How to Realize Clear Plastic Parts at Prototyping Stages?

When you are looking for clear plastic material for your new design, are you often confusing between acrylic and polycarbonate? Much more than that, do you know how many manufacturing ways to make clear plastic prototypes? Here in this article will present an overview of manufacturing solutions for clear plastic prototypes, so as to meet demand at different verification processes.

Generally speaking, there are 4 prototyping ways for clear plastic parts, including 3D printing, CNC machining, urethane vacuum casting, and rapid injection molding.

SLA 3D Printed Clear Plastic Parts

SLA 3D printing is a kind of automatic addictive manufacturing ways. Unlike the complicated CNC machining process, it has a quick turn-around which will print the parts at a stable and quick speed. Its time and costs simply depend on the model size, which allows the designer to control the costs by removing unnecessary material. Moreover, the printed clear parts can also achieve high transparency closely to machined clear parts through mirror polish. Generally, it can serve functions as windows or models.

Regarding to its limitation, the tightest tolerance of SLA printed part is around +/-0.1mm. For some clear parts used for optical functions, if it requires tighter tolerance than +/-0.1mm, then 3D printing is out of the choice. Besides, SLA printed clear parts are prone to forming clear bubbles inside the material, which can meet requirements on optical function or aesthetic appearance.

CNC Machined Clear Plastic Parts (Machined Acrylic V.s Machined Polycarbonate)

CNC clear acrylic-2

When talking about clear plastics, though acrylic (PMMA) and polycarbonate (PC) are the two most widely used materials, many design engineers may find it difficult to choose between them to realize their unique applications. For CNC machining, acrylic and polycarbonate blocks present distinct advantages and disadvantages.

CNC Machined Acrylic Part

On the one hand, it has superior clarity after mirror polish, transmitting light as effectively as glass; good strength, 4-8times that of glass; good durability, resistant to a wide range of UV radiation, temperatures, and weather; strong versatility, machined easily through kinds of ways and bonded with solvents and adhesives.

On the other hand, compared with polycarbonate, machined acrylic parts are more prone to cracking than polycarbonate; are more prone to chipping; has poor resistant resistance, losing structural integrity at temperatures over 160℃, and will warp or melt when exposed to open flames.

CNC Machined Polycarbonate Part

On the one hand, it has high strength, 200 times that of glass; high clarity, making it a suitable alternative to glass; good durability, with high impact resistance; good machinability, manipulated easily and shaped by various machining processes; minimal creeps, unlike other plastic materials to deform or warp under pressure.

On the other hand, compared with acrylic, machined polycarbonate parts are more prone to scratch; more prone to denting under the impact, due to better flexibility; harder to mirror polish, left inevitably tooling marks on the part surface.

Urethane Casted Clear Part

vacuum casting-3

When demand quantities come to dozens of clear plastic parts for a short turn-around, urethane casting is quick and inexpensive, no matter compared with CNC machining or rapid metal tooling.

As an alternative way between CNC machining and rapid tooling, urethane casting technology offers a wide variety of material types similar to finished plastics including clear parts. Varied Polyurethane brands are varied in material quality. For clear parts, Axson’s PX-5210 (PMMA-like) and PX-527 (PC-like), are frequently used due to its premium quality. It has water-clear high transparency, good UV resistance, high reproduction accuracy, and easy polishing after casting. Though the material is polyurethane only, with superior quality, it can be applied to industrial testing at the prototyping stage.

The finish quality of casted clear parts is determined by the quality of the master pattern. Most of the common masters are clear polished PMMA parts by CNC machining, which can meet tight tolerance such as +/-0.05mm. In addition, SLA printed clear masters will be considered when making parts with complicated structures.

Rapid Injection Molded Clear Part

As a bridge tooling from prototype to production, rapid injection molding technology produce clear parts in production-level material. You can designate certain materials with certain specifications. The material is the same as the production run so that the clear parts can be applied to almost all industrial tests before mass production. Unlike injection molding used in mass production, rapid tooling of aluminum or steel is able to turn over the specified part within 2-5weeks; also, due to semi-automatic operation, the mold structure is simplified so the mold costs are lower much compared to mass production.

Last But Not Least – Clear Polish Quality to Acrylic Part

optical prototype machining-mirror polish

Acrylic polishing can achieve the best clarity among all clear plastics. It requires special skills as acrylic is stress-sensitive and fairly brittle. Hand polishing takes processes in different grades with sandpaper and polishing paste.

Highly polishing will start from sanding work, from #400 / #600 sandpaper so as to remove the rough tool marks, then lifting sand-paper grits up to #800-#1000-#1500 and end by #2000. The polished surface becomes smooth without a tooling line or mark at all. Finally, polishing paste will be used to finish the process. Though all the processes, the finished surface of the acrylic part will present super clear & transparent, without any invisible sanding marks and scratches.

Until here, does this article clear most of your confusion and question about clear plastic prototypes? I hope so, and in case something is left still, please do not hesitate to contact us through our website.

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