The top layer of a 3D print is the most visible part of the model, and problems such as uneven surfaces, gaps, or brushing can affect the appearance and usability of the print. The right settings, techniques, and post-processing can minimize these defects. In this article, we will explore practical techniques and tips to help you smooth the top layer of a 3D print.

Common 3D Printing Top Layer Problems and Detailed Analysis

1. Rough or Uneven Surface (Pillowing)

The top layer surface may appear rough, uneven, or have a wavy, pillow-like structure. The main reasons are poor extrusion, insufficient material cooling, and low filling density. Insufficient material feeding will cause uneven distribution of the top layer material, and insufficient cooling fans will prevent the material from solidifying quickly when stacked, affecting the flatness of the surface. In large flat areas, if the filling density is low, insufficient support can also cause the surface to collapse and form a bulging, corrugated structure.

Source: https://www.reddit.com/r/FixMyPrint/comments/bby8p6/poor_quality_top_layer_not_pillowing/

2. Gap Problems Between Lines

The top layer surface may have gaps that are not fully filled, which is usually due to insufficient top layer thickness or low internal filling density. A top layer thickness that does not meet the recommended value (usually 4-6 layers) will reduce the integrity of the surface coverage, while insufficient internal filling strength will cause the top layer material to hang in the air, resulting in the inability to fill the surface gaps, which in turn affects the print quality.

Source: https://www.simplify3d.com/resources/print-quality-troubleshooting/gaps-in-top-layers/

3. Wiredrawing or excessive material accumulation

The top surface may have filament accumulation or material protrusions, which is usually related to the extruder settings. Wiredrawing occurs when the nozzle fails to retract the material in time during movement, resulting in excess material remaining on the surface to form filaments. Overextrusion is caused by the extrusion volume being set too high, causing material accumulation and irregular structures on the surface. These problems need to be solved by accurately adjusting the extruder parameters.

Source: https://techknowlab.com/3d-printing-top-layer-problems/

Operation Guide for Smoothing the Top Layer of 3D Prints

1. Ironing

Ironing is a technique that improves the surface smoothness by additional processing of the top layer after it is printed. This function is available in many modern slicing software. The ironing function improves the top surface by changing the way the nozzle works. When the ironing function is enabled, the nozzle no longer completely fills the top layer, but makes a slight transitional movement on the surface of the print with a higher temperature and lower extrusion. The nozzle slides back and forth on the surface of the top layer, reflowing and filling in the slight irregularities and gaps on the surface. This method effectively smooths out the small marks left by the normal printing path, making the top layer of the print smoother and more visually appealing.

Source: https://3dprinterly.com/how-to-use-ironing-in-3d-printing-best-settings-for-cura/

Common slicing software, such as Cura, PrusaSlicer, and Simplify3D, have this option. When the ironing function is enabled, the following parameters usually need to be adjusted:

Ironing temperature: The ironing temperature should be set slightly higher than the normal printing temperature to ensure that the material can flow and cover the surface during ironing.

Number of ironing layers: Usually set to the last layer of the top layer. Too many ironing layers may cause excessive material flow and unnecessary deformation.

Nozzle speed and extrusion: To ensure smooth nozzle movement, the speed should be moderate, and the extrusion volume needs to be reduced to avoid excess material accumulation.

2. Increase layer height and top layer thickness

Increasing the print layer height and top layer thickness is a direct way to improve the quality of the top layer. A larger layer height can reduce printing time and reduce the appearance of subtle textures during printing. Specifically, a larger layer height can reduce the subtle differences between each layer, which ultimately makes the top layer look smoother. The top layer thickness should also be increased appropriately. Generally, 4 to 6 layers of the top layer are recommended. This ensures that the top layer has sufficient material thickness to help fill small gaps and improve surface smoothness.

3. Adjust cooling settings

The cooling settings directly affect the curing process of the top layer, which in turn affects the quality of the printed surface. If the cooling fan is not working fully, the material of the top layer may not cure in time, resulting in an uneven or rough surface. To this end, the cooling fan speed can be increased, especially during the top layer printing stage, to ensure that the material cures in time and avoid defects caused by uneven material flow or overheating. The cooling settings should be adjusted for different material types, especially when dealing with materials that are easy to cool, such as PLA.

4. Reduce the printing speed

Reducing the printing speed is a common way to improve the quality of the top layer. Although a higher printing speed can save time, it may cause uneven extrusion of the material, resulting in an uneven surface. By slowing down the printing speed, you can improve the extrusion accuracy and ensure that each layer of material can be laid evenly, thus greatly improving the surface quality of the top layer. Especially when printing the top layer, appropriately reducing the printing speed can help ensure that the final top layer is smoother.

5. Try different infill settings

The infill settings have a direct impact on the smoothness of the top layer. The choice of infill density and infill mode will affect the support of the top layer. If the infill is too low or the mode is not selected properly, the top layer surface is prone to hanging or wavy textures. You can increase the infill density to 20%-30%, and choose a stable infill mode, such as triangle or grid mode, which can provide better internal support, help the top layer material remain stable, and avoid wavy or uneven surfaces.

In the 3D printing process, smoothing the top layer of 3D printing is an important part of improving the quality and aesthetics of printing. Through the above operations, the smoothness and surface quality of the top layer can be significantly improved. These tips are not only suitable for home printers, but also provide effective solutions for professional users who pursue high-quality printing results.

For users who need higher precision and quality control, JLC3DP provides advanced 3D printing services, supporting customized requirements of various materials and printing technologies, ensuring the best effect of the top surface of 3D printing. If you have higher printing needs, please contact us to learn more about high-quality 3D printing services.