Laser welding validation helps ensure product quality and facilitate FDA compliance.
It’s 10:30 p.m. at Top-Notch Devices, a hypothetical medical device company. Line supervisor John Smith is scratching his head, with an FDA noncompliance letter in one hand and a laparoscopic component from the most recent production run in the other. He’s tired and wants to go home, but his problems aren’t going away anytime soon.
Top-Notch’s mistake? The company didn’t do a full validation of its laser welding process. It thought it was enough to verify it carefully, but it was wrong. FDA decided that a weld failure could result in a component being left in the patient’s body, and the laser welding documentation didn’t demonstrate robust process control.
While verification is an important step to ensure a device is being manufactured according to specifications, validation is necessary to ensure that it actually came out the way the manufacturer (and the customer) intended. For example, you could make sure two people have the same sweater pattern, yarn, and needles—that’s verification. But their sweaters could come out different sizes because one person knits more tightly than the other—that’s where validation comes into play.
Naturally, using laser welding when manufacturing medical devices is much more complicated than knitting, and the potential consequences of using unvalidated processes are far more severe than creating a sweater that is too tight.
The medical device industry relies on lasers for precise processing of materials. Contract manufacturer Tegra Medical, for example, uses it to process materials such as nitinol, platinum, nickel, titanium, and stainless steels for manufacturing orthopedic, cardiovascular, gynecological, and minimally invasive devices. The company uses Nd:YAG lasers with a variety of beam delivery and motion-control integrations to provide diverse processing capabilities from tube and flat stock, including cutting, welding, marking, and engraving.
Laser welding works well with dissimilar metals and heat-sensitive assemblies, as well as in conditions where thermal distortion is a concern. Because it is a repeatable process, laser welding can be statistically proven and easily validated. Some manufacturers, however, either don’t perform validations properly or don’t conduct them at all.
No company wants to receive an FDA warning letter, especially because letters are posted publicly on the FDA Web site. The following laser welding validation issues are among the most common that FDA finds:
When your company is faced with a validation issue, you’ve got a host of problems to deal with, from embarrassing to expensive.
That validation can be costly shouldn’t be a surprise. The embarrassment is another unwanted side effect, and it can actually be serious. Anyone can search the FDA Web site for validation error letters. Your company’s reputation can take a big hit, and not only with the customer whose device failed validation. Your other customers might question their relationship with you, and potential customers might be more easily swayed to chose another supplier. If the validation problems are serious enough to require a recall, whether voluntary or mandated by FDA, expect an even bigger public-relations headache.
Taking into account the risk, the complexity of the parts, and your internal quality requirements, you’ll likely see that it makes more sense to do the validation right from the start. In the best-case scenario, your customers will require validation as part of the complete manufacturing process and will audit it closely.
Many of the benefits of validation are obvious, such as the fact that it ultimately improves the quality of your product and saves the expense of a failed production run.
Some of the other benefits become apparent with time and experience. You might even say that validation makes a company smarter. For example, it improves your ability to set parameters during the operational qualification study. Parameters used for validation and production of a laser welding process include the following:
When processes or parts are especially complex, validation provides a way to help control them. It enables real-time monitoring and process adjustments so you can improve processes statistically and evaluate your performance daily.
Given the risks and expense of not validating, it may seem obvious that most companies should implement this process. Some companies, however, do have their reasons (or excuses), some of which might even seem to make sense.
Customer pressure is one of the biggest reasons why validation has been neglected in the past. It may seem odd that a customer would request that a process not be validated— everything about validation would seem to benefit the customer. But validation takes money and time—sometimes a lot of the latter. And customers are often in a rush. They’re facing their own competitive pressures, and reducing the lead time from their suppliers is one strategy for remaining competitive. As a result, some companies skip the full-validation process, even if it would take a few days or weeks. These companies do the best they can as quickly as possible to meet the customer’s delivery requirements.
Companies don’t do a lot of validating because they don’t have the resources or even the necessary understanding. Companies that aren’t good at validating aren’t likely to encourage their customers to take this step and incur the associated expense and added costs.
Some companies require validation right from the start, and others don’t push for it. One approach is to always validate anyway, if only for the company’s own benefits. Especially if the firm is making a new product, it is helpful to understand the process parameter settings. The company can run qualifications and create documentation, which can be useful not just for the initial customer, but also for future customers.
Fortunately, validation is trending upward. Thanks to additional pressure from FDA, a growing number of customers are making it a firm requirement.
