Everything You Need to Know about DLP® 3D Printing

DLP® is a light projection technology. DLP 3D printing is used to create high accuracy parts with smooth surfaces, utilizing high-performance materials which add functional properties to the produced parts.  

This makes the technology highly suitable for production parts – a good alternative to injection molding for low volume manufacturing. 

An Introduction to Digital Light Processing (DLP) 

DLP is a digital method of projecting light, meaning it controls individual pixels on the screen: color, brightness, and contrast. At its core, DLP uses a digital micromirror device (DMD) to reflect light to the desired pixels.  

First developed by Texas Instruments in 1987, a DMD is comprised of thousands of microscopic mirrors. Ten years later, Digital Projection used this technology to create the first DLP projector.  

The projector can control each mirror individually to reflect light either towards the screen or away (to a beam dump). Furthermore, the mirrors can be rapidly rotated “on” and “off” to reduce the effective brightness of the color (or grayscale). 

Using DLP for 3D Printing

When it comes to DLP printers, the actual DLP projector is just one component (albeit a critical one) in a complex 3D printing machine. DLP 3D printers have four major components: 

• Resin vat 
• Build platform 
• DLP light source 
• Membrane/separation mechanism 

Here’s how they interact with each other to print a 3D part: 

1. The vat contains a photopolymer resin, meaning a type of plastic that hardens when exposed to light. 

2. A flexible membrane at the bottom of the vat (under the build platform) expands downwards, and a thin layer of resin flows in.

3. The DLP projector hardens an entire slice of the 3D printed part at once, by projecting an image of that slice onto the surface of the resin in the vat. 

4. The membrane contracts upwards to connect to the build platform and a thin layer of resin between the membrane and the build platform is cured. 

5. The build platform is raised (very slightly, this is the Z-axis resolution) to allow more resin to flow underneath. 

6. Steps 2-5 are repeated for each slice until the part is complete. 

Where Does DLP Fit in the World of Additive Manufacturing?

Additive manufacturing (AM) can be categorized in several ways, but perhaps the simplest is to start with the material used. To grossly oversimplify, these are the material categories: 

• Metal 
• Plastics/polymers 
• Thermoplastics 
• Thermosets, also called photopolymers 

All plastic types undergo a change from a more fluid or moldable state to their “end-result” state. The primary difference between thermoplastics and thermosets is the reversibility of this change. Thermoplastics undergo a fully bidirectional process when they harden or set into a “permanent” state.  

This process can be reversed to return the original raw material. By contrast, thermosets – as the name would suggest – are set in place. Once the plastic is cured, it cannot be returned to its original state. 

Another way to look at it is what happens when heat is applied to the set plastic: 

• Thermoplastics melt (and can be rehardened as needed)
• Thermosets burn (and will not return to original moldable state) 

Any given additive manufacturing technology (usually) works with only one type of material category. 

ISO recognizes seven major groups of AM technologies: 

ISO Term	Variations	Material Category Used
Binder jetting		Metal (and other non-plastic materials)
Directed energy deposition	LDW, EBAM, LENS	Metal
Material extrusion	FDM	Thermoplastics
Material jetting	PolyJet	Thermoset
Powder bed fusion	SAF	Thermoplastics
Sheet lamination		Metal
Vat photopolymerization	SLA, DLP, LCD	Thermoset

It is clear from this overview that DLP is most closely related to other forms of vat photopolymerization. That said, it is useful to compare all forms of polymer 3D printing to see when it is best to use DLP, and when other methods would be preferred. 

Advantages of DLP 3D Printing

Every method of additive manufacturing has its pros and cons, and DLP is no exception. That said, DLP may be the best all-around technology. With most AM technologies, there’s a clear tradeoff between aesthetics and performance. 

Fused deposition modeling (FDM) for example, excels when it comes to strength, performance, and durability. However, its accuracy and surface finish aren’t sufficient for certain end use parts. PolyJet on the other hand has surface finish, texture, and color that is truly best-in-class.  

