Designing with elastomers for medical applications requires attention to many factors: materials compatibility, performance characteristics, biocompatibility, and regulatory issues, to name a few. When working with a third party supplier, the supplier's role in the product development process must be defined and there needs to be good communication between supplier and customer teams.

A robust design process taps both the expertise of the elastomer supplier and the medical device manufacturer. Key areas to address include:

• Development of an understanding of the design, application, how the device will be used, and any risks associated with use.

• Identification of substances that will come in contact with the parts produced, such as drugs, reagents, or tissue cells, and the likely reaction of each substance with elastomers.

• Identification of material biocompatibility issues, customization, and toxicity approval.

• Analysis of the complexity of the parts, tools design considerations and manufacturing process requirements, along with an analysis on whether the process will produce any toxic waste or cross contamination.

• Early identification of qualification testing requirements for achieving approval for clinical trials and appropriate end market regulatory agencies.

Analysis of costs for global competition

When product development involves elastomer compound formation, the complete product development process includes design of experiment, concept development, prototyping, design for manufacturability (DFM), and management of third-party qualification testing, rather than simply prototyping and DFM assistance alone.

Initial focus is placed on DFM analysis for tooling, since it has the longest leadtime and impacts both quality and cost. Typically the customer supplies an initial sketch of the product. A preliminary manufacturing process is mapped out and studied. The DFM analysis evaluates tool design, tolerances, likely production volumes, and mold material. Often, tradeoffs must be considered.

For example, a very precise and complex part may have a short tool life, since tight tolerances will be impacted by tool wear. Similarly, tools can be automated to minimize manual processing. But, if mold automation is desired it is important to create a foolproof design that has only a single orientation, since tools that are incorrectly oriented will crash. The cost benefits of eliminating manual labor and increasing quality through automation must be evaluated against the higher tool cost both in terms of initial tooling cost and maintenance over time.

Mold material selection is also important. If the elastomer material is corrosive, it will corrode the mold. In those cases it is important to select a corrosion-resistant steel.

Secondary processes increase cost and can cause quality issues, so where possible tooling should be designed to minimize the need for secondary processes, such as deburring or deflashing. In terms of quality control only dimensional checks can be automated. To check for cracks, manual inspection is required.

The next step is selection of the molding compound material. The customer's functional requirements must be understood. How long does it need to last? How will it be used?

The material must be biocompatible. Under USP Class VI requirements, vegetable-based ingredients must be used, as animal-derived products may have a risk when used in drug-delivery systems. Cytotoxicity is another potential issue. The material must be antimicrobial. Additionally, reagents are changing so rubber surfaces may have lower metallic content.

Typically customers have several stages of qualification that include both product qualification and process qualification. Customers today do not simply audit a manufacturer's process. Instead they want to make sure the operation and equipment are in place. Normally, they evaluate in three phases:

• Installation Qualification (IQ), which looks at the equipment, manufacturing facility, and mold.

• Operational Qualification (OP), which looks at operations.

• Production Qualification (PQ), which looks at the production process.

Customers are also looking at downstream processes, since it is necessary to do a lot of compounding to make the elastomer. Typically customers want to audit all the front-end processes as part of their qualification process. This can present a challenge in supply base relations for the elastomer molder, because chemical or other material suppliers often view their processes as proprietary and may not want their standard processes audited. It typically is an area of negotiation in the qualification process.

Another potential challenge, given the length of qualification processes, can be regulatory changes. While compliance is ultimately the customer's responsibility, the elastomer supplier can also support the process. For example, Rayco Technologies Pte Ltd has an in-house laboratory. Its laboratory manager routinely monitors chemical updates for Europe and the U.S. related to regulatory requirements such as restrictions on hazardous substances. The ISO 170725-certified lab supports the design process by performing chemical and mechanical tests, in addition to making sure that manufacturing facility is aware of new regulations.

Once all three qualification phases are approved, control plans, inspection plans, critical dimensions, and work instructions are generated. DFM analysis is applied over the whole chain from design through manufacturing to quality and inspection. A buy spec, which specifies all the materials that need to go into the product, is also drawn up. Once the buy spec is generated and approved, full production begins.

Global issues

No discussion of the design process would be complete without discussion of cost issues relative to global markets. In any design process there are also hidden costs driven by geographic choices. Some key questions to ask in assessing these costs include:

• Will language barriers create an issue in design discussions?

• Does the supplier have the infrastructure to support recordkeeping and other requirements related to regulatory compliance?

• Is my intellectual property safe?

• Does the elastomer supplier have access to a strong network of suppliers capable of supporting medical products?

As an elastomerics solutions specialist, Rayco is able to answer these questions in the affirmative. Our company maintains design and laboratory facilities in Singapore, where a strong medtech support base is in place, English is the official language of business, and intellectual property rights are easily established and protected. Rayco capabilities include dispense-in-place gasketing (DIPG), liquid injection, compression and transfer molding. We can also overmold elastomers with materials such as plastic, metal and other substrates, as well as provide PTFE coating.