Designing With Photopolymers

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Photopolymers used in Stereolithography are epoxy or acrylate based resins. Since the general properties of photopolymers widely vary, it is important to know which type of material is right for your model. Photopolymers overall offer finer detail and give a “realistic” plastic feel to a model or prototype with very little finishing. Typically photopolymer materials are used to test designs as concept models, fit check assemblies, master patterns for molding techniques, and/or as small, limited functional prototypes.

What to Consider

As photopolymers have minimal strength and durability this material is better suited for models or prototypes. In addition, photopolymers are not UV stable and many have low heat tolerance; for this reason photopolymers are known to “creep” out of shape with heat or when carrying a heavy load for a long duration of time.

While these properties are essential considerations when working with photopolymers, there are some nanocomposites and formulated resins that were devised to have higher heat tolerances. One characteristic of photopolymers that makes construction difficult with this material is that it has very limited elongation abilities. Consequently, photopolymers are prone to breaking when heavily impacted or bent too much. Yet with photo-curing additive processes, designs with photopolymers obtain fine details and have rather smooth finishes; making them the perfect material when testing a particular look or functionality of prospective design.

Stereolithography

stereolithography-machine photopolymersStereolithography is a 3D printing process where you can create a 3D model or part from a CAD (computer-aided design) program, which cuts the design into cross-sections typically .004 of an inch thick. In stereolithography (SL or SLA) technology, there is a vat of UV curable photopolymer is placed below in the lower compartment of the machine; the machine begins to construct the 3D model by scanning and building one layer at a time. Each layer is constructed with a UV laser and as the laser traces the next layer of the object the material hardens on contact. Once the layer is complete the platform slips down to make room for the next layer, a re-coating blade evens out the model to remove excess material and the process repeats until all layers of the CAD are constructed, building from the bottom-up.

After the part is removed from the machine and ran through a chemical bath to remove excess resin, the part is then placed into a UV oven and then moved to post-processing, which includes sanding and painting to get the finished product.

Rapid prototyping by stereolithography has become the economical solution to rapid appearance models and concept prototypes. Many industries have now embraced rapid prototyping including aerospace, automotive, commercial goods and entertainment sectors.

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