SLA vs Polyjet: A Complete Guide
Numerous 3D printing technologies are available today. Learning the ins and outs of each technology will help you determine which one is best suited to your needs by providing a clearer picture of what to expect from final prints.
For resin 3D printing, two common processes are PolyJet and Stereolithography (SLA). These two methods are well-liked because they can make parts and prototypes of industrial quality in a variety of high-tech materials with precise dimensions, homogeneous internal structures, and a flawless surface.
Here, we'll compare PolyJet and SLA 3D printers side by side and help you choose the best one for your company by going over all the important details, including how much they cost, print quality, materials, applications, workflow, speed, and more.
What Is PolyJet 3D Printing?
PolyJet is an additive manufacturing process that uses material jetting. Stratasys acquired Objet, the company that developed the technology. While Stratasys does sell other material jetting printers, none of them go by the name PolyJet.
In contrast to conventional inkjet printers, which jet tiny droplets of ink, PolyJet 3D printers cure tiny drops of photopolymer plastic. Printing involves a print head moving in an X and Y axis across the build platform, spraying resin droplets onto the platform. The print head's ultraviolet light cures the build platform's droplets simultaneously with the movement. With one layer finished, the built platform descends to make room for the print head to distribute a second layer. Once this happens, the printed object will keep expanding until the procedure is complete.
The 3D printer spits out a detachable gel-like substance to help with more complicated geometries, like overhangs. The print heads can also combine different materials to create new ones, each with its own color palette and properties.
What Is SLA 3D Printing?
The original 3D printing method, stereolithography, emerged in the 1980s and remains a favorite among experts today. SLA 3D printers employ photopolymerization, a laser-assisted curing process, to transform liquid resin into solid plastic.
To facilitate the delicate removal of freshly formed layers, stereolithography (SLA) 3D printers include a resin tank with a see-through bottom and non-stick surface that acts as a support for the curing liquid resin.
As the build platform drops into the resin tank, the printing process begins, making sure there's enough room between the platform and the bottom of the tank to accommodate the height of the last completed layer or the build platform. Two mirror galvanometers focus the laser beam onto the appropriate locations on a grid of mirrors, which in turn focus the beam upward through the tank's base, curing a layer of resin. Separating the cured layer from the tank bottom allows fresh resin to flow beneath the build platform, which in turn raises the platform. This continues until the print job is finished.
As a next step in SLA 3D printing, Formlab 3+ and Formlab 3L utilize Low Force Stereolithography (LFS) technology. A Light Processing Unit (LPU) houses the optics in LFS 3D printers. An LPU galvanometer guides the high-density laser beam through a spatial filter, a fold mirror, and a parabolic mirror in the Y direction. This arrangement guarantees that the beam is always perpendicular to the build plane and produces accurate, repeatable prints. By slowly peeling the printed part away from the tank's flexible bottom as the LPU travels in the X direction, the print process puts much less stress on the parts.
Surface quality and print accuracy are both significantly enhanced by this state-of-the-art stereolithography process. The process has opened up a world of possibilities for advanced, production-ready materials, and lower print forces make it possible for light-touch support structures to tear away easily.
Similarities Between SLA and PolyJet
Among the several advanced 3D printing techniques now in use, PolyJet and SLA stand out for their remarkable accuracy and detail. Though they differ from one another, they share many worthwhile characteristics.
1. Changes Over Time With Light and Heat Exposure
Prints produced using SLA or PolyJet technology may fade under direct sunlight or at extremely high temperatures. This can cause the printed components to fade in color and lose structural integrity over time.
2. Accuracy and Fragrance
Two of the best technologies for creating intricately detailed components are SLA and PolyJet. Both can create thorough prototypes despite their differences, which is fantastic for industries including engineering, dentistry, and jewelry that depend on accuracy.
3. Fast Prototyping and Manufacturing
Owing to their fast printing speeds, both technologies are fantastic for quick prototypes and production. Using PolyJet or SLA means you won't have to compromise speed for quality.
