Stereolithography

Stereolithography (SL) is one of three additive processes available at Vikled Molding. SL uses an ultraviolet laser focused to a small point to draw on the surface of a liquid thermoset resin. Where it draws, the liquid turns to solid. This is repeated in thin, two-dimensional cross-sections that are layered to form complex three-dimensional parts. SL provides the widest selection of material, best feature resolution and smoothest surface finish. It works well for very small parts and complex geometries during early prototyping.

Process

When a 3D CAD model of a part has been uploaded by a customer, it is moved into a scheduling and build queue. All of the part files are downloaded and the geometry is analyzed for any potential manufacturability issues. If any issues do arise, a dialog between a Vikled Molding representative and the customer will take place to resolve the problem before the actual build begins.

Build preparation

As the stereolithography build prep begins, parts are digitally positioned onto the build platform and the necessary support structures are strategically placed onto the part. Automated supports are initially placed followed by supplemental supports done manually to provide a comprehensive final support system. Because part features are imaged on the surface of liquid, if the parts are not supported in the SL process, they would float away or collapse during the build.

Build prep technicians then go through a layer-by-layer review of the build to ensure that all of the features are adequately supported for a successful build (With an average build height of 1 to 2 inches, for example, there would be approximately 500 to 1,000 layers.) Once the review is complete, the technicians will digitally create the required amount of copies required for a particular order before it is ultimately sent to the SL machine.

Part production

The machine begins drawing the layers of the support structures, followed by the part itself, with an ultraviolet laser aimed onto the surface of a liquid thermoset resin. After a layer is imaged on the resin surface, the build platform shifts down and a recoating bar moves across the platform to apply the next layer of resin. The process is repeated layer by layer until the build is complete.

Post build

The tray containing the newly built parts is taken out of machine and into a lab where solvents are used to remove any additional resins. When the parts are completely clean, the support structures are manually removed. From there, parts undergo a UV-curing cycle to fully solidify the outer surface of the part. The final step in the stereolithography process is the application of any customer-specified finishes — unfinished, natural finish (sanding of the supported surfaces to remove any evidence of support), standard finish (400 grit matte finish with a grit blaster in addition to sanding supported surfaces) and custom finishing (ranging from colored paint to optically clear lenses to decals and lettering.)

Solvents Structures Finishing

Design Guidelines

With our additive processes, we’re able to deliver prototypes ranging from very small parts that meet extreme tolerance demands to large parts with precise patterns. Maximum build size for parts built by stereolithography is 29 in. by 25 in. by 21 in. (736mm by 635mm by 533mm).

Resolution

Vikled Molding excels in high-quality precision parts that are available in three different SL resolutions:

Normal Resolution:

Layer thickness of 0.004 in. with minimum feature size of 0.010 in.

High Resolution:

Layer thickness of 0.002 in. with minimum feature size of 0.004 in.

Micro Resolution:

Layer thickness of 0.001 in. with minimum feature size of 0.002 in.

Normal resolution

High resolution

Micro resolution

Tolerances

For a well-designed part, tolerances in X/Y dimensions are ±0.002 in. (0.05mm) for the first inch plus ±0.001 in./in. (0.001mm/mm) for each additional inch. Z dimensions are ±0.005 in. (0.13mm) for the first inch plus ±0.001 in./in. (0.001mm/mm) for each additional inch. Note that tolerances may change depending on part geometry.

Materials

We offer numerous material options that are constantly updated to meet prototyping and master fabrication needs. Our materials offer many different characteristics: resolution, color and clarity, stiffness and feel, durability, impact resistance, temperature tolerance, and water resistance.

• ABS-like
• Polycarbonate-like
• Polypropylene-like
• SLArmor (nickel-plated)

See full list of materials

Surface finishes

There are three standard finishes within stereolithography:

Unfinished:

Dots, or standing “nibs,” remain evident on the bottom of the part from the support structure remnants.

Natural finish:

Supported surfaces are sanded down to eliminate the support nibs.

Standard finish:

Supported surfaces are sanded, and the whole part is finely blasted for a consistent look. Note that the layers are still present.

Unfinished

Natural

Standard

Secondary options

Custom finishing — a service only offered within Vikled Molding — is a mix of science, technology and fine art that can transform a part to your exact specifications. Custom finishes include:

• Soft-touch paint

• Clear part finishing

• Paint finishes

• Chrome plating

• Masking

• Color matching

• Decals/graphic

• Texture

Special applications

In addition to our normal SL processes, we offer a few special applications unique to Vikled Molding. Our SLArmor process takes stereolithography to the next level by finishing off an advanced ceramic-filled epoxy material from DSM Somos® (NanoTool™) with a metal coating that gives parts the look, feel and strength of metal, but without the weight. The combination of NanoTool’s extreme strength, rigidity and temperature resistance with SLArmor’s nickel plating, takes strength, stiffness and impact and temperature resistance to a degree previously unattainable in SL parts. In fact, the composite nature of the process gives SLArmor a greater strength-to-weight ratio than some metals.

Using the Vikled Molding microfluidic fabrication process can allow you to dramatically shorten your development time for microfluidic devices of all shapes and sizes. If you intend to injection mold your microfluidic product, then the microfluidic fabrication process will allow you to design and test most features that you will employ in your injectionmolded product. This process eliminates the constraints created by the limitations of conventional or mask-less photolithography. Our microfluidic fabrication process is a modified form of high-resolution stereolithography that allows the creation of any 3D object(s) through a process of stacking two-dimensional layers of 50 microns thickness (0.002 in.). Stereolithography technology utilizes a liquid photopolymer that is polymerized into a solid by the application of ultra-violet light from a laser.

SLArmor

Microfluidic fabrication

Equipment

Vikled Molding employs multiple additive machines that offer large build sizes, accurate parts and quick production times. Our stereolithography machines consists of Vipers, ProJets, and iPros. In high-resolution (HR) mode, Vipers and ProJets can make parts with extremely tiny features and crisp details, while in normal resolution (NR) mode, they can build cost-effective parts very quickly. iPros have build volumes that are truly huge at 29 in. by 25 in. by 21 in. (736mm by 635mm by 533mm), and yet are still able to image highly detailed parts easily.