3D printing redefines the concept and possibilities of manufacturing. This emerging trend is providing stiff competition to traditional manufacturing methods. One of the reasons for its rapid success is the impressive surface finish of 3D printing, which we will explore in detail in this article.
Therefore, the discussion will focus on the surface finish of 3D printing, the factors that affect it, measurement methods, and different techniques to improve surface finish. Stay with us for a complete guide on this topic.
What is surface texture in 3D printing?
Let's start with an introduction to the concept of surface finish in 3D printing. Simply put, it is a qualitative measurement of how rough a part's surface is after printing. A very smooth surface is considered “fine”, while a rough surface has a “poor” surface finish.
This is a crucial step in any manufacturing process, as almost all products have strict surface quality requirements. For example, a piece of paper will not serve its purpose if it is too rough to write on and will not sell well in the market.
Therefore, achieving the desired surface finish is a top priority for 3D printer manufacturers. Generally, this is a post-processing process that uses several techniques, which will be explained shortly.
Furthermore, finishing 3D printed parts is particularly challenging due to the inherent properties of additive manufacturing processes. As parts are constructed layer by layer, their surface consists of a repeating pattern of bumps and depressions that are formed, maintaining the integrity of the required part. to be smoothed out.
Why is 3D printing finishing important?
There are several reasons to set specific surface finish goals for 3D printing. These reasons can be superficial and functional. Below is a summary list of several of these reasons.
1. Aesthetics
A good surface finish increases the aesthetic value of the piece. This includes visual elements such as color, texture and robustness (glossy/matte).
2. Mechanical and chemical properties
Surface finishing methods can improve the performance of 3D printed parts. For example, metal parts can be coated to make them corrosion-resistant and electrically conductive. Some methods provide high temperature and wear resistance in parts intended for difficult and demanding applications.
3. Functionality
Certain applications require a specific surface finish to function properly. For example, a press fit is highly dependent on the surface quality of the mating parts. Therefore, in other cases, a rough surface may be preferable to improve the surface for effective heat transfer.
4. Manufacturing Tolerance
Surface treatments are often used in the final processing of 3D prints to bring a part within its dimensional tolerance limits. For this purpose, additional material can be removed or additional material added.
What factors influence surface texture during 3D printing?
3D printing is a complex process with many influencing factors and moving parts. Each of these factors influences the surface finish of 3D printing in different ways. An engineer must have a solid understanding of this to know what to optimize to obtain the desired 3D printing surface.
1. 3D printing process
The surface finish in 3D printing varies significantly between different 3D printing techniques. FDM, for example, is prone to problems such as poor surface resolution and warping due to its layer-by-layer deposition process. Powder-based methods like SLS 3D printing understandably produce a grainy surface finish because the parts are made of powder particles.
2. 3D printer parameters
3D printing parameters play an important role in the final surface finish. For example, the lower the layer thickness (or resolution), the smoother the surface. Printing speed, curing process and filler are also important factors contributing to surface quality.
3. 3D printing material
3D printing materials have different properties and are compatible with different methods. Variations in surface finish may also be due to material limitations and properties.
4. 3D printer quality
The design and condition of 3D printers also affect surface quality. Cheap printers cannot produce parts with high surface quality. Likewise, an old and poorly maintained 3D printer will lose accuracy over time. Contributing factors include the condition of the 3D printer's rails and motors, frame/base orientation, control features, power source condition, etc.
The following table compares the 3D printing surface finish capabilities of the popular 3D printing process.
| 3D printing process | Surface roughness (Ra) |
| FDM/FFF | 10 |
| SLD/DLP | 3 |
| SLS | 13 |
| PBF | 15 |
How do you measure surface texture in 3D printing?
Measuring surface quality in 3D printing is performed with a profilometer. This is a highly sensitive device with a pointed probe/pen that “scans” the surface by sliding over a part of it.
During this scanning, the pen tip captures the exact shape of the surface, which is then used to calculate the surface roughness value (the quantitative equivalent of surface finish).
The most common measurement for evaluating surface roughness is the Ra value. This value is simply the arithmetic mean (average) of all measurements. This can be better understood with the following figure.
Common Methods for Improving the Surface Finish of 3D Printed Parts
We take a detailed look at various aspects of surface processing in 3D printing. Now we come to the various methods that engineers use to manipulate 3D printed parts.
These techniques vary significantly in effectiveness, cost, skill requirements, and overall methodology. Below we discuss some of the most important of these options.
