There is no denying that the interface of Cura can be very overwhelming due to the large number of settings you can configure, despite it being clean and intuitive.
As 3D printing is a delicate process with many factors involved, misconfiguration of even one of these settings often ends up with a failed print in some shape or form.
Today, we will be talking about one of the vital settings, extrusion multiplier, which is directly responsible for the amount of plastic your printer extrudes. As you can imagine, even a slight error in this setting can cause unintended results.
So, what is the extrusion multiplier setting in Cura, and how to configure it?
Extrusion multiplier is a setting that determines the amount of plastic the printer extrudes, which you can find with the name Flow Rate in Cura.
While this setting should stay at its default value of 100% in most cases, slightly increasing it if you’re experiencing under-extrusion or slightly decreasing it if you’re experiencing over-extrusion can be helpful.
As the effects of the Cura flow rate (extrusion multiplier) setting on your print can sound ambiguous at first, we will be taking a deeper dive into it and its importance for the printing process to go smoothly.
What Is Extrusion Multiplier (Flow Rate) in Cura?
Flow rate (extrusion multiplier) is a setting you can find under the Material section of the Print Setup menu in Cura.
The percentage value of the flow rate setting determines the amount of plastic the printer extrudes, with 100% percent being the default value.
Reducing or increasing this value impacts the amount of plastic the printer extrudes directly, which can be helpful to resolve issues related to under-extrusion, over-extrusion, poor layer adhesion, and more.
For instance, decreasing the flow rate to 90% causes the printer to extrude 10% less filament, which can solve problems such as blobbing due to over-extrusion.
Changing the flow rate is often considered a last resort solution as it’s a band-aid fix rather than directly addressing the cause behind a particular issue, which is why we recommend going through other settings before changing the flow rate.
For instance, if you face blobbing on your prints, you should ensure that you have configured all the retraction settings correctly, as properly configured retraction settings solve blobbing-related issues in almost every case.
A better use case for the flow rate setting is to compensate between different filament materials.
For instance, you can use PLA as your calibration filament and configure all the settings to achieve optimal prints with PLA.
When you switch to a different filament later on (for instance, PETG), you can adjust the flow rate setting to compensate for the difference instead of configuring all the other values from scratch.
While configuring the flow rate setting can seem straightforward as it’s only a singular percentage value, its misconfiguration can easily cause a complete disaster and ruin your prints.
How to Configure Extrusion Multiplier (Flow Rate) in Cura?
How you should configure the flow rate (extrusion multiplier) setting in Cura depends on the problem, as changing the flow rate value is a reactive solution for a particular issue.
Moving on, we will be talking about all the possible scenarios and symptoms where the configuration of the flow rate setting can be required.
Under-extrusion can present itself in many forms, such as gaps on your prints, filament grinding or skipping, weak infill, and many more.
As under-extrusion means that the printer isn’t pushing out enough filament for an optimal print, the suitable solution is to increase the flow rate in this case.
Since the flow rate is a sensitive setting with even a few percentages of difference causing a significant impact, it’s best to increase it in increments of 1 to 2 percent until you find the optimal value.
Increasing the flow rate too much will cause over-extrusion, which comes with its own set of issues.
The most apparent signs of over extrusion are stringing, oozing, blobbing, and layer shifting, all easily visible on a print.
In the case of over-extrusion, the printer pushes out more filament than needed, causing imperfections on the printed object. The appropriate solution is to decrease the flow rate in this scenario.
To find the optimal flow rate value, run test prints as you decrease it in increments of 1 or 2 percent until the problems are gone.
If you decrease the flow rate too much at once, you may face under-extrusion due to it.
Poor Layer Adhesion
Poor layer adhesion is when the layers of an object don’t stick to each other. While a handful of things can cause such an issue, such as incorrectly configured printing temperature, print speed, and more, changing the flow rate can be a solution.
In the case of poor layer adhesion, you will want to increase the flow rate setting. Increasing the amount of material the printer extrudes will allow the layers to form stronger bonds and adhere to each other.
Once again, increase the flow rate in increments of 1 to 2 percent to avoid over-extrusion problems that may come with a flow rate that is too high.
Poor Bed Adhesion
Poor bed adhesion refers to the first layer of an object not sticking to the print bed, and while there are plenty of other reasons that can cause this, similar to poor layer adhesion, increasing the flow rate can be helpful.
For poor bed adhesion, it’s best to increase the initial layer flow rate instead, as this setting will only increase the amount of plastic the printer extrudes for the first layer.
Since the initial layer flow rate setting does not impact the rest of your print, you can be more liberal with the incrementation and increase the value in increments of 5 percent.
That being said, as over-extrusion is still a risk, it’s best to run a few test prints to confirm that everything is working well.
Poor bridging refers to bridges becoming droopy instead of staying upright, and flow rate can directly cause or solve this issue.
For poor bridging, the correct course of action is to reduce the flow rate. Since bridges start drooping due to them being way too heavy, reducing the amount of plastic that goes into them can quickly solve this problem.
To find the optimal value, test print some bridges as you lower the flow rate by a percent or two with each try.
Remember to watch for signs of under-extrusion, as one problem being solved does not always mean that other issues won’t arise.
Extrusion Multiplier vs. Flow Rate
While extrusion multiplier and flow rate sound like two completely different things, they are the same exact thing.
Both extrusion multiplier and flow rate refer to a percentage value that determines the amount of plastic the printer will extrude, with 100% or 1.0 being the default value depending on the slicer.
Increasing or decreasing this value causes the plastic that the printer will extrude to become more or less on a percentage basis.
As both of these terms are viable alternatives that refer to the same thing, it’s possible to see either of them in the settings of your slicer software.
For instance, while the setting is called flow in Cura, you’ll find that it’s called extrusion multiplier in PrusaSlicer.
While its misconfiguration can easily ruin prints, the flow rate (extrusion multiplier) setting in Cura is certainly handy to have as it has the power to resolve a wide variety of issues, especially if you switch between different filaments often.
To get the best use possible from the flow rate setting, ensure that your 3D printer, especially the extruder and the retraction settings, is correctly calibrated.