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SLM is the next type of 3D Printing I want to introduce you guys to, SLM is the acronym for Selective Laser Melting it is the same as DLMS or Direct Laser Metal Sintering.
This is a very high end AM method and is mostly only used by huge companies in the Aerospace and Medical fields.
The development of the SLM Technology was started by a German research project held by a group of Fraunhofer Institute ILT in 1995.
The process is very similar to the other previous methods in that is starts with a 3D CAD file that needs to be brought into special software to “slice” the file and give exact parameters to each layer and this gets fed into the machine to start “Printing”.
But this is the same as SLS you might say, yes it is similar but unlike SLS with the SLM Process it fully melts the Metal Raw material powder into a 3D – dimensional part.
A layer of Fine Metallic Powder is spread onto a steel plate evenly, then each 2D Layer Slice image is intensively fused to the previous layer by applying very high levels of laser energy that is directed at the powdered plate. The energy of laser is so intense that metal powder melts fully and forms a solid object. This cycle is repeated over and over until the object is complete.
This Technology is used very often for parts that have complex geometry with hidden voids or thin walls. That is why industries like the aerospace use it because they are able to manufacture lighter and stronger parts that is not possible with other manufacturing techniques due to tooling and Physical Access problems.
A few materials that is commonly used for SLM is Titanium, Stainless Steel, Aluminium and Cobalt Chrome
I am hoping we will be able to start getting home versions of this technology soon but due to the High end Lasers and Material costs this requires a lot more certifications and approvals to become commercially viable.
I have chosen to combine these two technologies into one article today since the principles are very similar with how the objects get created.
The only major difference is the projection method, but more on that as we get into it later.
Stereolithography known as SLA is the oldest printing technology and is the first method developed for AM by Charles Hull in 1986 when he patented the technology. He later was one of the co-founders of 3D Systems. Inc. He designed a machine called a stereograph to convert liquid plastic resins into solid objects using ultraviolet lasers.
Now Digital Light Processing or rather DLP was created and patented just one year later in 1987 by Larry Hornbeck of Texas Instruments. What he did differently is that he did not use Ultraviolet lasers but rather use a series digital micro mirrors laid out on a semiconductor chip. The technology is applicable for movie projectors, cell phones and 3D printing, this is what is now days used in almost all Displays and projectors.
Both process start off the same as all the other processes we have already covered, with a 3D CAD File that has been converted to a .stl file and “sliced” according to the layer thickness required. That is where this technology holds its own, I mean if it’s the oldest 3D printing technology surely it is outdated and is no longer practical? That would be wrong, yes it is the oldest technology but there are still very few other technologies that can even come close to the print quality and layer resolution that these printers can achieve.
The reason will become evident as soon as I start explaining the process to you.
Both these technologies use a photopolymer as a source material to build the objects from, in SLA each layer gets scanned over by the Laser until the material of that layer has hardened, where with DLP the entire layer gets projected at once until it has hardened. The build platform with part on, then moves out of the way to allow new unhardened resin to flow in place then the build platform returns to start curing the next layer on the previous one.
With both these technologies you can achieve a much smaller layer thickness and the surface finish is amazing.
After the printing has completed the parts get removed from the build platform and are rinsed in a solvent and then placed in an ultraviolet oven to finish the hardening process. The fact that you are using a Liquid resin as a base material and it is allowed to ‘Flow” you get the unmatched surface finish.
Please feel free to leave any comments and questions below.
I decided to look into SLS Printing next since after FDM this is the second most widely known and used technology it is a very versatile technology since it allows for a very wide range of materials to be used, there are very few things in common with FDM other than the fact that it is still an AM process whereby the parts are built in layers.
Selective Laser Sintering is more commonly known as SLS Printing is a techniques that makes use of a powerful laser to form 3D objects from a powder raw material.
Here is a video I found that visually explains the process :
In the 1980s this techniques was developed by Joe Beaman and one of his students Carl Deckard from the University of Texas.
What lets SLS stand out from some of the other 3D printing techniques like Stereolithography and FDM is the fact that with SLS there is no need to use Support structures on overhangs since with SLS the “Un-sintered” material serves as its support.
In same way as all other Printing methods the process starts with the 3D CAD Model that needs to be designed on a computer CAD Program and then converted to a .stl format for printing.
Some of the materials that one could print with using this technology include the following, Nylon (the most common), some ceramics and even steels and Aluminium’s.
