3D printing is a very capacious definition for a number of technologies that differ from each other in manufacturing processes, the materials that are used, and the type of objects that can be made of them. At the moment, we can distinguish several dozen production methods, which can be described as additive – some of them differ in small technical nuances, others are completely separate manufacturing processes without virtually no common features apart from the name “3D printing”.
In this study, we present the most important additive technologies in the context of their advantages, disadvantages and differences, which we hope will help you understand what 3D printing is, will it be used in the context of your application – and if so, which particular solution should you use?
Let’s start with the basic thing, i.e. the definition of 3D printing:
Detailed information on 3D printing can be found in the following article:
As mentioned above, as 3D printing we can define at least several dozen different manufacturing techniques. Many manufacturers of 3D printers, when developing a given additive method, often patent its unique part, creating a separate technology from a formal point of view, although, as a rule, it is derived in a straight line from something that has been on the market for several dozen years. For simplicity, we can try to divide them into four main groups by the form in which building material is supplied to the 3D printer of a given type:
To the “other” category we can include a whole bunch of manufacturing methods, whose creators try to incorporate three-dimensional printing in a rather stretched way. They are e.g.
In this study, we will focus on the most popular, most common and most used 3D printing technologies comparing them to each other and trying to show which is the best from the point of view of a given application.
3D printing is the same manufacturing technology as any other – its goal is to produce things in a certain way, from specific materials. Some applications can be made better on 3D printers than on other types of machines, some will come out worse – we will also find those that cannot be printed or whose 3D printing is economically unjustified. Historically, incremental technologies have been brought to life as an alternative way of making prototypes. The advantage of this method over others was and are primarily:
Another advantage is the ability to print very complex geometries that are impossible to do with other manufacturing methods (in particular, techniques using powders).
We choose 3D printing technology when we need to produce something relatively quickly, cheaply and in quantities not exceeding several hundred – several thousand pieces, and at the same time we do not care about the quality of the surface such as in injection molding or casting technology.
One of the most popular and widespread 3D printing technologies. It comes in three dimensions: amateur, desktop and industrial. Although the principle of operation is exactly the same in every case, 3D printers from the amateur sector are not able to print well and accurately from professional-grade materials, which, in turn, do not pose a major challenge for industrial-grade machines (including polyamides, materials reinforced with carbon or glass fiber etc.).
The technology involves creating details by supplying plastic in the form of a line to the print head and warming it to a semi-liquid state. The print head applies material on the work table in XY axes by “drawing” the shape of a single layer. When it finishes, the head either rises up or the work table lowers down by the specified layer height and another layer is applied. Semi-liquid plastic binds under the influence of high temperature and quickly freezes to form a uniform structure. The difference in names (FDM / FFF) is due to the fact that FDM is a registered trade name of the creator of this technology – Stratasys.
SLA (stereolithography) is a technique of creating details from light-cured resins, hardened by irradiation with a laser beam. The container is filled with resin in which the work table is immersed. It is lowered to the height of the given layer (e.g. 0.05 mm from the bottom of the container), after which the laser beam “draws” the shape of the object in the XY plane, hardening the resin. The resin adheres to the surface of the work table, after which it is raised to the height of the next layer and the process is repeated – this time the new layer adheres to the previously hardened one.
UV LCD is a production process similar to SLA, except that the resin is not cured with a laser beam, but with the light emitted by the LCD screen with UV backlight mounted under the resin container. The advantage of this method is that the entire layer is exposed (cured) simultaneously. The disadvantage is that when curing large surfaces (with a length / width greater than a dozen centimeters), there is a large shrinkage of the resin cured at the same time. The alternative to this method is DLP, where the resin is cured with light emitted by the projector.
Technology developed in the 21st century by the HP group. It consists of scattering a layer of powdered polyamide PA12 (or flexible TPU) on the work table and selective spraying of the binder that bonds individual layers of the detail. At the same time, the material is welded with heat emitted by the lamps, creating a perfectly durable structure of any geometry. After finishing the work, the detail should be extracted from the unsaturated powder and cleaned – this is done in a dedicated, automated post-processing station.
In MJF technology (as in SLS) it is not necessary to use support structures, because their form is fulfilled by unsolidified powder. This enables details to be printed with geometries that cannot be achieved using other traditional manufacturing techniques. Another advantage of the MJF system is high production efficiency – HP 3D printers are adapted to the production of low production series and are in this respect incomparably more efficient than 3D printers working in FDM / FFF technology as well as SLA and UV LCD.
Another important feature of MJF technology is the possibility of 3D printing of details in full color using PA12 plastic.
3D printing from metal is one of the most desirable and also the most difficult to use additive technologies. It consists in even distribution of successive layers of powdered metal alloys and their selective melting by means of a laser beam. 3D metal printers are industrial grade machines, using, among others protective gas atmosphere. Many popular metal alloys, including stainless steel, titanium or aluminum, can be used at work.
DMP (direct metal printing) technology is the original additive method of 3D Systems. At the same time, there are many varieties on the market that, in principle, work and rely on the same, but differ in technological nuances – and hence the name. Techniques called SLM (selective laser melting), DMLS (direct metal laser sintering) and others describe the same manufacturing process.
Each of the above incremental methods has a number of advantages and disadvantages. To choose the right one we need to know the specifics and expectations of the created application. The factors we consider in comparison are:
| FDM | SLA | UV LCD | MJF | DMP | |
|---|---|---|---|---|---|
| Size | ***** | ** | * | **** | *** |
| Accuracy | * | ***** | **** | ** | *** |
| Geometry | * | **** | *** | ***** | ** |
| Durability | *** | ** | * | **** | ***** |
| Quantity | **** | * | ** | ***** | *** |
| Price | ***** | ** | *** | **** | * |
FDM / FFF technology will be used where large 3D prints are involved and the low price is important. It works well in low-volume production. Depending on the material used, prints can be either very durable (PC, PCABS, PA6) or cheap (PLA). This is not the best method when it comes to high quality surface details or the print geometry will be extremely complicated.
SLA technology is excellent in applications where surface quality and precision of 3D prints are important. Unfortunately, it is not very effective in low-volume production and is definitely dedicated to the production of individual parts.
UV LCD technology is slightly inferior to SLA in terms of accuracy and the differences in this area are really small. It is better for low-series production of small components, because in this respect it is much faster than SLA. Prints will also be slightly cheaper. In principle, however, UV LCD and SLA are very similar manufacturing methods, differing in small nuances.
MJF technology is perfect for practically any type of application, and its only disadvantage may be the price in the production of unit elements with simple geometry, where the advantage of FDM / FFF will be significant. It is an ideal manufacturing method for the rapid implementation of production series of several dozen / several hundred / and even several thousand pieces of detail. The low quality rating is quite unfair here, because in fact the quality of the prints is many times higher than that offered by FDM / FFF.
DMP technology has one key advantage over all others, and it is possible to print metal details. This type of material determines all other comparative factors. One thing to consider is price – 3D printing from metals is expensive.