3D Printing – Difference between SLA, DLP, and LCD

July 12, 2021 7 min read

Are you just embarking on your dental 3D printing journey and trying to make an informed decision on which printer to purchase?
You probably have heard of SLA, DLP, andLCD 3D printers – but unless you have done some thorough research, you might still be confused about what these abbreviations mean and which impact they have on your dental lab or clinic. 
We’re here to help you out – Let’s cover the basics first:

 

 Why these 3 types of 3D printers? 

They are the most commonly used 3D printing technologies in the dental industry. All three use photosensitive resins, which means that layer by layer is cured using a light source. This process transforms liquid resins into solid layers and, eventually, whole parts.
This makes it sound like the 3 technologies are the same – but they’re not. 

 

Do I just need to buy a 3D printer?

No, you will need to:

Ackuretta 3D printing solutions ecosystem

Here are our quick facts: 

 

SLA

DLP

LCD

Technology

The light source is a laser that moves across the resin tank.

Projection using a mask – giving shape to the print.

Projection but with LEDs exposing light through the LCD screen

Resolution Performance
High resolution = smooth 3D print surface

High-end SLA printers = very smooth

Least smooth results = unsuitable for dental application

Smooth results = suitable for dental applications

Accuracy and Precision

High accuracy + high precision 

Comparably lower accuracy + precision

Almost as accurate and precise as SLA

Speed

Slow – 8mm/hour to 16mm/hour

Fastest – 30 to 60 mm/hour.

15mm to 50mm/hr

Overall

Ideal for Dental Professionals

Less ideal for delicate parts & patient care

Ideal for Dental Professionals

Types of printers

Stereolithography (SLA)

SLA was the first 3D printing technology produced and currently is considered to be one of the most accurate processes on the market. Since it was first developed in the 1980s, not much has changed. 


Unlike DLP and LCD technologies, the light source used is a laser. The laser beam sweeps across the resin tank and solidifies the material layer by layer. Today you can find two different types of SLA printers: 1) the laser acts from top to bottom and a plate that will descend with each new layer and 2) the laser acts from the bottom up including a platform that will rise as well.

 

Digital Light Processing (DLP)

DLP 3D Printing

Digital Light Processing was invented in 1987 by Texas Instruments and originally applied in the production of projectors. 

In 3D printing, DLP does not use a laser, but a projector. The moment the light hits the resin, it’s not restricted to a single spot as with SLA. Instead, the whole layer is formed at once. Here, patterning of the illumination is critical to achieving the desired shape for each layer. This is accomplished by using a “mask”, which is produced by a digital micromirror device (DMD). This part sits between the optical path of the lamp and the resin. One example of a high-volume producing DLP printer is Ackuretta’s 

DIPLO, seen in the image above.

 

Liquid Crystal Display (LCD)

DENTIQ LCD 3D Printer

LCD 3D printing is very similar to DLP, as it flashes entire layers at once curing resin inside the resin tank. What differentiates the two technologies is the light source. LCD technology does not employ a projector, but an array of LEDs exposing the UV light through an LCD screen. The screen only lets the light pass through areas that are to be cured, simplifying the process and removing the need for any moving parts. It is a simpler and robust construction, relatively easy to assemble. 

An example of a specialized dental 3D LCD printers are Ackuretta’s DENTIQ and SOL.

QUALITY

In reality, the print quality of an LCD 3D printer compared to a DLP or SLA 3D printer depends on the 3D printer used and its components. The 3D print quality is heavily influenced by four key factors: resolution, accuracy, precision, and maybe less importantly, speed. Thus, finding a printer that fulfills the standards you set for your dental applications, has to be measured along with those criteria. Of course, a 3D printer will only perform well if it is paired with a good design, high-quality resins, and a well-executed post-processing procedure.

 

RESOLUTION

Let’s cover the technical aspect – for each type of 3D printer resolution is defined as follows:

  • LCD 3D Printers: XY resolution is defined by the pixel size of the printer’s LCD. In the case of Ackuretta’s DENTIQ, the resolution is 47 μm.
  • DLP 3D Printers: XY resolution is determined by the pixel size of the tiny mirrors on the DMD.
  • SLA 3D Printers: XY resolution will depend on the average spot size of the laser beam and the increments at which the laser beam is controlled.

What does this mean for me?

If it ends up in your patient’s mouth, it should be smooth → so pick SLA or LCD printers. 


The resolution has only a very minimal impact on the accuracy of the print. Its major role in 3D printing is the smoothness of the application’s surface. High-end SLA printers will produce parts that are smooth as silk. LCD printers coming in a close second. Comparably, DLP printers produce less smooth results and thus, are not ideal for dental applications such as temporary crowns or dentures. 

