Pegasus sla 3d printer

1) 2) 3)

1) A platform is placed in the tank with liquid photopolymer, at the same height from the resin surface.

2) The UV laser then selectively cures the required areas of the photopolymer resin according to a predetermined algorithm.

The laser beam is focused on a given path using a set of mirrors called galvos. Then the entire cross-sectional area of ​​the model is illuminated. Therefore, the resulting part is completely solid.

3) When one layer is finished, the platform moves to a safe distance and the mixing foot inside the tub mixes the resin.

This process is repeated until the part is printed. After printing, the part is not fully cured and requires further post-processing under the UV lamp . At the end of UV illumination, the part acquires very high mechanical and thermal properties.

The liquid resin solidifies through a process called photopolymerization: during solidification, the monomer carbon chains that make up the liquid resin are activated by an ultraviolet laser and become solid, creating strong, inextricable bonds with each other.

The photopolymerization process is irreversible, and there is no way to convert the resulting parts back into a liquid state. When heated, they will burn, not melt. This is because the materials that are produced by SLA technology are made from thermoset polymers, as opposed to the thermoplastics that FDM uses.

On SLA systems, most print settings are set by the manufacturer and cannot be changed. The only inputs are the layer height and the part orientation ( last, locates the supports ).

The typical layer height in a SLA print ranges from 25 to 100 micron .

The lower the layer height, the more accurately the complex geometry of the model will be printed, but at the same time the printing time and the likelihood of failure will increase. A layer height of 100 microns is suitable for most common geometries and is the golden mean.

Another important parameter for the operator is the size of the platform. It depends on the type of SLA printer. There are two main types: orientation top to bottom and orientation from bottom to top .

In the first case, the laser is above the tank, and the part is face up. The platform sits at the very top of the resin vat and moves down after each layer is sintered.

In " bottom up " layout on SLA printers , the light source is placed under the resin tank (see picture above) , and the part is built upside down.

The tank has a transparent bottom with a silicone coating that allows the beam of light to pass through but prevents the cured resin from sticking. After each layer, the cured resin separates from the bottom of the tank as the platform moves up. This is called the sintering step.

The orientation " bottom to top " is mostly used in desktop printers like Formlabs. The " top - down " orientation is used in the industrial SLA printer .

Printers SLA " bottom-up " are easier to manufacture and operate, but the size of the possible print will be smaller, since the forces applied to the part during the sintering stage can cause printing to fail.

Top-down printers, on the other hand, can print very large parts without much loss in accuracy. The wide possibilities of such systems naturally cost more.

The following are the main characteristics and differences between the two orientations:

Popular brands:

FORMLABS

Printable area: Up to 145 x 145 x 175 mm

Typical layer height and print accuracy: 25 to 100 µm and ± 0. 5% (lower limit: ± 0.010 to 0.250 mm) respectively

Popular brands:

PRISMLAB

Print area size: Up to 1500 x 750 x 500 mm

Typical layer height and print accuracy: 25 to 150 µm and ± 0.15% (lower limit ± 0.010 to 0.030 mm) respectively

Supports are always required at Print SLA . Structural structures are printed from the same material as the part and must be manually removed after printing.

Part orientation determines the location and amount of supports. It is recommended that the part be oriented so that surfaces that require maximum quality do not come into contact with supports.

In different types of SLA printers, support is used in different ways:

For top - down printers , support requirements are the same as FDM . They are essential for accurate printing of overhangs and bridges ( the critical overhang angle is typically 30 degrees ).

The part can be oriented in any position and is usually printed flat to minimize the number of supports and the total number of layers.

In printers like " from bottom to top " everything is more complicated. Overhangs and bridges also need to be supported, but minimizing the cross-sectional area of ​​each layer is the most important criterion.

Forces applied to the part during the sintering step can cause it to come off the platform. These forces are proportional to the cross-sectional area of ​​each layer.

For this reason, the parts must be oriented at an angle, and minimizing supports here is not a primary concern.

On the left - a detail oriented on the SLA printer "from top to bottom" (support minimization).

On the right is a part oriented on the SLA printer "from the bottom up" (minimizing the cross-sectional area).

Removing supports for an SLA printed part

One of the biggest problems with the accuracy of parts made with SLA is curling. This problem is similar to the deformation in FDM when materials shrink.

During curing, the resin shrinks slightly when exposed to the printer's light source. When shrinkage is significant, large internal stresses develop between the new layer and the previously cured material, causing the part to twist.

SLA printed parts have isotropic mechanical properties. This is due to the fact that one pass UV beam is not enough to completely cure the liquid resin.

Further passes help the previously hardened layers to fuse together. In fact, in the SLA of printing, curing continues even after the printing process is complete.

To achieve the best mechanical properties, parts printed using this technology should be post-cured by placing them in a chamber under intense ultraviolet radiation ( and sometimes at elevated temperatures ).

This greatly increases the hardness and heat resistance of SLA , but does not make it stronger. Rather the opposite.

For example.

materials

Photopolymer resins (thermosetting

materials)

Dimensional accuracy

± 0.5% (lower limit: ± 0.10 mm) - domestic
± 0.15% (lower limit ± 0.01 mm) - industrial

typical size

print area

Up to 145 x 145 x 175 mm - for desktop printers
Up to 1500 x 750 x 500 mm - for industrial

Total layer thickness

25 - 100 µm

Support

Always required

(Needed to make an accurate part)

• SLA print is best for producing visual prototypes with very smooth surfaces and very fine detail.

• Desktop SLA 3 D The printer is ideal for making small, about the size of an adult's fist, injection molded parts. Moreover, such a printer can be purchased at an affordable price.

• Industrial SLA 3 D printers can produce very large parts (up to 1500 x 750 x 500 mm)

Well, that's all we have! Thank you for being with us, see you soon. Further it will be more interesting!

