FDM | SLS | DLP | SLA | MJF | DMLS
Learn more about 3D print manufacturing trends for 2019
There are many methods of 3D print manufacturing available in 2019. Each method requires a 3D printer of its own and comes with unique advantages and disadvantages. This article provides a detailed overview of the various methods used in the process of 3D printing or additive manufacturing in 2019. Most importantly, we will be discussing when to use each technique and will provide an overview of the best applications for each 3D print manufacturing method.
Judging by the number of 3D printers sold on an annual basis, the FDM or the fused deposition modeling technique is, by far, the most common type of 3D printing method. So it makes sense to start this article off by covering FDM 3d print manufacturing first:
Fused Deposition Modeling (FDM)
It is also most commonly referred to as the most cost effective 3D printing or rapid prototyping method. The process of extrusion plays the key role in this 3D printing technique since the thermoplastic filament is melted, extruded and finally deposited by a print nozzle in the form of layers. After the deposition process, the final product is obtained.
A wide variety of thermoplastics can be used for FDM 3D printing. The most commonly used thermoplastics are designated types of PLA, ABS, PET and their composites. The FDM 3D printing method is most widely used for prototyping of relatively simple components quickly and at the lowest cost possible. FDM 3D print manufacturing is typically used for obtaining a visual concept or functional prototype.
FDM is best used when low cost and functional prototypes are required
When compared to SLS or SLA methods, the resolution provided by the FDM is the lowest. Resolution on high-end FDM 3D printers is typically limited to 50 μm layers. XY resolution is also limited with minimum feature sizes of 400 μm or greater required for processing through the extrusion nozzle. For this reason, it is not suggested to be used for the design and printing of small parts with complex and complicated dimensional makeup having intricate characteristics. These small intricate parts are much better suited for SLS, SLA or DLP whereas FDM will be able to produce a much more cost effective part for large and relatively simple geometries.
When parts generated from the FDM 3D printing process are subjected to polishing by mechanical or chemical finishing techniques, improved surface quality can be obtained. Part strength of FDM 3D prints can also be improved with annealing and chemical post-processing. With these post-processing advances and the constant introduction of new engineering materials for FDM 3D printing, many companies are now using FDM 3D printing to go beyond rapid prototyping. We are now seeing a rise of FDM 3D print manufacturing being used for end-use production on commercial and industrial equipment across many industries.
The SLA 3D printing method was invented and introduced in the 1980s and is known to be the very first method by which a 3D model was obtained. With how fast technology advances, It may be surprising to note that the SLA technique is still in use today. The functioning mechanism of SLA 3D printing is the process of photopolymerization in which a special type of laser is used for the purpose of curing a resin (previously stored in liquid form inside the 3D printer reservoir) to form hardened plastic.
SLA is best used when high accuracy is required
The advantages of using the SLA 3D printing technique apply mostly to accuracy, as it provides the highest resolution of any of the rapid prototyping methods. Clarity of smallest details and smoothest finishes of the surface can be achieved with the SLA printing method. Formulations of special resin for SLA 3D printing have been carried out by material manufacturers around the world. Newly developed SLA materials have high thermal, optical and mechanical properties that are capable of being used as industrial and engineering plastics. Resolution of 10 μm or better can be achieved with stereolithography printing.
Due to the relatively new formulation of these resins, material costs are typically 3-4x that of a comparable thermoplastic material. In many cases the high accuracy and material properties more than justify the increased cost compared to FDM. The most common uses of SLA printing include the manufacturing of models, jewelry, dentistry etc. The method is highly recommended if smooth surfaces and tight tolerances are required e.g. in design patterns, molds and small functional parts.
Selective Laser Sintering (SLS)
As far as industrial applications are concerned, the most commonly used method for 3D printing is selective laser sintering (abbreviated as SLS).
In a typical SLS 3D printer, the fusing of the small particles in polymer powder is done by means a high-power laser. During the process of printing, unused powder provides support to the part that is built above it. This rules out the necessity of special support structures which is why it is the best method for obtaining products with complicated dimensional parameters and geometries. The products include undercuts, walls with small thickness, interior and negative features. Upon completing the production process – the part must be removed and post processed to reach its final properties.
The mechanical parameters obtained by the SLS laser sintering procedure have high values. In fact, the mechanical parameters are comparable to those of products obtained from the injection-molding process. However, material selection is limited for SLS due to the production process involved. Nylon is the material that is widely employed by the SLS process for the purpose of additive manufacturing. SLS nylon has very high mechanical values and is a very popular engineering polymer. This material exhibits high strength, flexibility, low density and resistance against the attack of chemicals, UV light, water, dust/dirt and impact loading.
