as ABS filament), warping can occur and destroy an otherwise perfect print.
If this happens, use more adhesion to the bed (depending on the surface of your bed). 2–3 layers of glue on the bed are usually enough for a correct adhesion of the first layer, also using the blue painter’s tape.
A 2–3 second spray should be sufficient for prints on glass.
Avoid uneven application of glue or incredibly thick layers that could interfere with printing.
The printer does not extrude any material:
If the extruder is rotating correctly, but the filament is not flowing:
Make sure the extruder is at the correct temperature. If not, you should have the printer checked. There is likely a loose connection or the electronic board has shorted out (assuming the printer is still connected and responding to its host software).
Reduce the print speed. If the extruder is hot but the print runs too fast, the filament may not melt completely before it is pushed through the nozzle. If this happens, back pressure can build up and the filament will begin to grind against the extruder gear.
Clean drive gear and adjust tension. If the extruder gear grinds on the filament, over time the gear will wear out and have less grip. You will need to brush the gear to remove the small pieces of plastic, then make sure your tensioner is solid against the filament. Too much tension can also prevent extrusion and is more common with direct drives.
Remove any obstructions. You may have a small particle at the tip of your extruder that is blocking the plastic. Push a little bit of filament by hand to clear any clogs and allow the filament to flow well.
We hope it will be useful and we wish you excellent impressions with this wonderful material.
