As it offers a straightforward printing process that usually is successful without requiring complex hardware or highly-optimized configuration, PLA is often the choice for 3D printing enthusiasts picking the hobby up for the first time.
On the other hand, while not the most challenging filament type to print successfully, there is no denying that printing PETG brings some difficulties to the process compared to PLA, especially when switching from PLA for the first time.
Today, we will be taking a deep dive into switching from PLA filament to PETG filament, a topic that many 3D printing enthusiasts struggle with due to how differently PETG can behave and make the printing process harder as a result.
So, how to switch from PLA to PETG?
To switch from PLA to PETG, you will need to clean both the build plate and the hot-end, ensure that the surface is suitable for printing PETG, and re-configure settings such as print temperature, bed temperature, print speed, cooling speed, and Z-offset to be compatible.
Moving forward, we will analyze the process of switching from PLA to PETG in three major subheadings, which are preparation, configuration, and troubleshooting.
Switching from PLA to PETG – Preparation
The first phase for switching from PLA to PETG is preparation, where we will be preparing the 3D printer for printing PETG by removing what’s left of PLA.
The first step for the switching process to go smoothly is to clean the hot end and remove any remnants of PLA that might be in there from previous printing processes with PLA.
Purging the extruder (preferably with cleaning filament) or entirely disassembling it are both viable ways of ensuring that the extruder is clean and ready for printing with PETG.
While purging is often the more popular option as it requires no disassembly, more than one cycle of it can be necessary for all the PLA to clear out of the extruder, which is something to keep in mind.
After cleaning the hot end, the next step is to clean the build plate, ensuring no leftover PLA exists on the build surface from the previous prints.
By spraying a mixture of isopropyl alcohol (IPA) and water on the build surface and gently wiping it with the help of a microfiber towel, you should be able to entirely get rid of any leftover PLA on the build plate.
Finally, we need to ensure that the build surface is suitable for PETG, as the strength of adhesion drastically varies between PLA and PETG for different build surfaces.
Powder-coated PEI is the most optimal build surface for PETG and shouldn’t require the application of any adhesives or separating agents.
On the other hand, glass, BuildTak, and smooth PEI are materials that PETG sticks very firmly to, requiring a separating agent, such as Windex, glue stick, painter’s tape, or Kapton tape, which prevents the plastic from directly bonding to the surface.
Now that we have completed the preparation phase – let’s get down to configuration.
Switching from PLA to PETG – Configuration
The second and the most vital phase of switching from PLA to PETG is configuration, where we will be configuring the settings of the 3D printer to make them suitable for PETG.
As there are a sizable amount of parameters to configure while switching from PLA to PETG, let’s continue by going into each of them individually and in detail.
Since the melting point varies between PLA and PETG (and even different brands of the same type of filament), the print temperature is the first parameter we require to configure.
While the best way to find out the optimal print temperature you should use is to refer to the filament packaging or the manufacturer’s website, we can consider a range of 230 to 250 degrees Celsius suitable for an average spool of PETG.
As PLA and PETG have different glass transition temperatures, we need to configure the bed temperature correctly to accommodate the differences.
Once again, referring to the packaging or the manufacturer’s website is the best way to find out the optimal bed temperature as these figures can change between different brands, but on average, a range of 75 to 90 degrees Celsius should be a good starting point for PETG.
Due to PLA and PETG having entirely different material properties, print speed is also a parameter that requires modification for the plastic to behave as intended.
A range of 40 to 60 millimeters per second is a good starting point for printing PETG, as going for higher values can cause print quality and layer adhesion issues.
Compared to PLA, the print speed value is lower on average, as adhesion strength is much less of an issue with PLA.
Since the cooling speed directly impacts the inner temperature of the plastic, it’s another vital component that we will need to modify to ensure that we can print PETG successfully.
To avoid issues related to bed adhesion, we recommend turning the fans off for the first few layers, which will ensure that the layers don’t cool down before they can form strong bonds.
After the first few layers, you can use a high cooling speed for prints that require strong layer adhesion and a low cooling speed for models with aesthetical purposes.
Compared to the standard of 100% for printing PLA, we can see that the optimal fan speed for PETG is quite variable due to how different these two filaments act when it comes to bed and layer adhesion.
While Z offset is a parameter you may not be expecting to see here, it indeed does require a slight bit of modification while switching from PLA to PETG.
We recommend increasing the Z offset parameter by a range of 0.02 to 0.05 millimeters compared to the value you print PLA with, as PETG requires more space and less squish.
First Layer Height
Last but not least, the first layer height is a parameter we will need to re-configure for the switching process.
We recommend using a first layer height value that is slightly higher (such as 0.04 mm) than the standard layer height, as this will allow the first layer to stick more firmly to the bed.
While PLA doesn’t need this as it doesn’t have any issues sticking to the bed, bed adhesion issues are common in PETG and require optimal configuration to prevent.
Switching from PLA to PETG – Troubleshooting
Finally, the last phase of our guide for switching from PLA to PETG is troubleshooting, where we will take a look at some of the common issues that occur upon switching from PLA to PETG for the first time and find out how to solve them.
Below is a list of the most common 3D printing issues that arise while printing with PETG filament after switching from PLA, along with their causes:
- Stringing and blobbing – A low travel speed, a high nozzle temperature, and misconfigured retraction settings (too little retraction or too great retraction distance) are the primary causes of stringing and blobbing while printing with PETG.
- Weak bed adhesion & warping – A too low bed temperature, a too high cooling speed, a too high Z-offset, and a build surface that PETG doesn’t stick well to, combined with the absence of adhesives, can all contribute to weak bed adhesion and cause warping as a result.
- Poor layer adhesion – A too high print speed, too much cooling, and low nozzle temperatures are the primary culprits behind poor layer adhesion while printing with PETG.
- Over-sticking – Using surfaces such as smooth PEI and glass without separating agents is usually the culprit for over-sticking, as PETG naturally adheres very firmly to these materials.
- Poor bridging – High print temperature, low cooling speed, and a high print speed are usually the reasons behind poor bridging. Using supports and rotating your model to have fewer bridges are also feasible ways of solving this problem.
While there are a lot of factors to be aware of while switching from PLA to PETG, which may make the switching process look challenging, it’s not likely that you will face any issues if you go through the steps carefully.
To quickly recap, here is a quick list of the things we recommend doing to switch from PLA to PETG successfully:
- Clean the extruder to ensure there are no PLA remnants left in it.
- Clean the build plate to ensure there is no residue left on it.
- Prepare the build plate by applying adhesives or separating agents if necessary.
- Re-configure the printer settings such as print temperature, bed temperature, print speed, cooling speed, Z offset, and first layer height.
- Run a test print with PETG, and observe the printing process to ensure issues such as warping and stringing don’t occur.