Keys to classifying failures for quality engineers


Medical device failures are a common-and costly-occurrence. They can lead to a product recall, affect the product development cycle, and result in extra expenses for manufacturers. The reasons devices fail can be complex, making it difficult for quality engineers to classify the problem.
 
What can quality engineers do to remedy this problem? Consider these factors:
 
  • Understand why failures occur: Most device failures are caused by a misunderstanding of how a material’s properties, processing, and environment work together. In many cases, failures can result from a combination of wrong material selection, poor chemical resistance, high-stress design, or inconsistencies in manufacturing processes.
  • Collaborate with your supplier: Working with material suppliers on material selection, testing, part and tooling design review, and secondary operations can give quality engineers access to knowledge and resources they may not otherwise have.

A safer connection for stopcocks

Drug- and lipid-resistant polymers are playing an increasingly important role in enhancing patient safety. Stringent sterilization techniques can cause cracking, crazing, and hazing in commonly used plastics. They can also have a yellowing effect on certain polymers, which can impact color-coding systems in connector applications.

Eastman Tritan copolyester is resistant to a wide array of medical fluids, such as oncology drugs, drug carrier solvents, and lipids. Along with its toughness, low residual stress, and color stability post-sterilization, Tritan is an excellent choice for fluid management components.

Regulations in the medical market are constantly changing. When Elcam Medical, a world-class manufacturer of disposable medical devices for the OEM market, wanted to further improve the safety and efficacy of its fluid management devices, they turned to Eastman to find a polymer that complies with new regulations while still optimizing performance.

Secure connections for safer devices

Small-bore connectors are important components of many enteral feeding devices. Good design is critical, as tubing misconnections or failure can put patients at risk for serious injury or death.

Global design standards for tubing connectors are now helping improve patient safety and device efficacy. ISO 80369 requires small-bore connectors to be made of semirigid and rigid materials, making incorrect interconnections less likely. Enteral devices were the first of all the clinical applications to undergo this change.
To meet this standard, you may have to adjust your design, which means you may need a new mold or new materials. Eastman Tritan copolyester is a rigid material with the properties needed to comply with these regulations.

Polymer compatibility with oncology drugs

As part of the continued effort to improve cancer treatment, pharmaceutical companies are developing new and improved oncology drugs. However, advanced oncology drugs and carrier solvents challenge the chemical resistance of polymers used in delivery devices. Such conditions can prevent devices from working properly or cause them to fail prematurely. When there is a pattern of compromised device performance or life cycle, regulatory agencies may tell manufacturers to stop using certain materials to protect patient safety.
 

Putting device durability to the test

When choosing a polymer for a medical device, it’s crucial to understand how the material will perform in the real world. Eastman’s 4-step test helps show how plastics hold up when exposed to frequent disinfection, but it’s also important to see how that translates into actual performance in the field.

 
That's why we developed the housing drop test. This test can be used alongside the 4-step method to understand how a well-designed device will respond to impact after being disinfected.

 

UCSF Biomed Shares Medical Device Breakdown

Watch this fascinating conversation with Richard Fechter, a principal developmental engineer at the University of California, San Francisco Medical Center.

Thank You for Asking.

We often receive great questions about molding with Eastman medical grade polymers and are always glad to provide answers and more information. Here is a response to a recent query from our inbox:
 
“What is the heat deflection temperature for Eastman MXF221 copolyester?”
 
Heat deflection temperature (HDT) is the temperature at which a polymer or plastic deforms under a specified load. The HDT of our latest offering, Eastman MXF221 copolyester, is outlined here.
 
Thermal properties
Deflection temperature  
  0.455 MPa (66 psi) 시 ASTM
D 648 
94°C (201°F)
  1.82 MPa (264 psi) 시

Eastman Tritan™ copolyester: Innovative properties for medical devices

Eastman Tritan copolyester offers a unique blend of processing and performance properties, including clarity, toughness, and heat and chemical resistance. It can also often be substituted into existing molds with minimal adjustments to processing parameters. This total balance of performance and processing gives Tritan advantages and design flexibility over many other commonly used polymers. Some qualities that make Tritan an excellent choice when it comes to molding parts for the medical market include:
 
  • Toughness: Exceptional toughness and durability. Medical device housings made with Tritan are impact- and shatter-resistant and have the ability to withstand extreme conditions.
  • Clarity: Outstanding clarity and color retention before and after gamma and e-beam sterilization.

Reducing stress in the assembly process

Parts made from Eastman Tritan copolyester can be assembled using a variety of joining techniques, including chemical, mechanical, or thermal methods. The choice of assembly method will depend on the end-user requirements of your application. With whatever method you choose, however, the assembly process can cause stress in devices.
 
The good news is that Tritan is an inherently tough material and can stand up to these stresses. Consider mechanical joining methods. In this technique, molded-in bosses are commonly used to accept screws or threaded inserts, while molded-in or postmold inserts are commonly used where a plastic cover or part must be removed repeatedly.
 

This Old Mold 3 - Hot runner systems

Tips for optimizing existing molds to run Eastman Tritan copolyester
 
Selecting the best hot runner system for your needs can vary greatly depending on the size of the part, polyester formulation, and part design. That’s why it’s critical that runner design and selection be discussed together. When using Eastman Tritan copolyester in an existing mold, consider the following factors when designing and processing hot runner systems.
 
디자인 안내서
When properly designed, hot runner systems can eliminate sprue and runner regrind, mold with lower pressures, reduce cycle times, and improve processing windows. Good hot runner systems should:
 

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