1. Grinding
Grinding is the most common method of finishing 3D prints. This is a simple process of rubbing rough sandpaper over the surface of the piece to smooth it. Imperfect surface features, such as protrusions and sharp corners, break or are flattened by friction during this process.
It is a very practical technique, as it is very intuitive, cheap and effective and works on most materials. Sandpaper comes in different grit sizes that vary in grit. Coarse grits have larger grain sizes and remove more material, leaving a rougher surface.
Typically when sanding, you start with a coarse grit and then gradually move to a finer grit as the surface becomes smoother.
However, you need to be careful when sanding, as it is easy to remove excess material and ruin the piece. Therefore, it is also a time-consuming process and may not be suitable for work that requires high productivity.
The final surface finish of 3D printing is not shiny and smooth. Instead, it has a matte surface. To further improve the surface quality, you can use polishing cloths, extra-fine sandpaper or paint/coating.
2. Machining/grinding
Although 3D printing and CNC machining are often portrayed as opposing production technologies vying for industry dominance, there are several areas in which they complement each other. One of these hybrid applications is the finishing of 3D printed parts.
Many 3D printing processes are unable to achieve the fine surface quality of subtractive processes such as machining and grinding.
Therefore, a final machining/grinding cycle after 3D printing is very common. It is extremely effective when it comes to maintaining tight tolerances and exceptionally smooth surfaces. Additionally, machining is a versatile tool, useful in hard-to-reach areas such as internal holes or curved features.
Furthermore, it is compatible with most 3D printing materials, both plastic and metal.
3. Pearl blasting
Shot peening is another popular abrasive finishing technique for 3D printing. As the name suggests, small plastic or glass beads are scattered on the rough surface. The impact smoothes surface defects.
This is a quick method compared to grinding. Additionally, the granules can be targeted to hard-to-reach areas and smooth interior surfaces that are not easily accessible with hand sanding.
Typically, blasting begins with low pressure to assess the abrasion rate. This is necessary because additional pressure can remove additional material or damage the surface. With adequate visual inspection and experience, the operator can increase jet pressure to optimize the surface finish of the 3D print.
Additionally, there are several other similar processes such as sand blasting, shot blasting and water blasting, each slightly different from the other.
4. Coating
Electroplating involves electrically applying a thin layer of metal to a plastic or metal surface. Due to its multiple benefits and ease of use, it is a common method for finishing 3D printed parts.
In most cases, the coating improves several properties of the part material. 3D printed plastic parts are understandably weak and prone to breaking. Coating them with a suitable metal can increase their durability and wear resistance and give them the ability to withstand higher temperatures.
Additionally, electroplating can provide metal parts with several useful properties, such as corrosion and oxidation resistance, weldability, and electrical conductivity.
In addition to these functional purposes, coating also serves as an excellent way to improve the aesthetics of a 3D printing surface. Metallic coatings such as gold, silver and chrome give the pieces a superior aesthetic.
5. Painting
Painting is an uncomplicated and easy to understand process. It serves the same purpose as anywhere else: better optics. Because when painting, the user has the opportunity to choose practically any color and look.
Normally the painting process is preceded by a layer of primer and putty. This will slightly smooth the surface, filling gaps and depressions to some extent, and better prepare the surface for a coat (or layers) of paint.
Furthermore, painting also serves the practical purpose of sealing to some extent. Although it is not a sealant in the strictest sense, it can act as such in a secondary role. Given the porosity problem prevalent in 3D printing, this is a beneficial effect.
Introduction to 3D printing services at WayKen
We also offer a range of machining processes, including CNC machining services, milling, turning, rapid injection molding, etc. We specialize in rapid prototyping and manufacturing, supporting our customers throughout the entire product development process. Contact us today and let us bring your design to life.
University Degree
It's time to conclude this article. It is intended to be a complete guide to surface finishes in 3D printing and we hope it provides useful information. However, it is a huge topic that evolves more and more every day with 3D printing.
Additionally, if you have further questions about 3D printer finishing, read the FAQ section below or contact our experts for guidance.
Common questions
Which surface processing process in 3D printing is best?
This depends entirely on the application. Because each method has its advantages and disadvantages and is suitable for a specific class of products. If you only care about aesthetics, painting or coating is the best option. If your product has functional requirements such as: Such as electrical conductivity, you should consider a suitable material for electroplating.
Does 3D printing offer a better surface finish than CNC?
In general, CNC machining is superior to 3D printing in terms of surface roughness. However, with the correct surface finishing techniques and printer/method selection, this difference can be significantly reduced.
