Stereolithography (SLA)

Stereo lithography

Stereolithography (SLA or SL; also known as Stereolithography apparatusoptical fabricationphoto-solidification, or resin printing) is a form of 3-D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photopolymerization, a process by which light causes chains of molecules to link together, forming polymers. Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Charles (Chuck) W. Hull in 1986 when he patented the process. He then set up 3D Systems Inc to commercialize his patent.

The basic printing process goes like this:

  • You create a 3-D model of your object in a CAD program
  • A piece of software chops your CAD model up into thin layers -- typically five to 10 layers/millimeter
  • The 3-D printer's laser "paints" one of the layers, exposing the liquid plasticin the tank and hardening it
  • The platform drops down into the tank a fraction of a millimeter and the laser paints the next layer
  • This process repeats, layer by layer, until your model is complete

The main requirements of Stereolithography are:

  • a movable table,
  • a laser knife edge,
  • the scanner system,
  • photopolymer,
  • Vat and eventually the Sealed Chamber where the whole process occurs.
  • Many of the Stereolithography systems are tightly sealed to inhibit the leakage of vapor from the resin, since it is harmful and contains an odor smell.

Working Process

The process that builds parts with a laser beam.

We now have two FDM modelers (Dimension) and three Poly Jet printers (Objet).   There are many types of rapid prototyping machines and methods. At Omnica we use the CNC (computer numerically controlled) machinery method, which can produce “real” parts made from the actual engineering materials. However, when we need fast turn-around on complex shapes or models to be used strictly for appearance purposes, and we can't print them with one of our five RP machines, we sometimes contract with a service bureau for Stereolithography (SLA) parts.

Concepting with CAD

When we concept designs, first we create a CAD (computer-aided drawing) solid-model, which is a computerized 3-dimensional virtual object. When the concept is finalized, we save it as an STL file. That file is then electronically sent to an SLA service. Their proprietary software virtually “slices” the three-dimensional STL file, so the solid model is converted into thin (about the thickness of a human hair) horizontal sections stacked on top of each other. (Imagine a solid block of cheese that has been sliced into thin sections.) The Stereolithography machine is now ready to read the modified file and physically build an actual three-dimensional model.

 Building the Stereolithography part.

The STL file, interpreted by the closet-sized, computer-controlled machine, guides the motion of a motorized ultraviolet laser, which is suspended above a pool of photosensitive liquid. The laser beam rapidly scans back and forth, “drawing” the shape of the first thin section on the fluid. It hardens to a depth of about 0.003” only where the beam strikes. Underneath, that section is supported by a metal platform. The platform and the cured section are then lowered below the surface of the pool until it is covered with fresh liquid, and the laser process is repeated. The laser continues to draw and build the layers. The platform and the hardened model move down, deeper into the pool of uncured fluid. Eventually, the submerged, stacked sections resemble the original solid CAD model.

When the laser-writing process is over, the platform and the newly created object are raised from the depths of the pool. The solid object, now referred to as an SLA model, is cleaned, and finally cured in a UV chamber. The service bureau delivers it to us, and we inspect, and hand-detail the model. Next we give it to Andy March (now fifteen years with Omnica) who gives it a nice paint job. When it is completed, the SLA model looks just like the original computerized concept. Start to finish, from concept to handheld model, the process can take as little as three days.

Applications of SLA

Industry Specific Applications:

Stereolithography extends its solution to many industries as being the best form of prototyping and product analysis.
Specifically, the material selection provides high-temperature and high durability options for those industries dealing with high product standards.

 

Superior Product Evaluation

​With a 3D model in your hands, you can evaluate your product concept for feasibility, manufacturing capability, ergonomics, aesthetics, and functionality.

Direct Digital Manufacturing

Print your model straight from a CAD file. Industries like the medical, electronic, packaging and defense (to name a few) all use DDM as an SLA application.

Rapid Prototypes/Manufacturing

Design appearance models, proof of concept prototypes, form and fit, design verification, wind tunnel testing (NDT), force testing (gravity, temperature, drops, shock, etc.) all use SLA technologies to rapid prototype their ideas from paper to CAD file to working model. Stereolithography helps you with your product design lifecycle/process.

 

Injection Molding and Metal Casting

3D Prototypes created by stereolithography are now strong enough to be machined and
can be used as master patterns for injection molding and even metal casting processes. Being cost and time effective in comparison to molding and tooling.

Finishing Possibilities

With the versatility of the end-product, SLA 3D models can be finished in a variety of ways, including, surface coatings, lacquers, nickel plating, laser etching, hand painting, vapor deposition, Epoxy, water based Urethane, dip coatings, and many others.

Ready to find out more?

MKS Technologies Pvt Ltd

Ph No - 0863-2224357

Email/www.mkstechgroup.com

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