Fused Deposition Modeling (FDM) is a 3D printing technology that builds parts by extruding a melted plastic filament onto the build plate one layer at a time. Digital Light Processing (DLP), on the other hand, creates parts by polymerizing a liquid photopolymer resin by projecting a single UV light image of the part cross-section onto the build plate. DLP produces isotropic parts with very high levels of surface detail and resolution. It can also produce parts extremely quickly. FDM printers are cheaper than DLP printers and have a wider range of materials available.
This article will compare FDM vs. DLP in terms of their differences, materials, and printing technology.
FDM Definition and Comparison to DLP
Fused deposition modeling is the most well-known 3D printing technology. It was first developed by Scott Crump in 1988 who later commercialized the first FDM printer. The process is relatively simple. It involves guiding a thin filament of thermoplastic through a heated nozzle/hot end. The plastic exits the nozzle and is placed on the build plate in the pattern of the part cross-section. Once a layer is complete the print nozzle moves up one layer and deposits the plastic on the previous layer until the part is complete.
FDM is a simpler technology when compared to DLP. This makes it significantly cheaper for hobbyists. There are many different rigid thermoplastics and even flexible thermoplastic polyurethanes available. A typical FDM printer is shown below:
A typical FDM printer.
Image Credit: Shutterstock.com/R_Boe
What Are the Advantages of FDM Compared to DLP?
Listed below are some key advantages of FDM vs. DLP:
- FDM printers are significantly cheaper than DLP 3D printers
- FDM has a wider range of material colors. Parts can also be made to be significantly stronger than those made with DLP printers.
- FDM printers can produce larger prints when compared to DLP printers
What Are the Disadvantages of FDM Compared to DLP?
Listed below are some key disadvantages of FDM vs. DLP:
- FDM has a poor surface finish and cannot produce very fine features
- FDM parts have a high level of anisotropy in the z-direction. This is due to the poor interlayer bonding strength common with FDM parts.
DLP Definition and Comparison to FDM
Digital light processing was invented in 1987 by Texas Instruments. This photopolymer-based 3D printing technology works by projecting a UV light onto the build platform to polymerize each layer of the part. The layer cross-section needs to be masked so that only the required areas are polymerized. This masking is done with a DMD (Digital Micromirror Device). The DMD uses a micromirror to either direct the light to the photopolymer or direct it to a heat sink below. Alternatively, LED screens can be used as a light source. The masking is done by simply turning off the LEDs wherever polymerization is not required. The resolution of a DLP 3D printer depends on the resolution of the LED or DMD array as well as the distance from the light source to the polymerization zone. DLP parts are made up of cubic volumes called voxels. This means any curved edges look as if they were built from many smaller cubes.
DLP printers are more expensive than FDM printers. They also have smaller build volumes and fewer material options but can print faster at much higher resolution and surface quality. A typical DLP printer is shown in the image below:
A typical DLP printer.
Image Credit: Shutterstock.com/Moreno Soppelsa
What Are the Advantages of DLP Compared to FDM?
Listed below are some key advantages of DLP vs. FDM:
- DLP printers can produce parts with very small features and high resolution
- DLP parts are isotropic. This means the mechanical properties are the same regardless of the direction of the applied load.
- DLP can print extremely quickly. It can also print multiples of a part at the same time it takes to print one
What Are the Disadvantages of DLP Compared to FDM?
Listed below are some key disadvantages of DLP vs. FDM:
- DLP printers are generally more expensive than FDM printers
- DLP parts require additional post-processing steps like solvent rinsing and UV light post-curing
- DLP printers have much smaller build volumes when compared to FDM printers
Comparison Table Between FDM and DLP
The table below lists some of the more common properties of FDM vs. DLP as well as how they compare with each other:
Print resolution
25 to 300 Microns
50 to 500 Microns
Can print large parts
No
Yes
Wide range of material colors
No
Yes
Minimum feature size
100 Micron
1 mm
Can produce high-strength parts
No
Yes
Has isotropic material properties
Yes
No
Minimum wall thickness
0.1 to 0.3 mm
1 mm
Parts need support structures
Yes
Yes
Largest print volume
192 x 108 x 370 mm
1000 x 1000 x 1000 mm
Table. FDM vs. DLP Comparison
DLP printers have smaller build volumes but can produce higher quality parts. FDM printers have a wider range of material options and colors.
