How to Get Started with 3D Printing Metal
What is 3D metal printing?
3D printing with metal has primarily been limited to sintering or powder bed fusion. There have been huge developments in 3D metal printing technologies, but the basics of these processes remain the same: metal powder is bound using lasers and the parts are post-processed in a heated environment to solid metal prints. Due to the size and tech in these machines (and the cost of materials), traditional 3D metal printing is still not accessible to the general public.
3D metal printing for hobbyists
Just because the 3D metal printing process is expensive does not mean that hobbyists can’t enjoy metal parts. Fused filament fabrication (FFF) is a well-established printing process that is typically applied to thermoplastics. Metal injection molding (MIM) is another common process that is widely applied in manufacturing to generate precision parts.
These two technologies have been joined to develop metal filament that can be used in desktop 3D printing process. While the average 3D print maker probably won’t be able to create full metal parts at the drop of a hat, the development of fused metal filaments has made metal printing much more accessible.
Metal 3D printing filament is similar to the thermoplastic filaments you’re probably familiar with. This filament has some percentage of added metal and can be used with a regular desktop FDM printer—certain filaments just require specialized nozzles. Metal filaments can be infused with various materials such as bronze or stainless steel.
Prints made with metal filament tend to feel heavier and have a similar appearance with cast metal parts. There are also numerous post-processing techniques makers use for different filament types to make their parts look like solid metal.
There is a range of 3D printer metal filaments on the market. These filaments vary by weight, metal content, and printing requirements. This article focuses on printing full-metal parts (or as close to it as we can get) using metal filaments, but if you just want a sturdy part with some metallic features that can be printed normally, you may want to try a lower-percentage metal filament like Formfutura’s Ancient Bronze PLA filament.
Using “full metal” filaments
For makers who want to produce full metal parts, specialized high-percentage metal filaments are advantageous. The most popular and reliable nearly 100% metal filament is BASF’s Ultrafuse 316L filament. This material was designed with manufacturers and small makers alike in mind. It’s perfect for small batch manufacturing of metal parts or prototyping.
The Ultrafuse metal-polymer filament produces austenitic stainless steel type 316L parts using standard FFF printer systems. The filament is compatible with consumer desktop printers with minor modifications. To yield nearly 100% metal parts, a standard debinding and sintering process is required.
When jumping into the marvelous world of 3D metal printing, you’ll come across the following key terms. Understanding the mechanics of 3D metal printing is important for ensuring that your setup is sufficient for your intended application.
Green parts refer to parts obtained just after printing that have not been subjected to debinding and sintering.
Brown parts refers to parts that have been subjected to debinding but not sintering. This stage is crucial to consider because it is when parts are the most fragile.
Debinding removes the plastic filament base from the green part before sintering.
Sintering converts the powdered metal in the brown part into solid metal through heat.
Design considerations for 3D metal printing
Designing a 3D model for printing from scratch can be an undertaking for any hobbyist, and designing models for metal printing can be even more daunting. There are a handful of main considerations to keep in mind to avoid print quality problems and to ensure the stability and utility of the part.
Most 3D print hobbyists don’t need to have a comprehensive theoretical design and engineering foundation to jump into model design, but understanding the basics can help avoid headaches down the road. 3D printing operates within a specific set of parameters that need to be considered. Most traditional manufacturing is subtractive, meaning that wood, metal, or plastic is carved away from the resultant part, while 3D printing is additive, meaning that the material is laid in along a specific pattern to ensure stability and produce the intended design.
If your design is starting out in the most fundamental way—pencil and paper—it’s important to remember that it will be built from the ground up. Cutouts, protrusions, and any nooks and crannies must be placed carefully to allow the machine to add material in the right locations.
If you’re on this site, that means you have probably already used a 3D printer or are familiar with some of the basics. Anyone who has tried to print a part is familiar with the concept of bed adhesion, which is the quality by which a print adheres to the build plate during the printing process.
When printing highly detailed parts with filament as specialized as high-percentage metal filament, ensuring that the model has a solid foundation is crucial. Particularly for utility parts and prototypes that require a small margin of error on tolerances, printing a model with a flat side can help keep it steady and avoid warping.
Proper aspect ratios
When working with metal filament, you have to consider all aspects of the printing process. Brown parts are weak prior to sintering. A stable design is more likely to yield a strong part after the sintering process. There are many factors that affect stability, but one of the most important is aspect ratios. Consider the length or width to height ratio of the part and evaluate any joints or connecting points that may require additional support before the part has hardened.
Homogeneity and simplicity
Homogenous design doesn’t mean that your part can’t have any unique characteristics or must be perfectly symmetrical. Homogeneity in 3D print modeling just means that the part thickness should be even throughout.
A thick part with fine, delicate features is likely to fail during sintering because the largest parts will deteriorate by overheating while the finer features are still hardening. When designing the part, considering the geometry along all planes is critical for making sure that all parts of the print harden within a relatively similar time window.
Due to the nature of the debinding and sintering process, no support material can be used that isn’t part of the final print. Bridges and overhangs cannot just be removed easily like with normal thermoplastic prints, so overhangs that are angled into the print are beneficial to avoid sagging and breaking.
