How thermal imaging enables real time, non-destructive QC

4-Nov-2015

Most packaging relies on sampling a small quantity of product and therefore will never pick up all defects. Forest Rain Marcia, Marketing Communications Manager, DIR Technologies, describes a new method of real-time package seal inspection through dynamic thermal imaging

Ensuring package sealing integrity has long been an industry challenge, and one in which the stakes are exceedingly high. Hanging in the balance are the sort of quality control standards that not only mandate pharmaceutical manufacturers’ adherence to strict guidelines and low tolerances, but also define their priceless reputations. This is, of course, because quality control issues are a matter of public safety and brand prestige rather than mere product efficacy.

Given quality assurance’s heightened importance in the pharma industry, the primary method being used today – sampling – is simply archaic. Inspecting a minute percentage of the millions of packaged units rolling off production lines is a process no different from the inspection performed in, for example, a toy factory: every toy sampled is one removed from the marketplace, reducing overall production capacity without entirely proving that its fellow un-inspected toys are free of defects. The huge difference is that pharmaceutical defects can cost not only money but, in the worst-case scenario, lives.

Finally, however, technology has caught up to pharma’s packaging integrity inspection conundrum. The technology — dynamic thermal imaging — allows pharma companies to inspect 100% of packaged products in a totally passive manner without having to touch them.

Dynamic thermal imaging is the best of both worlds: it can restore the potential profits lost to destructive sampling (or the even bigger material and labour waste and costs when a defect is discovered via sampling) while ensuring that every single package that leaves a facility is properly sealed, thus maintaining the necessary barrier to protect product efficacy.

Figure 1: Trend example showing how typical problems can be identified and remedied in real time

Figure 1: Trend example showing how typical problems can be identified and remedied in real time

The science behind thermal imaging is not in itself new. Originally developed for the defence sector, thermal imaging provides information unavailable through other means. It has been used as a ‘see-through’ technology in some of the most highly demanding operational environments, including the military, top-level security details, firefighting and gas leak detection. The level of detection this technology affords can also be highly valuable for scientific and medical research, as well as in predictive maintenance studies for buildings and public infrastructure projects.

Until very recently, however, the sophisticated technology used for seal integrity inspection was not accessible to the consumer market. The pharma industry marks one of thermal imaging’s first forays into the global marketplace, with forward-thinking companies such as Pfizer currently utilising the technology on selected production lines.

Harnessing infra-red

Thermal imaging is an infra-red imaging technique that detects the naturally emitted radiation in the infra-red range of the electromagnetic spectrum (roughly, for standard available commercial detectors, 3,000–14,000 nanometres or 3–14µm), then translates this radiation data into images called thermograms. Because infra-red radiation is emitted by all objects above absolute zero, thermal imaging makes it possible to examine products in an environment without physical contact or visible illumination.

Thermal imaging can detect changes in temperature so slight that they were previously undetectable

The amount of radiation emitted by an object increases with temperature; therefore, thermal imaging reveals variations or irregularities in the object’s heat signature. At the height of its precision, thermal imaging can detect changes in temperature so slight – as small as 0.02°C – that they were previously undetectable or, in the case of commercial ventures, not available.

Through DIR Technologies, this situation has changed, and the resulting enhanced level of inspection has the potential to overhaul and upgrade package inspection practices throughout high-stakes industries such as the pharmaceutical and chemical sectors.

Dynamic thermal imaging is a convenient and remarkably accurate tool for package integrity and fill level monitoring. By detecting the amount of radiation emitted by objects, dynamic thermal imaging makes it possible to examine an environment without touching or even illuminating an object. The application of this technology is game-changing, enabling real-time testing of 100% of products on a line at very high throughput and with no production slowdown. In a recent application for induction sealed bottle cap liners, speeds of 400 bottles per minute were achieved. In sachet and pouch seal and fill monitoring, multi-lane format applications can yield even higher speeds.

Figure 2: I<sup>2</sup>VS can detect several quality issues through the closed cap

Figure 2: I2VS can detect several quality issues through the closed cap

This groundbreaking combination of precision and non-invasiveness makes thermal imaging ideal for seal verification of plastic or glass bottles as it is capable of inspecting the seal, through the closed cap as if the cap is invisible. This technology is suitable for inspecting the quality of virtually any process that has heat involved, such as heat sealing integrity inspection. It also can be used for tablet and liquid fill level inspection.

