Complete Guide to Understanding Retraction Speed in 3D Printing

What is Retraction Speed?

How to Fix Stringing through Retraction Photo Credit: BCN 3D

Retraction speed in 3D printing refers to how fast the filament is pulled back (retracted) from the nozzle during non-printing moves. It helps prevent oozing and stringing (unwanted filament trails between print sections). Retraction is critical for maintaining print quality, especially in models with frequent moves between different areas.

Purpose of Retraction in 3D Printing

When the print head moves from one area to another without depositing material, retraction helps to stop the filament from leaking out of the nozzle, which can otherwise create strings or blobs on the model. Proper retraction settings ensure cleaner, smoother prints.

Non-Retracted vs Retracted Filament Photo Credit: Kingroon

What Happens if You Use the Wrong Retraction Speed?

The wrong retraction speed can impact print quality, and here is a list of some causes and effects due to this:

1. Too High Retraction Speed:

   
   

   • Effects: When the retraction speed is too high, the extruder may struggle to pull the filament back smoothly, leading to grinding or stripping of the filament. It could also cause partial blockages or damage the filament, leading to under-extrusion when printing resumes.

   • Signs: Gaps or inconsistencies in the layers, clicking sounds from the extruder, or filament being chewed up.

     
     

     

     High Retraction Speed Leading to Gaps in the Filament Photo Credit: Reddit

     
     

2. Too Low Retraction Speed:

   • Effects: If the retraction speed is too slow, it won’t pull the filament back fast enough, leading to stringing or oozing.

   • Signs: Stringing (thin filaments of plastic between parts of the model), excess blobs or bumps on the print, or messy surface finishes.

   
   

   For more information about how to prevent stringing, click the link here:

   - Say Goodbye to Stringing: Top 5 Tips for Perfect 3D Prints

   
   

   

   Too Low Retraction Speed Leading to Stringing of the Filament Photo Credit: Reddit

Units of Retraction Speed

The metric system typically measures retraction speed in millimeters per second (mm/s). In the imperial system, this would be converted to inches per second (in/s).

• Metric System (mm/s):

  The standard unit in 3D printing. For example, a retraction speed of 50 mm/s means the filament retracts at 50 millimeters per second.

  
  

• Imperial System (in/s):

  To convert millimeters per second to inches per second, divide the value by 25.4 (since 1 inch = 25.4 mm).

Calculation Example

Let’s convert a typical retraction speed of 50 mm/s to inches per second:

50 mm per second / 25.4 mm = 1.97 inch per second

Similarly, for a lower retraction speed of 20 mm/s

20 mm per second / 25.4 mm = 0.79 inches per second

So, in imperial units:

• 50 mm/s ≈ 1.97 in/s

• 20 mm/s ≈ 0.79 in/s

This conversion helps if you’re more familiar with the imperial system, although most 3D printing software uses metric units.

Final Tips for Dialing in Retraction Speed in 3D Printing

• Start with Recommended Values: Use the filament manufacturer's suggested retraction speed as a starting point, and test with small models to fine-tune it.

• Use Test Models: Print small test models designed for stringing and retraction optimization. Many models are available online specifically for this purpose.

• Tweak in Small Increments: If stringing or other issues occur, adjust the retraction speed in small increments (e.g., 5 mm/s) to see if performance improves.

Understanding retraction speed and how to adjust it for different filament types can significantly improve the quality of your 3D prints, reduce stringing, and improve the overall surface finish.