Preparing your design for 3D metal printing
Anisotropic shrinking, which refers to shrinkage that happens differently along different axes or directional lines, is expected in the debinding and sintering process. Typically, parts should be scaled to +120% (+119.82%) of the required final dimension along the X/Y axes and +126% (+126.10%) of the required final dimension along the Z axis.
A program like MatterControl can help you modify an existing model with these parameters so you don’t have to re-design it from the ground up.
Using Ultrafuse metal filament
To print with Ultrafuse 316L filament, your desktop 3D printer must meet the following requirements:
- Equipped with a heated bed that can reach 100 °C
- Equipped with a glass bed with a spray adhesive designed for FFF like Dimafix
- Equipped with a clean, hardened nozzle
- A brass nozzle can be used for metal printing, but it will need to be changed after approximately 1 kg of material has been used.
- We recommend purchasing a designated hardened nozzle that is used only for metal printing to ensure cleanliness, avoid filament contamination, and reduce wear on other parts.
Ultrafuse printing settings
- Bed temperature: 100–120 °C
- Hot-end temperature: 215–235 °C
- Recommended layer height: 0.10–0.25 mm [.15 or lower recommended for higher density filament]
- Recommended speed: 15–40 mm/s
- Infill: 100% Lines or concentric infill patterns are optimal for uniformity depending on the part’s geometry.
- Turn off part cooling.
When printing anything on a 3D printer, first layer settings and bed adhesion are always important. However, because of the sintering process, ensuring that all settings are calibrated is critical to avoid part failure after the print.
How to prepare green parts
Green parts must be treated carefully to keep them free of oil, dust, debris, etc., as any contamination can mess up the debinding and sintering processes. Parts printed with Ultrafuse are typically easy to clean up as they are somewhat soft after printing.
At this stage, remove any rafts, brims, blemishes, and artifacts using tools like files and scrapers. Remember, your part is still partially plastic at this stage, making it much easier to modify than after it becomes hardened metal.
If you see any warping at this stage, take the time to sand the base surface of your part flat. As noted earlier, a flat plane is crucial for stability during the subsequent processing stages.
How to debind and sinter parts
Set up a designated debinding and sintering workspace
Note that professional debinding and sintering equipment and materials is expensive and requires specialized knowledge to operate. There are some tools to purchase for home use, but these are typically only cost-effective and reasonable for small parts. We strongly recommend that makers only get these materials if they will be making many metal parts and can establish a dedicated work environment that is safe. PPE and proper ventilation are critical when working with refining materials.
After post-processing, catalytic debinding and sintering will transform your parts from soft models to metal prints. Catalytic debinding decomposes the primary polymer, which is the that binds the metal powder in the green part. This process is carried out in a gaseous acid environment at high temperatures.
The products of this reaction are then burnt off using a natural gas flame at much higher temperatures (above 600 °C!), yielding a brown part. This is done within an enclosed, controlled system designed specifically for this entire process. Because sintering is required to harden the metal powder, debinding is a crucial step as any remaining plastic can cause sintering to fail.
The next step is sintering. A specially designed furnace set just under the melting temperature of the metal being used removes the secondary binder from the brown part and facilitates fusion between the metal particles. After sintering, the part’s composition is changed and becomes nearly 100% metal.
Due to the safety and cost considerations, the vast majority of hobbyists getting started with metal 3D printing should not jump straight into owning their own debinding and sintering machines. There are a number of professional services that can take care of this for you at a reasonable rate.
Use a professional debinding and sintering service
One of the greatest wonders of the world of 3D printing is the immense size and strength of its community. For every type of 3D printing, there is likely a committed group of hobbyists and handful of professional services available to help even the newest maker.
For metal 3D printing, service houses equipped with the proper machines and materials to facilitate debinding and sintering are available. All you have to do is prepare your part, ship it to one of these services, and they’ll handle the rest.
BASF, the manufacturer of the Ultrafuse filament, provides an outsourcing service for makers to send their parts to dedicated service houses. MatterHackers makes this process even easier by providing a processing ticket for your project, which allows you to skip the hassle and get straight to finalizing your parts.
Post-processing 3D printed metal parts
Typically, 3D printed metal parts can be treated like any other metal part after sintering when using a high-percentage filament like Ultrafuse. After the process, the part is likely to have a somewhat rough exterior. Depending on the intended use, parts can be polished, ground or filed down, or machined to meet design specifications.
Is 3D printing metal parts right for you?
The potential for 3D printing anything out of metal from the comfort of your home is massive, but we aren’t quite there yet. We want to help demystify the process of working with metal filament for the average 3D print hobbyist and professional alike. Anyone can get started with 3D printing metal parts provided that they have the resources and patience to outsource some of the process.
If you have a small business or are looking to break into the world of small batch manufacturing, rapidly developing and prototyping metal parts will be a huge advantage. Outfitting a desktop printer to work with a high-percentage metal filament and developing relationships with service houses for debinding and sintering can help you scale up operations quickly without wasting time or money on plastic-only parts or outsourcing injection molding.
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