Additive manufacturing is one of the most exciting technological advancements of recent years, especially for inventors and designers. While some of the public hype surrounding 3D printing has diminished, the technology has only been improving, and the capacities and possibilities of rapid manufacturing are expanding at an accelerated rate.
3D printing holds great potential for entrepreneurs and inventors. But, like any other kind of cutting edge technology, all the terminology and jargon involved with 3D printing can be daunting to the newcomer. If you’ve ever wondered what 3D printing is all about, or how direct metal laser sinter differs from selective laser sintering, then read on! We’ll cover the basics of 3D printing and the most common 3D printing technologies.
What is 3D Printing?
3D printing is another term for additive manufacturing. There is a variety of different 3D printing techniques, but they all share in common a novel approach to rapid manufacturing. We’ll go over some of the most common types of additive manufacturing below, but what they all share in common is that they build parts by gradually laying down layer after layer of material in a three-dimensional space until the completed object emerges.
3D printers are actually more similar to regular 2D printers than you might think. Except that, instead of laying down a single layer of ink onto a piece of paper, 3D printers lay down thousands upon thousands of layers of material, each one on top of the previous.
This is what sets 3D printing apart from conventional methods of manufacturing, where an object is created by cutting material away from a block (hence subtractive versus additive). In 3D printing, successive layers of material are laid out by a computer-controlled printer that reads CAD files to create the part.
Important 3D Printing Terms
- Accuracy: Refers to the degree of precision that can be achieved by a particular machine. This accuracy is measured in the thickness of the layers that the printer can produce.
- Support Material: Because parts are built up in three-dimensions, some types of 3D printers need to include structural supports to maintain the structural integrity of a part while it is being produced. These need to be removed afterward during the finish stage. Support material is often needed when there are large gaps or overhangs in the design.
- Slice: A single layer of a 3D printed model in progress. Layers vary in thickness depending on the accuracy of the machine.
- Nozzle: The part of the machine which extrudes the material used to build the parts.
- Print Bed/Built Plate: The interior surface within the 3D printer upon which the part is manufactured.
There are two primary advantages to 3D printing. The first is build-time. With 3D printing, you can produce a high-quality, functional and even end-use part much, much faster than with conventional manufacturing techniques. You can also produce much smaller batches — even a single part can be 3D printed, instead of having to do a run of thousands. This is largely because additive manufacturing is a self-contained process that requires no tooling or preparation outside of creating the CAD file that the 3D printer can read.
The other great advantage is the ease with which 3D printers can handle pretty much any shape imaginable. It is no harder for a 3D printer to produce a complex, convoluted geometrical shape than it is to create a rectangle. Because objects are built up layer by razor-thin layer, shapes that would be prohibitive or impossible to produce otherwise become easy.
The technology has not by any means reached its full potential, and it is not yet the best solution for all projects. That said, 3D printing is now suitable for a variety of applications, from end-user parts with high tolerance requirements, to functional prototypes, to presentation models, and everything in between.
Fused Deposition Modeling (FDM)
Fused deposition modeling, or FDM, is one of the most widely used additive manufacturing techniques. Most of the consumer-grade 3D printers employ FDM technology. The commercial-grade printers are much the same, but are able to provide far superior surface finish and to print to a higher degree of accuracy.
FDM works by extruding layers of various different thermoplastic materials. A plastic cord is passed through the heated nozzle, which melts the material. This is then deposited to create a layer (or slice) of the part. The material then cools and hardens.
Modern FDM printers are able to produce parts with mechanical properties close to, if not equivalent to, conventionally manufactured parts. FDM printers can produce high-quality thermoplastic parts in ABS, PC, UTEM, and other production-grade materials. FDM uses the same materials as injection molding, but without the need for costly and time-consuming molds.
Because of the ever improving quality of the thermoplastics, FDM printing can be used to create end-use parts and parts which need to meet high tolerances. High-end FDM printers are also able to realize a high degree of surface accuracy, which makes it an appropriate technology for creating presentation models as well as functional prototypes and end-use parts.
Selective Laser Sintering (SLS)
SLS is one of two popular laser sintering methods for 3D printing (more on the other below). Selective laser sintering is quite a bit different than FDM. Instead of extruding material from a nozzle to build up the slices of the object being printed, SLS printers fire a CO2 laser into a thin layer of powdered material, usually (but not always) some kind of nylon polymer. The powder hit by the laser gets fused and is then covered by another layer of powder.