The drawback of this technology is the fact that it is considerably more expensive than FDM and as a result of this it is more often found in larger companies and not so much amongst Enthusiasts and Hobbyists, It is however starting to become more and more accessible as more and more 3D Printing bureaus start coming into the marketplace.
It is very often used for Prototyping and Product development, and I have even seen a strong growth in low volume production runs where the quantities are too low for other methods but to high to justify the costs of an Injection moulding tool.
Next time we will have a closer look at SLA and DPL together since these two are so different but are so closely used.
FDM Printing is probably the most commonly known method of AM ,
What I mean is if we say 3D Printing this is what most people think of.
but lets try to better understand what it actually is :
FDM is an acronym for Fused Deposition Modeling , this is however a trademarked name by Stratasys inc.
so in a more correct term to use would be FFF , Fused Filament Fabrication.
This is the process of building your 3D CAD model that has been sliced into layers by Melting the Filament that normally comes in Spools or rolls and then laying them down layer by layer and building the part from the bottom up.
It is a technology that was developed by Scott Crump near the end of the 1980's and was finally commercialized in 1990.
To take a deeper look at the process I will try explain it :
As with most AM techniques you start off with a 3D CAD model, normally a .stl file format that is Sliced and setup on software that is specialized for the Printer you are going to use with all the parameters depending on your intended outcome.
this Software outputs a .g code (or similar) that is fed into the Printer giving it the instruction set it needs to Print your part.
now the printing process itself involves the material getting unwound from the spool or roll and fed to the Extruder and out the Nozzle onto the Print bed at a controlled rate.
In the Extruder head itself there is normally the Drive gear to pull (or push for Bowden type extruders) the material from the roll into the Hot-end where the material gets melted and finally gets pushed through the nozzle into the Build chamber,
The Extruder Head then places the material down Layer by Layer to build the part from the bottom up.
It does this by moving around the Build Area along the X and Y Axis, being controlled by a Computer numerically Controlled (CNC) System and the bed lowers slowly as the part gets built on top of each layer.
So after our first Stop at FDM we will continue our Journey through 3D Printing with another Printing Techniques next time.
If you have any more interesting Questions or Comments please leave one below
With 3D printing developing and advancing so rapidly it has become a bit of a whirlwind of information when you sit at your desk and hit Google with “”3D printing.””
Intrigued you might be but where do I start?
You want to get into printing and you want to figure out what you can use this amazing technology for that everyone is making such a fuss about.
First you need to understand what it is and then we will talk about the different technologies available and the advantages and disadvantages of each.
3D Printing is a method of Additive Manufacturing so this is already where it deviates from what we all understand as a manufacturing process, Manufacturing in the normal sense of the work refers to taking some raw material and shaping and removing parts of that material until we end up with the product we are making. An example of this would be someone making a bushing for a bearing; he will start off with a piece of stock round bar that is approximately the right size or a bit larger than his final product he will use a CNC Lather to then cut and trim this Stock down too his desired size, this can be done relatively quickly. However this might be quick he is wasting and throwing away all the material he removed from the original Stock.
Now, Additive manufacturing on the other hand also starts with a raw material and also needs to be manipulated and joined to become the end product, so how this is accomplished is by breaking the part up into layers and using various methods to place the material of the part only where the parts is to be formed.
3D printing on the other hand is defined by the action or process of making a physical object from a three-dimensional digital model, typically by laying down many thin layers of a material in succession.
And as these two are so very close by definition the terms are often interchanged and used both ways.
Let’s start figuring out what how the process can be defined, to do this we can look at the things that are common with all the technologies and that is that they all start by a computer CAD Model that has to drawn or designed using 3D design software.
This 3-Dimensional CAD model then gets read by the 3D Printier or AM Device which gets its data from the CAD model to determine the .g code (this is the most common format but not the only one) for the printing process.
At this point the operator can enter many variables to change and fine tune the desired outcome of the Product.
This is a very rough explanation of the process involved.
I also just want to mention that AM is not only 3D printing but there are a few other less commonly implemented AM process as well namely :
Rapid Prototyping (RP)
Direct Digital Manufacturing (DDM)
But out of interest we will be focusing on 3D printing and all the wonders about this technology.
We will be going through a few of the different 3D technologies over the next while, so check back soon and join me on the journey through printing.
Here are the methods we will be looking at :