Although heavily embraced by the automotive, aerospace, and medical sectors, metal 3D printing has yet to fully reach a mainstream audience of makers, product designers, and engineers. However, it is starting to find its place in smaller niche markets, such as jewelry making. It may not be too long before you consider a metal 3D printed part for your next unique project, but it is important to note that designing for metal 3D printing can be tricky.
Knowledge for 3D printing plastic does not perfectly translate to 3D printing metal. A part that is designed for CNC machining or another subtractive manufacturing process cannot simply be metal printed. To create a metal part with 3D printing, it must be specifically designed for the 3D printing process for metals. Seems like an obvious statement, but you’d be surprised. If you are interested in designing a metal part to be 3D printed, there are some common pitfalls that need to be avoided.
Different rules apply to different metal powders being used, but following these rules will make for a safe design:
Mind the Gap
When a gap or hole is designed too small, you run the risk of the sides merging together and filling the space. Gap and hole minimums will depend on the printer being utilized, the metal used for printing, and a part’s geometry. However, 0.5mm is a safe minimum to abide by. Holes larger than 10mm will need supports added for structural integrity.
Beware of Thin Walls
0.5mm is the thinnest thickness you’ll want your wall to be at any one point for metal 3D printing. Any thinner than that and you’ll risk the wall collapsing under its own weight. For plastic 3D printing, the minimum wall thickness is around 1mm.
Hanging in There
Overhangs on a part should also not exceed 0.5mm. Also, downward facing structures need to be designed so that they are more than 45 degrees from horizontal (this is known as a chamfer) with a concave or convex shape, so that the part can support itself. It is possible to exceed these design rules. However, support structures will need to be added to do so.
Sometimes You Need a Little Support
In order to hold a part to a substrate plate, supports are needed. They are also vital for heat dissipation. When dealing with most metals, areas below 45 degrees from horizontal need supports added to the design. This rule of thumb, however, does not apply to all metals. For example, Ti64 (an alpha-beta titanium alloy) will allow parts to be designed with walls angled as low as 30 degrees, without the need for supports.
Knowing the Right Direction
Part orientation must be considered prior to printing. 3D printing creates parts that have different mechanical properties in different build directions. Parts have higher tensile strength in the X and Y directions, when compared to the Z directions. This is important to consider for any part that will undergo pressure or stress in its end use. This can be the difference between a part working as designed or cracking under pressure.
Does it Need to be Pretty?
There is also an aesthetic element to part orientation. When a part is 3D printed, downward facing surfaces will have a rougher surface finish as opposed to top-facing surfaces. For complicated designs, part orientation needs to be optimized so that supports can be removed. That’s especially true for those that influence the function of the part. As opposed to 3D printing plastic, where supports can sometimes be simply snapped off by hand, 3D printing metal requires post-machining to remove supports. Where supports were in contact with the part will be noticeable, unless further machining is done to the part to uniform the surface.
Do Your Homework
A major step that can be taken to ensure that a design is sound, is to research the machine that the part is going to be built on and the material that will be used. While general rules help avoid common pitfalls, each machine and metal powder has its own intricacies that should be accounted for. Being armed with this knowledge could pay dividends.
Utilize Free Resources
Designing for metal 3D printing can be a struggle. There are a lot of misconceptions when it comes to designing for this process. The industry has started to recognize this, and, as a result, manufacturers have started to take it upon themselves to begin educating the market with videos, step-by-step instructions, and other resources. A quick Google search will most likely produce a good amount of free designs for additive manufacturing knowledge. You can find our tutorials from Star Rapid on our YouTube channel.