By Scott Rishell, Design Engineer, Mack Molding and Kathleen Murray, Communications Manager, Synectic Engineering
One of the largest advantages of choosing Synectic Engineering for your next project is its relationship with its parent company Mack Molding. As a leading custom plastics molder and contract manufacturer serving a range of markets – medical, industrial, transportation, energy/environment, computer/business and consumer – Mack’s customers are varied and so are their needs. Mack’s 95+ years of molding allows them to choose materials based on customer specifications, moldability of design, and cost. Choosing the right material early in the design process, streamlines the time and cost to market by picking the correct path every time. This a value add in the design cycle, for both our clients and our design process.
To meet the diverse requirements presented by so many programs, Mack has vertically integrated services, including design, prototyping, supply chain management, machining, sheet metal fabrication, molding, painting, assembly, testing and even fulfillment. Working together, we are able to offer our client’s a full portfolio of services from concept to production. Synectic and Mack combined have over 130 years of knowledge and experience allowing us to stay competitive in an always changing market.
One area where we often find the most distinctiveness is in resin selection. Mack has a wide portfolio of molded parts, and each is unique based on the customers’ requirements. Beyond aesthetics, like color, a material’s properties, processability and cost all play a key role in determining a resin’s suitability for an application. With thousands of grades to choose from, and new ones being developed to fill market niches, customers often turn to us to help them navigate the resin selection process.
Here are some of our key considerations we weigh when making a selection:
A part’s strength requirements need to be considered as resin classes have various tensile strength, tensile modulus and elongation at break. Thermoplastic resins offer a variety of strength properties that can often be modified with fillers like glass or carbon fiber.
Many customers are concerned about how chemicals, including cleaning solvents and process reagents, interact with their resin selection. In these cases we consult published testing data from resin manufacturers that show a material’s performance in each chemical. In some cases the data may not exist and testing with specific chemicals will be requested.
Parts that will be exposed to extreme hot or cold conditions need to be made with resins that are rated accordingly, making the long term service temperature and heat deflection temperature critical performance metrics. Other conditions to consider include exposure to UV light and high humidity.
Commodity vs. Performance
Whenever possible Mack strives to pair customer applications with commodity resin grades due to the inherent cost and availability advantages that come with higher volume raw material production. Some projects call for specific properties – strength, heat resistance, etc. – which is where performance resins excel.
Amorphous vs. Semi-crystalline
Selecting amorphous resins can often be advantageous as they can provide wider processing windows and improved dimensional control due to their random molecular structure. They can be transparent and are compatible with many adhesives. Semi-crystalline materials offer improved mechanical and thermal properties but can be more difficult to process.
The amount a resin shrinks during the molding process can have a huge impact on the ease of building a tool or developing a successful molding process. For this reason we try to select resins that have lower shrink rates whenever possible.
Once all of these factors are accounted for, the list of suitable resins is typically cut down to a manageable number to consider. It is here that the Synectic and Mack team leverages its proficiency with particular materials, coupled with expertise in design and development, to make the final determination of a grade.
Are you considering using plastic injection molding for your next project? Contact Synectic today and we will work with you to develop a product with the most optimal material selected for product performance and moldability. Let us show you how we can bring your ideas to life!
Check out our other article in this series How to Choose: The Truth About Fixed-Fee vs. Time-and-Materials
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