The Quality System Regulation (QSR) known as 21 CFR Part 820 and ISO 13485:2003 require that validation include installation qualification (IQ), operational qualification (OQ), and process qualification (PQ). The Global Harmonization Task Force (GHTF) published guidance that defines these terms as follows:1
Laser welding IQ typically begins with a close look at equipment design. For example, when installing CNC-controlled machines, you would examine the material from which the equipment is constructed as well as installation conditions, wiring, utilities, distributed numerical control configuration, and functionality. One of the key function tests to perform is known as GxP. The name of this test refers to good manufacturing practices (the x represents a variety of requirements). GxP is applicable if the equipment performs one of the following functions:
FDA guidelines on electronic records and electronic signatures should be followed. For instance, as part of its IQ processes, Tegra automatically includes equipment calibration, preventative maintenance and cleaning schedules, safety features, and all supplier documentation, including prints, drawings, manuals, and software documentation. The company determines if it needs to validate the machine software, creates a spare parts list, and assesses all environmental conditions, temperature levels, and humidity. After the machine meets all requirements per the IQ plan, it is released for the OQ and PQ validation activities.
During this phase, a company will typically create parameter settings. It’s important to know the range within which laser parameters must be set in order to make a product that meets specifications.
Other parameters you might examine during the OQ phase would be how long the process takes, temperature, software requirements, and pressure. Setup conditions are also important to track, along with sample size, process control limits, raw material specifications and handling, as well as employee training.
Additionally, you want to do a short-term stability and capability analysis of the process and evaluate a potential failure mode. This can be accomplished in two ways. The first is through planning documentation, such as developing a process flow plan and process control plan. The second is process failure mode and effects analysis (PFMEA) or fault analysis.
During OQ, any statistically valid techniques can be used to determine the capability of your process. These include design of experiments (DOE), which can optimize the process; process capability studies (known as gage repeatability and reproducibility (GR&R) or measurement system evaluation), and control charts to monitor the process in real time. Depending on what that process is, you should be able to put the proper techniques in place to deliver product that fully meets the customer’s requirements.
Performing OQ for a laser welding process also requires destructive testing to better understand exactly what conditions could cause the material to fail. This test uses a statistically significant sample plan such as a size of 60 parts based on a reliability and confidence level of 95%.2 The purpose of this test is to provide a ductile failure (when two parts are being welded, the raw material should fail before the weld). The outcome of the test is torque or tensile data that shows with 100% accuracy how the material will hold up under different conditions.
In the PQ phase, you want to challenge your process by ensuring you can repeat the setup and operation at the derived nominal parameter settings. So, you would run your laser welding process parameters at the nominal condition three times in a row by starting and shutting your process. During the PQ, the welding process parameters used are the nominal conditions obtained during the OQ study. These conditions are used to conduct three consecutive studies by starting and shutting the process. It is very important that each test run focus on different operators, different machines, different shifts, and different raw materials. This ensures that when any one of those variables is changed, the parameter settings will still meet the customer requirements.
The testing should include the following steps:
Once you have finished challenging your process leave it alone. Occasionally, certain processes may require tweaking. As long as you are within the parameter settings established during the OQ study, it is acceptable to make the changes. Process changes can be made based on process capability studies and outcome from the in-process real-time control charts.
You want to challenge the process, to simulate conditions that will be encountered during actual manufacturing. This way, by the time you start full production, you will already have an excellent understanding of your process and all the issues that might arise. You’ll know how to address problems by robustly analyzing them through a statistical applied technique. By eliminating all issues and concerns, you start running production with product that meets all quality requirements.
Laser welding is just one of many processes that a medical device company needs to validate. The best way to ensure good validation processes across the company is to have a devoted quality and regulatory department that will work side-by-side with engineering and manufacturing specialists.
Engineers should consider validation during the design phase. They should investigate the process being chosen to produce their part and make sure it is statistically capable of meeting specifications. This will streamline the validation process.
The quality and regulatory department needs to be aware of and understand all FDA regulations. It must ensure no changes are made to the manufacturing process after approval, because changes will necessitate revalidation. Validation training is key; team members must be familiar with different types of validation, when and how to validate, and when to verify. They will make sure customers understand the time and money involved in validating, so there won’t be any misunderstandings.
If you’re in the business of manufacturing medical devices, you understand how much time, work and investment goes into the entire process. And you know that the stakes are high – a product failure isn’t just a fiscal problem, it can cause devastating personal consequences, even death. Validation helps minimize the risks and ensure you’re manufacturing devices your customers can depend on.
1. GHTF/SG3/N99-10:2004 Edition 2, (PDF) “Quality Management Systems—Process Validation Guidance.”
2. Juran’s Quality Handbook, McGraw Hill 3rd edition, 1974 section 6.4.1.
Jean Mattar is vice president, quality assurance and regulatory affairs at Tegra Medical (Franklin, MA).