Selective Laser Sintering(SLS) 3D printing advantages and disadvantages

Of the technologies that have been developed for 3D printing, Fused Deposition Modeling (FDM) is by far the most popular. Stereolithography (SLA) comes as a distant second. Identifying which technology comes third is far from definite, but a strong case could be made for Selective Laser Sintering (SLS). If you also are thinking to try SLS 3D printing and want to know about the advantages and disadvantages of SLS 3D printing then you are at the right place. In this post, we will discuss SLS’s major advantages and disadvantages in a very simple way.

SLS Printing Advantages In Detail
No Supports Needed
In SLS printing technology the 3D model is printed between the powder raw material layer by layer thus there is no need for supports to hold overhangs or other parts of the model. As the 3D model is carved layer by layer a complete layer of powder is coated every time which is fused together according to the model with the help of a laser. This leaves the untreated powder in between the layers.

This extra powder in between the 3D model has both advantages and disadvantages, for the plus point it gives support to the next layer if needed, and thus there is no need of designing supports in SLS 3D printing as we do in FDM or SLA 3D printing. But, this also increases our post-processing work of removing powder stuck inside of prints, we will discuss this in its respective heading below.

Batch Printing
SLS 3D printers which are made for personal or normal use have a printing volume of 165x165x300 (mm3), now if your 3D model’s dimension is much smaller than this suppose 50x50x50 mm3 then you could easily fit many (say 50) models at a time in the volume of the printer You should take proper gaping and time into consideration before starting 3D prints.

This is possible as first there is no need for supports, the second laser is used to bind nylon particles (raw material) with each other thus there is no layer adhesion problem and it could easily work on a wide area.

Fast Printing
Although SLS printers are not the fastest 3D printers in the industry still they give pretty high printing speeds. Generally, SLS printers print in the range of 20mm/hr to 48mm/hr with the help of high-powered lasers.

The raw material used in SLS 3D printers sets very rapidly once treated with a high-power laser beam. The raw material is also preheated in the bed to avoid warping. This pre-heating also escalates the printing process.

Robust Prints
The 3D prints obtained from SLS 3d printers are very robust and thus they are preferred for experimentation and prototyping purposes. All of the prints obtained from SLS printers are having industry-level strength and mechanical properties.

The strength and robustness of 3D prints come from the raw material used i.e. Nylon powder (PA-12), this powder binds together when melted due to the laser beam and forms a very strong bond between layers of the prints.

Mechanically stating the SLS 3D prints generally have the tensile strength of 47.8 MPa and an elastic modulus of 1.75 GPa. Although this could change depending upon the raw material used. But, this rigidity makes it prone to break when elongated

SLS Printing Disadvantages In Detail
Despite the benefits of SLS printing, it is far from being an all-encompassing solution for all rapid prototyping needs. SLS printing on a desktop scale is even more problematic, as the complexities and costs associated with SLS are hardly attractive for the casual 3D printing enthusiast.

Porous and brittle
The same porosity that makes SLS prints excellent for dyeing also compromises their structural integrity. Although SLS prints have a comparable tensile strength compared to SLA prints, they are much less flexible and can undergo less deformation before failure. For this reason, SLS prints are best used as proof-of-concept prototypes and not as functional parts.

Prone to shrinkage and warping
Much like SLA and FDM, SLS prints are also prone to warping and shrinkage. The nylon powder needs to be subjected to elevated temperatures to enable sintering, which means that the printed object will undergo a cooling process almost immediately after the solid layer has formed. As the print cools, it contracts or shrinks in all directions which can lead to a dimensionally inaccurate product. The stress due to the contraction can also accumulate in certain parts of the print, particularly in sharp edges and corners, resulting in these parts getting warped or distorted.

Unlike in FDM printing, there is no intervention or modification of the SLS printing process that can be done to reduce warping. Shrinkage will inevitably happen at a rate between 3% to 4%. This needs to be considered in the design phase by adjusting the volume of the model accordingly.

Warping can be reduced by avoiding or reducing the volume of flat areas in the design. Cutouts can also be integrated into the design that can absorb some of the stress caused by absorption without distorting the rest of the print.

Produces a lot of waste
In some ways, SLA printing looks similar to SLS printing. Instead of nylon powder, SLA printing uses a liquid resin solution that is polymerized by a beam of ultraviolet light. Although the liquid resin that SLA uses is a bit expensive, the silver lining is that any remaining resin can still be reused.

This is not the case for SLS. As we have mentioned, the powder inside the build chamber needs to be pre-heated so that it can be sintered with just the slightest exposure to the laser. This preheating step is enough to compromise the quality of the powder. Based on experience, an SLS print made using 100% recycled powder comes out so brittle that it can fall apart with just the slightest pressure.

Most SLS printing experts recommend using only a maximum of 50% recycled powder. Since you will always end up with a portion of unused powder with every single print, you will inevitably accumulate so much unused nylon powder that you’ll need to throw some out. With this single detail, SLS printing already generates much more waste compared to FDM and SLA.

Expensive
Ultimately, the most significant factor that is preventing SLS printing from becoming mainstream technology is its cost. While it’s possible to get a high-quality FDM printer for less than $500 and a beginner SLA printer for less than $1000, a desktop-scale SLS printer will set you back at least $5,000.

The SIntratec Kit, which sells for a little more than $5,300, is a very basic SLS printer that is capable of a modest 100 mm x 100 mm x 100 mm build volume. Scaling up will bring you closer to the $10,000-mark, which coincides with the price of the popular Formlabs Fuse 1. Premium desktop-scale SLS printers can even cost as much as $40,000.

With such a price range, it’s no wonder that SLS printing has not picked up among the desktop 3D printing community. SLS printing is simply not the kind of thing that you can go into out of pure curiosity or as a hobby.

WKproto is a professional rapid prototyping and low-volume production manufacture specializing in 3D printing, CNC machining, and Vacuum Casting. Our factory and parter factories enable rapid prototyping of designs from our customers and low volume production for market verification.

We have three factories. 3D printing factory meets the demands of most 3D printing services with 100 SLA machines, 10 SLS machines, 10 MJF machines, 10 SLM machines, and 20 FDM machines. CNC machining factories for processing metals, plastic and more materials with more than 200 machines for CNC milling/CNC lathes/EDM / Wire EDM and the Vacuum Casting factory is for low volume production for ABS、PC、PP、PE、PA、POM、PMMA、PVC.