When it comes to a new project, return on investment is a key metric to indicate success. One of the first challenges you’ll face on a new project is how to reduce time and cost without jeopardizing quality or brand awareness. For injection molding, your answer may be to change the material your injection mold is made from. Have you ever thought to use aluminum instead of steel molds? In certain situations it makes perfect sense, but others it won’t. Not sure how to choose when to use aluminum or steel molds? Read on to learn the criteria to choose from:
Steel Has History
Steel has historically been the mold material used most often. It has advantages for strength and repeatability, but it requires more time to develop. These reasons may indicate that steel is the better option for your project:
- Steel molds can produce millions of parts year after year with repeatable results. That fact may bring amortization costs lower on a part-by-part basis if the mold needs to be used for a long period of time.
- Repeatable means consistent quality, and steel molds can hold tighter tolerances over a longer period of use or for more molding shots. This also allows for increased design intricacy and multiple inserts for complex parts.
- Complex designs may require more cavities in the mold to produce everything needed. A steel injection mold can utilize more than 8 cavities, which makes it a great choice for complex designs with multiple components.
- Higher-end quality products may require specific or multiple surface finishes to stand out from the competition. Steel molds offer more finishing surface finish options and allow for deeper texture than aluminum. That may be a large deciding factor in which type you use.
Steel has more history and is more commonly used in multiple industries. That means most injection molding facilities can run a steel mold without too many issues. You may need to ask questions centering on steel molds when researching a new molding facility. What is their history with steel molds? How do they clean and maintain them? Simple questions, but they can give you an idea if the molder is a good potential partner for your business.
When is an Aluminum Injection Mold the Better Choice?
You may have not realized there were other options beyond steel for injection molding. Aluminum is a common choice for certain projects that may need shorter development time or only require a reduced number of shots to be made. Is aluminum a better choice? These reasons may say yes:
- Aluminum molds typically require less time to produce than steel molds. Aluminum can be ready for use in three or four weeks depending on the design, while steel can take eight to twelve weeks or more depending on the complexity and surface texture.
- Aluminum molds are generally lower cost than steel. Some manufacturers can quickly develop an aluminum injection mold for half the cost of steel, and those savings can be used elsewhere in the project.
- Aluminum molds are less durable than a steel mold and need a different maintenance plan than a steel mold. Don’t let that deter you if you need a large quantity of parts molded though. Aluminum molds can withstand many thousands of shots in a year with proper care.
- Aluminum molds can use many similar plastic resins as steel molds, so material choice shouldn’t be a concern when choosing a mold material. Over a hundred resins can be chosen from including PP, PC, LCP, ABS, POM, and liquid silicone rubber. Aluminum molds are common with thermoplastic and thermoset resins, but be cautious when using abrasive resins in aluminum molds. Aluminum is a softer material and can be damaged with certain resins. Surface texture and tight tolerances can be lost with tough resins.
- Aluminum molds are typically made from three primary aluminum types: Hokotol, Alumold 500, and QC-10 by Alcoa. If you request a quote from a mold maker, expect to see one of these three options listed most often.
- Aluminum is more difficult to modify, so if your design has many revisions to make aluminum not be the best choice initially.
- Aluminum dissipates heat better than steel, so the mold design may or may not require cooling lines to increase cooling during use. That can reduce costs for manufacturing, mold design complexity, and reduce setup time. All of these factors can reduce cost for the project.
As mentioned previously, aluminum requires a similar but slightly different maintenance plan than a steel mold. Aluminum molds will also require different molding machine settings. If your molder isn’t familiar with aluminum, it may take a longer time to develop the correct settings for optimal molding conditions. Take that into consideration if you’re searching for a new business partner.
Can I Mix Materials in Injection Molds?
You may have a situation that requires benefits from both aluminum and steel, but don’t want the cost of steel or the lower durability of aluminum. Can you have the best of both materials? Absolutely! Aluminum can be a quicker turnaround, and you can have steel inserts in strategic places for durability. You can also add aluminum details in steel molds that may be harder to cool or require a deeper draw creating challenges. There isn’t a perfect scenario of which material goes where and when, so it should be a discussion point with your mold maker. Strategic material choices can also be included when discussing project timelines, volumes, and investment budget.
Choosing between aluminum and steel for an injection mold seems like an easy decision, but the truth is no one scenario defines what material is best. You may need benefits of both, without the limitations of either, to ensure your project has a successful future. SEA-LECT Plastics has an elite team that produces world-class prototypes and products. We can offer support to determine what type of mold you need, what resin to choose, and how to invest in your future. Give us a call at (425) 339-0288 or email us at email@example.com. Your injection mold material is just one key item to discuss for your project. We look forward to offering support and advice on your next project.
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.