The development of engineered resins over the last few decades have brought new opportunities for plastic injection molding to become a dominant material choice for manufacturing. Many parts that were only considered for metal are now a feasible option for injection molding. Companies that have made a change in materials from metal to plastic have found a cost savings of 25 % – 50% through the manufacturing process.
Plastic injection molding has thousands of resins to choose from, and the right combination of fillers and base resin will produce a part that can outperform metal. Beyond the material, design can incorporate ribs and gussets to add additional engineered strength. That strength can exceed the capabilities of metal without extra manufacturing or cost for additional parts needed to compete with a comparable plastic part.
Some of the benefits when converting from metal to plastic include:
- Reduced Manufacturing Costs – Plastic injection molding does not produce many side effects and has very little scrap material after the process. Extra lubrication, runners from the molding process, and extra labor isn’t a requirement. Negating those, plus other manufacturing restrictions, will reduce the overall cost of manufacturing. That can equal increased profit and a reduced cost that will make your product more competitive.
- Reduced Initial Tooling Investment – Metal casting and stamping dies can take 12-16 weeks to complete after the initial design is complete. Plastic injection molding dies can be done as quickly as 6 weeks. Reducing the development time in half means you can start producing parts sooner. Beyond the initial tool time and cost, plastic injection molds can last up to six times as long as casting and stamping molds before they will need to be replaced. That can save additional money over the life-cycle of the product. As crazy as it may sound, the molding dies themselves can be made from plastic too. Imagine plastic dies that produce plastic parts!
- Infinite Design Possibilities – Complex designs specified for metal products require a significant amount of development time and cost. Casting can use molten metal to form complex shapes, but it doesn’t offer crisp corners and tight radiuses well. Plastic injection molding has the ability to use pressure to fill the mold completely regardless of the corner conditions. Plastic offers the option of simple embosses for extra part attachment which wouldn’t be easy to create in a metal part. Plastic also can weigh less and cost less to package and ship.
- Environmental Corrosion Resistance – Plastic is naturally corrosion resistant by nature, where most metals need a secondary or tertiary operation to apply a coating to resist corrosion. Those extra processes add extra cost, and alloys developed for corrosion resistance are also costly.
- International Regulatory Compliance – An additional issue with a secondary coating may be tied to regulated materials in foreign countries. Converting a product to plastic may negate the need and cost of a secondary coating, plus make it easier to export to foreign markets. The markets can mean new business, and an ever expanding global operation.
While those benefits make plastic sound like an obvious choice, the design needs to incorporate considerations for structural strength, chemical resistance, and environmental temperatures. Additional ribbing, bosses, and engineered resins may be a requirement to handle the stresses applied to the part, and the temperature may be high or low enough to make plastic a poor option. It will be up to the design team to verify what design changes will be required for a given part when moving from metal to plastic.
Many industries are already making the conversion from metal to plastic through replacement tooling and new product development. Some of the ideas are coming from these industries:
Aerospace: With the note of plastic weighing less than metal, many metal parts are being replaced with engineered plastics that can reduce the overall weight of the airplane. Reducing weight decreases fuel usage while in the air.
Automotive: The Saturn brand was known for major body panels made from plastic. It was a bold move at the time, but the trend could come back in to favor with better engineered resins and niche markets producing low volumes. Smaller brackets and support features are being converted to simple plastic parts too. With the aftermarket able to 3D print large parts on a reasonable scale, replacement and new products may be developed with plastic in mind to reduce cost and weight.
Home Appliances: More and more appliances, both large and small, are being converted to plastic. The individual components can be made more efficiently with plastic molding, while the exterior body could be design for plastic to reduce weight and secondary coatings. Why offer a product in a single color or a reduced amount when you can offer almost any color imaginable for almost the same cost?
Supply Chain: With more global commerce and exports happening ever year, packaging is being converted to reusable plastic that can be shipped anywhere in the world. Shipment by large cargo ships encounter corrosive sea water that doesn’t affect a plastic container. Individual parts and bulk packaging are also not affected, which makes the plastic packaging indefinitely reusable.
When you’re thinking of converting from metal to plastic, you need to ask what the end goal is from the change. Reduced weight? Reduced cost? Reduced secondary manufacturing and handling operations? What environment the part will operate in and how it functions will also help to dictate if the change is a good choice. If you have a potential design option or an idea to move from metal to plastic, we’d like to hear about it. When you’re ready to collaborate with our elite team, call (425) 339-0288 or email us at firstname.lastname@example.org.
Matthias Poischbeg was born and raised in Hamburg, Germany. Matt moved to Everett, Wash., after finishing his bachelor’s degree in business in 1995 to work for Sea-Dog Corporation, a manufacturer, and distributor of marine and rigging hardware established in 1923.
In 1999, Matt took over the reins at Sea-Lect Plastics Corporation, a sister company of Sea-Dog and a manufacturer of plastic injection molded products with an in-house tool & die shop. Matthias Poischbeg is also a contributor to Grit Daily.