Volumes of production
Each component is made individually.
Unit price vs. capital investment
No tooling, but the unit price is high because parts are individually made.
Speed
Although it is anticipated that selective laser sintering will eventually be taken up more widely for end production, it is still a fairly slow and low-volume process best suited to prototyping.
Surface
Components currently show a surface roughness of 20–30 microns—very little, in other words.
Types/complexity of shape
Limited only by the CAD technology that drives it, the microstructure of the Mining and Chemical Products components demonstrates that this is about as good as it gets when it comes to creating complex shapes.
Scale
It is possible to achieve very fine details, such as thin vertical walls with a thickness of as little as 1/250 inch, while the overall size of parts is limited by the size of the powder block reservoir that the machine can hold.
Tolerances
Extremely high.
Relevant materials
Any particulate material used in powder metallurgy: metals, including steel and titanium, and plastics.
Typical products
SLS, principally a form of rapid prototyping, was initially used to test models before production. However, designers are pushing the technology toward production of finished products. This particular technology can be used to make anything from jewelry and heat sinks for computers to medical and dentistry implants.
Similar methods
Other CAD-driven technologies including deposition prototyping (contour crafting, p.244, for example), stereolithography (SLA) (p.246), and three-dimensional printing (such as adapted inkjet printing, p.240).
Sustainability issues
To make efficient use of materials and eliminate waste, components are built up in layers to the exact contours of the design thus eliminating secondary cutting or manufacture. The levels of complexity that can be achieved in these microstructures also allow for reductions in material use and therefore weight. Because of the minute size of the components being made, several parts can be produced within the powder bed to increase productivity and energy efficiency. Unlike stereolithography, SLS does not require a support structure so waste and material consumption is lower. As with all rapid production methods, tooling is eliminated and in the future local production will eliminate transportation costs.
Further information
www.renishaw.com
Smart MandrelsTM for Filament Winding
Shape-memory alloys and polymers are big news in the world of materials. Characterized by their ability to be “programmed” to a particular shape, once heated and softened they can be bent out of this shape and re-formed into a new shape, which is retained once the material has cooled. The clever part is that when reheated, the part will return to its original “programmed” shape.
The US-based company, Cornerstone Research Group, one of the major world players in shape-memory technology, has exploited such materials to develop a patented tooling system, Smart MandrelsTM, for producing mandrels for the process of filament winding (see p.158). This system can be used in two ways. In the first case, a single-shape memory mandrel can be formed into a specific shape, used to produce the relevant components, and then reheated, re-formed, and reused to form a new shaped mandrel for an entirely different component. The second application is in the forming of a complex mandrel, one that might otherwise have been impossible to remove from inside the final component because of undercuts, and so on.
Filament winding using Smart MandrelsTM means that the filament can be wound around the mandrel, which is subsequently heated, softened, and returned to its “programmed” straight tube shape. This allows the completed filament winding to be easily removed.