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Author: Aleksey Chekhovich

Author: Aleksey Chekhovich

SLA: laser stereolithography | DLP: Digital Light Processing | LCD: photopolymerization with LCD screen | The main differences between the three technologies | Print Quality Comparison | Comparison of 3D printers | Comparison of photopolymers | Print speed | Conclusion

SLA, DLP and LCD are three similar technologies for stereolithographic 3D printing, and users often have a question: which method to choose for additive manufacturing tasks?

All three technologies are based on the use of a photopolymer resin that is layer-by-layer cured during printing in a special tank of a 3D printer, in other words, on the process of photopolymerization in a bath. Let's look at the differences to consider when buying a 3D printer (SLA, DLP or LCD) or when using a 3D service.

We will select a 3D printer for your production tasks! Call +7 (495) 223‑02‑06 or leave an online request for a free consultation:

Book a consultation with 3D experts

SLA: Laser Stereolithography

SLA (Stereolithography Apparatus) is the oldest additive technology. It was introduced in the mid-1980s by 3D Systems. The invention of SLA more than thirty years ago marked the beginning of 3D printing, which has changed millions of lives.

SLA printers use a laser. It selectively illuminates the photopolymer resin in the printer's tank. The laser beam shines on the bottom of the tank and is guided by mirror galvanometers to the precise area to be cured.

This continues until the layer is completely cured, then the build platform is raised one layer, and the process is repeated until the model is printed.

DLP: Digital Light Processing

The DLP (Digital Light Processing) method was invented somewhat later - at 1987 by Larry Hornbeck of Texas Instruments, though not for additive manufacturing, but for film projection, where this technology has found wide application.

DLP printing uses a projector rather than a UV laser like SLA. The projector emits light at once on the entire layer of resin, selectively curing the part with the help of thousands of tiny mirrors, called digital micromirror devices (DMD), directing the light projection.

These projectors use pixels to create images and layers are made up of voxels, just like conventional 2D or 3D cameras.

LCD: photopolymerization with LCD screen

Recently, inexpensive LCD printers have become popular, offering better quality than FDM machines at the same price. This type of photopolymer printer uses LED-backlit liquid crystal panels to cure the resin, similar to DLP-based equipment.

As in the case of DLP, LCD printing consists in the simultaneous illumination of entire layers to cure the photopolymer, but without the use of mirrors. Instead, powerful LCD panels emit light onto the model using LEDs. The LCD panel blocks backlight in areas that cannot be cured.

The LCD screen only allows light to pass through the areas to be cured onto the finished part, simplifying the process and eliminating the need for any mirrors or galvanometers.

Key Differences Between SLA, DLP and LCD

Although SLA, DLP, and LCD technologies are similar in many ways—they are all based on the layer-by-layer curing of photopolymer resin—there are a few key differences between them.

The main difference between SLA and DLP/LCD is the method used for photopolymerization.

DLP uses a projector, LCD uses an LCD screen, and SLA uses a UV laser to mark the dimensions of the printed model. DLP and LCD printers are faster than SLA machines because they can create entire layers at the same time, while laser stereolithography requires manual tracking of the dimensions of each layer with a laser.

The RAYSHAPE Shape 1+ Professional DLP Printer is a compact solution ideal for a dental or manufacturing lab

There is another less significant but noteworthy difference: DLP printers usually have smaller resin tanks. If you want to save money, then this will be an advantage: the consumption of unused expensive resin will decrease.

Print Quality Comparison

Resin 3D printing is known as one of the most precise additive processes, and even budget LCD printers are capable of creating complex geometries that technologies like FDM simply cannot match.

An example of LCD printing of industrial parts

The print quality of an LCD printer compared to a DLP/SLA printer depends on the specific hardware. An expensive SLA machine is expected to be much better than a budget DLP due to higher quality components and better resolution and accuracy.

The technologies themselves are similar in their ability to create accurate models, and it is execution that affects quality.

Comparison of 3D printers

Do you hesitate between SLA and DLP printers? Analyze your 3D printing priorities.

If print speed is most important to you, choose a DLP solution, in most cases it will provide significantly better performance.

If you value reliability, choose a brand known for print quality. To reiterate, the differences in technologies are not so great as to make a choice between them; choose a printer based on your individual requirements.

Likewise, if you're making molds for jewelry or dental models, choose a 3D printer that's designed for those tasks.

Printing Dental Products with the Wiibox 280 Plus LCD Printer at 5K Resolution

If you're looking for a cheaper printer that can print usable prototypes at home and are satisfied with slightly worse print quality, get an LCD printer.

Photopolymer comparison

Some photopolymer resins are suitable for both DLP and SLA installations, as well as for DLP and LCD printers. But this is not always the case. Some equipment manufacturers provide an open material system (i.e. use any third-party photopolymers), while others restrict their use to their proprietary materials.

The choice of photopolymer depends on the goals you want to achieve with SLA, DLP, or LCD printing. There are basic resins for hobbyist projects, and there are specialized resins for 3D printing casting models, dental, engineering or jewelry.

Photopolymer resin in containers and products created by DLP printing

Higher-quality industrial and professional grade photopolymers cost more. Budget materials, in turn, will not provide the same level of quality in production, even on high-end printers.

When choosing a photopolymer, you need to find out the wavelength of the printer's light source. It is also indicated on the consumable. The most popular SLA/DLP/LCD printers on the market today use 405nm illumination and related resins.

Print speed

In the SLA machine, the laser passes through every part of the cured part, while DLP and LCD-based equipment can instantly cure entire layers. Thus, DLP and LCD technologies provide faster printing than SLA.

When comparing the speed of DLP and LCD printing, it depends on the 3D printer.

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