Choosing the Right Rapid Prototyping Services for Clear or Translucent Parts.
Nov 02, 2020
Businesses can benefit from making rapid prototyping services in clear materials. But which manufacturing processes are best for creating transparent or translucent objects?
Product designers can desire transparent parts, which are fully clear like a glass window, or translucent parts, which are partially clear like frosted bathroom glass, for different reasons.
Some parts must be clear in order to be functional: optical equipment like camera lenses, lighting components, beakers, test tubes, pipettes, and kitchen measuring jugs will only serve their end purpose if they are transparent. In these cases, there is no alternative to the fabrication of clear parts.
Other parts contain clear elements that provide function but are not fundamental to the purpose of the part. For example, some ink pens have a transparent window that allows the user to gauge how much ink remains in the cartridge. This feature is not essential to a pen, but it is still functional and serves a “clear” purpose. Items like food containers or storage boxes can also be transparent so the user knows what is inside without having to remove the lid.
In some cases, product designers introduce transparency or translucency purely for aesthetic reasons, to make a product stand out from opaque alternatives. These products include items like consumer electronics housings (which show the electronic components within), pencil sharpeners, kitchen utensils, tool handles, bowls and vases, and even apparel like backpacks and raincoats.
Whether you need clarity for functional or aesthetic reasons, it can be difficult to choose the right rapid prototyping services for clear parts. This guide discusses four realistic options, outlining the respective advantages and disadvantages of each.
Clear Parts with Stereolithography 3D Printing
Stereolithography is a type of 3D printing (or additive manufacturing) that excels at making clear parts and prototypes. The SLA process involves directing patterns of laser light onto a thermosetting material in order to cure (harden) it in the desired shape, layer by layer.
Many SLA material suppliers offer clear thermosetting polymer resins for SLA printers, and these materials can produce a high level of detail.
Speed is a big advantage of 3D printing clear parts, especially for one-off rapid prototypes. The operative can turn a CAD design into a printed clear part in a matter of hours with only a small amount of post-processing required. However, printed SLA parts have limited practical functionality since they are very brittle.
Clear SLA 3D printing is often used in the dental industry to make clear aligner models, splints, and other devices, and the technology can also be used for aesthetic products like jewelry.
Materials: Thermosetting polymer resins
Advantages: Very short lead times, excellent detail level
Disadvantages: Fragile parts unsuitable for physically demanding applications, less suitable for high volumes, limited material and color options.
Clear Parts with CNC Machining
One of the most popular rapid prototyping services for clear parts is CNC machining. With this process, a CNC machine like a mill or lathe can cut rugged prototypes from a block of acrylic or polycarbonate.
Acrylic is the most popular clear CNC machining material for two reasons. First, it is easy to machine, which reduces fabrication time and allows machinists to achieve a higher level of accuracy. Secondly, it produces a high-quality, glass-like finish with a normal amount of polishing.
Polycarbonate also produces good results, but it offers lower machinability and requires more extensive polishing in order to produce good transparency. Acrylic is therefore preferable for genuine optical parts.
Like all machined parts, clear machined parts are usually stronger than comparable 3D printed parts and can therefore have a range of uses. However, CNC machining is more expensive than some processes and offers no economy of scale.
Materials: PMMA (acrylic), PC
Advantages: Strong parts, similar to end-use parts
Disadvantages: May require extensive polishing, less suitable for high volumes
Clear Parts with Injection Molding
Injection molding is rarely used for one-off prototypes but is still a viable rapid prototyping service when combined with the rapid tooling of aluminum molds.
By using clear plastic resins of materials like nylon, PET, and acrylic, it is possible to create clear injection molded prototypes that are very similar to end-use parts. However, the fabrication of clear molded parts requires a greater level of expertise than the fabrication of, for example, clear SLA printed parts, and common problems include cloudiness, flow marks, and surface glossiness defects.
Despite the potential pitfalls, mass manufacturers regularly use injection molding to make clear parts like medical devices and food packaging.
Materials: Nylon, PC, PET, PMMA, etc.
Advantages: High quality, similar to end-use parts, material options, color options
Disadvantages: Requires a high level of expertise, impractical and expensive for low volumes
Clear Parts with Vacuum Casting
For lower-budget projects, vacuum casting may be a better alternative to injection molding for transparent or translucent prototypes.
Vacuum casting uses silicone molds instead of expensive metal tooling, and these molds can produce around 20 copies of a part, which may be ideal for R&D applications. The cast parts are fairly flimsy so are more suited for visual applications than functional ones.
Companies often seek out vacuum casting explicitly to make clear parts, since polyurethanes are available in clear formulations and produce an excellent surface finish requiring minimal post-processing. Additionally, it is easy to add colored tints to the cast parts.
The process is often used to make display prototypes, containers, and housings or enclosures for prototype devices.
Materials: Polyurethanes that mimic acrylic, PC, etc.
Advantages: Exceptional surface finish, much cheaper than injection molding, minimal post-processing
Disadvantages: Weak parts with limited functional use
The Right Rapid Prototyping Services for Your Clear Parts
Choosing the right rapid prototyping services for clear parts depends on several factors: the type of prototype you need (display, mechanical, final-stage), the project budget, and the number of units you require.
Processes like SLA and vacuum casting fall short when it comes to functional and mechanical prototypes, but they are good for visual prototypes because they produce a high-quality finish. Furthermore, they are cheaper than CNC machining and injection molding. For one-off prototypes, SLA and CNC machining are the most viable, while vacuum casting and injection molding are better for medium and large order volumes, respectively.
If you want to know more about the best rapid prototyping services for your next project, contact RapidDirect and we’ll guide you to the right solution.
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