In a completive global economy, many manufacturing firms have turned to rigorous inspection procedures thinking that will cut costs while boosting quality. However, what many companies do not realize is that quality control cannot be an afterthought, especially when it comes to medical devices.

In fact, firms that try to inspect quality into manufacturing are usually plagued by product waste, high failure rates, and inefficiency. In contrast, companies that design quality into the whole development process and focus their inspection protocols can boost their efficiency, smooth regulatory approvals, and even gain a competitive edge.

Naturally, the question arises, how do companies build quality into the entire product cycle? First, begin product development by identifying all the product requirements. The goal of future quality checkpoints then becomes ensuring these requirements are consistently met.

Next, make sure all specified attributes are measurable. For example, it is not sufficient to specify that a device's material must be “soft” for proper performance. Instead, it's necessary to determine the exact hardness levels and tensile strengths needed. The quality-testing system must have the capability to test whether the material has the exact properties required and that these properties will not be altered by exposure to heat, moisture, or vaporized solvents during manufacturing and production.

Design verification is essential to ensure product reliability because it measures and tests critical attributes of each device component. The goal is to verify that a design has inspectable dimensions and to demonstrate that the finished device performs in conditions similar to actual production. A product should be released to manufacturing only after the successful completion of its design verification.

When designing a manufacturing process, the goal is to efficiently produce finished products that meet functional specifications, and with a no-failure rate. To meet this objective, it is necessary to build-in inspection as early in production as possible, before steps that significantly add value. This cuts manufacturing costs, reduces product waste, and boosts productivity.

When products are inexpensive to produce, it would be optimal to complete an entire manufacturing procedure without intermediate inspection points. But it is not hard to see that it is wasteful and prohibitively costly to discard complex under-performing products once completed.

For these products, it's important to decide where in production to implement inspection steps. Typically, inspection should begin with the verification of components. Factors to consider when implementing an inspection system include the speed of the line and the company's cost requirements. Base both on forecasted production volumes. Manual, semi-automatic, and automatic lines all require different inspection modes.

Of course, the product being manufactured is also important. Disposable devices, implantables, and capital-equipment products have different testing and inspection needs. Consider that disposable devices are mass produced while capital-equipment products are often low volume. They also typically use complex and diverse software, electrical, and mechanical components that impose a different burden on quality control. A production line in this case might require manual assembly and 100% inspection — prohibitively costly with disposables. In contrast, implantables such as pacemakers and stents require rigorous scrutiny.

Custom or off-the-shelf?

Having made the design-verification decisions, a choice becomes whether to incorporate custom or off-the-shelf inspection systems, or a combination of the two. For mechanical products such as snap gauges and laser micrometers, off-the-shelf equipment is often most cost effective. The correct inspection equipment, easy to maintain and usually certified and traceable to a reliable standard, helps garner regulatory approval.

But this inspection equipment is not adequate for precision devices such as micro-surgical instruments. However, this doesn't mean that custom solutions are necessarily the next-best option. At times, it's possible to modify an off-the-shelf system. For these cases, contact the manufacturer. It will know if this is correct.

A custom inspection system is necessary when these options are not feasible. For example, consider a device that requires identifying the yield strength of critical screws without breaking them. By definition, yield strength measures the force required to break a component. So this quality test probably requires a custom system to avoid breaking large quantities of parts. Obviously, custom systems are the most costly to develop, implement, calibrate, and maintain. Therefore an ROI analysis should be conducted.

Examples of custom equipment

In one job, our company designed a packaging line for a periodontal product that required continual in-process inspection. Production required inserting a bio-absorbable antibiotic into pill pockets cut in the package. Inspection had to identify that pills were properly inserted, not located within the package's sealing area. This would violate the seal and damage the product. So we adapted a vision-inspection device to identify that pills were inserted into the correct package area. After the package was sealed, another inspection point verifies the seal's integrity.

In another case, we designed a custom manufacturing and packaging line for a disposable test kit. Quality control was especially important to prevent the kits from producing inaccurate results. Reagents were spotted onto a matrix material but were not visible to human eyes. To identify that the reagents were present, we built a UV-based vision inspection system to check the size and shape of the reagents. Trend analysis determined if the spot size or shape were moving in a certain direction. The custom system was flexible enough to handle many other kits manufactured by the company. These included those for pregnancy, strep throat, and scarlet fever.

Watch your P's and Q's

To build quality into manufacturing operations, it is absolutely critical to conduct Installation Qualification, Operational Qualification, and Performance Qualification (IQ/OQ/PQ) tests for the manufacturing and inspection equipment. IQ/OQ/PQs ensure the manufacturing method can make products that meet the original requirements. IQ/OQ/PQ is also essential to determine that, in fact, the inspection method can detect and reject a product that does not meet specifications.

In more detail, Installation Qualification provides guidelines to test the installation area to determine it provides the necessary conditions to operate the equipment. These might include, for example, voltage, particulate count, temperature, or humidity.

Operational Qualification is conducted after installing manufacturing and testing equipment. For this qualification, conduct a run without product to make sure the equipment functions as needed.

During Performance Qualification, conduct a minimum of three runs using lots of different components. Run at the upper and lower process limits to demonstrate the line's capability to handle production. For products that are prohibitively expensive, it might be cost effective to conduct Performance Qualification with mock components or representative parts. However, most of the time, it's best to evaluate production performance with actual products.

Neglecting any of these qualifications can cast negative consequences on production. These might include product damage, misaligned parts, and failure to identify poor-quality products. For example, consider a company with a production line requiring 115 to 120 Vac at 15 A that elects not to conduct Installation Qualification. The manufacturing equipment appears to perform properly despite voltage levels below the designated requirement of 115 Vac. When problems arise in Performance Qualification or in production, it will be difficult to trace them because the voltage was not tested in installation qualification. This delays troubleshooting and increases downtime.