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Taking the Complexity Out of Inspection

Thu, 09/16/2010 - 11:38am
Steve Wong, Business Development Manager, Pharmaceutical & Medical, Banner Engineering

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The importance of product inspection in pharmaceutical applications cannot be understated: Patients rely on pharmaceuticals to relieve an ailment, and an incorrect or tainted product will fail to produce the relief required. Worse, a tainted product may lead to a serious, and potentially lethal, allergic reaction in sensitive patients.

It is for this reason that companies take great pains to ensure each tablet and capsule is properly counted, packaged and labeled before it reaches consumers. For many users, "pain" is an accurate representation of the process, as oftentimes inspections require sophisticated equipment only fully understood by the specialists who service them. Inspection systems may also require auxiliary equipment such as laptops to be present on the plant floor in order to monitor and modify parameters, adding hassle and expense to an already complicated process.

pharmapp

A high-accuracy, yet simple-to-use sensor can significantly improve pharmaceutical product and packaging quality.

Inspection isn’t always so complex. The sophistication built into many of today’s easy-to-install and configure sensors results in efficient, accurate product inspection with less operator training and limited auxiliary devices required.

Common packaging defects and risks

Sensors are used for inspecting both primary packaging, including bottle and blister pack filling and sealing, as well as secondary packaging—which includes steps such as tamper-proof band wrapping, label application and adding an insert or outsert. The defects a sensor must detect, if present, are different in each of these areas. Likewise, the sensor selected in each case varies by the inspection task at hand.

Primary bottling operations require sensors capable of detecting:

• A hopper’s fill level, to ensure the hopper is not prematurely emptied during a filling cycle

• A bottle’s fill count, to avoid over count or under count per unit-of-sale

• The presence of a desiccant pack within each bottle, to prevent moisture damage

• A bottle’s UV tamper-evident seal, to ensure the seal is present and correctly placed

• A bottle cap, to assure correct height and orientation for reliable cap closure—preventing exposure to moisture or air

Primary blister packaging applications employ sensors to ensure each blister is filled and complete — identifying any broken or partial product.

In secondary packaging operations, sensors must perform more sophisticated tasks:

• Label inspection, to confirm the label is present, correct and properly aligned

• Insert/outsert verification, to ensure the correct insert is placed face-up in a package, or that the proper outsert is positioned correctly on the outside of the package

• Expiration date and lot number (date/lot code) and bar codes, to affirm that each code is correct and properly placed for product identification and consumer safety

pharminsert

Inspecting a tablet carton to ensure it contains the proper insert is one critical step in secondary packaging operations.

Failure to inspect pharmaceutical packaging at each step of the process can lead to product contamination or misrepresentation, posing a significant risk to consumer safety. It can also lead to costly product recalls and immeasurable damage to a pharmaceutical manufacturer’s reputation. To ensure the highest-quality products, the following sensors are designed to provide cost-effective, easy-to-implement inspection solutions.

Photoelectrics for Fast, Accurate Inspections

Perhaps the most common sensor for simple discrete applications, the photoelectric sensor pairs a light emitter with a receiver to detect a target object. Depending upon the sensing mode selected, the target object will activate the sensor by "breaking the beam"—preventing the emitted light from reaching the receiver—or by "making the beam." In an opposed-mode configuration, the emitter and receiver are mounted opposite of one another, with the target object passing between the two on a packaging line. If a retroreflective mode sensor is used, the emitter and receiver are combined in the same sensor housing and the object itself is used to reflect the light beam back toward the receiver, activating the sensor.

This arrangement can prove to be feasible for primary packaging operations such as bottle cap inspection. A separate emitter and receiver are positioned on opposite sides of the bottling line, with the bottles passing between them. The narrow beam of light is adjusted to cross the bottling line at a point immediately above where a properly capped bottle will reach, so that each "good" product will pass underneath the beam. A cap that is improperly oriented or tightened will be slightly cocked and trip the light beam during the inspection pass—activating the sensor and indicating that this product should be rejected from the packaging line.

As photoelectric sensors provide a very quick response time, they are ideal for high-speed packaging tasks. One type of photoelectric sensor, the fiber optic sensor, adds flexibility to fast response—making it an effective sensor for detecting small objects in space-confined areas. Instead of the traditional emitted beam, a fiber optic sensor uses an amplifier to emit and receive light through fiber optic light-guides. The optical fibers are made of either plastic or glass constructed into light bundles. Their small size and flexibility ensures fiber optic assemblies can be shaped so that the light beam is distributed, or fanned, across a two-dimensional area to detect small objects.

This type of sensor provides high-accuracy results in applications such as inserting a desiccant pack into a bottle. These packs will freefall between an emitter and receiver installed above the height of the bottle, with the fiber optic sensor emitting light right above the bottle’s rim. Here, the desiccant pack will break the light beam when it drops into the bottle—and any container that passes without activating the sensor will be rejected.