FDM vs. DLP: Technology Comparison
FDM and DLP have completely different technologies and materials and are not directly comparable. FDM uses a thermoplastic filament that gets heated and extruded layer by layer to produce a part. A DLP printer, on the other hand, polymerizes a liquid photopolymer resin with a UV light layer by layer to produce a part.
FDM vs. DLP: Material Comparison
FDM makes use of a wide range of rigid thermoplastic materials as well as flexible thermoplastic polyurethane. Specialized filled filaments are also available to further improve part strength. DLP printers also have access to both rigid and flexible photopolymers, however, colors are limited.
FDM vs. DLP: Product Applications Comparison
FDM parts exhibit higher strength and toughness. They are usually made for more mechanically inclined applications like assembly jigs, functional components like brackets, or functional prototypes. The high visual fidelity of DLP printers makes them better suited for finely detailed applications. This includes: patterns for casting jewelry and visual prototypes of fine-featured products.
FDM vs. DLP: Print Volume Comparison
FDM printers have significantly larger build volumes when compared to DLP printers. FDM printers can reach sizes of up to a cubic meter. DLP printers on the other hand have smaller build volumes. This is due to some limitations in the underlying UV projection technology. DLP printers are limited by the resolution of the projecting screen and the distance from the light source to the polymerization zone.
FDM vs. DLP: Surface Finish Comparison
DLP parts have significantly better surface finishes when compared to FDM printers. DLP parts look injection molded and only have a loss of fidelity on complex organic surfaces or features. This is due to DLP printers not being able to create true curves but rather approximate curves using cubic voxels.
FDM vs. DLP: Cost Comparison
FDM printers are significantly cheaper than DLP printers due to the much simpler technology employed. An entry-level FDM printer can cost as little as $150 whereas an entry-level DLP printer can cost $500. It must be noted that the cost of DLP printers has been steadily falling in recent years.
What are the Mutual Alternatives to FDM and DLP?
Despite the benefits of FDM and DLP, there are alternative technologies that can achieve similar results. An example is:
- Polyjet: Polyjet printing works by spraying photopolymer drops onto a build plate. A UV light then passes over these droplets to solidify the layer. The next layer is then deposited on the top of the previous one until the part is complete. Polyjet printers have extremely high resolution. They can print parts from many different materials with different properties and colors in the same part. This makes polyjet printers a good potential replacement for both FDM and DLP printers.
What Are the Similarities Between FDM and DLP?
Listed below are some of the similarities between FDM and DLP:
- FDM and DLP printers can only print plastic materials
- FDM and DLP printers can print rigid and flexible plastic parts
- Support structures are required for both FDM and DLP
What Are the Other Comparisons for FDM Besides DLP?
Listed below are the comparisons for FDM besides DLP:
- FDM vs. SLS: Selective laser sintering also manufactures parts from thermoplastics using heat. SLS prints almost exclusively in polyamides whereas FDM has a much wider range of material options. SLS also melts the plastic with a laser instead of a heated nozzle. For more information, see our article on SLS vs. FDM.
What Are the Other Comparisons for DLP Besides FDM?
Listed below are the comparisons for DLP besides FDM:
- DLP vs. SLA: Stereolithography is a printing process that also uses a UV light source to polymerize a photopolymer. SLA printers however make use of a UV laser that scans the part cross-section instead of projecting the entire layer at once. SLA can produce higher quality surfaces when compared to DLP. For more information, see our article on SLA vs. DLP.
Summary
This article provided a summary of the differences between FDM and DLP 3D printing technologies. To learn more about FDM vs. DLP and which technology is better suited to your application, contact a Xometry representative.
Xometry offers a full range of 3D printing services for your project needs. Visit our Instant Quote Engine to get a free, no-obligation quote in minutes.
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