In this way, the object is built up gradually. At the end of the process, the completed part has to be sifted out from the left-over powder. A great advantage of this process is that the un-fused powders act as a support structure for the part as is it being built, which also allows for multiple parts to be stacked one on top of the other during the build process for improved efficiency.
There are now a number of different materials available for SLS printing, ranging from flexible and rigid thermoplastics to metals, as well as soft, rubber-like materials. SLS can produce parts with considerable durability, and so it is valued for prototyping and end use parts.
A drawback of SLS printing is that, because the material is essentially being heated by the laser, there can be some warping of particularly thin sections.
Direct Metal Laser Sintering (DMLS)
DMLS is a very similar to SLS. A newer technology, DMLS differs in that the laser is fusing metal powders, resulting in considerably different properties compared with SLS. DMLS allows for the 3D printing of solid metal parts, which is really quite amazing. With this technology, it is even possible to print functional rocket engines.
DMLS can produce parts made from a variety of metals, including titanium, stainless steel, chrome, aluminum, and cobalt. The greatest advantage of DMLS is as an alternative to much more labor intensive casting and machining, which tend to be unrealistic for low-volume production runs. With DMLS, you can produce high-quality metal parts that are functionally very similar to die-casted parts cost effectively without having to justify all the labor and expense of tooling. This is a great boon for inventors and entrepreneurs who are looking to produce custom metal parts on a budget.
Something to be aware of with DMLS as compared to SLS is that the powder is not sufficient to act as a support structure in DMLS printing, and so support structures may need to be included in the design. Depending on the material being used, these can be somewhat difficult to remove after the fact, and so demand perhaps a bit more time and effort spent on finishing than with other additive manufacturing methods. This also means that you can’t improve efficiency by stacking parts in a DMLS print as you can with SLS.
Stereolithography, also known as optical fabrication, is arguably the oldest 3D printing technology (though, really, they all sprang up in the early to mid-80s). SLA uses UV lasers to solidify photopolymer resins, and so is somewhat similar to the laser sintering process.
As with other additive technologies, stereolithography now offers a range of options when it comes to the photopolymers available. SLA resins can mimic the properties of ABS, polypropylene, and polycarbonate, and can be clear or opaque.
The greatest advantage that SLA offers is its extreme degree of accuracy. SLA can produce layers as thin as 0.002 inches (50 microns). This allows for precise detail and a smooth finish right from the printer, with dimensional accuracy within thousandths of an inch.
Parts produced though SLA aren’t as tough as those that can be made through the other methods covered above. However, the technology is well suited for applications where detail is more important than durability. This includes models, sculptures, form-and-fit checks, and master patterns for molding.
That SLA can be used to create very highly detailed master patterns is perhaps its most interesting application.
PolyJet printers work by extruding resins which are then cured by UV light. PolyJet printers are even more accurate than SLA, and are able to produce layers as thin as 16 microns. This makes PolyJet the most accurate 3D printing technology currently available.
In addition to its remarkable accuracy, PolyJet is notable in that it can print in multiple materials at once. Two or more resins can be mixed so that the end product has a combination of material properties and/or colors straight out of the printer from a single build. PolyJet also produces objects with very fine surface finishes, which often require no additional finishing.
Parts produced by PolyJet printers are not very durable, though, and tend to degrade faster than those produced by other means. It is also not well suited for larger parts. It is ideal for smaller parts that demand an extremely high level of detail, or that would benefit from the capacity of PolyJet printers to print with multiple materials.
3D printing has really started to take off in recent years. The technology is always improving, and as it does the possibilities it opens up for inventors, entrepreneurs, and product designers will continue to grow in ways that we can’t fully predict. It’s a technology that really has the potential to transform manufacturing to a degree that we haven’t seen since the launch of the industrial revolution.
Cad Crowd is proud to offer an array of 3D printing design and contract 3D printing services. Whether you’re looking to create the CAD file you need to communicate with 3D printers or are looking to find a 3D printing service provider, Cad Crowd has the expertise you need to realize your project goals. Get a free quote today.