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SLM (Selective laser melting) is an additive manufacturing technology developed in 1995 by German scientists. After years of development and advancement, it is widely available today and is also one of the most popular types of 3D printing utilized for both rapid prototyping and mass production.
Same as SLS, SLM is part of the powder-bed fusion (PBF) process. An SLM machine has a chamber filled with metal powder, which is then spread across the build plate by a coater blade. Then, a high-power laser selectively melts the powdered material to fuse a 2D slice of the part.
Subsequently, the build plate descends to the height of a single layer, and the coater meticulously applies a fresh layer of powder onto the surface. Until the completed component is obtained, the process is repeated.
While this whole process is done inside the machine, the part can be removed from the build plate with a bandsaw once it is built. However, as SLM requires support structures, it requires removal, and it is often a time-consuming process. Lastly, some parts may need post-processing since their surface finish is rough.
Feedstock | Finishing | |
SLM | Metals | Requires support structures |
SLS | Polymer materials (PA) | Does not require support structures – Allows freeform shapes |
Table 1. Comparison between SLM and SLS
While both SLM and SLS are within the powder bed fusion (PBF) category, they have two main differences: type of feedstocks and finishing structures.
SLM is specifically for metals, and SLS uses mainly polymer materials (PA). Consequently, SLM requires support structures to be added to overhanding features, as metals are heavier than polymer materials.
In contrast, since polymer materials can provide support, they generally don’t require added support structures. Thus, SLS could realize freeform shapes and features to a larger extent when compared to SLM.
Advantages | Disadvantages |
Shorter lead times (no need for tooling) | Expensive |
Large range of metals available | Requires skilled labors for operations |
Can produce multiple parts at once | Limited to producing small parts |
Can realize complex shapes | Rough surface finish |
Requires lots of post-processing |
Table 2. Advantages and drawbacks of SLM
Advantages
- Wide selection of metals available
- Shorter lead times since no tooling is required
- Part consolidation, enabling the production of several parts simultaneously
- Capability to realize complex internal features or shapes (which would be very costly or difficult to accomplish via traditional manufacturing)
Disadvantages
- Expensive (Due to higher cost of equipment, labors, materials, post-processing etc.)
- Rough surface finishing
- Currently limited to smaller parts
- Requires extensive post-processing
- Requires specialized knowledge and abilities for design and manufacturing skills
- Aluminum (Accuracy ±0.3mm)
- Stainless steel (Accuracy ±0.3mm)
- Titanium (Accuracy ±0.3mm)
- Tool steel (Accuracy ±0.3mm)
- Healthcare or medical industry
- Automotive industry
- Scale models
- Aerospace industry
- Consumer goods
- Robotics
- Education industry