Should You Upgrade Your Sheet Metal Parts and Enclosures to Plastic Thermoforming?

Plastic Thermoforming vs Metal
The heavy gauge thermoforming process offers key advantages as an upgraded replacement for many parts currently manufactured from metal. Weight reduction is a key advantage – plastic parts are lighter than metal. Further, custom plastic thermoforming can be used to produce complex geometric part shapes that are not possible with sheet metal at a feasible cost, allowing greater design freedom. This versatility gives manufacturers faster design and production cycles, while also providing the opportunity for innovation with structure and design. Additionally, thermoforming can eliminate the need for secondary part finishing. The industrial market demands lightweight and durable products and high levels of customization, with an eye towards environmental concerns about the use of recyclable materials. Custom heavy gauge thermoforming meets these demands better than sheet metal.

The Impact of Thermoplastics on Industries

Thermoforming can present a substantial upgrade over traditional sheet metal fabrication, metal stamping, metal spinning, and metal casting manufacturing processes and materials. Although sheet metal fabrication exists as a low-cost method for producing parts, the use of sheet metal sacrifices flexibility in design, capabilities, and application. Complex parts manufactured with sheet metal require secondary processes that can involve cutting, bending, welding, and bolting. Producing the same part with thermoforming can eliminate these secondary processes by easily incorporating complex 3D part designs, mating points, and various surface finishes and branding directly into the part’s tooling.

Medical Device with Plastic Thermoformed Enclosure

Large medical device with plastic thermoformed enclosure. Complex shape design and continuous design lines spanning over multiple parts.

The same differences become apparent when comparing metal stamping, metal spinning, and metal die-casting with thermoforming. Manufacturers use bending and stamping to produce low-cost parts that have a simple geometry. Any attempt to add complexity to a part requires additional assembly steps and cost. The unique process of metal spinning forms complex shapes from aluminum, steel, alloys, and other metals. Rotating a disc or tube of metal at high speeds produces axially symmetric parts and improves the tensile strength of the metal. Metal die-casting produces parts that have high heat resistance, high strength and stiffness, and low thermal expansion qualities.

In contrast, thermoforming provides higher rates of production with a level of detail and complexity that greatly exceeds the capabilities of metal processes. For example, the application of plastic thermoformed enclosures, housings, and covers for medical diagnostic equipment shortens the development and production cycles. Moreover, the use of thermoformed materials establishes lower cost tooling for applications that must comply with global safety standards.

Weight Considerations – Plastic Thermoforming vs. Metal

Plastic thermoforming allows manufacturers to use materials that have a lower density and thinner walls. Both qualities allow weight-conscious industries such as automotive and aerospace manufacturing to achieve significant weight reduction while retaining strength and durability. The use of thermoplastics improves fuel economy and reduces emissions with decreased weight and lowered friction losses in the powertrain. Reducing the weight of gears causes a reduction in inertia and an increase in automotive efficiency. The use of thermoplastics also reduces noise and vibration levels.

For electrical components, the capability to produce strong, lightweight parts also promotes the production of lightweight, wall-mounted or pole-mounted enclosures. Using thermoformed plastics for the electrical enclosures allows easier lifting than seen with aluminum or steel enclosures. When comparing the weights of thermoformed objects to metal objects, noticeable differences exist. With two same-sized objects constructed from polycarbonate and fiberglass, the polycarbonate object weighs approximately ½ pound less. An aluminum same-sized object will weigh twice the amount, an object made from steel will weigh more than six times as much.

The following chart depicts the differences in specific gravity density for different types of thermoplastic and metal materials. Specific gravity equals the ratio of density of the material to the density of water at 39°F. Because the thermoplastics shown in the chart have superior strength-to-weight ratios than the metals, the lighter thermoplastics have equivalent strength and stiffness.

Material Specific Gravity
High-impact ABS 1.03
Polycarbonate 1.19
Acetal copolymer 1.41
Aluminum 2.55 – 2.80
Cast Iron 7.03 – 7.13
Titanium 4.5
Cast Rolled Brass 8.4 – 8.7
Stainless Steel 7.7
Copper 8.89
Carbon Steel 7.8
Tool Steel 7.70 – 7.73
Tungsten Carbide 14.29

 

Durability Comparisons – Plastic Thermoforming vs. Metal Manufacturing

Polycarbonate has become a popular alternative for enclosures because of its strength and durability. The durability and impact resistance of polycarbonate allows the use of enclosures in all types of weather and environmental conditions in industries such as oil exploration, agricultural irrigation, wind turbines, and maritime. A polycarbonate enclosure has a tensile strength of 900 pounds per square inch and has a high impact resistance. In addition, polycarbonate enclosures resist damage caused by ultraviolet rays and have high NEMA ratings for dust and moisture protection.

Time and Cost Savings Achieved with Thermoplastics

Medical Device with plastic thermoformed enclosure

Medical device enclosure manufactured and assembled from multiple plastic thermoformed parts

While a stainless steel enclosure offers the same resistance, stainless steel costs three times more than polycarbonate. The cost comparison between thermoplastics and metals goes beyond direct monetary costs and includes indirect costs such as time. Again, using polycarbonate enclosures as an example, thermoplastics offer the advantage of easy modification. Machining a stainless-steel enclosure requires special tools and additional time.

The weight reduction seen with a polycarbonate enclosure also factors into time and cost savings. Rather than requiring two installers for the attachment of an outdoor stainless steel enclosure, the installation of a polycarbonate enclosure requires only one installer. In addition, the shipping costs for lighter weight polycarbonate enclosures are lower than the shipping costs for metal enclosures.

Direct cost savings with thermoplastics occur through repeatable manufacturing processes that produce less scrap. Given the durability of thermoplastic materials, tools and parts have a much longer service life. Manufacturing costs also decrease because of the design flexibility to consolidate parts and to produce complex mechanisms without secondary processes. Because of the numerous thermoplastic options, manufactures can carefully select materials that optimize manufacturing to production ratios and reduce lead times.

Summary

Thermoplastics have replaced the use of carbon steel, stainless steel, titanium, aluminum, magnesium, brass, and bronze in many industrial applications. Along with weight reduction, thermoplastics offer enhanced performance, greater design freedom, and decreased total system costs. Enhanced performance occurs through corrosion resistance, lower friction, increased fuel efficiency, and the capability to handle large loads at higher speeds in harsh environments.

Thermoplastics have become standard materials for parts such as medical diagnostics equipment components, enclosures, fender wells, rear bumpers, seating and interior trim components, window masks, wall paneling, decorative signs, and construction cab interiors.  Heavy gauge thermoforming eases the process of manufacturing those components by forming a two-dimensional rigid sheet of thermoplastic into a three-dimensional shape that fits industrial needs and standards.  Intricate designs with molded colors and textures occur at lower costs and with faster production cycles.

 

Productive Plastics is top contract manufacturer for heavy gauge thermoforming, including vacuum forming and pressure forming. Contact us or request our complimentary thermoforming design guide for more information.

Please contact Productive Plastics for more information on the thermoforming process
Please download our complimentary thermoforming design guide for more information on the thermoforming process

 

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