However, most PolyJet materials won’t stand the test of time. Each of these (and other) additive manufacturing technologies are exceptional for certain applications and should of course be used in those cases.  

DLP, on the other hand, combines very good part quality with functional materials and low cost per part. 

Other benefits include: 

• High speed – This is mainly thanks to the fact that the DLP projector cures each layer instantaneously.
• Excellent accuracy and repeatability 
• High resolution and surface tolerance 
• Material versatility – DLP can print a wide variety of functional materials, such as general purpose, tough, elastomers, and heat-resistant products.
• Isotropic parts, meaning uniform properties in X, Y and Z directions.  

DLP vs. SLA vs. LCD: What’s the Difference?
Let’s take a closer look at vat photopolymerization and its various forms.  

Stereolithography (SL or SLA)

SLA shares many features with DLP: 

• They both work with photopolymer resin materials
•  Vat photopolymerization is the base technology 
•   A UV source cures the resin to create a 3D-printed part 

The main differences are related to the type of UV source and direction of printing: 

• SLA uses a UV laser with galvanometer mirrors to direct the UV source to each individual spot that needs to harden. While the laser can scan very quickly, this isn’t going to match the speed of DLP (or LCD) which projects the entire layer image at once. 
  
  
• SLA prints “right side up,” with the laser source hitting the upper surface of the resin. After each layer is complete, the build platform lowers slightly, and the next layer begins. This is a more intuitive way to print, and it removes the necessity for a special membrane mechanism. Instead, a moving blade recoats each layer to ensure that the resin covers the surface of the build uniformly. 
  
  
• SLA uses different UV wavelengths; DLP operates at 385 nm, while SLA works at 355 nm wavelength. (See Wavelength Comparison below for more details.) 

LCD (mSLA) 3D Printing

Schematic of LCD 3D printer, from ResearchGate 

LCD is even more closely related to DLP 3D printing. In this case, both technologies use a projected image to cure each layer at once, and both technologies expose the photopolymer resin from the bottom. Here are the differences between the two: 

Whereas DLP uses a projector with DMD (microscopic mirrors) to reflect UV light onto the photopolymer resin, LCD uses an array of UV LEDs that are partially masked by an LCD screen to determine which points should be cured. For this reason, LCD is sometimes called masked SLA (mSLA) 3D printing. DLP is a more mature AM technology and is based on components that are more reliable and long-lasting, if more expensive. It also provides higher irradiance than LCD, which means it can manage a wider variety of materials. LCD is susceptible to pixel bleeding and uneven degradation of the light source, which is why it’s usually seen more in hobbyist 3D printers, as they can sacrifice some level of repeatability and precision in favor of a lower cost. 

Resin Printer Comparison – Summary

At the risk of overgeneralization, let’s sum up the core differences between DLP, LCD, and SLA printers. Most of the values in the table below vary significantly based on price point, material, and other factors. However, it should provide a general idea of strengths, weaknesses, and when to use each of these 3D printing resin-based technologies:

	SLA	LCD	DLP
Light source wavelength	355 nm	405 nm	385 nm
High performance materials	Broad Range	Limited	Broad range
Print speed	Medium/fast	Very fast	Fast
Build size	Small to Large	Small to medium	Small
Price (hardware)	Medium to high	Low	Medium to high
Accuracy and Precision	Excellent	Medium	Excellent
Typical applications	Functional prototyping  Tools and jigs  Master patterns (investment casting)	Hobbyist use  Some concept modeling	Fit and function prototyping  Tools and jigs  Production parts (low volume or custom)

DLP 3D Printing Applications

DLP is used in a variety of additive manufacturing applications. The common denominator is any case which requires both high part accuracy and precision, or fine surface finish, as well as a high-performance material (such as tough, rigid, elastic, or high temperature resistant materials). Here are some examples of use cases where DLP 3D printing excels: 

