Retraction is one of the things we can consider being fundamental for a successful printing process, known for its role in preventing common 3D printing issues such as stringing and oozing by pulling the filament back from the nozzle whenever necessary to achieve its goal.
On the other hand, as with most other things in the world of 3D printing, retraction isn’t something we can enable and forget about – since a set of correctly configured retraction settings is the lifeblood of the retraction feature that allows it to serve its purpose as optimally as possible.
Today, we will take a deeper look into the retraction settings specifically for printing with TPU filament, as we believe getting these settings correct is paramount for printing TPU without experiencing stringing and blobbing issues that cause prints to become unsuccessful.
So, what are the optimal retraction settings for TPU?
Even though finding the exact optimal settings primarily comes down to running experiments with the hardware you own, the values we have listed below should act as a starting point that should provide fairly optimal results:
- Retraction Speed – 20 millimeters per second
- Retraction Distance – 6 millimeters for Bowden extruders, 2 millimeters for Direct Drive extruders
- Retraction Minimum Travel – 1.5 millimeters
Next up, we will examine each retraction setting in more detail to find the optimal values for TPU, go through configuring retraction settings specifically for TPU in Cura and PrusaSlicer and look at the symptoms the usage of incorrect retraction settings would bring.
What Are the Optimal Retraction Settings for TPU?
Due to retraction being a pretty extensive category with many parameters that require careful configuration with values based on experimentation, initially optimizing these settings can be slightly challenging.
As each retraction parameter is equally significant for retraction to work correctly, we will be going into the retraction speed, retraction distance, and retraction minimum travel parameters separately and share the values that we found optimal for printing with TPU.
The retraction speed parameter determines the speed at which the extruder pulls the filament back.
Based on our experiments, we can consider a retraction speed of 20 millimeters per second optimal for printing with TPU filament.
In the case of TPU, we recommend keeping the retraction speed value as low as possible at the point where you don’t face any issues related to stringing and blobbing, which will reduce the chance of a nozzle jam occurring.
Moving up or down in increments of 1 mm/s based on the results you observe (up for over-extrusion, down for under-extrusion) is the best way to move forward to optimize the retraction speed as best as possible.
The retraction distance parameter determines how far the filament gets pulled away from the nozzle by the extruder.
For Direct Drive extruders, a retraction distance value of 2 millimeters should suffice.
On the other hand, for Bowden extruders, we have found that a value of 6 millimeters for the retraction distance works best for printing TPU filament.
An important rule to keep in mind is that the retraction distance value should always be less than the length of your printer’s nozzle to avoid issues with retraction.
We recommend moving up or down in increments of 0.1 to 0.2 millimeters based on the results, where it’s suitable to move up for over-extrusion and down for under-extrusion.
Retraction Minimum Travel
The retraction minimum travel parameter determines the smallest distance that a travel move should be taking before the printer triggers a retraction.
We recommend a value of 1.5 millimeters for the retraction minimum travel parameter while printing with TPU, allowing a healthy number of retractions to occur during the print.
For TPU, we recommend keeping this value as high as possible to avoid unnecessary retractions causing a potential nozzle jam and slowing the print down in general.
In the case of too little or too many retractions, we recommend running a series of test prints while moving down or up in increments of 0.1 mm, respectively.
How to Configure TPU Retraction Settings in Cura?
Applying the appropriate retraction configuration for TPU and saving it for later usage in Cura is a pretty effortless task that won’t take too much of your time.
Below is a step-by-step guide you can follow to configure TPU-specific retraction settings in Cura:
- Navigate to the Prepare tab of the Cura, which you can find at the top of the window.
- Click the middle pane to bring up the material profile dropdown.
- Click the Material dropdown menu, and choose TPU 95A from the Generic section.
- Click the rightmost panel for Print Settings, and navigate to the Custom tab if you haven’t already.
- Click the three lines icon next to the search input, and choose the All option to make all print settings visible.
- Type “retraction” into the search input, which will make all retraction-related parameters visible and ready for configuration.
Following these steps will load Cura’s default settings for TPU as the baseline and allow you to overwrite the baseline retraction settings, which you can save into a profile afterward.
How to Configure TPU Retraction Settings in PrusaSlicer?
It’s also a pretty straightforward process to configure the retraction settings for TPU in PrusaSlicer, where the approach isn’t much different than in Cura.
Below is a step-by-step guide you can follow to configure TPU retraction settings in PrusaSlicer:
- Navigate to the Plater tab located on the top of the PrusaSlicer window.
- Click the Generic FLEX option from the Filament dropdown. If the option is not available, you can enable it through the Add/Remove Filaments option in the same dropdown.
- Click the Printer Settings tab.
- Click the Expert tab on the top-right of the window.
- Navigate to Extruder 1 on the left pane, where you will find all the retraction-related settings.
Upon following these steps, PrusaSlicer will load the generic settings for TPU filament and allow you to edit the retraction settings, which you can save into a separate profile if you wish.
Signs of Incorrect Retraction Settings While Printing with TPU
While retraction settings are pretty powerful when configured correctly, incorrect configuration of these settings will, without a doubt, affect the printing process negatively.
To start, let’s take a look at what you may experience if you’re using too much retraction while printing with TPU.
In a nutshell, applying too much retraction while printing with TPU is highly likely to cause a nozzle jam due to the high elasticity of TPU, which will cause under-extrusion in the case of a partial blockage or entirely prevent the printer from extruding in the case of a complete jam.
On the other hand, as you may have predicted, too little retraction can also cause problems for your print.
The issues that can happen with too little retraction are, as always, over-extrusion problems that plague many prints in the form of stringing and blobbing, where unwanted fragments of plastic end up on the model during the printing process due to the plastic oozing uncontrollably out of the nozzle.
With these two major problems on either side of the spectrum, it’s vital to configure the retraction settings as optimally as possible for a successful printing process with TPU filament.
Ensuring that the retraction settings are optimal while printing with TPU is vital to avoid stringing and blobbing issues that plague many prints and render them unusable, especially considering that these issues are highly likely to occur while printing with TPU.
To quickly recap, as TPU is a soft material that can easily jam the extruder due to too much movement, it’s best to stay on the lower side when it comes to retraction.
With a retraction speed of 20 millimeters per second, a retraction distance of 6 millimeters (2 mm for Direct Drive extruders), and a retraction minimum travel value of 1.5 millimeters, you should be able to avoid both stringing and jamming for the most part with TPU filament.
As always, we highly recommend running your experiments to find the best possible retraction values before committing to a large print that takes a lot of time and material.