Common Problems in 3D Metal Printing - and How You Can Fix Them

Metal 3D printing has made impressive advances in recent years. Companies are increasingly investing in technologies for highly complex industrial applications. In addition to the advantages in manufacturing lightweight and demanding metal components, however, several challenges must be overcome in the metal 3D printing process. In today's tutorial, we will examine the main problems in 3D printing of metals and their solutions.

In 3D metal printing, there are various printing processes. These can be broadly divided into three groups: Powder bed fusion processes (SLM, EBM) Direct energy deposition (DED) Metal binder jettingPowder bed fusion is the most common method for manufacturing metal parts using AM and involves the use of a laser beam (SLM) or electron beam (EBM) to selectively melt a layer of powder material uniformly on the build platform.Direct energy deposition covers a range of technologies and typically involves a process in which the material is melted by a laser or electron beam before being deposited on a build platform. The object is then formed layer by layer. While polymers and ceramics can be used with this process, DED is typically used with metals in powder or wire form.Metal binder jetting uses a print head to apply a liquid binder to powder layers, causing the powder particles to fuse together layer by layer. The bound powder can then optionally be infiltrated with another metal (normally bronze) to achieve higher density.Each of the processes has its strengths and limitations, but common challenges generally arise in 3D metal printing. These challenges must be addressed in order to achieve the best possible mechanical properties for your 3D metal printed parts.

3D-printed metal parts are often plagued by high porosity, which occurs during the printing process when small holes and cavities form within the part. These tiny, usually microscopic pores can cause low density - the more pores present, the lower the density of your part. They can also directly influence the mechanical properties of a part, making it prone to cracking or other damage, especially when exposed to high loads. For highly porous 3D-printed metal parts, there are generally two main reasons: either this is due to a problem with the powder manufacturing technique or the 3D printing process. For example, the use of gas atomization can sometimes cause pores to form in the powder material. However, the more common source of such tiny holes is the printing process, when the energy in the holes is insufficient and the metal therefore cannot melt properly. The opposite can also be true: excessive laser energy can cause droplets of molten material to spatter, resulting in pores.

How to Reduce the Porosity of Your Metal Parts

Fortunately, there are several ways to eliminate porosity in your 3D-printed metal parts and achieve stronger, more durable parts: since material quality can sometimes be the source of high porosity, be sure to purchase raw materials from a trusted supplier.

Industrial applications of 3D metal parts frequently require high mechanical properties, which is why the density of a part is extremely important. When a part operates under cyclic stress, its density determines whether the part fails under load or not. In other words, the lower the density of a part, the more likely it is to crack under pressure. With powder bed technologies (SLM, EBM), components can be manufactured with densities of 98% and higher, which are critical for demanding applications.

To ensure that a part has consistent quality and density, the specific parameters of the material such as particle size, shape, distribution, and flowability must be optimized. Spherical particles, for example, can lead to higher density, as they can achieve maximum relative density compared to other shapes. However, since there are a number of variables that can influence the density of a part, the rule of thumb is to first consider the quality of your metal powder and adjust the process parameters accordingly.

Heating and subsequent cooling are common characteristics of metallic AM processes. However, when a component is exposed to such extreme thermal changes, this can lead to residual stresses. The residual stress has an adverse effect on the integrity of a manufactured part and leads to different deformations. The highest residual stress concentration is found at the contact surface between the bottom of a printed part and a build platform. Reducing residual stress

Since residual stresses can make the difference between a successful metal print and structural failure, this issue should be addressed properly. There are various options for this:

Residual stresses can be very destructive, leading to a range of structural problems in a part, with crack formation and distortion being the most common. Such problems typically occur when the molten metal cools after printing. The cooling causes contraction, causing the edges of a part to curl and distort. In extreme cases, stresses can exceed the strength of the part, which can cause the part to tear (crack formation can also occur if the powder material was not properly melted). Prevent tearing and warping

There are two main methods to prevent cracking and warping of your metal part. One way is to preheat the build platform, another is to improve the adhesion of a part to the build platform and place the required amount of support structures. Thermal post-processing can also help repair minor cracks, while determining the correct number of support structures on your end essentially serves to avoid warping.

Typically, metal parts are not ready for their final applications on the first print run and must undergo post-processing, such as powder and support removal, thermal treatment, and surface finishing. However, in the post-processing steps, you often encounter some challenges. For example, you could have difficulty removing the support structures from your parts. This can be the case, for instance, when your metal part has supports in small holes and tubes. These can be difficult to remove without damaging the part, and subsequent machining is required. Surface roughness is another issue. Additively manufactured components for demanding applications require an average surface roughness. 3D-printed parts, however, are often produced with rough surfaces and require additional post-processing such as machining, grinding, or polishing to achieve a better finish. Since surface roughness is directly related to layer thickness, it can be reduced by printing with thinner layers. However, manufacturing a part with finer layers can significantly increase build time. Rough surfaces can also result from improper powder melting. This occurs when insufficient energy was applied to completely melt the metal. In this case, surface roughness can be reduced by increasing the power of your laser.

While there are a number of potential challenges in using AM to manufacture metal parts, understanding these challenges is the first step toward producing high-quality and reliable components. With the continuous growth of metal 3D printing, we will certainly see increased use of additively manufactured metal components in industrial applications.