Key considerations for evaluating injection molding material costs
By Travis Minyard, Sr. Costing Engineer, Injection Molding
When you think of the cost of injection molding, your mind might immediately jump to molds and tooling — namely, their cost. Molds alone can cost anywhere from $2,500 to $100,000 or more. However, the actual cost of plastic injection molding is more than the cost of the mold alone. You also have to keep injection molding material costs in mind. Still, many material options are available, and selecting the most affordable plastic or the material you’re most familiar with might not yield the best results.
Where do you start? Here’s what you need to consider when performing an injection molding material cost comparison.
Injection molding material cost rules of thumb
Generally, the harder and more heat-resistant a material is, the more expensive it is. In some cases, buying a pricey material like polyetheretherketone (PEEK), a high-performance plastic that’s resistant to creep, heat, and corrosive substances and costs between $50 and $100 per pound, may be necessary. In others, a cheaper, more generic polymer may be enough, making the hard, heat-resistant material an unnecessary splurge that will impact your profit margin. It all depends on your product’s requirements.
Also, remember that materials similar to one another generally perform the same mechanically. If they differ in price, you can either opt for the one that’s a little cheaper or spend more money to purchase the material that can help you better fulfill your requirements.
You can also cut costs by introducing readily available (and relatively inexpensive) additives to your material. Using a material that is glass-filled, like PA6 GF30, will lower the amount of resin needed to create a product, replacing it with a less expensive alternative. However, using additives can also raise your costs, depending on the material. For example, carbon fiber is extremely strong, stiff, and resistant to heat and chemicals, but it’s still relatively rare and thus more expensive.
If you want to learn more about specific injection molding material options, visit the manufacturing materials section of our website for detailed information about the industrial-grade materials available for your next injection molding project.
Now, let’s move on to specifics.
How to evaluate injection molding material costs
Selecting an appropriate injection molding material isn’t as simple as choosing a material you’ve used in the past. After all, every project is different, so past performance isn’t an automatic indicator of future success. Instead, you should let part requirements, first and foremost, guide the material selection process. Here are some key factors to think about:
1. What your part is going to do
Start by thinking about the part’s function and whether the prospective material you’ve selected is well-suited for your part’s intended end-use. It’s tempting to prioritize budget concerns when evaluating injection molding materials, but the part’s function, being able to provide a long-term warranty, and preventing failures in the field are far more critical. After all, the plastic you’d use to manufacture a disposable spoon is not the plastic you’d want to use to manufacture a lawn chair, no matter how affordable it is.
Plus, deciding what your part will do makes evaluating injection molding material costs easier. For example, if you know you’re building a simple prototype to validate your design choices, you also know that choosing a less expensive plastic will suffice because the part doesn’t need to withstand wear and tear. You can then narrow down your material options considerably and avoid choosing a costly material that doesn’t suit your purposes.
2. Where your part is going to be
Once you’ve figured out what your part will be doing, you’ll need to consider where it will live. Will your product be inside or outside? Will it be used in a hot or cold climate? Will it be regularly exposed to water or sunshine?
Asking these questions will allow you to narrow down your options to materials that can withstand your part’s surrounding environment. For example, if you’re designing a lawn sprinkler, it will likely be outside most of the time, so your material will need to be resistant to UV rays. It will also frequently come into contact with water, so you can restrict your options to materials resistant to both water and UV rays. Finally, you may want to consider using an impact-resistant material, as someone could hit it with a lawnmower or landscaping equipment during everyday use.
3. Any chemical requirements
It’s also important to take chemical requirements into account. Think about whether your product will be exposed to acids, alkalis, or other chemicals, and then select a material that is resistant to such conditions.
4. Any post-processing concerns
Finally, you’ll want to consider post-processing. For example, if you know your part will need to be pad printed, you’ll need to select a material compatible with that process. On the other hand, if you’re creating an electronic housing, you’ll need to choose an electrically resistant material.
Once you’ve evaluated all of these factors, you can select an elastomer, general thermoplastic, or engineering resin that will meet your part’s requirements.
An overview of cost-effective injection molding materials
From polyethylene to polyetheretherketone, there are many injection molding materials available today. Among the most cost-effective injection molding materials are:
- Polyethylene (PE): This versatile variable crystalline thermoplastic is available in several types, grades, and formulations. Popular forms of PE include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and ultra-high-molecular-weight polyethylene (UHMWPE). Each form of PE has its advantages and disadvantages, but they are generally flexible, affordable, and resistant to chemicals and impacts, making them ideal for containers, toys, packaging, and pipes.
- Polyethylene terephthalate (PET or PETE): PET is a lightweight and recyclable clear plastic that’s resistant to oils, greases, alcohols, and diluted acids. It also offers low gas permeability, low moisture absorption, and excellent electrical insulation and is most often used in food and beverage packaging. You can also find PET in everything from mouthwash bottles to valve components.
- Polystyrene (PS): PS is popular for food packaging applications, as it’s non-toxic, light, resistant to water, and FDA compliant. It also offers high impact strength and good dimensional stability, though it is brittle and will dissolve when it comes into contact with hydrocarbon substances. Tubes, Petri dishes, lighting fixtures, yogurt containers, silverware, and single-use party cups are often made using PS.
- Nylon 66: Nylon 66, a member of the nylon family, contains several combinations of different monomers. It’s strong, stiff, and resistant to chemicals, making it suitable for luggage, airbags, carpets, underhood applications, and more. Adding glass fiber to nylon can lower costs, but your part won’t be smooth, and it may cause your mold to wear faster.
- Acrylonitrile butadiene styrene (ABS): This durable, strong, abrasion- and impact-resistant engineering thermoplastic contains acrylonitrile, butadiene, and styrene polymers. Sturdy yet inexpensive, ABS is used across many industries and is found in everything from computer keys to dashboard components.
Injection molding with Fast Radius
To effectively evaluate injection molding material costs, don’t think about cost at first. Instead, let your part’s requirements guide you. Create a list of everything you need your product to do or be, and then search for materials that match those requirements. After that, you’re free to start narrowing down material options by cost.
While other companies simply offer quotes based on your current design and chosen materials, Fast Radius goes above and beyond. Contact us today to speak with an expert about your next injection molding project, or create an account and upload your part file to get started with design insights and more.