 

 

ACCURACY AND PRECISION

Dart Board Accurate and Precise
Sounds like it means the same thing – turns out, it doesn’t. We must first define a goal to be able to measure accuracy. 
Let’s draw a mental picture here. Imagine you are playing darts – your goal is to ALWAYS hit the two bull’s eye circles.
  1. If all your darts are close to each other next or inside the bull’s eye, then you have achieved high accuracy and high precision. Exemplified by the image on the right.

  2. You will have low accuracy, but high precision if all your darts are on the number 7 field closely next to each other. But obviously, you did not achieve your goal of hitting the bull’s eye. Thus, your result is inaccurate. 

  3. This in turn means if all your darts are scattered but at least close to the bull’s eye, then you will have an accurate result that’s not very precise.

  4. Finally, the picture below shows you what low precision and low accuracy look like. All your darts are far apart and none achieved the goal of hitting the bull’s eye.

So what’s my goal in 3D printing? 

Bull's Eye

You want the end result to be as close as possible to your original CAD design – your personal bull’s eye. Thus, if your end result fits perfectly with what you need, then you know your print is accurate.

 And how do I measure precision?

Precision measures repeatability. In other words, outcome consistency, which translates into reliability. This is especially important if you need several dental models for one patient – ideally, all of them are exactly the same.

How is this relevant for my 3D printing process?

3D printer manufacturers will give you a spec sheet for each 3D printer and might claim that high resolution equals high precision and accuracy – that’s not correct!
Actually, accuracy and precision depend on several factors: printer quality, technology, resins, software settings, finishing process, and calibration, therefore a printer can only be judged by its final outcome.

 

So which 3D printer produces accurate and precise results?

Least precise & least accurate: With DLP projectors, manufacturers need to deal with the non-uniform light distribution on the build plane and optical distortion of the lenses. 


Most precise & most accurate: SLA 3D printers use the same light source for every part of the print, which means it’s uniform by definition, but they still require extensive calibration to account for distortions.


Very precise & very accurate: LCD 3D printers are getting close to the accuracy and precision provided by traditional SLA 3D printers. Proper calibration components make sure that each resin layer receives an equal amount of UV lighting during the printing process, increasing the efficiency of how light passes through the LCD screen and at the same time projecting each pixel size precisely and accurately. But of course, the quality of your LCD printer depends heavily on the manufacturer – be sure to only buy from companies that you can trust. 

How do I know I am buying a high-quality printer?

It is advisable to evaluate accuracy tests with real scan data of printed parts. Before buying a printer, ask for a print sample to compare with the original design. If you see there are noticeable differences, don’t buy that printer – Here at Ackuretta, we are sure your patients would like to have parts in their mouth that fit perfectly. 

 

(No) Need for SPEED?

Ackuretta SOL LCD 3D Printer

As we said before, the potentially most accurate and precise printers are SLA. But they are by far the slowest. Because of the highly localized nature of its polymerization approach, it could print something the height of a coin in 4 hours. Print speed ranges from 8mm/hour to 16mm/hour

 

DLP printers are the fastest in the 3D printing industry – They will give you a coin in 2 hours – at a rate of 30 to 60 mm/hour. You start to really compromise on accuracy and precision with any print larger than 200 x 120 mm. However, dentistry is not an industry that forgives inaccuracy, which is why we recommend LCD 3D printers, like our Ackuretta – SOL and DENTIQ.

 

Why do we think LCD combines the best of both worlds for dental professionals?

 

An LCD 3D printer takes about 2.5 hours to print a coin – which is significantly faster than most SLA printers and just slightly slower than DLP. High-quality 3D printers can produce prints up to 350mm x 200mm by curing an entire layer of resin at once, while not comprising the accuracy or precision of the design. With a printing speed anywhere between 15mm to 50mm/hr, LCD 3D printers are gaining popularity for both small and large print areas.


Specialized LCD 3D printers will give you repeatable, accurate results at a fairly fast speed. You are best served to buy a quality printer that was custom-designed for dental professionals. 

 

CONCLUSION

If you’re choosing between an SLA, DLP, or LCD 3D printer, what’s best for you depends largely on your printing priorities. For dental professionals, we recommend prioritizing accuracy, precision, and high resolution as those have an immediate impact on your patients. 


If you need a printer capable of producing dental models, pick a printer that specializes in that. If you’re a professional who needs high detail and fast print speeds, you might want to look into professional LCD printers like Ackuretta’s DENTIQ, which is suitable for beginners in resin 3D printing as well. For high production volume and consistency, the DLP powerhouse DIPLO is ideal.

However, the company behind the 3D printer might be the most important part of this purchase


From our experience, we can tell you that dental labs or clinics require specialized 3D printers that come with an all-around solution, including not just biocompatible materials and finishing kits that ensure the safety and quality of the end results, but also reliable and multilingual customer service. 

 

Julia Kemmesies
Julia Kemmesies



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