Photoelectric sensors offer excellent optical performance, a compact size and a rugged, often IP67 rated design to handle harsh plant conditions. They also require only minimal configuration and, with a simple present/not present design, results are easy to interpret. However, as these sensors are based on optical signal strength, any object that is not "visible" will not be detected—requiring a more sophisticated photoelectric solution.

Specialty Sensors for Challenging Materials

Some photoelectric sensors detect clear materials through an emitted light beam with a wavelength that identifies light at levels beyond that which is visible. A luminescence sensor detects the presence of luminophores (or luminescence agents) in certain materials; these luminophores are commonly used in tamper-proof bands, glue and some plastic containers. The sensor emits UV light that creates a luminescence effect by the luminophores, resulting in the emission of a visible blue light. The sensor then detects the presence of this blue light on the material being tested.

luminescence

A luminescence sensor can be used to detect transparent materials such as tamper-evident seal on a pill bottle.

This sensor is often used to inspect the tamper-evident seal on a bottle, as this seal is often comprised of transparent materials. Users must ensure the presence of luminophores on this ring to ensure the sensor can detect this sealing method more accurately. If this seal is missing, the bottle can be rejected from the packaging line.

Clear materials, such as the PVC used in blister packs, also present a challenge. Photoelectric sensors depend upon the target object to block, reflect or transmit the emitted light for accurate detection. Because a tablet covered by a clear PVC material affects the emitted light in a very similar manner as an uncovered tablet, the contrast between these two components is too minor to allow the use of a standard photoelectric. However, a specially designed, highly sensitive clear object/material sensor can be used to detect the minute differences in light attenuation needed—identifying differences in contrast down to a single-digit percentile. This allows the sensor to reliably determine if the filled blister packs are sufficiently protected.

Ultrasonics for Color-Indifferent Sensing

Photoelectric sensors provide an ideal solution for identifying a single target object or feature of interest should appear identical in each instance, as it can simply determine the abnormalities in these conditions that indicate a faulty product. However, these sensors prove problematic in applications where the "good" condition may contain products that vary significantly in color, thereby affecting the photoelectric’s emitted beam in inconsistent ways.

Here, an ultrasonic sensor proves ideal. Rather than sensing light, the ultrasonic sensor detects sound waves at frequencies just above that which is audible to humans. The sensor serves as both emitter and receiver, sending sound energy toward the target object and "listening" for the echo that returns. The sensor is programmed to listen for a user-defined time period before retransmitting the signal.

This arrangement is particularly suitable when inspecting a hopper for fill level at a tablet fill station. If the hopper becomes empty before the filling cycle is complete, it results in incorrectly filled bottles and can result in significant downtime—and loss in productivity—to halt the process to refill the hopper. In these instances, an ultrasonic sensor can be installed above an open hopper containing tablets of many shapes, sizes and colors. The ultrasonic transmits a sound wave and evaluates the hopper’s fill level based upon the time delay before the echo is received. If the echo is delayed beyond the user-defined time period, operators identify that the hopper must be refilled before the filling process begins, saving potential product loss and downtime.

Vision Made Simple for Sophisticated Inspections

Photoelectric and ultrasonic sensors are based on identifying a single point—therefore, they are best used for confirming the presence/absence of a single feature, target object or product level. When several aspects must be analyzed at once—such as a label’s contents or a date/lot code’s presence and legibility—a vision sensor provides an ideal solution.

Vision solutions consist of two primary parts: vision hardware, consisting of the camera, lens, image processor and lighting; and vision software, which provides the logic behind the inspection. Vision software allows the user to define a "good" product and set the parameters that a product must meet in order to pass the inspection. These systems traditionally required several auxiliary devices, including a computer to run the software and a lighting apparatus to properly illuminate the target object. Plus, many required complex programming involving sophisticated logic and machine vision knowledge to set up and modify an inspection. This arrangement made it difficult to train operators and often required a third-party professional to set-up and service the inspection equipment.

barcode

Vision sensors featuring an all-in-one design—combining lighting, camera and vision tools in a single package—provide a user-friendly solution for bar code inspection.

 

To simplify vision and make it more user-friendly, some systems now offer all these components in a single, compact sensor package. The sensor contains an imager, plus integrated lighting that establishes sufficient contrast between the feature of interest—such as the label or date/lot code—and its background. Behind the camera is a touch screen interface that allows users to capture and assign a "good" part, set inspection parameters, and then monitor the inspection onsite. This design speeds operator training and facilitates inspection modifications onsite when required to adjust parameters or accommodate product changeover.

To solve label and insert/outsert inspections, users capture and assign the "good" part designation to a product containing the proper label, insert or outsert—one that is not only present and correct but also properly oriented. In this instance, products that are missing or incorrectly displaying the proper label, insert or outsert will fail the inspection. The vision sensor can then communicate this fail status to an in-line device such as a diverter to remove the product from the packaging line. Date/lot code and bar code inspections can be solved in the same manner, even if the code exhibits low contrast. It is one of the final steps in ensuring a pharmaceutical product is properly packaged using simple to apply, yet exceptionally accurate sensors—thereby increasing product quality and, most importantly, protecting consumers.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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