• Functional prototypes 
  You can use DLP to print highly sophisticated prototypes that look, feel, and function just like the final product. 
• Jigs & fixtures 
  DLP can print end-of-arm tooling and production aids with mechanical or functional requirements and high accuracy and/or surface finish. In particular, the speed and low cost per part associated with DLP 3D printing make this a prime application. 
• Industrial production parts 
  When it comes to end-use industrial parts, the question is typically about quantity. High volume and mass production usually mean injection molding will be the most cost effective. Below a certain threshold (depending on geometry), additive manufacturing becomes more effective, yielding a lower cost per part. DLP lets you create high-mix/low volume production series for connectors, seals and other parts with mechanical or functional specs. 
• Other tooling applications 
  DLP 3D printing can also be used to make molding tools, even for high temperature, rigid, and durable mold inserts. 

Materials Used with DLP 3D Printing

DLP can 3D print using materials with a variety of properties. Its 385 nm UV light source is well suited to cure a wide range of resin materials. The common denominator of all compatible materials is that they must be a photopolymer. (Remember the whole process of DLP printing is based on curing resin with light.) 

DLP photopolymers can be grouped into the following functional categories: 

• General purpose 
• Tough 
• Elastomers 
• Heat resistant 
• Medical 
• Other/special purpose 

High temperature-resistant materials tend to be more brittle, whereas more elastic or tough materials tend to have lower temperature resistance. This should be kept in mind when determining the material best suited for your application. 

General Purpose DLP Materials

These materials are the jack-of-all-trades when it comes to 3D printing with DLP. They have the following benefits: 

• Good all-around properties 
• Easy to use for printing/processing 
• Suitable for a wide range of applications 

Tough DLP Materials

Tough materials can withstand impact or repetitive motions. While their elasticity can vary, they generally share high impact strength. Tough DLP materials can be categorized by the type of thermoplastic they mimic, e.g.:

• ABS 
• Impact-modified polypropylene 

Elastomers for DLP 3D Printing

These materials mimic rubber in various forms, for application such as: 

• Seals and gaskets 
• Vibration cushioning 
• “Springy” rubber 

Elastomeric photopolymers are quantified by: 

• Shore hardness, where higher values are ascribed to harder materials 
• Tear strength 
• Elongation at break 

Generally speaking, materials with lower Shore values can stretch farther (longer elongation at break). Harder elastomers can be used for form, fit, and functional prototypes, while softer elastomers might be more commonly used in seals and gaskets. 

Heat-Resistant DLP Materials

These are DLP materials that can withstand sustained exposure to heat, typically quantified with a measurement of its heat deflection temperature (HDT). They may also be certified to handle flame, smoke, and toxicity (FST). Heat-resistant materials also tend to resist moisture well, leading to better long-term dimensional stability. Note that high temperature materials usually are more brittle than other categories of materials. Applications involving repeated strain, impact, or risk of dropping should avoid using these materials. 

Medical DLP Materials

High accuracy and smooth surface finish make DLP suitable for printing medical devices, using special medical-grade materials that have been certified according to the relevant regulatory requirements and standards. 

Special-Purpose DLP Materials

The above general categories can be used for many applications. For use cases that require specialized properties (e.g., ESD protection, flame retardancy), other special purpose materials can be used. These 3D materials can be delineated by the traditional thermoplastic material they replace, for example: 

• Nylon 6/12 
• PBT (polybutylene terephthalate) 
• ESD materials
• Aluminum silicate 
• ABS (acrylonitrile butadiene styrene) 
• Polypropylene 
• TPU (thermoplastic polyurethane) 

Designing for DLP 3D Printing

Design for additive manufacturing (DfAM) is the idea that 3D printing doesn’t only start with the actual printer. It starts with the design of a part. Current design is done with the limitations of traditional production methods in mind. As we’re dealing with a fundamentally different method of production, part design shouldn’t be limited by irrelevant restrictions. DfAM lets you harness the full potential of additive manufacturing. 

