Machine Vision for Packaging Blends Science, Engineering and Art
Vision systems are essential for maintaining product and packaging integrity and quality, but their integration requires a healthy mix of art and science.
By César Hernández, PE, Packaging Engineer, Pfizer, Inc.
The machine vision systems used to automate pharmaceutical packaging processes stand right at the intersection of science, engineering and art. Successful applications don’t depend exclusively on any of the three, but rather a bit of each.
Automated vision systems, once considered too expensive and impractical for drug packaging, are now mainstays for many drug manufacturing facilities, allowing users to monitor line performance, eliminate operator error, and ensure that the supply chain is free of counterfeits. “Machine vision systems are contributing to pharmaceutical product quality to the point where production lines do not run when the vision systems are down,” says Pedro Santiago, a packaging engineer at Eli Lilly del Caribe, Carolina. “That is how important they have become.”
Today, vision sensors, smart cameras and embedded vision processors sell for well under $10,000 yet provide many capabilities. “Most modern vision systems perform optical character recognition (OCR), optical character verification (OCV), and can read bar codes and 2-D Matrix, maximizing the short- and long-term capital investment,” says Iván Avilés, a packaging engineer from Pfizer, Caguas.
Manufacturers can justify installing machine vision at many locations along a packaging line, with each performing a single inspection to verify quality following each specific value-adding function. This article will outline the critical uses of machine vision systems for pharmaceutical packaging and discuss best practices from some of the leading packaging professionals in the Puerto Rican pharmaceutical industry.
Machine vision (MV) is not computer vision (CV), nor artificial intelligence (AI), digital image processing (DIP), or pattern recognition (PR). However, for most pharmaceutical processes, these technologies must be integrated to meet time, cost and quality demands, consistently. The U.S. Food and Drug Administration's 21 CFR Parts 210 and 211 require extensive monitoring and documentation of pharmaceutical production lines. Machine vision systems monitor product and packaging integrity, and ensure that packaging fulfills its fundamental requirements: to contain, protect, dispense and communicate (see below).
APPLICATIONS OF MACHINE VISION INSPECTION
|Primary Packaging: Solid Dosage and Liquids
||Primary Packaging: Solid Dosage Blister and Pouch
||Secondary and End-of-Line Packaging
|Bottle, vial integrity
||PVC/aluminum film integrity
||Cartoning, tray packing, case packing, palletizing operations
Using machine vision systems to ensure the integrity of product and packaging components is one of the most important applications today. A vision system can inspect a bottle or vial for the correct size, color, shape, dimensions and other critical properties such as neck finish or the presence or absence of particulate contamination. When, for example, any passing bottle diameter is out of specification, the vision system will detect it, reject the non-conforming unit, shut down the operation if consecutive faults are detected, display an "error" message and sound an alarm.
Tablet or capsule integrity can be guaranteed by a machine vision system that determines whether the product is in the correct position, and also detects whether the product is broken, partial or contaminated with a foreign particle.
Blister packaging’s complexities
Inspecting tablets in blister packs has become more complicated as branding efforts have prompted pharmaceutical companies to package products in colors close to that of the tablet itself.
The keys to successful color, shape and size inspection include:
- homogeneous lighting;
- high-resolution optical elements (lenses, filters, cameras);
- high-speed image processors with corresponding software.
“All these elements are equally important, and none should be underestimated,” says Luis Reyes, packaging engineer of Merck Sharp & Dohme, Arecibo. “Each needs to be carefully addressed in Design Specification documents issued by the systems’ provider,” adds José Rivera, another packaging engineer, from GlaxoSmithKline, Cidra.
These documents vary. User Requirement Specifications (URS) tend to be fairly general: “The Labeler shall have a Vision System integrated to verify Lot Number, Expiration Date, Part Number and label presence.”
Detailed Design Specifications (DDS) are more specific: “The Labeler incorporates a high spatial resolution camera of 1024 x 1024 pixels using Optical Character Verification (OCV) methods to inspect and verify the Lot Number, Expiration Date as printed on the label by the steered beam laser printer with Futura 14 font, the pre-printed label Part Number, and label presence.”
Vision systems are also used to verify the correct assembly of packaging components, which requires full knowledge of the characteristics to be inspected. Monochromatic inspection can be useful when components’ colors are standardized. However, color inspection is more commonly used today because requirements vary in different international markets. For example, a pump assembly for the Japanese market requires a blue color clip, while markets in the rest of the world require a white color clip.