SLS provides a great balance between cost, strength and resolution
The perks of using the nylon SLS method for 3D printing your parts are relatively low per component cost (when compared to SLA), high level of productivity, and final products made with high mechanical integrity. All these factors combine to make Selective Laser Sintering (SLS) very popular in the field of functional rapid prototyping. SLS is actually the third most cost effective method of additive manufacturing. It comes in at roughly 3x the cost when compared to FDM 3D print manufacturing. It is just marginally more expensive when compared to MJF. SLS is thought to be a cheaper alternative to injection molding for industrial small batch production. However for larger parts and high volume production runs, plastic injection molding is still recommended as the most cost effective and reliable method of production.
Digital Light processing (DLP)
The DLP 3D print manufacturing method produces solid concepts from 3D CAD models by means of digital light processing (DLP) technology. When the 3D mode is received by the 3D printer, the DLP projector throws a special type of light on a container of liquid polymer. Note that complete control of lighting conditions must be maintained during this process. An image of the 3D model is displayed onto the surface of the liquid polymer by the DLP projector. After this process, the hardening of the liquid polymer takes place while the build plate moves down to expose additional liquid polymer to the projected light. The same process is repeated until the whole liquid is converted to the required solid model.
Use DLP for fast processing of high resolution parts
You can easily describe DLP 3D printing as a faster and slightly less precise version of SLA printing. Both the DLP and SLA 3D print manufacturing use the same types of resin materials with similar benefits and limitations. The process of DLP 3D additive manufacturing is quite rapid and provides products that have relatively high resolution levels. The Lunavast XG2, MiiCraft, the envisionTec Ultra are some examples of 3D printers that utilize digital light processing technology. DLP 3D printing provides many of the same benefits as SLA printing but with much higher productivity. The material cost differential between producing parts in DLP vs SLA is negligible. The technology that proved to be the foundation of the DLP 3D printing technique was invented by an employee of the “Texas instruments” corporation. His name was Larry Hornbeck and he did this in the year 1987.
Multi-Jet Fusion (MJF)
Multi-jet fusion or MJF is a comparatively new 3D print manufacturing method that allows printing of components with complex components at a relatively low cost. 3D printing with MJF is suitable for both rapid prototyping as well as large-scale or batch production. Batch production is done by setting up printing of multiple parts into a 3D grid. This type of 3D printing offers rapid prototyping and batch production of complex parts at a cheaper price than SLA. From our experience, producing an MJF part costs roughly 2-3x that of FDM parts in large volumes.
MJF 3D printing is ideal to be used for applications with details that will be hidden. Some examples complex ductwork in walls with small values of thickness, wiring clips, brackets, connectors etc. MJF has proven beneficial for the transportation industries because the technique has the capability of large scale production with industrial part strength. HP MJF 3D printing is particularly recommended in short runs, spare parts and pre-production applications.
The MJF technique is particularly useful to obtain products with relatively complicated and complex design at a lower cost. The cost of the materials is related with the volume of the part. Production costs are similar to that provided by SLS 3D printers, but comes coupled with much higher productivity rates. Less waste occurs in MJF 3D printing when compared to CNC machining or SLS/DMLS laser sintering techniques.
MJF is best used for producing highly complex geometry at a lower cost
The cycle-time for manufacturing with MJF depends on the height and quantity of the batch of parts being produced. The average cycle for a particular unit can be reduced considerably by merging multiple batches by means of nesting. The dimensional accuracy of the products obtained by the MJF procedure is more than that of the laser sintering technique. Moreover, the strength and other mechanical MJF technique products is also high.
Direct Metal Laser Sintering (DMLS)
DMLS is basically a “laser powder bed fusion” or “Direct Metal Laser Sintering” process. It is used for the purpose of obtaining metal parts with complicated and complex geometry. Applications are usually focused on parts which would otherwise be impractical or impossible to obtain from other metal manufacturing methods.
The strength and density of the products obtained via Direct Metal Laser Sintering can be improved after high temperature annealing. In fact, annealed DMLS part strength can actually be higher than those obtained using the investment casting processing. The quality and quantity obtained from the DMLS method is also high. Metallic 3D printing is particularly advantageous in the oil and gas industry. It can also be used for the manufacturing the medical guides, and components of aerospace devices and instruments. Functional prototypes with exceptional mechanical properties are produced by the DMLS additive manufacturing method.
The direct metal laser sintering or the DMLS method offers a great number of advantages and benefits. The products obtained from the DMLS require considerably less stock material weight vs. cast or tooled metal pieces. This is because the the process only uses the amount of material required to create the geometry. These products also have high strength and durability. The design limitations encountered with conventional metallic manufacturing techniques do not exist with DMLS manufacturing. The lead times are reduced because of the high speed of the process relative to conventional metal part production methods.