While correctly configuring your Cura settings is a vital part of obtaining a successful print, it’s not always easy to do so, considering that there are so many different settings that sound ambiguous at first look.
Due to the complexity of these settings, most 3D printing enthusiasts, especially those who are just starting, don’t even consider configuring them. As you may predict, misconfiguration of these settings presents itself as problems with the object you have printed.
Today’s topic is one such setting called retraction extra prime amount, and correctly configuring it can solve many print-related issues even though it’s not a setting that you hear about often.
So, what is retraction extra prime amount in Cura?
The value of the retraction extra prime amount setting determines the added amount of plastic the printer will extrude after performing a retraction and the subsequent travel move that comes after.
The idea behind this setting is to compensate for the plastic that the nozzle loses due to oozing during the travel move by priming an extra amount of filament for the upcoming print action.
As we can certainly agree that it’s a confusing concept to understand at first look, let’s take a deeper look into the retraction extra prime amount setting and the problems it can solve or cause depending on whether it’s correctly configured or not.
What Is Retraction Extra Prime Amount?
Retraction extra prime amount is a setting that you can find in the Retraction Settings section of Cura.
The value that you input for the retraction extra prime amount setting determines the amount of extra filament the printer will prime after a retraction and the travel move that follows it.
Configuring this setting allows the printer to compensate for the plastic lost to oozing after a retraction and a travel move and prevent the appearance of gaps and holes due to the lost plastic.
As oozing is a problem that you should directly solve by configuring the retraction settings in Cura correctly instead of compensating for it, we recommend setting this value to either zero; or its default value unless you’re using it as a last resort.
You can calculate the default value for the retraction extra prime amount setting by cubing the nozzle size of your printer. For instance, if the nozzle size of your printer is 0.4 mm, you should be inputting 0.064 as the value.
By doing so, you will remove the risk of incorrectly configuring this setting and entirely remove its chance of causing blobs or gaps.
Effects of Retraction Extra Prime Amount
If you cannot solve the oozing problem and would like to use this setting as a last resort, there are a few things to be mindful of before you start.
Since this setting can directly increase the amount of plastic the printer extrudes, incorrectly setting it to a value that is too high can cause blobbing due to over-extrusion even if you configure all the rest of the retraction settings correctly.
On the other hand, setting the retraction extra prime amount value to a value that is too low (in the negatives) can cause the opposite of blobbing by directly reducing the amount of extruded plastic, which is holes and gaps as a result of under-extrusion.
As a result, configuring this setting the right way requires a lot of experimentation and test printing until you can find the sweet spot where neither blobs nor gaps appear on your prints.
Using a Negative Retraction Extra Prime Amount Value
While using a negative retraction extra prime amount value may sound like an odd thing to do, there is good reason to do so in some scenarios.
Inputting a negative value for the retraction extra prime amount value setting reduces the amount of filament that is primed after a retraction and a travel move, which can be helpful to combat blobbing as a last resort solution.
When inputting negative values into this setting, remember to move down in small increments and experiment as you go, as too low of a value can completely prevent extrusion due to the printer not priming any filament at all.
Does Retraction Extra Prime Amount Apply to All Travel Moves?
A common question is whether retraction extra prime amount setting applies to all the travel moves or just the ones that follow a retraction.
The retraction extra prime amount setting applies only for travel moves that follow a retraction, as the name suggests.
Since there is no need for the printer to prime the filament if it doesn’t retract it first, this value also becomes entirely obsolete in such a scenario.
Configuring the Retraction Extra Prime Amount Setting for Ender 3
Questions related to Ender 3 make up for the largest amount of questions in the 3D printing community due to its popularity, which is why we have decided to share how you can configure the retraction extra prime amount setting for Ender 3.
To find the default value for this setting, the only piece of information you require is the nozzle size of your printer, which is 0.4 mm in the case of an Ender 3.
The default retraction extra prime amount value for the Ender 3 is 0.064 m^3, which we have found by calculating the cube of 0.4 mm (the nozzle size of Ender 3).
While retraction extra prime amount in Cura isn’t a setting that you hear about often, it can easily cause blobbing if you misconfigure it due to the extra filament the printer extrudes as a result of it.
On the other hand, even though its usage shouldn’t be necessary with properly configured retraction settings, it can also solve the issue of your prints having holes on them due to filament being lost to oozing during travel after a retraction.
In either case, retraction extra prime amount is definitely a setting that every 3D printing enthusiast who uses Cura should be aware of, even if it’s only to verify that it’s correctly configured.
Mike started his 3D printing journey with the Anet A8 when it first came out back in 2017, and has been obsessed with 3D printers ever since. Nowadays, he primarily uses his Ender 3 to print functional parts that make his life more convenient whenever possible.