Additive Manufacturing Processes
There are many different additive processes, each of which has its own different purpose. We get asked about these processes fairly often, so have listed them in this Q&A guide.
The surge in popularity of additive manufacturing
One of the most exciting new developments, additive manufacturing has burst onto the scene with the possibility of using the technology in a variety of different industries, including both manufacturing and medicine.
In reality, the technology isn’t new at all, having been around for three decades but the potential has only recently been really explored, with rapid advances in what’s on offer.
The Variety of Materials Which Are Used
Additive manufacturing materials
A number of different materials can go through the additive manufacturing process; each starts with the material being laid down, one ultra-fine layer at a time, using layers to bind and shape each piece. It’s this painstaking process which ultimately leads to the creation of the final product.
Polymers are one of the most popular materials which go through additive manufacturing often being used in 3D printers sold commercially. However, there are other materials too, such as metals, which are only suitable for use in industrial machinery. Visit our additive manufacturing materials article for further information.
Creating the CAD design
Regardless of the material being used, the process for additive manufacturing begins, in the same way, each time. First of all, the design for the item needs to be created; this is achieved using CAD software. This isn’t as easy as it sounds although a large part of the work is done by the software.
Although a lot of work needs to go into the design to create a piece which is physically possible, the process is far quicker than conventional means. The ability to make changes to the project, or tweak the design is far quicker than having to get changes completed than with more conventional manufacturing processes; this is one of the major advantages of the technology. This is why this technology is so ideal for rapid prototyping and small batch production.
Once a viable design has been agreed upon, the final details are input into the software and it’s this which prepares the theoretical model ready for physical creation. The CAD design is saved as a. STL (short for stereolithography) file. The file needs to be converted into a format readable by the printer, and the software also slices it into a series of wafer-thin cross-sections, horizontal slices which can be viewed virtually. These slices are how the powder will be laid down, and ultimately fused to create the final shape.
Printing the Design
When you’re ready to print, you first need to fill the machine with a powered version of your desired material. This chamber then releases the powder to be laid down, one layer at a time. Each layer is wafer-thin, sometimes taking days to build up to the full-sized model. The powder is solidified by a laser that runs over it gradually layer by layer, starting from the bottom and moving to the top.
This design is particularly economical because any powder that’s left over can simply be re-used for the next project, there’s no waste. In conventional manufacturing methods, such as turning, where the material is taken away, up to 95% is thrown away and discarded. This makes additive manufacturing a particularly cost-effective way of working.
Explained: the various additive manufacturing processes
There are different types of additive manufacturing processes which can be used to achieve the same result; this can be partially due to the materials being used, but also the end result which is desired.
Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS)
Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS) are essentially all metal additive manufacturing processes, but with the former typically used for materials other than metal additive manufacturing.
Sintering is one of the most frequently used additive manufacturing processes. The fundamental requirement for the process to be “sintering” is that the additive manufacturing powder is heated (sintered) to just below the melting point. This is achieved by directing the laser pulse to heat the material.
The 3D printer will print sintered material layer by layer, so that the sintering process over time fuses the powder together into one solid form. The programmatically controlled printer will simply follow the instructions of the software and continue to print until the object is complete.
Please also read our very detailed article on this topic, for further guidance – Direct Metal Laser Sintering & Selective Laser Melting.
Our redPOWER 500W is the perfect tool for the sintering process.
Selective Laser Melting
Selective Laser Melting (SLM) is a slightly different process, achieving a full melt rather than sintering the powder. The two different types of processes are very similar but they’re not suitable for everything. Metal alloys which contain different types of materials typically are sintered; this is because they have different melting points so it’s impossible to achieve a temperature which is right for all of the alloys contained within. Metals which have a particularly high melting point may also be sintered rather than fully melted.
In DMLS and SLS, the Lasers heat the powder sufficiently for the molecules to merge and bind together. This creates a strong surface which combines and holds the finished shape.
Melting takes the process one step further, raising the temperature sufficiently for the metal to fully melt; this then hardens as a new compound. Melting the metal has the effect of creating a surface which isn’t porous, something that can’t be fully achieved with sintering.
Having a porous surface may be desirable, and for these products sintering will be required.
There is another process often referred to: Laser Cusing. Although there are some very minor technical differences, it’s essentially a type of melting. However, rather than being a generic title, it refers to a trade name, rather like the difference between Ibuprofen and Nurofen.
Just to make things even more confusing, there’s a trade name for Laser melting known as DMLS, the same acronym used for sintering!
Sintering and melting are extremely similar processes but because there are some key differences which could potentially make or break a design it is imperative to understand the subtleties.
Why choose additive manufacturing?
There are many advantages of additive manufacturing, it’s not practical to list them all here as it’s a separate article – so read Additive manufacturing – typical applications and advantages for detailed guidance.
It’s worth mentioning though that additive manufacturing is renowned for its cost-effectiveness, as there is no powder waste. Any which is unused can be re-used later. This is fundamentally different to traditional “subtractive” type manufacturing processes, which cut/drill, etc. a solid object to create the final product and discard materials not required.
With other benefits such as rapid prototyping and small batch product, one thing is for certain, additive manufacturing in all its flavours and different processes is here to stay!
Support from SPI Lasers
We’re always delighted to hear from you, to discuss any aspect of additive manufacturing technology including metal additive manufacturing processes give us a call on 01489 779 696 or alternatively please complete our online enquiry form.
Our continuous wave (CW) fiber lasers are ideal for implementing additive manufacturing processes. Investing in an SPI fiber laser also gives access to other laser drilling applications such as drilling, cleaning and welding.
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