Definition and Technology
3D printing definition
It is better to start from the beginning, so please take a quick look at the definition below to get a clear understanding on what 3D printing is.
Additive manufacturing or 3D printing is a process of making three-dimensional, solid objects from a digital model. 3D printing is achieved using additive processes, where an object is created by laying down successive layers of material. 3D printing is considered distinct from traditional machining techniques (subtractive processes) which mostly rely on the removal of material by methods such as cutting and drilling.
The technology is used in jewelry, footwear, industrial design, architecture, engineering and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, and many other fields.
Though the 3D Community is formed around Fused Deposition Modeling (FDM) type printers, this is not the only 3D printing option. The FDM 3D printers are great and will continue to develop, but Makers need high resolution solutions, and this is where resin-based 3D printing enters the game.
Resin Based 3D Printing System
A UV or visible light sensitive monomer called microstereo lithography is used for three-dimensional printing. Using a DLP video projector with a UV output, the printer creates incredibly thin polymer layers and builds objects layer by layer.
For most applications the Ultra Violet or visible light curing method is much faster and superior and to any other rapid modeling methods. The name 3D-printing is actually a misnomer. A better title for it is “Layered UV cured modeling.” Even though this method uses resin to buildup every layer, it is not mechanically applied at every layered level. Because it is a low viscosity liquid, it uses gravity to fill the building gap for the next layer of curing. For that reason we do not categorize it as deposition modeling. Resin-based 3D printing has great resolution and uses minimal moving parts.
There are two major groups for the resin based 3D printers. These are;
○ Bottom up
○ Top down
Bottom-Up style 3D printing
In Bottom-Up process, the light source (DLP projector or UV laser) is placed on top. The elevator platform lowers down in a liquid resin filled tank. A resin-filled blade sweeps across the cross section of the part, re-coating it with fresh material.
Light source generates the part pattern on the surface of the liquid resin. Exposure to the ultraviolet light cures and solidifies the pattern on the resin, joining it to the layer below. After the pattern has been cured, the Stereolithograaphy (SLA) elevator platform descends by a distance equal to the thickness of a single layer, typically 0.05 mm to 0.15 mm (0.002″ to 0.006″). Then, a resin-filled blade sweeps across the cross section of the part, re-coating it with fresh material. On this new liquid surface, the subsequent layer pattern is cured, joining the previous layer. A complete 3-D part is formed by this process.
Top-Down style 3D printing
In the Top-Down process, the light source is placed at the bottom of the system. It projects the 2D cross-sectional image on the build platform. The platform raises a distance equal to the thickness of a single layer the 3D object formed under the build platform. The advantage of this system is that you do not need a tank of liquid resin which may be cost prohibitive. With this system, you simply fill the resin vat with enough resin to create your object.
After the 3D object is built, the parts are immersed in a chemical bath to clean them of excess resin before being cured in an ultraviolet oven.
Digital Light Processing (DLP)
Digital Light Processing (DLP) technology is the heart of our system.
Digital Light Processing (DLP) is a brand of projector technology that uses a digital micromirror device. It was originally developed in 1987 by Dr. Larry Hornbeck of Texas Instruments. DLP is used in a variety of display applications, from traditional static displays to interactive displays and also non-traditional embedded applications including medical, security and industrial uses.
DLP technology can be found in DLP front projectors (standalone projection units primarily used by classrooms and business) as well as DLP rear projection television sets and digital signage. It is also used in about 85% of digital cinema projection.
In DLP projectors, the image is created by microscopically small mirrors that are laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one or more pixels in the projected image. The number of mirrors corresponds to the resolution of the projected image (often half as many mirrors as the advertised resolution due to wobulation). 800×600, 1024×768, 1280×720, and 1920×1080 (HDTV) matrices are some common DMD sizes. These mirrors can be repositioned rapidly to reflect light either through the lens
Advantages and disadvantages
Advantages of resin-based 3D printers:
•For most applications the Ultra Violet or visible light curing method is much faster and far superior to any other rapid modeling methods.
•It has better resolution than FDM printers.
•It uses minimal moving parts.
•Prototypes made by this system are strong enough to be machined and can be used as master patterns for injection molding, thermoforming, blow molding, and various metal casting processes.
Disadvantages of resin-based 3D printers:
•Although the process can produce a wide variety of shapes, it is often expensive. The cost of photo-curable resin ranges from $80 to $210 per liter, and the cost of machines are higher then popular low-level FDM printers. However, costs will be reduced as more people adopt the resin-based 3D printing systems.