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3D Printing SLA Dragon Egg

By <a href="https://mfg.trimech.com/author/andrew-miller/" target="_self">Andrew Miller</a>

By Andrew Miller

Posted on April 20, 2023

Design to manufacture is a series of projects showcasing the talents of our SOLIDWORKS and Hardware experts, as they team up to execute 3D printing part design and production. In tandem, they brainstorm part geometry, 3D model the part in SOLIDWORKS, and utilize our in-house Stratasys machines and GrabCAD Print to create the final SLA 3D printed part.

Like many great inventions, the 3D printed SLA Dragon Egg started as a conversation and a handful of doodles on a piece of scrap paper. Ben Colley and Andrew Miller wanted to create a 3D printed piece that would adequately demonstrate the capabilities of the Neo 450.

Sketch

Sketch

Creative Engineering

Their brainstorming session covered:

  • The hardware: The constraints and character of the Neo 450 Stereolithography (SLA) printer, which offers a fine, 50-micron (0.002”) print resolution, allowing for highly detailed surfaces and intricate designs.
  • The material: The properties of the Somos® WaterShed Black, which give printed parts high durability and a glossy smooth finish.
  • The part: The use-case for the printed part which would be frequently handled by printer reps and clients. It needed to be small enough to fit comfortably in the hand (baseball-sized or smaller), have an attractive surface design, no sharp edges, and demonstrate complexity and tight tolerances. Some possible features to incorporate would be threads, fine lettering, an assembly design with multiple components, and a unique surface pattern for the exterior.

Ben and Andrew initially landed on some form of puzzle cube with assembled parts that would thread together. After some virtual calls and late-night doodling sessions, they came up with a dual-threaded spherical puzzle that could be assembled and disassembled by twisting the center piece.

Designing and Modeling the Dragon Egg

Ben took the design to SOLIDWORKS and worked out the general function of the assembly.

The large-diameter inner shaft allowed for a hidden cavity where a 5/8” diameter pin could be stored. This gave Ben and Andrew a fun way to incorporate lettering into the design. The Flex command in SOLIDWORKS was key to the twisted faces and lettering.

SLA twist part

For the outer finish of the sphere, Andrew suggested that the exterior should have a dragon scale feel to it. Instead of modeling actual dragon scales, Ben checked out the patterns available to the 3D Texture tool in SOLIDWORKS. He liked the effect of a knurled bump projected from the top plane onto a semi-sphere, so he used that as a starting place for the outer finish.

3D texture tool

The faceted surface generated by the 3D Texture tool wasn’t going to provide the finish that Ben and Andrew wanted for the final print, so Ben used 3D sketching and surfacing tools to replicate the surface with standard BREP geometry. Because of the symmetry in the semi-sphere design, only 1/8th of the semi-sphere had to be modeled, and the rest could be mirrored and patterned. Then, surface trims were used to cut out the decorative channels that broke up the surface into a more interesting pattern.

Because all of the components were being designed in a single multibody part, rebuild times were becoming burdensome. To eliminate this issue, Ben activated the Freeze Bar to prevent SOLIDWORKS from rebuilding earlier features.

Freeze Bar

Ben added some finger grips to the center wheel to make it easier to twist, mirrored the top components down, checked the assembly for interference, and sent the Dragon Egg to the hardware team.

The 3D Printing SLA Results

TriMech’s Advanced Manufacturing team used their Stratasys Neo 450 in HD mode to print off this Neo Dragon’s Egg part. GrabCAD Print can take the SOLIDWORKS Solid Part or Solid Assembly file directly without the need to convert to an STL, OBJ, etc.

SOLIDWORKS BOM

The variable diameter laser of the Neo printers could refine its size to print fine details such as the smooth surfaces, flat faces, and the lettering on the pin and then switch to a larger beam size for a dense infill. The Neo uses a powerful laser measuring two watts of energy at the surface of the resin. Resins such as Watershed Black do not require the full power of this laser for great energy absorption and rapid curing. This means faster parts of a high quality!

3D printed threads The high resolution of this laser meant that the support structures needed for this part were their smallest diameter at the point of contact with the part. This means the support structures could be torn off like Velcro when designed correctly and leave few or no traces. A quick IPA and TPM bath plus a quick UV cure and the part was ready!

The weight of the part is unexpected due to its dense infill. It is at least twice as heavy as a baseball yet roughly the same size. The smooth features of the part are akin to injection molded quality yet there are no surface stitches. There is practically no friction in the threads and the lettering on the pin is easily readable.

Learn more about 3D Printing SLA

Learn more about the Stratasys’s Neo450 and SLA 3D printed parts.

Article by <a href="https://mfg.trimech.com/author/andrew-miller/" target="_self">Andrew Miller</a>

Article by Andrew Miller