The right materials

Plastics are often selected because they are relatively inexpensive and there are many from which to choose. If a device, such as syringe, must undergo extreme pressure, polycarbonates are used because of their strength. PVC is commonly used for tubing because it is inexpensive and flexible. Reusable devices, on the other hand, are typically made of more costly, sturdier materials such as ceramics or steel.

It seems obvious to consider end use when choosing a material for a device, but it's also important to consider shelf-life and material availability. Making the best selection calls for asking what kind of stresses and pressures the device must withstand. What temperatures will it encounter? How long must the material last? And where will it be manufactured? Some materials may be available in Europe, but not in the United States.

Assembly

Materials and assembly methods must complement one another. Disposable devices rely primarily on injection-molded plastic, assembled by bonding, gluing, ultrasonic welding, or radio-frequency welding. Changing raw materials is often viewed as an easy way to squeeze out costs. But the wrong material can make for a costly and inefficient assembly operation.

Manufacturing also influences disposable-device design. The entire manufacturing operation should be evaluated to determine where efficiency opportunities lie. For example, consider a device assembled from multiple injection-molded parts. The development team could simplify the injection-molding process. But this thinking also leads to increasing the number of parts in the device. The additional mold costs may be minimal but the extra parts add assembly steps. This lengthens the time to build the device, and could increase the risk of product failure in assembly.

Alternatively, the team could simplify assembly work by designing a device with fewer but more complex injection-molded parts. While this would require more complex and hence expensive molds than the simpler parts, assembly benefits from a streamlined operation. This way, the risks of product failure shift to molding. An analysis would first be required to determine if the more complex parts can be efficiently molded. The efficiencies gained in assembly may be lost because of longer molding cycles or in secondary operations such as annealing. These are possibilities and should be considered.

Ultimately, the best solution strikes a balance between molding and assembly operations to assure that the overall manufacturing of a device is repeatable and reliable. Assess the product-failure risks and decide where in the manufacturing process it should be addressed. This risk-based approach is a relatively new concept spurred by the FDA and the International Organization for Standardization (ISO) in Europe, two main entities that oversee the medical device industry.

In the past, the FDA evaluated each step of a product's lifecycle separately. Today, the FDA takes a systems approach based on risk that evaluates processes together.

ISO 9001: 2000, a quality management system outlined by ISO, looks to eliminate inefficiencies and therefore costs. Similar to the FDA standards, the intent is to minimize product defects.

ISO 14971:2007 for medical devices specifies processes to identify hazards associated with medical devices, estimate and evaluate the associated risks, control these risks, and monitor the effectiveness of the controls. The requirements of ISO 14971:2007 are applicable to all stages of the lifecycle of a medical device, and are not isolated to just one step or department.