Design Guide For Metal 3D Printing

Introduction of DMLS and SLM

Being able to quickly and cost-effectively produce complex metal parts or part prototypes, is a problem in modern manufacturing, and metal 3D printing solves this problem very well. Whether it is a designer or a manufacturer, metal 3D printing is undoubtedly the best choice.

Among them, DMLS and SLM stand out as the most efficient and widely used technologies.DMLS (Direct Metal Laser Sintering) and SLM (Selective Laser Melting) are two very similar powder bed fusion (PBF) technologies. Each technique efficiently melts a specified pattern of metal powder using laser beams. By repeating this process in successive layers, the machines build up complex parts, often using advanced metal alloys. DMLS is a trademark of EOS while SLM is a trademark of SLM Solutions. Both technologies fully melt metal powder instead of sintering it the way most metal 3D printing technologies do, making them the top choice for designers and manufacturers.

Attribute	SLM	DMLS
Laser point diameter	80 to 160 microns	40 microns (for smaller machines)
Number of lasers	Machines with 1, 4, and 12 beams are available	4

8 design tips for Metal 3D Printing

Of course, to print reliable metal parts, it’s crucial to understand and follow some basic rules when designing. These 8 tips are essential for your success in metal 3D printing.

1. Wall thickpost-treatmentness 

The minimum wall thickness required to ensure a successful 3D print with most materials is generally considered to be 0.5mm.

This thickness is crucial because it provides the necessary structural integrity and durability to the printed object, preventing it from being too fragile or prone to breaking during or after the printing process. When designing a 3D model, it is important to keep this minimum thickness in mind, especially for parts that will bear any kind of load or stress. Thinner walls may not only fail to print correctly but could also lead to issues such as warping, cracking, or incomplete layers. Additionally, the 0.5mm threshold is a good rule of thumb for ensuring that the printer can accurately reproduce the details of the design without compromising the overall quality. However, it’s worth noting that the exact minimum thickness can vary slightly depending on the specific material being used, the type of 3D printer, and the resolution settings. For instance, some high-resolution printers may be able to handle slightly thinner walls, but 0.5mm remains a safe and widely accepted standard for most common 3D printing materials like PLA, ABS, and PETG.

2. Pin diameter

The minimum reliable pin diameter for most 3D printing applications is generally considered to be 1mm.

This diameter ensures that the pin maintains sufficient strength and structural integrity during and after the printing process, reducing the risk of breakage or deformation. While it is technically possible to print pins with smaller diameters, doing so often comes with trade-offs, particularly in terms of contour sharpness and overall detail quality. Smaller diameters, such as those below 1mm, may result in less defined edges and a loss of precision, as the printer may struggle to accurately reproduce fine details at such a small scale. Additionally, thinner pins are more susceptible to bending, snapping, or failing under even minimal stress, which can compromise the functionality of the printed part. Therefore, when designing 3D models that include pins or similar features, it is advisable to adhere to the 1mm minimum diameter guideline to ensure reliability and durability. However, if smaller diameters are absolutely necessary, it is important to carefully consider the material properties, printer capabilities, and intended use of the part to mitigate potential issues. For example, using a high-resolution printer and a strong, flexible material like nylon may improve the chances of successfully printing smaller pins, but even then, the results may not be as sharp or robust as those achieved with a 1mm diameter.

3. Hole size

For accurate 3D prints that require no support structures, it is recommended to design holes with diameters between 0.5 mm and 6 mm. Within this range, the printer can typically produce clean, precise holes without the need for additional support, as the overhangs are minimal and manageable. However, when designing holes with diameters between 6 mm and 10 mm, the ability to print without support becomes orientation-dependent. This means that the success of support-free printing for these larger holes will largely depend on how the part is positioned on the build plate. For instance, if the hole is oriented vertically, the printer may be able to bridge the gap without support, but if the hole is oriented horizontally, the overhang may become too significant, leading to sagging or deformation. In cases where horizontal holes with a diameter of 10 mm or larger are required, support structures are almost always necessary to ensure the structural integrity and accuracy of the print. These supports help to maintain the shape of the hole during the printing process, preventing issues such as drooping or incomplete layers. It’s important to note that while supports can improve print quality, they also add to the post-processing time, as they need to be carefully removed after printing. Therefore, when designing 3D models, it is crucial to consider the size, orientation, and placement of holes to minimize the need for supports while still achieving the desired level of detail and functionality.

4. Escape holes

Holes are essential in hollowed metal parts produced through additive manufacturing processes, such as 3D printing, to ensure that unmelted powder trapped inside the part can be properly removed. Without adequate holes, the residual powder can accumulate within the hollow structure, leading to issues such as increased weight, uneven density, or even contamination during post-processing.

To facilitate effective powder removal, it is recommended to design boreholes with a diameter between 2 mm and 5 mm. This size range strikes a balance between providing sufficient space for the powder to flow out and maintaining the structural integrity of the part. Smaller holes may not allow the powder to escape efficiently, while larger holes could compromise the strength of the component, especially if it is subjected to mechanical stress or load-bearing applications. Additionally, the placement and number of holes should be carefully considered to ensure complete powder evacuation. For instance, holes should be positioned at the lowest points of the hollowed structure to take advantage of gravity, and multiple holes may be necessary for complex geometries. It’s critical for achieving the desired mechanical properties, surface finish, and overall quality of the final product. Furthermore, proper powder removal can reduce post-processing time and costs, making the manufacturing process more efficient and reliable.

5. Overhangs

In 3D printing, 45 degrees is widely recognized as the minimum angle at which support material is generally not required.

