The most widely used process in 3D metal printing is probably selective laser melting. A contract manufacturer gives design tips to achieve the best results for this process.
3D metal printing, or more precisely selective laser melting (SLM), is a cost-effective and fast method for manufacturing prototypes and is suitable to produce complex geometries. With an optimized design and a large number of parts to be produced, the process offers enormous economic advantages. In 3D metal printing, a powder layer of 0.02 to 0.06 mm is applied to the building platform by a scraper or coater. Then the laser starts melting the first layer. In the next step, another layer of powder is applied after the building platform is lowered by exactly one layer. The laser then fuses the first layer with the next. This process is repeated layer by layer until the entire component is completed. When the last layer of the part is finished, the metal powder is removed and the part attached to the platform appears.
In usual 3D metal printing, support structures are both important and a burden because they slow down the manufacturing process. Good design practice can, however, reduce the number of supports required and thus the additional work involved to a minimum.
In order to get the most out of this technology, Protolabs names five tips to achieve a production-oriented design in 3D metal printing.
- Wall thickness: A wall thickness of less than 1 mm cannot be produced with all materials and depend on geometry. The rule of thumb is: Ratio height to wall thickness 40:1 (at > 1 mm).
- Self-supporting angles: Angles of 45° are optimal. Angles below this value require support structures in order to keep the object stable during production.
- Overhangs: If the layer to be exposed to the laser is larger than the underlying layer, this is referred to as an overhang. Overhangs of 0.5 mm can be realized without support material.
- Channels and holes: Channels and holes are self-supporting features up to a certain diameter and do not require supports. However, all holes in the X/Y direction generally collapse during the manufacturing process.
- Residual stress and distortion: Changes in the cross-sectional areas can lead to distortion of the component. In the worst case, building platforms and shear bolts bend when large volumes accumulate.
The Limits of Selective Laser Melting
Additive manufacturing is not the solution to all problems. 3D metal printing using the SLM process, has the following geometric limits:
- Minimum wall thickness: 1 mm
- Minimum dimensions of protruding details: 0.5 mm high and wide, 0.8 mm in order to achieve legible text and clear images.
- Minimum dimensions of indented details: 0.5 mm deep and wide, 1 mm wide for legible text and clear images
- Diameter of exit holes: minimum 4 mm for one exit hole, 2 mm for two or more exit holes.
This article was first published by MM MaschinenMarkt