4. Industrial Uses and Cost Range
Although PolyJet and SLA have different price points, industrial environments find great use for both. PolyJet printers are typically more expensive; you can find both technologies in machines ranging in cost from $1,200 to almost $100,000. The features and capabilities of the machine determine the price rather directly.
Differences Between SLA and PolyJet
Though they have many things in common, SLA and PolyJet differ greatly in key respects that affect their performance, material capabilities, and fit for particular uses.
1. UV-Curable Materials
PolyJet's focus is on photopolymer resins that cure UV light. The printing process solidifies successive layers of a liquid material using UV light. This makes it possible to print both precise details and use several materials.
Selective laser lithography (SLA) is based on layer-by-layer curing performed under a laser rather than UV light. The technique uses a different approach to curing photopolymers, but the end result stays a solid printed object.
2. Capacity to Manage Several Materials
PolyJet technology offers a big advantage in that it can print concurrently using many materials. This opens the path for the synthesis of complex parts with different colors, textures, and qualities.
With SLA, printing several materials is not feasible. It cannot create very complex builds with a broad spectrum of textures and finishes since it just uses one type of resin for every print.
3. Tensile Strength
Usually, PolyJet parts have great tensile strength. Printed in fine layers and composed of UV-curable materials, parts created thus are strong and long-lasting.
Generally speaking, SLA prints have less tensile strength than PolyJet prints. Although the material may not be as strong, detailed prototypes—instead of functional components—are better produced using SLA because of their great degree of detail.
4. Layer Thickness
PolyJet technology allows remarkably thin layers, enabling a minimum layer thickness of 16 microns. The surfaces are thus smoother, and the models have more detail.
For stereolithography (SLA) printers, the bare minimum layer thickness is roughly 50 microns. PolyJet's finer layer resolution, compared to other techniques, lets more detailed and smoother finishes without compromising accuracy.
5. Resolution
PolyJet offers exceptional resolution with a layer size ranging from 0.00063 inches. This makes it ideal for printing extremely small, highly detailed prototypes or incredibly delicate components.
Although PolyJet boasts ultra-fine resolution, SLA typically generates decent resolution ranging from 0.005 to 0.002 inches. Still, for most complex applications SLA stays accurate enough.
6. Color Options
One of PolyJet's main points of appeal is its capability to print in a range of colors—translucent, opaque, and even mixed colors. It's amazing because it allows one to produce prototypes almost exactly like the finished goods.
Usually grey or clear resins, SLA prints restrict the color spectrum. You might have to post-process in order to acquire the desired colors or finishes.
Best 3D Printing Software: SelfCAD
Having looked at the various 3D printing technologies, it’s also important to have a look at the best CAD software that you can use to design, customize the files, or even prepare them for 3D printing. Many are available, but we recommend using SelfCAD. It is one of the easiest 3D design software available that you can use to create simple and complex 3D models. It comes with all the necessary tools to bring your ideas to life.
After 3D modeling, the software comes with an in-built online slicer that you can use to slice your files and generate the G-code to send to your 3D printer.
SelfCAD also comes with many learning resources, including the SelfCAD academy, interactive tutorials, and many YouTube videos. It’s also affordable, and there is a free version that you can use to test the software and see if it’s fine with you.
Choose Smarter, Print Better
A trademark of PolyJet and SLA 3D printing technologies is their ability to create exact and detailed prototypes. Still, your personal needs will guide which one is best for you. If you need high-quality printing, a rainbow of colors, and the ability to work with several materials, PolyJet is the choice for you. Its strong points are detailed prototypes, parts constructed of several materials, and quick production.
Conversely, if you want great accuracy at a reasonable cost over a range of diameters, SLA could be the better choice. Regarding large models and complex designs, SLA performs better than multi-material printing as well. Knowing the differences between these two technologies will help you decide which 3D printing technique—functional part, complex model, prototype, or another—best fits your project.
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