Why not steel or aluminum?

Metal materials such as steel, aluminum and others have been used for years in many different industries. Each of these materials has its strengths but these strengths come at a cost. Thus, I thought it would make sense to type up a little series of blog post showing some of the reasons why people choose plastic or fiberglass for their parts over various types of metal.

Non-traditional material such as fiberglass and thermoformed plastic often times have the ability to meet the requirements for a specific project without some of the problems that plague traditional materials.

Stainless Steel, Aluminum, other forms of steel, etc have been used by many different industries for many years. Many times people will choose these because they want something durable, stiff and with a high tensile strength. These materials offer impressive values for all of these properties. However, these materials also have some distinct disadvantages as well as noted below:

  • They are heavy and can be expensive…especially when buying by the pound. On parts where weight is a factor (in the transportation industry for instance), steel and aluminum can be an issue.
  • Texturing steel or aluminum is very expensive. If you are trying to match the texture of another part, this can often times be a challenge
  • Painting/Coating aluminum, steel, etc can be very expensive and time consuming
  • Fabricating aluminum or steel to meet specific geometry can be expensive and without the right tooling, can be very labor intensive. With the right tooling, much of the labor expense is eliminated. Unfortunately, tooling for these materials (like stamped parts) can be very expensive, heavy and difficult to move.
  • Many of these materials will rust when exposed to water
  • These materials are also conductive making them difficult if not impossible to use in certain applications where they may be exposed to electrical current.

So where does Fiberglass and Plastic fit and how do they address the issues above?

  • Both fiberglass and plastic are lighter than most any kind of metal. So when you have an application where you have critical weight requirements, much of that concern is eliminated by utilizing plastic or fiberglass. Although plastic and fiberglass don’t have quite the same tensile strength as metal, there are plastic resins and composites available that get very close and will still work for the product’s intended purpose. In regards to a strict strength to weight ratio, fiberglass (or carbon fiber) cannot be beat. The beauty of composites is they can be custom formulated for each application ensuring that critical strength requirements are met…and done so only where needed. Areas that don’t need the extra strength won’t have it…thus saving money. For thermoplastics, glass filled versions of materials available to thermoformers are coming out thus allowing for even stiffer parts than what was available previously.
  • Texturing a thermoformed part is very easy. Please follow the link to a blog post that discusses this in more detail. Texturing a fiberglass part can be done as well but is not quite as easy to do as it requires texturing the surface of the fiberglass mold
  • Both thermoplastic and fiberglass allow for molded in color…thus, when a plastic or fiberglass part is chipped or scratched, it will not be as noticeable as you would see on a powder coated part. Both of these can also have a separate coating put on top to allow for additional gloss or to mimic a certain look. For instance, our fiberglass facility currently makes several products that mimic granite. See pictures here. With plastic, a variety of different laminates can be added to the top of a part and some can be coextruded onto the sheet. For instance, we produce parts that have a beautiful metal flake look that is made possible by using a durable, scratch resistant acrylic cap. Then there are laminates. Laminates can allow for a part to look like: camouflage, carbon fiber, chrome, wood/burl, and everything in between. If a part has to be painted, this is also possible with fiberglass and plastic parts.
  • One of the biggest reasons people choose to use fiberglass or thermoformed plastic instead of some type of metal is due to the ease of producing complex geometry. In all metals, as mentioned above, geometry is produced via welding, roll forming, bending, shearing or stamping. Many of these processes are expense and labor intensive. Stamping, although very affordable when it comes to piece pricing, requires purchasing an extremely expensive tool. With fiberglass or plastic, the tools are very affordable. Complex geometry can be easily produced utilizing a hand sculpted or CNC cut pattern…both of which Arrowhead offers. No welding or expensive tooling is required. Additional geometry, fasteners, stiffening ribs, etc can also be added to a fiberglass or thermoformed plastic part after the part is molded.
  • Neither fiberglass or plastic will rust so you don’t need to be concerned with these materials being exposed to water.
  • If you are worried about flammability, both fiberglass and plastic have resins and materials available to meet even the most stringent of fire ratings.
  • Worried about electrical current? Both fiberglass and plastic ofter electro static dissipative resins and/or top coatings thus allowing them to be used around electrical current.

As you can see, thermoformed plastic and molded fiberglass parts offer a lot of advantages over materials such as steel and aluminum. Can they replace every part? No. Metal will always have its place. But as polymer and resin technologies continue to advance, the few advantages mentioned above that metal has over fiberglass and plastic gets less and less. Fiberglass and plastic are getting stronger, stiffer, more durable, more impact resistant and more affordable as the technology continues to evolve.

Wondering if switching to molded fiberglass or thermoformed plastic is a good idea for your part? Give me a call and let’s talk about it.

About the Author:

Mark Kishel
Mark KishelSales Engineering Manager
Arrowhead Plastic Engineering, Inc.
1151 N Harford St
Eaton, IN 47338
765-396-9649 fax