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Fiberglass vs. Thermoforming

The Thermoforming Process Compared with Fiberglass Molding

Plastic Thermoforming Process vs. Fiberglass – How to Choose?

Productive Plastics’s core competency is the design, engineering and manufacturing of custom heavy gauge plastic thermoformed parts.

Plastic thermoforming and fiberglass molding can be used to make similar parts, but there are distinct advantages and disadvantages that should be taken into account when choosing the process that is right for a specific plastic component. The information on this page provides some general guidance on how to choose between fiberglass and thermoforming.

Plastic thermoforming is a plastic production process that heats a two dimensional rigid thermoplastic sheet and uses vacuum and/or pressure to form that sheet into a three dimensional shape. Thermoforming is typically used for production quantities of 250 to 3000 annually, offering lower tooling costs, rapid product development cycles, and parts with color and texture.

Fiberglass molding (FRP/GRP) is a process in which fiberglass reinforced resin is formed into useful shapes. The resin is applied in multiple layers to increase strength and to attain desired thickness. This process and material is best suited to making large structures requiring high strengths, however it carries high tooling cost and slower production rates.

Request Fiberglass to Plastic Thermoforming Comparison and Conversion Guide

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Compare fiberglass and plastic thermoforming processes, review data on part weight and production time differences, get tips on converting from fiberglass to thermoforming, and more. Request Productive Plastics’ Fiberglass to Plastic Thermoforming Comparison and Conversion Guide (PDF) now for instant download.

Choosing the Best Manufacturing Process for Your Plastic Part

Productive Plastics works with customers to make sure the technology, production processes, and materials are right for each job. Here are some guidelines and considerations for deciding between thermoforming and fiberglass molding (FRP/GRP).


Fiberglass (FRP/GRP) parts are mainly utilized in smaller production volumes and prototyping projects. Thermoforming is more cost effective when compared to fiberglass when used for production quantities of 250 to 3000 annually. Neither thermoforming or fiberglass molding processes is cost effective at high production volumes.


Thermoplastic PolyOlefins (TPO) is the plastic material of choice for replacing fiberglass parts. This material is more durable, crack resistant, UV resistant, conductive, and lighter when compared to its fiberglass counterpart.

There is also a wide selection of specialty raw material products, each designed for specific industries and environments with varying performance characteristics in tensile strength, flammability, chemical resistance, and weight to name just a few. Many are engineered to meet industry standards such as EN 45545, DIN 5510-2, NF P 92-501 ( -504, – 505), NF F 16-101/102, FRA Type I, FRA Type II, ASTM E162, ASTM E662, SMP-800C, or BSS 7239.

For more information on matching the ideal industry compliant thermoplastic with your project’s needs, please contact us.

Lead Time

Thermoplastic vs FRP cycle time graph

The fiberglass molding process is labor intensive and often requires multiple tools for the production of a single part which results in slower production rates, higher costs, and longer lead times compared to thermoformed plastic production.

The thermoforming process, on the other hand, is highly automated, relatively simple, and typically requires less labor. Most applications utilize only a single tool per part. Consequently, lead times tend to be shorter, and the tooling and labor costs reduced when compared to the fiberglass molding process. From a purely process perspective, thermoforming is often both faster and cheaper than the fiberglass counterpart in smaller production volumes of 250-3000 parts annually. Productive Plastics completes tooling and first production runs, on average, in less than 10 weeks.

Design, Finish, and Branding

The fiberglass process produces a high quality finish but is limited in scope. Thermoformed plastics are available in a wide variety of colors and finished textures. Silk screening, distortion printing, and post-process painting can also be utilized to increase branding and graphic potential on thermoformed plastic parts. Capabilities to produce precise tolerances for mated parts, and complex geometry design are just a few of the possible applications that are otherwise difficult or costly to fabricate with fiberglass. These advantages give designers the freedom to create complex modern designs that are more aesthetically pleasing and functional.


Thermoplastic vs FRP tooling cost by volume graph

Due to the complexity and labor intensive, open contact molding process associated with fiberglass part production, multiple tools are often required to complete a single part. This generates increased tooling costs and production time requirements for each part.

The thermoforming process is highly automated, requires less labor, and most applications require only a single tool per part. Consequently, the tooling costs are less and the production rate drastically increased compared to the fiberglass molding process.

Weight Considerations

Thermoformed plastic parts are lightweight and can offer substantially reduced part weight when compared to fiberglass. Typical thermoformed parts are, on average 30% lighter than their fiberglass counterparts. A fact reinforced by comparing specific gravity weights of raw material product on industry material provider websites from companies such as Covestro (formerly Bayer MaterialScience) or SEKISUI SPI (formerly KYDEX,LLC).

Thermoplastic vs FRP spec gravity weight graph

Thermoformed plastic and the manufacturing process is environmentally safe, its material is recyclable, and most raw thermoplastic materials are VOC free. The fiberglass process produces large amounts of environmentally hazardous styrene and is non-recyclable.

Industry Examples

Here are two examples of recent projects in which fiberglass parts were converted to thermoformed plastic.

The top photo shows a tow truck manufacturer that opted for the more durable and impact resistant thermoformed plastic material over fiberglass when they redesigned their rear fender and light assembly.

The second photo highlights a utility vehicle that took advantage of the benefits of a lighter material when the hood and steering assembly were converted from fiberglass to thermoplastic.

Converting from Fiberglass to Thermoformed Plastic

There are many advantages to using thermoformed plastic in place of fiberglass parts. Whether converting an existing fiberglass part to thermoformed plastic or creating a new one, Productive Plastics has the experience and expertise in design, engineering, and lean manufacturing to meet the needs of even the most challenging projects. Please Contact Productive Plastics to start the process of converting a plastic part from fiberglass to thermoformed plastic.

Thermoforming Alternatives

There are some circumstances where other manufacturing processes such as fiberglass molding are a better choice. These circumstances include high strength and very complex designs. Please Contact Productive Plastics for assistance with choosing the best process.

TPO Thermoplastic Material vs Fiberglass
[Thermoforming Technical Webinar Recording]

Technical Webinar with Productive Plastics (plastic thermoforming custom manufacturer) and SIMONA PMC (thermoplastic material producer) on the technical characteristics and cost advantages of using TPO over metal and fiberglass for your applications and parts. Explore the wide range of TPO grades available for performance or aesthetics, comparisons, case studies, details on designing for plastic thermoforming, and more!

Fiberglass Comparison Guide

Download a FREE Fiberglass vs. Thermoforming Comparison and Conversion Guide from Productive Plastics

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