You want to discover everything there is to know about retraction in 3D printing. At Imprimy, we are here to answer all your questions.
What is retraction in 3D printing?
Retraction in 3D printing refers to the backward movement of the filament during the 3D printing process. This retraction varies in different ways depending on certain parameters.
How retraction works
Retraction in 3D printing is a mechanism that helps avoid strings and blobs when the nozzle moves without extruding filament. When a non-printing move is detected, the printer slightly pulls the filament back into the extruder before pushing it forward again once extrusion resumes. This process reduces material oozing and improves the sharpness of prints.
Its effectiveness depends on several parameters, including the retraction distance and speed, which vary depending on the type of printer (direct drive or Bowden) and the material used. Therefore, precise adjustment is crucial to avoid both “stringing” (thin threads between printed parts) and under-extrusion.
The goals of retraction
The main goals of retraction in 3D printing are to improve print quality by reducing defects related to nozzle movements. It helps avoid strings that appear when filament continues to flow unintentionally between two print areas. It also helps minimize blobs and droplets that can degrade the final appearance of the part.
Proper retraction settings also help prevent over-extrusion and maintain better dimensional accuracy. Finally, it optimizes the material flow, ensuring smooth and consistent extrusion, which is essential for producing clean and detailed parts.
Retraction based on other 3D printing parameters
Retraction in 3D printing is closely related to several other printing parameters, which influence its effectiveness and settings. The extrusion temperature plays a key role: if it is too high, the filament becomes too fluid and is more likely to ooze, requiring more retraction, while a temperature that is too low can cause under-extrusion.
The print speed and retraction speed must be properly calibrated to avoid too slow retraction, which would be ineffective, or too fast, which could lead to a clogged nozzle. The type of extruder is also crucial: a Bowden setup typically requires a higher retraction distance than a direct drive system, due to the length of the PTFE tube.
Finally, the material used strongly influences retraction: flexible filaments (such as TPU) often require minimal retraction to avoid clogging, while PLA, PETG, and ABS each have specific settings to minimize stringing and optimize print quality.
What are the common issues related to poor retraction?
The issues associated with retraction are under-retraction or over-retraction.
Under-retraction
Under-retraction occurs when the filament is not retracted enough during non-printing moves. This can lead to oozing or stringing, where excess filament drips or forms thin strands between different areas of the print. As a result, the final print may have unwanted strings or blobs, which can affect the appearance and precision of the object. Adjusting the retraction distance and speed can help resolve this issue.
Over-retraction
Over-retraction occurs when the filament is retracted too much during non-printing moves. This can lead to issues such as under-extrusion, where not enough filament is fed into the nozzle when printing resumes, resulting in gaps, weak layers, or incomplete prints. Over-retraction can also cause clogs or difficulty in restarting the extrusion process. Adjusting the retraction distance and speed to appropriate levels is crucial to prevent over-retraction and maintain consistent extrusion.
How to properly adjust the retraction of your 3D prints?
You can make adjustments to the retraction distance, retraction speed, and the influence of temperature.
Adjustments to the retraction distance
Adjustments to the retraction distance are crucial for optimizing 3D print quality and avoiding defects such as strings or blobs. The retraction distance determines how many millimeters the filament is pulled back into the extruder when no extrusion occurs during the nozzle movements. If this distance is too short, oozing may occur, while if it is too long, there may be under-extrusion when extrusion resumes.
The adjustment of the distance varies depending on the type of extruder: for a direct drive system, the retraction distance is generally shorter, around 1 to 2 mm, due to the proximity of the extrusion motor, while for a Bowden system, the distance can be longer, around 4 to 7 mm, because the filament has to travel a greater distance through the PTFE tube.
Depending on the material used, such as PLA, ABS, or TPU, the distance may also vary. It is recommended to perform retraction tests to fine-tune this distance and avoid print quality issues.
Adjustment of the retraction speed
Adjustment of the retraction speed plays a crucial role in avoiding stringing while ensuring smooth extrusion. If the speed is too low, the filament may not retract quickly enough, leading to excessive oozing between the nozzle movements. Conversely, if the speed is too high, it can cause clogs or skipping due to excessive pressure in the extruder.
In general, the retraction speed ranges from 20 mm/s to 100 mm/s, depending on the type of printer and filament. For Bowden extruders, higher speeds may be required (around 40-60 mm/s), while for direct drive extruders, lower speeds (around 20-30 mm/s) may suffice. It is important to test these values to find the optimal balance based on the filament characteristics and the desired results.
The influence of 3D printing temperature on retraction
The printing temperature plays a crucial role in the behavior of retraction in 3D printing. When the extrusion temperature is too high, the filament becomes more fluid, which can lead to excessive oozing of the material during the nozzle movements, increasing the risk of stringing (threads between printed areas). In this case, more retraction may be needed to compensate for the filament’s fluidity.
On the other hand, if the temperature is too low, the filament becomes stiffer and may clog or deform in the nozzle, reducing the effectiveness of retraction and potentially causing under-extrusion. Therefore, it is crucial to find the ideal temperature for each material (for example, between 190°C and 220°C for PLA, or 230°C to 250°C for ABS), while also adjusting other parameters like retraction distance and retraction speed.
Advanced retraction parameters
Advanced retraction parameters allow for fine-tuning 3D printing to solve specific issues like stringing, blobs, or bavures. Some of these parameters include:
- Coasting: This feature slightly stops extrusion before the nozzle moves, helping to reduce the excess filament that could leak out after finishing the print of each segment. It prevents droplets and blobs by minimizing material oozing.
