What Is the Best Extrusion Multiplier for Printing PETG?

Extrusion multiplier, also known as flow rate, is the parameter responsible for controlling the amount of plastic that comes out of the extruder during the printing process.

While the default value of 100% is often preferred, slight adjustments to the extrusion multiplier parameter can be necessary when switching between filament types; or even different spools of filament to account for under or over-extrusion.

Today, we will look at the extrusion multiplier parameter in relation to PETG, in particular, as it’s one of the values that often requires changing after switching to PETG from PLA for the first time, which a lot of 3D printing enthusiasts do at some point.

So, what is the best extrusion multiplier for printing PETG?

We recommend using an extrusion multiplier value between 0.95 (95%) and 1 (100%) while printing with PETG in most cases.

Since the value you should use for the extrusion multiplier parameter largely depends on the situation, experimentation is vital for finding the number that works best for you.

Moving forward, we will take a deeper look into the optimal extrusion multiplier values for printing PETG, find out how you can calibrate extrusion multiplier for a new spool, and discuss the effects of different extrusion multiplier values on the printing process.

What Is the Best Extrusion Multiplier (Flow Rate) for Printing PETG?

Since extrusion multiplier is a sensitive parameter where even a misconfiguration of one percent can cause under or over-extrusion and cause issues with your print, getting it exactly right is paramount.

The optimal extrusion multiplier for printing PETG usually falls into the range of 0.95 to 1, since decreasing the extrusion multiplier than the default value of 1 is sometimes necessary to ensure that PETG does not over-extrude.

While the recommendation is to keep the flow rate value default and modify other settings (such as retraction) to ensure that under or over-extrusion does not happen, changing the flow rate is a quick solution, especially if you’re switching to PETG for the first time from PLA.

That being said, as coming up with an extrusion multiplier value for PETG that will work as optimally as possible in each scenario is basically impossible, you will need to run your own test prints and experiment until you can find the value that works best.

How to Calibrate Extrusion Multiplier (Flow Rate) for a New Spool of PETG?

As each spool of PETG is different than the other, calibrating the extrusion multiplier once your previous spool of filament is over is vital to ensure that your prints with the new spool will be successful.

Below are the two different methods you can use to calibrate the extrusion multiplier for a new spool of PETG.

Precise Calibration

Precise calibration refers to the usage of precision tools for conducting the calibration process.

Here are the steps we recommend following to perform a precise calibration of the extrusion multiplier:

  1. Print a standard cube with your 3D printer. As the dimensions don’t really matter, a 20x20x20 cube will suffice.
  2. With the help of calipers, measure the wall thicknesses from a few different points.
  3. Calculate the average thickness by using the values you have collected.
  4. Calculate the extrusion multiplier value by dividing the line width (or the wall thickness for multiple walls) by the average thickness value.

Repeat the steps until the average thickness value you have calculated equals the line width (or the wall thickness for models with multiple walls) value you use in your slicer.

While this method is the more advanced one between the two, it also provides the best results.

Basic Calibration

Basic calibration is the method of calibrating the extrusion multiplier without the need for any extra tools.

Here are the steps we recommend following to perform a basic calibration of the extrusion multiplier parameter:

  1. Print a standard cube. Since dimensions aren’t significant, a 20x20x20 cube will do the job.
  2. Inspect all sides of the cube for imperfections, such as gaps and or too much plastic.

If you observe gaps, increase the extrusion multiplier value by 1%, and repeat the steps.

On the other hand, if you observe the gathering of too much plastic, decrease the extrusion multiplier value by 1%, and repeat the steps.

While this method is more undemanding due to it not requiring any tools, it may not always yield the best results.

What Are the Effects of Extrusion Multiplier (Flow Rate) on Printing PETG?

For understanding whether your extrusion multiplier value is correct or not, the best course of action is to learn more about the effects of this parameter on your prints and keep an eye out for these signs during the printing process.

To start off, let’s take a look at the signs you would observe if the extrusion multiplier is too high while printing with PETG.

In a nutshell, an extrusion multiplier value that is too high will cause over-extrusion, and as a result, will bring symptoms related to over-extrusion.

Stringing, blobbing, and deformation of the printed model are the main signs of over-extrusion, as all of them are due to the printer extruding more plastic than required.

Now, let’s find out the symptoms that would appear if the extrusion multiplier is too low.

When the extrusion multiplier value is too low, under-extrusion will take place, and signs that we associate with under-extrusion will be present on your model.

Gaps, holes, inconsistent layers, layers smaller than they should be, and reduced structural strength are the main signs of under-extrusion.

How to Set Extrusion Multiplier (Flow Rate) for PETG in Cura?

If you’re looking to change the extrusion multiplier in the Cura slicer software, here are the steps you can follow to do so:

  1. Navigate to the Prepare tab on the top of the Cura window.
  2. Click the rightmost pane, which should bring the Print Settings dialog up.
  3. Click the Custom button if you haven’t before, which will switch the Print Settings to Custom mode.
  4. Click the icon (three lines) next to the search input, and choose the All option from the dropdown menu to make all settings visible.
  5. Type “flow” in the search input, which should bring up the Flow parameter and its sub-parameters.

As the extrusion multiplier parameter is called Flow in Cura, you can modify the parameter by inputting the value you desire into the input next to the Flow box.

Since Cura also makes it possible to configure the extrusion multiplier separately for different parts, such as the walls and the infill, you can also use these parameters to fine-tune the configuration even further.

Wrapping Up

Even though it’s not a value that requires tweaking way too often, the correctness of the extrusion multiplier is paramount for a successful PETG printing process due to the issues it can cause, even if it’s slightly misconfigured.

To quickly recap, we recommend using an extrusion multiplier value of 0.95 to 1 for printing PETG, which you should fine-tune by experimenting with test prints to obtain the most optimal value possible.

As PETG can over-extrude a bit compared to PLA, taking a few percentages off the flow rate usually comes in handy in many scenarios to compensate for this difference and keep the printing process moving successfully without changing too many settings.

Happy printing!