Why Design for Additive?

When using additive manufacturing for production parts, designing for the technology is critical in order to tap into the true benefits of AM. Good DfAM can help you improve quality, functionality, and throughput, leading to lower overall costs and a greater number of viable applications for additive production. Furthermore, if you design for additive, you can often consolidate parts into a single, integrated part, reducing assembly labor and the quality challenges often linked to precision manual assembly processes.  

How to Design for Additive

Step 1 – Consider the part and application: 

• Is there a suitable AM material available for the application? 
• Will it fit inside the printer’s build volume? 
• Are there any features/walls smaller than 200 μm (0.2 mm)? 
• Are there overhangs? 
• Are supports needed on critical surfaces? 
• Are there areas where resin can’t escape?  

Step 2 – Choose an AM material: 

• Rigid 
• Tough 
• High-temperature 
• Elastomers 
• Special purpose 
• Etc. 

Step 3 – Consider print part orientation: 

• The height (Z-axis) is the primary factor in print time. If possible, orient the part for the shortest possible height. 
• Can a flat surface of your design be placed against the build head for a stable print which requires fewer supports? 

Part orientation can also affect surface quality: 

• The best surface will be a flat surface printed directly parallel to the build platform. Obviously, this doesn’t leave much room for design freedom.  
• The second-best surface quality will be a curved or flat part that is angled to the build head (not a perpendicular flat surface). Most surfaces of most parts will fall into this category.  
• The most challenging surface orientation is a flat surface that is perpendicular to the build platform, as you’ll notice subtle layer lines in the Z direction. This can be mitigated somewhat by using a printer (such as Origin® Two) with a rigid build platform structure, to create a stable and uniform Z-axis. 

Step 4 – Consider support requirements: 

• Will the part need supports? 
• What’s the supporting strategy?
•  Will there be supports on critical surfaces? 
• How tall will the supports be? Taller supports need to be thicker. 
• Materials that print with lower green strength (pre-cure strength) need more supports. 

Step 5 - Cleaning and post-curing: 

• It’s important to consider the cleaning process when designing your part. 
  Viscous resins, like elastomers, will be harder to clean than resins with a lower viscosity, such as rigid materials. 
• Very dense lattices can also be challenging and time-consuming to clean. 
  The key to success in DfAM is to step back and reexamine parts from a system level and optimize parts for weight, performance, and throughput. 

DfAM Example: Support and Nesting Considerations

For example, the venturi valve shown below (as a cross section) is fully self-supporting, as long as it is printed in the orientation shown at left (three ports facing downwards, one upwards). If it were printed in the other orientation, the central internal fluid outlet, (marked in red) would need support. 

However, to print this part in volume, nesting density plays a major role. If all parts had the same orientation, fewer could fit in a single print, reducing throughput. Therefore, there was a need to use both orientations, requiring support for one of them. 

Using support material in DLP is not a problem as such, but in this case, it did pose a challenge. The logical way to add support would be like this (green lines): 

However, placing support structures inside a closed tube would make them almost impossible to cleanly remove. Instead, by slightly altering the design, the venturi valve is fully self-supporting in both orientations: 

This solution adds self-supporting buttresses (highlighted blue) connecting the side wall and the central internal fluid outlet to support the unsupported port while still allowing unimpeded airflow. 

Future Trends in DLP 3D Printing Technology 

DLP 3D printing technology is already used to print high quality, repeatable, fully functional parts. And it’s poised to get even better: 

• More materials with new properties, even better performance, supporting a wider range of industry standards 
• A continued reduction in cost per part, thanks to improvements in printer performance, economies of scale in printer manufacturing, as well as advances in software that allow for more parts nested in a single build 
• Faster throughput 
• Sustainable resin, made from plant-based or renewable sources 
• Multi-material 3D printing 
• Additional automation (e.g., auto-calibration) to improve repeatability, reduce errors, minimize manual labor, and scale for production. 