- Wipe: This parameter involves moving the nozzle across the print surface before starting a new path to “clean” the filament’s tip and reduce the appearance of threads. This can be particularly helpful for materials prone to accumulating on the nozzle.
- Z-hop (or “Lift”): Z-hop raises the nozzle slightly when moving from one area to another without printing, preventing it from touching or damaging the ongoing print. This setting is useful, especially for high-resolution prints or when retraction is not enough to prevent the nozzle from contacting already printed parts.
- Retraction Extra Prime Amount: This parameter adds a little more filament after retraction to compensate for any material loss during retraction and improve the continuation of extrusion. It can be adjusted to correct under-extrusion or a slow restart.
- Combing Mode: This setting prevents the nozzle from moving over unprinted areas, limiting unnecessary movements through the air and reducing stringing. Combing allows the nozzle to move only over already printed parts, minimizing visual defects.
These advanced parameters allow for better control of the filament flow and adjustment of the printer’s behavior, resulting in cleaner, more precise, and aesthetically successful prints while reducing retraction-related defects.
What tests and calibrations should be performed to optimize retraction?
To reduce the negative effects of poor retraction, you should not hesitate to perform specific tests to optimize your various settings.
Printing specific tests
Printing specific tests is a crucial step to optimize retraction settings and improve 3D print quality. These tests help evaluate the effectiveness of retraction settings, including distance, speed, and temperature, while identifying issues such as stringing, blobs, or under-extrusion. Here are some commonly used tests:
- Stringing or Retraction Tower Test: This involves printing a small model, often in the shape of a tower, with frequent non-printing movements to observe the presence of thin threads between different sections. This test helps adjust the retraction distance, retraction speed, and printing temperature to avoid unwanted strings.
- Blobs and Droplets Test: This test involves printing a small model where the printer performs multiple successive extrusions, allowing you to check for blobs (filament droplets) at each transition. It’s useful for adjusting the coasting function or extrusion speed.
- Over/Under-Extrusion Test: It is important to verify the amount of filament extruded, especially after retraction. You can print simple layers and check if the surface is smooth and even. If the surface has holes or under-extrusion areas, you’ll need to adjust the extrusion and retraction settings.
- Z-Hop Retraction Test: If you have issues with bavures (smearing) caused by nozzle movements, a Z-hop test checks whether raising the nozzle during non-extrusion movements prevents unwanted contact with the ongoing print.
These tests help to precisely calibrate each retraction parameter based on the materials used and the printer’s specifications. Once adjustments are made from these tests, it’s recommended to perform a full print test on a larger object to verify the results across the entire piece.
Iterative adjustment of parameters
Iterative adjustment of parameters is a key method for fine-tuning retraction settings and achieving high-quality 3D prints. This approach involves making small, successive adjustments to parameters and testing each change by printing a test model. The idea is to proceed step by step, observing the results of each modification to find the optimal settings for flawless retraction.
- Start with basic parameters: It’s recommended to begin by setting standard values for retraction distance and speed, based on the type of printer and filament. For example, an initial retraction distance of 4 to 6 mm and a retraction speed of about 30 mm/s can serve as a starting point for many materials like PLA.
- Test and observe the results: After each test print, carefully examine the piece for defects such as stringing, blobs, or holes. If you notice strings between printed sections, you’ll likely need to increase the retraction distance or reduce the printing temperature.
- Gradually adjust the parameters: If a problem is detected, make incremental adjustments. For example, if strings appear, try slightly increasing the retraction distance or speeding up the retraction speed. If blobs are present, the coasting parameter may need adjustment. Remember that each change should be followed by a new test to evaluate its effectiveness.
- Balance all parameters: It’s important not to adjust a single parameter without considering the others. For example, a larger retraction might require a lower temperature, or a higher retraction speed might affect filament flow. Adjustments should always be balanced based on tests and observations.
- Keep track of parameters: As you make these adjustments, record the parameters and results for each test. This allows you to easily return to settings that provided the best results and avoid future mistakes.
Iterative parameter adjustment is, therefore, a systematic process that, while time-consuming, helps optimize print quality and reduce retraction-related errors for each type of filament and printer.
Conclusion: 3D Printing and Retraction
Retraction is a critical aspect of 3D printing that significantly impacts the quality of prints. By controlling the retraction distance, retraction speed, and extrusion temperature, you can effectively minimize issues such as stringing, blobs, and under-extrusion. Achieving optimal retraction settings requires a careful balance and fine-tuning of multiple parameters, including advanced settings like coasting, wipe, Z-hop, and combing mode.
The process of iterative adjustments and conducting specific test prints is essential to identify and resolve issues effectively. Regular testing and observation allow you to make gradual changes that lead to improvements, ensuring smooth, clean, and precise prints.
By understanding and adjusting these parameters according to the material used, printer type, and desired print quality, you can achieve high-quality, defect-free 3D prints with enhanced detail and minimal flaws. Through consistent calibration and optimization, the retraction process becomes a powerful tool to enhance your 3D printing experience.
Image generated by DALL·E, an artificial intelligence model developed by OpenAI.
The articles published on Imprimy.com are for informational purposes only. They are intended to provide general advice and information related to 3D printing. Imprimy.com cannot be held responsible for the results obtained or the consequences arising from the application of the shared information. We recommend always checking the specific instructions for your hardware and materials before use.