PAT for packaging

An equally significant aspect of thermal imaging is the real-time process monitoring – complete with full records, including photos, for every product – it affords. For some time, pharma manufacturers in particular have been hearing the drumbeat from regulatory bodies stressing the importance of Process Analytical Technology (PAT). Indeed, recent years have seen significant upgrades in quality control systems and protocol as they pertain to the actual product.

However, these systems have largely ignored an important question: isn’t primary packaging a significant part of the overall product? To use a food industry analogy, is Grade A beef still Grade A if the shrink wrap isn’t airtight? Of course it isn’t.

Systems using thermal imaging to inspect primary packaging seals are the embodiment of PAT

Systems using thermal imaging to inspect primary packaging seals are the embodiment of PAT. As mentioned, these systems are recording detailed information, including images, of each and every product passing through its purview. In other words, it is using technology to analyse the process — the antithesis of sampling because, by definition, one can’t have PAT without analytics.

Thermal imaging systems employ sophisticated algorithms that enable swift, in-line analysis of data, an immediate accept/reject of all packages and, when a faulty seal is detected, an indication of why the problem occurred. It is simple, really: the most efficient route to fixing a problem starts with an understanding of its origin.

Commonly used sampling methods allow for only a percentage of units to be inspected – a challenge that has not been overcome by the development of other real-time, 100% testing methods. The reason for this is simple. While other techniques may offer real-time testing, they are nonetheless limited by one or more drawbacks. As shown in Table 1, other sealing integrity and fill level monitoring verification methods come up short in various areas, including reliability, process control, analysis and speed. These shortcomings run counter to the bedrock principles of PAT.

This comparison shows that only thermal imaging meets all of the criteria for a robust system, particularly in the areas of process control, non-invasiveness and report and trend analysis.

Table 1: A comparison of various testing methods
Method
Vacuum decay
Pressure squeeze
EM tester
Sampling
Thermal imaging
Real time 100% testing
X
No production slowdown
X
X
X
Process control
X
X
X
X
Non-interfering
X
X
X
X
Report and trend analysis
X
X
X
X
Small footprint
X
X
Reliability
X
X
X

DIR Technologies – a spin-off from SemiConductor Devices (SCD), one of the largest manufacturers of advanced infra-red sensors – has filed several thermal imaging patents that have since been used in the production of specialised units for the in-line monitoring of primary packaging seal integrity. One such system tests inline the seal integrity of induction-sealed cap liners on bottles. It is the first of its kind capable of inspecting 100% of the bottles undergoing induction sealing in a totally passive, non-destructive way. Known as the I²VS (Induction Integrity Verification System), it provides continuous process verification without resulting in production slowdown and with a small footprint. The process is completely validatable, regulation compliant and, for serialisation applications, can assign a 2D thermographic image of a specific bottle’s seal integrity verification.

Inspection on the I2VS is performed through the cap by means of high-sensitivity thermal imaging. Any defective bottles detected are removed from the production line. The system can measure most bottle and cap sizes and types. Transition between bottle types is achieved seamlessly, by choosing the corresponding bottle on a touchscreen, user friendly menu.

Dynamic thermal imaging is a powerful new technology that has the potential to bring a paradigm change to in-line quality control

In conclusion, compared with thermal imaging, traditional inspection techniques are insufficient. Verification via sampling or camera systems is incomplete and in the case of sampling, destructive. A sampling is just that: a minute portion of a much larger sum. For an industry with unsurpassed quality control requirements, sampling has become increasingly inadequate. Camera systems using even extremely high sensitivity colour cameras can perceive faults only in the relatively narrow visible spectrum.

Dynamic thermal imaging is a powerful new technology that has the potential to bring a paradigm change to in-line quality control by replacing sporadic, destructive package sampling with continuous, non-invasive process verification. This technology puts power in the hands of the packager, providing knowledge that was previously unavailable and enabling smarter, data driven decisions.

We should collectively look forward to a time when the safety and integrity of pharmaceutical packaging is completely assured by the thorough inspection and detection capabilities afforded by this groundbreaking technology.

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