Process:
The SLS process begins with the atmosphere preparation in the process chamber, which is heated to the operating temperature and filled with nitrogen. The 3-D CAD data in the .STL file format is input into the SLS system. The system slices the part into its cross-sectional data. Typical slice thickness is 0.005 to 0.006 in. One powder feed piston rises to distribute a layer of material. At the same time, the part building cylinder lowers to the desired layer thickness. The other powder feed piston also lowers to accommodate any surplus material, which the leveling roller transfers across the build area. The deposited powder is heated to a temperature just below its melting point. Using a raster scanning pattern, the laser draws one cross section of the desired part to sinter the powder particles. Unsintered powder remains to support the next layer, which is then distributed, leveled, and sintered. This process continues until the part is complete. The part building cylinder then raises to allow the part to be removed for cooling. Excess powder is cleaned off the part by brushing or air blowing. With the exception of the use of ceramic materials, no post- production curing is required with this system.
Materials:
Advantages and Disadvantages:
As one of the fastest and most capable types of 3D printing, it’s no wonder that selective laser sintering has taken the 3D printing industry by storm.
But what are the advantages and disadvantages of selective laser sintering?
The important primary advantages and disadvantages of selective laser sintering are that a large volume of parts can be printed quickly and it does not need a support structure. However, it tends to have a rough, porous surface, and the post-processing cooling can lead to shrinkage.
There has been a lot of hype about selective laser sintering, and with good reason. It bests many other 3D printing technologies in several ways. It also seems the best for many, considering its many applications. However, as with any technological invention, selective laser sintering has capabilities and limitations.
SLS, more commonly referred to as Selective Laser Sintering, is a 3D printing technology where a powder is melted by a high-power laser beam to form the layers of a component. The laser heats the powder until it becomes melts enough for the molecules to join together to create the required shape.
SLS printing is broadly classified under Powder Bed Fusion, where a powder bed is filled with powdered plastic, metal, ceramic, or glass and then heated to cause the powder to adhere to one another.
Here is a more detailed look at the pros and cons of the selective laser sintering process.
There are a number of key advantages that make selective laser sintering a good choice for production.
The capacity to print a considerable volume of parts in a short amount of time is selective laser sintering’s primary benefit. SLS allows customers to tightly stack their models inside the build volume, which is impossible with other 3D technologies, even automatically through a nesting feature, reducing printout times.
High throughput at a low cost per part is possible when combined with a quick laser speed, specialised unpacking stations, and powder replenishing stations. SLS printing won’t disappoint those hoping to increase production rates or successfully scale manufacturing capabilities.
Efficiency results from densely packing the build volume and filling it to capacity. SLS is a great manufacturing option for the manufacture of large quantities because of the precision and consistency of the products generated using it.
This 3D printing technology can accomplish things that most traditional manufacturing processes cannot, which is saying a lot. This is because of the accuracy of the laser. Without support structures, SLS can generate parts with a high degree of precision and total flexibility of form.
SLS printing is, without a doubt, a terrific fit and well worth the investment for those with applications that call for particularly complicated geometries or precise shapes. Essentially, as long the design specifications are adhered to, producing complex geometries is a significant advantage of this 3D manufacturing technique.
Additionally, selective laser sintering offers intriguing mechanical benefits that make it possible to create useful components.
SLS is the way to go if you’re looking for a 3D printing technique that produces more than just prototypes. SLS pieces have material qualities that are unmatched by other 3D techniques. PA12, the most popular, yields mechanically robust and impact-resistant products.
Because of this, it is not surprising that the parts are suitable for end-of-use. For instance, they are ideal for usage in industrial settings.
Selective laser sintering is excellent for individuals with designs that heavily rely on particular functionalities like compliant mechanisms.
Support structures are not required because the 3D product is created inside a power bed during the selective laser sintering process.
This makes features like moving pieces inside themselves, or overhanging structures, conceivable in a way that is impossible with conventional production, and multiple parts can even be printed together as one assembled unit.
The variety of SLS materials is considerable and is still expanding, whether you need something sturdy and durable or soft and pliable.
As a result, SLS printing offers great material flexibility. Users can swap different powdered materials, for instance, without the inconvenience of having to wash the printer, thanks to a unique function.
Selective laser sintering parts are very competitive in terms of dimensional precision. They offer arguably the finest quality of all rapid prototyping techniques.
Finely detailed elements, such as thin vertical walls, can be easily manufactured in SLS products. Essentially, shapes that are lightweight while being efficient can be created.
In contrast to many other additive manufacturing techniques like Stereolithography, selective laser sintering does not need support structures because the powder works as a self-supporting element.
The printed parts largely support themselves because the powder is equally dispersed throughout the print area, decreasing the requirement for labour and resource-intensive support post-processing procedures.
Parts can be produced without a lot of material being wasted.
When compared to subtractive manufacturing processes, where a lot of waste material is produced, SLS 3D printing is much more efficient, only using the amount of powder needed to create parts is used to build the final product.
Once components have been printed, the excess powder can be collected and reused for future production.
Despite being one of the most effective 3D printing methods, Selective Laser Sintering does have some restrictions and drawbacks.
One of the primary drawbacks of selective laser sintering is shrinkage brought on by post-production cooling.
The print bed is preheated to eliminate temperature gradients and minimise shrinking, but there can be significant shrinkage in the size of the constructed product after the entire process is complete as a result of cooling.
This shrinkage must be taken into consideration in the design file. Parts of the printed product can become distorted during the cooling process, especially if they are big and flat. Because of the temperature difference in the part, tension builds up, causing the part to bend.
SLS parts are known to lack a smooth surface. They instead tend to be porous because of the powder particles used in the process. This happens during the melting process as some parts cannot be melted.
This leads to the quality of the final product being somewhat diminished, however, there are post-production finishing methods that can achieve a smoother finish where required.
Another drawback of selective laser sintering is primarily brought on by the post-cleaning procedures.
The cleaning process can be tricky as it requires removing the components from the metal or polymer powder cake, a process known as unpacking, and spraying the end product with compressed air.
The fine powder used in selective laser sintering can also cause potential respiratory problems, particularly when metal is used.
As well as being a potential respiratory hazard, some powders can also be a potential explosive hazard, meaning there needs to be a number of safety procedures and equipment in place.
Those from an FDM background may struggle slightly as there is a learning curve for designing SLS parts as the design for the two processes is completely different.
There is also a limited amount of material options available to use in SLS production, meaning it’s not suitable for all applications.
As can be seen by looking at the numerous advantages that outweigh the cons, the potential of selective laser sintering is staggering.
More people are yet to be open to the idea of SLS. Nevertheless, this 3D printing technology makes it possible to create complicated and complex geometries.
It also makes it possible for production rates to increase. There aren’t many tech innovations that can beat it.