Are you also frustrated by the noticeable layer lines on your 3D prints? Whether it's for aesthetic display models or functional parts requiring precise assembly, layer lines affect the final quality. The good news is that with some adjustments, you can significantly improve the printing surface.
The nature of FDM printing makes it difficult to completely eliminate layer lines, but we can minimize them to the point where they're almost invisible to the naked eye. Here are 7 proven techniques, from simple to advanced, to help you achieve smoother print surfaces.
1. Optimize Basic Settings: Reduce Layer Lines at the Source
Before trying any advanced techniques, ensure your basic print settings are optimized—this is the most important step.
Reducing layer height is key. Lowering the layer height from the standard 0.2mm to 0.12mm or 0.16mm can significantly reduce vertical layer lines. Although print time will increase, surface quality will noticeably improve.
Linear Advance is another often overlooked but powerful tool. It eliminates spots caused by sudden acceleration and deceleration of the extruder motor, making extrusion smoother and reducing surface defects. Enable and calibrate it properly in Marlin firmware.
2. Calibrate Your Extruder: Avoid Over-Extrusion
Over-extrusion is a major cause of visible layer lines. When more material is extruded than needed, excess plastic accumulates on the sides of the print, creating unsightly vertical lines.
Extruder calibration steps:
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Mark 110mm from the extruder entrance
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Extrude 100mm of filament through the printer interface
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Measure the actual distance from the mark to the entrance
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If the actual extrusion length isn't 100mm, adjust the e-steps value
The correct formula is: New e-steps = (Current e-steps × 100) ÷ Actual extrusion length
3. Control Print Temperature: Find the Optimal Balance
Print temperature directly affects layer-to-layer bonding and surface quality. Temperature that's too high makes material overly fluid, creating a "drooping" effect, while temperature that's too low affects interlayer adhesion.
Temperature tower testing is the best method. Print a tower with different temperatures at different heights, and observe which section has the best surface quality with the fewest layer lines. Each material—and even different colors of the same brand—may have different optimal temperatures.
It's worth noting that lowering the temperature by 5-10°C often improves surface finish, but ensure it doesn't affect interlayer bonding strength.
4. Set Proper Cooling: Optimal Solidification
Cooling fan settings significantly impact surface quality. Excessive cooling can cause poor layer-to-layer bonding, while insufficient cooling can lead to print deformation.
For most PLA printing, it's recommended to completely turn off the cooling fan for the first layer, then gradually increase it to 100% in subsequent layers. However, for small details and overhangs, more cooling may be needed.
PETG material is more sensitive to cooling—typically 30-50% fan speed is recommended. ABS usually works best with the fan completely off, unless printing small details.
5. Try Different Infill Patterns: Reduce the "Show-Through" Effect
Certain infill patterns, like grid, can "show through" the outer walls at regular intervals, creating visible patterns. Switching to patterns like concentric, lightning, or adaptive cubic can reduce this effect.
Increasing wall thickness is an even more effective method. Try using 3-4 walls instead of the standard 2—this better conceals the infill pattern.
6. Advanced Techniques: Variable Speed Printing and Line Width Optimization
Variable speed printing is an advanced technique that uses different speeds for different areas. For example, use slower speeds (20-30mm/s) for outer walls and faster speeds for infill and supports. This improves wall quality without significantly increasing total print time.
Optimizing line width settings is also helpful. Try setting the outer wall line width to 90-95% of the nozzle diameter—this produces more tightly packed lines, reducing visible gaps.
7. Post-Processing Techniques: Achieve Extremely Smooth Surfaces
If you're still unsatisfied after all the above adjustments, post-processing is the final option.
Sanding is the most common post-processing method but requires patience. Start with coarse sandpaper (like 200 grit) and gradually move to fine sandpaper (1000 grit or higher). For PLA, wet sanding prevents plastic overheating and sandpaper clogging.
Chemical polishing provides the smoothest surface. For ABS, acetone vapor polishing works excellently, but must be done in a well-ventilated area with proper safety precautions. For PLA, you can try epoxy resin coatings, which smooth the surface while increasing strength.
Filling and painting is another effective method. Use 3D printing-specific filler (like Bondo Spot Putty) to fill layer lines, then sand smooth, and finally paint. This method can achieve injection-mold-like smooth surfaces.
Special Technique: Non-Planar Printing
This is the most advanced layer line elimination method. Non-planar printing doesn't build layers horizontally but aligns the printing surface with the model geometry's curvature, completely eliminating horizontal layer lines. However, it requires special slicing software and complex settings.
Practical Suggestions: Gradual Approach
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Start by calibrating the extruder
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Optimize basic settings (layer height, temperature, cooling)
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Adjust advanced settings (line width, speed)
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Try different infill patterns
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If necessary, proceed to post-processing
Don't change too many variables at once. Adjust one setting at a time, print a test model (like a 20mm cube or Benchy), record results, and compare quality.
Summary: Perfect FDM print surfaces are achievable but require patience and systematic adjustments. Start with basic calibration, gradually optimize all parameters, and eventually you'll find the best combination of settings for your printer, materials, and specific models.