This angle is often referred to as the “overhang angle” and is a critical factor in determining whether a part can be printed successfully without additional support structures. When a feature of a 3D model slopes at an angle of 45 degrees or less relative to the build plate, the printer can typically bridge the gap without the need for supports, as each successive layer is adequately supported by the layer beneath it. However, if the angle exceeds 45 degrees, the overhang becomes steeper, and the risk of sagging, drooping, or incomplete layers increases significantly. In such cases, support structures are necessary to provide a foundation for the overhanging sections, ensuring that the print maintains its shape and accuracy. Designers should also consider the geometry and orientation of the part, as well as the intended use, when deciding whether to incorporate supports.

By adhering to the 45-degree rule, designers can often minimize the need for supports, reducing material waste, post-processing time, and overall print complexity. However, testing and iteration may be necessary to optimize the design for specific printing conditions and requirements.

6. Unsupported Edges

In metal 3D printing, the maximum length of a cantilever-style overhanging surface is typically limited to 0.5 mm to ensure successful printing without the need for support structures. A cantilever-style overhang refers to a horizontal surface that is supported on only one end, leaving the other end unsuspended. Beyond 0.5 mm, the risk of sagging, drooping, or layer separation increases significantly due to the lack of underlying support. On the other hand, an overhanging horizontal surface that is supported on both ends can extend up to 1 mm in length without requiring additional supports. This is because the dual support points provide greater stability, allowing the printer to bridge the gap more effectively.

Designers should also consider the intended use of the part, as functional components subjected to mechanical stress may require additional supports or thicker layers to ensure durability.

7. Embossed Features

Embossed details in 3D printing must be designed with a minimum height to ensure they are visible and clearly defined in the final print. Typically, such features should have a height of at least 0.3 mm to guarantee that they stand out and are not lost during the printing process. If the embossed details are smaller than this threshold, they may fail to appear visible or could blend into the surface, resulting in a loss of detail and clarity. To further enhance the visibility and quality of embossed features, it is recommended to design them slightly larger than the minimum suggested size. For example, aiming for a height of 0.4 mm or more can provide a buffer to account for any minor inconsistencies in the printing process, such as layer adhesion issues or slight variations in resolution. Additionally, the width of the embossed details should also be considered, as very narrow features may not print accurately even if they meet the height requirement.

By following these guidelines and allowing for some extra size, designers can ensure that embossed details are not only visible but also crisp and well-defined, enhancing the overall aesthetics and functionality of the printed part. This approach is particularly important for parts that require fine text, logos, or intricate surface patterns, where clarity and precision are critical.

8. Engraved Details

In the Direct Metal Laser Sintering (DMLS) process, the heat generated by the laser dissipates into the surrounding powder, which can cause text and engraved details to close up and become less visible if they are not designed with sufficient depth and width. This occurs because the heat can slightly melt or sinter the nearby powder, filling in fine details and reducing their clarity. To prevent this issue, it is crucial to design engraved details with a minimum depth and width of at least 0.5 mm each. This ensures that the details remain distinct and visible after the printing process, even as the heat affects the surrounding material.

To further improve the results, designers can consider increasing the depth and width slightly beyond the minimum recommended values, as this provides a buffer to account for any minor inconsistencies in the printing process.

Commonly used post-treatment

The process of creating a smooth and shiny surface by rubbing it is known as polishing. This technique involves using abrasives, polishing compounds, or tools to remove imperfections, scratches, and roughness from the material’s surface, resulting in a clean and highly reflective finish. Polishing enhances the material’s appearance by producing a significant specular reflection, which gives it a mirror-like shine. This process is commonly used on metals, plastics, glass, and other materials to improve their aesthetic appeal, reduce friction, or prepare surfaces for further treatments like coating or plating.

Propelling a stream of abrasive material (include sand, glass beads) against a surface under high pressure is known as sandblasting or glassblasting. This process is used to achieve various surface finishes, such as smoothing a rough surface, roughening a smooth surface for better adhesion, shaping a surface, or removing contaminants like rust, paint, or dirt. Sandblasting is widely used in industries such as automotive, construction, and manufacturing to prepare surfaces for painting, coating, or further processing, ensuring a clean and uniform finish.

Anodizing is an inorganic, electrochemical process that creates a durable and protective aluminum oxide coating on the surface of aluminum. This process involves immersing the aluminum in an electrolytic solution and passing an electric current through it, causing the surface to oxidize and form a hard, corrosion-resistant layer. The anodized coating not only enhances the material’s resistance to wear and corrosion but also improves its aesthetic appeal by allowing for the incorporation of dyes to create various colors.

Heat treatment is a controlled process that involves heating a metal or alloy to a specific temperature, holding it at that temperature for a predetermined period, and then cooling it in a particular manner to alter its physical and mechanical properties. This process is primarily used to harden the material, making it stronger and more durable, but it can also improve other characteristics such as ductility, toughness, and resistance to wear and corrosion. The cooling method, whether it be rapid quenching, air cooling, or furnace cooling, plays a crucial role in determining the final properties of the metal. Heat treatment is widely applied in various industries, including automotive, aerospace, and manufacturing, to enhance the performance and longevity of metal components.

Conclusion

Of course, in addition to design considerations, some of the above factors are also affected by the printing direction, layer height, and even the printer.

If you require professional metal 3D printing services, feel free to reach out to us via email at info@protosoon.com. Our expert technical team is dedicated to providing top-notch support and ensuring the success of your projects. With our advanced technology and commitment to quality, we are here to guide and safeguard your project every step of the way. Let us help you bring your ideas to life with precision and reliability. Contact us today to get started!