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Transparent Plastic Casting

Transparent Plastic Casting

We provide professional transparent plastic casting services for optical-quality prototypes, lighting components, and clear functional parts. Using vacuum casting and optically clear urethane resins, we deliver glass-like transparency, accurate geometry, and short lead times — all without the cost and tooling lead time of injection molding.
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Description

Core advantages:

 

  • PMMA-equivalent and PC-equivalent clear resins with high light transmittance
  • First samples typically in 7–10 working days
  • ISO 9001 certified quality management system

 

What Is Transparent Plastic Casting?

 

Transparent plastic casting is a low-volume manufacturing process in which optically clear, two-component urethane resins are vacuum-cast into silicone (RTV) molds taken from a high-quality master pattern. The process is well suited to clear lenses, light pipes, display covers, fluid-flow models, packaging mock-ups, and short-run end-use parts where glass-like transparency is required.

Compared with alternative processes:
 
 

vs. injection molding:

no hard tooling required - much lower upfront cost and faster first samples for quantities up to a few hundred parts.

 
 
 

vs. SLA / SLS 3D printing:

true clear-cast urethane achieves higher optical clarity and a more uniform refractive surface than 3D-printed clear resins, which usually need extensive post-polishing or coating to approach optical quality.

 
 
 

vs. CNC machining:

supports complex internal geometries and one-piece optical bodies that would require multi-axis machining and extensive polishing.

 

 

Materials & Optical Properties

 

We work with optically clear urethane systems and clear ABS-equivalents. Properties below are typical values for representative material families - the exact resin is selected to match your specific optical, mechanical, and thermal requirements.

Resin Family

Simulates

Light Transmittance (typical)

Refractive Index

Heat Deflection Temp

Typical Use

Optically clear urethane (e.g. PX5212-class)

PMMA

~88–92%

~1.50

~70–80 °C

Lenses, light pipes, transparent housings

High-clarity rigid urethane

PC

~85–90%

~1.49–1.51

~75–90 °C

Impact-resistant clear covers

Tinted clear urethane (custom colors)

Tinted PMMA / PC

Color-dependent

~1.50

~70–85 °C

Coloured lenses, signal indicators, lighting effects

Flexible clear urethane

Soft PVC / TPU (clear)

~85–90%

~1.48–1.50

Hardness Shore A 40–80

Clear gaskets, soft-touch parts

Typical values; actual properties depend on resin lot, casting parameters, and post-processing. We provide datasheets for the specific resin selected for your project.

 

Surface Finish & Optical Quality

 

Optical clarity in cast parts is determined as much by surface finish as by the resin itself. Our finishing options for transparent castings:

As-Cast Surface (with polished pattern)

When the master pattern surfaces are polished to optical quality, the silicone mold reproduces that finish, and the cast part comes out of the mold transparent without further polishing. This is the standard approach for visually clear bodies.

Hand Polishing & Buffing

Surfaces affected by parting lines or vents are polished using progressive grit sequences and final buffing compounds, restoring local optical clarity.

Clear Coating / Lacquering

A thin clear urethane lacquer can be applied to the part to fill micro-scratches and restore transparency. Used selectively on high-visibility surfaces.

Tint, Frost & Custom Effects

Bulk tinting (color added to the casting resin) and surface frosting (matte texture on the silicone mold) are both supported. Tints are reproducible from a Pantone reference.

 

Technical Capabilities

 

Parameter

Specification

Notes

Maximum part size

Up to 800 × 600 × 400 mm

Larger parts on request, subject to mold-frame size

Wall thickness range

1.0 – 10 mm

Thicker sections may show internal stress lines unless degassed carefully

General tolerance

±0.2 mm or ±0.2% (whichever larger)

Reflects resin shrinkage; per typical urethane casting practice

Typical mold life

20–25 castings per silicone mold

A rigid master can be used to create multiple silicone molds

Standard lead time

7–10 working days for first castings

From confirmed master pattern

File formats

STEP, IGES, SolidWorks, STL

Full DFM report provided

 

Application Scenarios

 

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Lighting & optics:
lenses, light pipes, automotive lamp prototypes, signage components.
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Consumer electronics:
transparent housings, display covers, indicator windows for prototype validation.
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Medical devices:
fluid-flow visualization models, transparent housings for diagnostic equipment, training models.
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Industrial design & marketing:
presentation models, exhibition prototypes, packaging mock-ups.
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Engineering validation:
transparent flow channels, fluid-mechanics studies, internal-geometry visualization.

 

Process Walkthrough

 

Master pattern preparation:

CNC-machined or SLA-printed master with surfaces polished to optical quality.

01

Silicone mold making:

high-quality RTV silicone is poured around the master under controlled conditions and cured.

02

Vacuum casting:

the two-component clear urethane is mixed, degassed, and poured under vacuum to prevent bubble inclusions.

03

Curing:

the part is cured in a heated oven, then demolded carefully to preserve surface quality.

04

Finishing & inspection:

trimming, polishing of parting lines, optional clear lacquering, and visual + dimensional inspection.

05

 

FAQ

 

Q1: How clear are the cast parts compared with injection-molded PMMA or PC?

Optically clear urethane systems typically reach light transmittance of 85–92% - comparable to injection-molded PMMA or PC for visual purposes. They are not optical-grade in the strict sense (lower hardness, slightly different refractive index, and higher absorption in some wavelengths), but for prototypes, lighting components, and visual mock-ups they look and behave very similarly to acrylic.

Q2: How many transparent cast parts can I produce from one mold?

Each silicone mold typically supports 20–25 cast parts before mold wear and aging affect surface quality. A rigid master pattern can be used to create multiple silicone molds, supporting hundreds of total parts.

Q3: Can the cast parts be tinted to a specific color?

Yes. Bulk tinting to a Pantone reference is supported, as are translucent and frosted finishes. Provide your color reference at quotation.

Q4: What tolerances can be achieved on transparent castings?

General tolerance is ±0.2 mm or ±0.2%, whichever is larger - typical for urethane casting and driven primarily by resin shrinkage. Critical features can be machined post-cast where higher precision is required.

Q5: Are cast urethane parts suitable for end-use applications?

For appearance, fit-and-function testing, marketing samples, and short-run end-use parts in non-critical applications, cast urethane parts perform well. For long-term outdoor exposure, very high temperatures, or strict optical requirements, injection-molded PMMA or PC is generally recommended for production volumes.

Q6: What is the lead time for transparent plastic casting?

Typically 7–10 working days from a confirmed master pattern. If we are producing the master pattern as part of the project, total lead time is usually 12–15 working days.

Q7: Do you provide DFM support?

Yes. We review every part for wall-thickness uniformity, draft angles, vent locations, and bubble-trap risk before mold-making, and recommend changes that improve castability and optical quality.

 

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