DLP 3D Printing: FAQs

1. What is DLP 3D technology, and how does it work? 

Digital light processing (DLP) is a display technology used in projectors and 3D printers. It uses digital micromirror devices (DMD) to reflect light and create images. In 3D printing, DLP printers use a digital light source to cure liquid resin layer by layer to build a 3D object. 

2. What are common issues with DLP 3D printers? 

Common issues with DLP 3D printers include poor print quality, misaligned prints, resin not curing properly, layer separation, and print failures due to incorrect exposure time or damaged projector components. (See next question to avoid these issues.) 

3. How can I fix poor print quality in DLP printing? 

Follow these best practices to fix poor print quality: 

• Check the tray and vat for dust/dirt. 
• Ensure proper calibration of the printer.
•  Use high-quality resin within its shelf-life timeframe. 
• Make sure that the build platform is clean and leveled before starting the print. 

4. What are the advantages of DLP over other 3D printing technologies? 

DLP offers faster printing speeds compared to other resin technologies like SLA, thanks to its ability to cure entire layers at once. It also delivers high-resolution prints with high accuracy (up to 50 µm in some systems), fine details, and smooth surfaces, making it ideal for intricate models, ergonomic tooling, and dental applications.  

In addition, it can print high performance materials for various applications. 

5. What materials can be used in DLP 3D printing? 

DLP 3D printers use liquid resins that are cured by light at 385 nm wavelength. These resins come in various formulations, including general-purpose resins, tough resins, flexible resins, and biocompatible resins, allowing for different applications ranging from prototyping to low volume manufacturing. 

6. Is DLP suitable for large-format 3D printing? 

DLP is better suited for smaller to medium-sized prints, as it projects light onto a build platform and cures the resin layer by layer. Large prints may require longer curing times and may not be as practical with DLP technology. For large prints, other technologies like stereolithography (SLA) or fused deposition modeling (FDM) might be more efficient. 

7. How precise is DLP 3D printing? 

DLP technology is known for its high precision and fine detail. It can achieve print resolutions as small as 50 microns (0.05 mm), making it ideal for detailed models and end use parts, which require high accuracy and tight tolerances. 

8. What industries use DLP 3D printing technology? 

DLP technology is used across various industries, including automotive, aerospace, consumer applications, industrial machinery components, and others. These industries use DLP to print prototypes, manufacturing aids, and end-use production parts.  

It's also widely used in healthcare for creating dental models and implants, as well as components for medical devices and equipment. 

9. What are the key differences between DLP and LCD 3D printing? 

• Light source: DLP uses a digital projector, while LCD uses an array of LEDs. LCD can be less uniform and suffer from “pixel bleed.”    
• Curing: LCD technology often has lower irradiance which can cause inferior mechanical properties, and/or require more supports.   
• Resolution: DLP has a maximum 4K resolution. The bigger the projected area, the bigger the projected pixels (and the lower the resolution). LCD screens can be made in larger sizes, so LCD technology is better suited for printing larger objects.  
• Tolerances: The DMD chip (DLP’s underlying technology) is manufactured with very tight tolerances, whereas the LCD panel is made to be inexpensive.
• Wavelength: LCD technology uses 405 nm light, whereas DLP incorporates a 385 nm light source. DLP can print a wider range of materials – especially high-performance resins. 
• Purchase price: LCD technology is typically cheaper than DLP technology. LCD printers have a simpler design and require fewer expensive components, making them more suitable for a limited budget.   
• TCO: As the UV light quickly degrades the LCD printer’s screen, it needs to be replaced often. This makes it a consumable item that can add to the overall cost of operating an LCD printer. The initial cost of a DLP printer is higher though costs less to operate. When comparing the cost of different technologies, make sure to calculate Total Cost of Ownership rather than only the purchase price of the printer. 

10. What are the key differences between DLP and SLA 3D printing? 

Both DLP and SLA use light to cure resin, but the key difference lies in how they project the light. DLP uses a digital projector to cure an entire layer at once, whereas SLA uses a laser that traces the shape of each layer.  

