While 3D printing has revolutionized many aspects of manufacturing, one of its ongoing challenges is achieving high-quality surface finishes, especially for industrial applications. Parts produced using technologies like Laser Powder Bed Fusion (L-PBF), Binder Jetting (BJT), and Material Extrusion (ME) often exhibit rough finishes, which can limit their use in applications requiring precision and smoothness.
This article explores the current challenges, advanced solutions, and practical tips for improving the surface quality of 3D-printed parts.
Many 3D printing technologies inherently produce rough surfaces, particularly those based on powder or wire processes. For example:
Polymer processes like Laser Powder Bed Fusion and Material Extrusion struggle to match the smooth finishes of conventional methods like injection molding.
Metal wire- and powder-based technologies often leave rough surfaces, necessitating extensive post-processing to meet functional requirements.
While resin-based technologies such as VAT Polymerization (e.g., SLA and DLP) yield smoother surfaces, they are not universally applicable, especially for industrial-grade materials.
Achieving the desired surface quality in 3D printing often requires a combination of advanced technologies and post-processing techniques. While some processes inherently produce smoother surfaces, most additive manufacturing (AM) technologies require additional steps to meet industrial standards. These solutions can broadly be categorized into subtractive methods, which remove material, and additive methods, which add layers or coatings to refine the surface. Here’s an in-depth look at the available options:
Subtractive methods are commonly used to achieve smooth and uniform finishes by removing imperfections from the surface. These techniques are highly effective for both polymer and metal components:
Additive methods enhance surface quality by depositing material onto the part. These techniques can also add functional properties, such as increased durability or corrosion resistance:
Emerging technologies are transforming how surface quality is improved in 3D printing:
In many cases, achieving the required surface quality involves combining multiple techniques. For example, a part may first undergo tumbling to remove major imperfections, followed by coating or plating for a polished finish. This hybrid approach is often the key to meeting both functional and aesthetic requirements.
By leveraging these solutions, manufacturers can overcome the inherent challenges of 3D printing and produce parts with the desired surface finish, ensuring both quality and performance in industrial applications.
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Understand the most important topics to get started with Additive Manufacturing
The sinter-based AM (SBAM) technologies have, as the name suggests, the sintering process in common. In this process, the printed green part is consolidated into a dense part and receives its final properties. The green part can be printed in advance using different technologies.They all have in common that metal powder is bound to the desired shape by a binder. The best-known printing technologies include Binder Jetting and Filament Material Extrusion.
In this section, you learn everything about the sinter-based AM process chain and get an overview of the different printing technologies.
This course is aimed at engineers, designers and other professionals that are working closely with sinter-based AM technologies. The goal is to cover the most important aspects that will enable engineers and designers to fully grasp the capabilities and technical limitations of the printing technologies and the sintering process to succeed in technology selection and part design. Besides going through the course from the beginning until the end, this course can also act as a constant source of knowledge while working on AM projects.
The course is structured into the following sections.
This section will start with an overview of the sinter-based AM process chain and its printing technologies, followed by a technology deep dive into the most important aspects of the BJT technology, followed by a closer look at the debinding and sintering step also including sintering simulation .
The second section will provide an overview of the different materials that are available as well as part characteristics that can be achieved with the BJT process and typical methods for quality assurance. Finally, several common defects in the BJT process are presented.
The last section will act as a guideline for designers. Besides generally describing the process when designing for Additive Manufacturing, actionable restrictions and guidelines for the BJT process are provided. The final section will present several design examples from different industries.
Simulation to compensate the deformation during the sintering step, nesting of parts and definition of printing parameters
Through various printing processes, different feedstocks such as metal powders, filaments, pellets or dispersions are processed into green parts
Unpacking of fragile green parts needs to be done carefully and is typically a manual process.
Debinding describes the process of removing the binder which results in a brown part
To reach the structural integrity of a metal part, a sinter process is required. The powder particles fuse together to a coherent, solid structure via a mass transport that occurs at the atomic scale driven via diffusional forces.
The brown part shrinks ~13-21 % in each direction.
The process chain of sinter-based technologies differs from other AM Technologies. Especially the post-printing processes (debinding and sintering) are crucial to achieve the intended mechanical properties.
Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.
The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.
Afterwards the build platform moves downward by the amount of one layer thickness and a new layer of powder is applied. Again, the liquid binder is deposited and hardened in the required regions of the next layer to form the green body. This process is repeated until the complete part is printed. After the complete printing process is finished the parts have to be removed from the “powder cake” meaning the surrounding loose but densified powder. To improve the removal of the excess powder from the green body often brushes or a blasting gun with air pressure are used.
To create a dense metal part the 3D printed green body has to be post-processed in a debinding and sintering process. Similar to the metal injection molding process BJT parts are placed in a high temperature furnace, where the binder is burnt out and the remaining metal particles are sintered together. The sintering results in densification of the 3D printed green body to a metal part with high densities of 97 % to 99,5%, dependent of the material.
In classic Binder Jetting systems such as the ones distributed by EXONE or DIGITAL METAL the liquid binding agent is selectively deposited with a single print head. Meaning the width of the print head does not cover the full width of the powder bed. Therefore, the print head moves multiple times in xy-direction over the powder bed to completely cover the printing area and distributing the polymer binder.
The SINGLE PASS JETTING technology was developed by DESKTOP METAL and HEWLETT PACKARD. The width of the printing head covers the full width of the powder bed. When the printhead passes over the powder bed, binder is released from more than 30,000 small nozzles and the whole powder layer is selectively immersed in binder in one pass. The process is bi-directional which means that the binder deposition takes place in both moving directions of the printhead. With these modifications the printing speed is significantly increased.
A similarly fast technology is the METAL JET process by HEWLETT PACKARD. In a single pass, a liquid printing agent is applied to the powder layer and subsequently partially evaporated to form the binding polymer around the metal powder. After the completion of the print an additional curing to achieve the full green body stability is needed.
3DEO combines the Binder Jetting process with a subsequent machining process. Different from conventional Binder Jetting processes, the binder is not only deposited selectively but onto the entire powder layer. After hardening of the complete layer, the part geometry is shaped through a milling process every couple of layers by cutting the part contour out of the binder powder composite.
Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.
The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.
Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.
The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.
Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.
The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.
Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.
The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.