The technologies also use different wavelengths, which require different materials, thus making them suitable for different applications. DLP tends to enable higher performance materials and be faster than SLA, while SLA enables larger parts. Both provide high-quality prints. 

11. What are the key components of a DLP 3D printer? 

The main components of a DLP 3D printer include the digital light source (projector), the resin vat, and the build platform (where the print is created). Heaters are optional but allow for a broader range of materials, including high performance materials. 

12. Can DLP 3D printers print multiple materials at once? 

Currently, most DLP 3D printers are designed to print using a single material at a time. However, some advanced systems can support multi-material printing by using different resins in different layers or by switching between resins during the print, but this is less common and requires specific setups. 

Stratasys P3™ DLP Technology 

P3™ is our patented version of DLP technology, using programmable photopolymerization. While all DLP 3D printers are based on the second two ‘P’s (photopolymerization), Stratasys Origin printers add a tight, closed-loop system of sensors that allow full control over the process, including: 

• Light 
• Temperature 
• Pull forces 
• Pneumatics (more on this soon) 

Keeping a close eye on these parameters not only allows power users an extremely granular level of process control, but also makes for a very reliable and repeatable process. P3 DLP technology is also unique for its patented pneumatic separation mechanism. All DLP machines must have some separation mechanism, as the layers are printed at the bottom of the vat. The part is built layer by layer from the bottom up, with the platform rising slightly after each layer is printed. (See above, “Using DLP for 3D Printing.”) Without a separation mechanism, the last printed layer can stick to the bottom of the machine instead of to the build platform or partially built part. 

There are various ways to overcome this issue, but not all are created equal. 

The P3 patented pneumatic method applies a separation force which gradually peels the new layer off the membrane instead of releasing the full layer in one go.  

P3 DLP uses a pneumatic separation mechanism to apply far less separation force. The membrane gradually peels off each cured layer as the build platform goes up.

This method has several advantages: 

• It allows for very high surface finish. 
• Delicate features can be printed without breaking during the separation process.
•  Large cross sections can be printed. 
• Less support material is needed (meaning less post-processing required). 
• Maximum geometric flexibility can be achieved. 

DLP 3D Printing Case Studies H3 

DLP is used in a variety of industries which require high accuracy, reliability, high quality surface finish, and high-performance materials. The main industries which use DLP successfully include: 

• Automotive 
• Aerospace 
• Other transportation, such as railway and industrial vehicles 
• Consumer applications 
• Industrial machinery components 
• Dental 
• Medical devices 

Below are a few examples of case studies from some of our customers. 

Automotive Tooling: Valiant TMS 

Challenge: 

Valiant TMS makes production automation systems in the automotive and aerospace industries. When working on a handle for manual operation, they struggled to meet all requirements in one part: ergonomic, strong, and lightweight. 

Solution: 

Each requirement helped to narrow down their options: 

• Lightweight – plastic (not metal) 
• Strong – use a tough material 
• Ergonomic – high surface finish 

For any two of the three requirements above, there would be more freedom to pursue alternate solutions. But to meet all three, DLP 3D printing was the best (perhaps the only) solution. 

See full case study here: 
P3 Technology produces the right 3D printed surface finish for Valiant TMS 

Stratasys Origin Two DLP Printer 

Building on Origin One’s excellent foundation, Origin Two made several improvements for use in manufacturing: 

• Accuracy and tolerances of ±50 μm for validated applications (otherwise, ±100 μm) 
• Injection molded surface finish 
• Repeatability and control 
• High precision build platform 
• Automatic calibration 

Conclusion 

There’s no such thing as a magic bullet, one-size-fits-all solution to every problem. But DLP might be the closest thing when it comes to 3D printing. It offers a unique combination of high performance materials, reliability, and aesthetics. 

For more information about our DLP printer Origin Two, click here.