New Technologies to Reduce Package Gapping While Increasing Read Rates

small package gap but dataman can still successfully read 1d barcode

Growth in e-commerce initiatives, such as buy-online-pickup-in-store (BOPIS), and expectations of same or next-day delivery are driving a need for throughput increases that do not impact quality. Operations teams have a few options to increase throughput. They can increase line speeds, reduce gaps between items or packages, do both, or build entirely new facilities.

Decreasing product gaps during processing without reducing read rates can increase throughput at significantly less cost than other possible solutions such as increasing line speeds or expanding and adding facilities.

The issue of gapping

Advances in material handling such as encoders, sensors, and sophisticated conveyor sections that can accurately establish optimal gapping have enabled predictable, narrower gaps that increase throughput. Singulation, which is uniformity in spacing and alignment, makes downstream automated sorting considerably easier.

But the tighter that gap, the greater the challenges to barcode reading, especially when distribution centers want to move from older topside-only scanning to 6-sided scan tunnels to reduce no-reads and improve other aspects of their operation.

One benefit of a barcode reading tunnel is that packages do not need to have any specific orientation to have their barcodes read, minimizing the need for material handling for orientation. But the narrow gap creates several problems in reading any codes that appear on the sides of the gap.

No matter what the lighting, the tight area between the packages will be shadowed and significantly darker than the surrounding areas, creating a dark read image.


Since the barcode reader can only look into the gap from a high perspective, the image of the barcode will be significantly distorted, making it hard to decode.


These problems are bad enough when all cartons or totes are the same size, but if there is a wide range of carton sizes, it is usually necessary to keep the gap wide enough that readers do not miss a box by misassigning barcodes.



Additionally, not all distribution centers are at the cutting edge of material handling. These DCs suffer from the problem of irregular and unpredictable gapping, which also causes no-reads and other code scanning problems, like assigning the barcode to the wrong box and shipping it to the wrong location.

Unwanted limitations on gapping

The industry has accepted several gapping restrictions to minimize the problems of missed or misread barcodes.

One is to maintain a minimum gap size equal to 60% of the tallest box that might go to sortation, or simply hard-limit gaps to 14” or more. The other is simply to limit the number of package sides scanned to a maximum of four and making sure to arrange boxes so that barcodes do not appear on the leading or trailing sides of any package.

These restrictions significantly limit throughput while increasing labor costs. Distribution centers have been frustrated by these limitations.

Peering into the gap

Several new technological innovations from Cognex together now make barcode reading possible even with much tighter gaps, at high speeds.

Contrast-optimizing the image

High dynamic range technology has been around for a while. Dynamic range is the difference in brightness between the brightest pixels and the darkest ones in the image. Dynamic range can be increased by making improvements to the CMOS sensor in the camera, or by using more sophisticated algorithms.

Cognex’s HDR and HDR+ image-based barcode readers have a CMOS image sensor with 16 times the resolution of a conventional sensor. HDR+ uses an advanced algorithm that allows for optimizing contrast in localized areas of the image where contrast is more important.

The combination of hardware and software improvements makes Cognex barcode readers with HDR+ dramatically better at reading barcodes from extreme angles in the dark region between two or more packages.


Improving barcode decoding

In addition to increasing contrast, improving the decoding of both 1D and 2D barcodes can significantly improve readability, especially when operations teams are seeking to improve throughput through reduced gapping and extreme reading angles make successful reading very challenging.

Perspective-Hotbars_500x200 no_finder_500x200

Cognex has developed many industry-leading decoding algorithms, one of which is called Hotbars, that further increases the speed with which the camera finds and acquires the 1D barcode, giving the decoding algorithm more time to do its work. Hotbars is around 20 times faster than the previous method of acquisition, so 1D barcodes, even in narrow gaps, can be read at high speeds.



Cognex’s 2DMax algorithm with PowerGrid does the same for 2D codes.


3D barcode assignment

Further methods are being developed to improve readability in the gap. Often, when two boxes are too close together, a barcode reader will miss one or another of the barcodes. Sometimes this means the same code gets assigned to two boxes, sometimes that one box, though properly labeled, gets through without being read. This results in boxes becoming lost or misrouted, increasing labor and reducing throughput.

There is a way to significantly reduce misassigned barcodes.

Every barcode reader in the tunnel can be precisely calibrated in 3D space with the assistance of 3D technology. When two cameras see the same barcode from different angles, the exact location of the box and its barcode in 3D space can be calculated. With this, two barcodes on two different boxes can be more clearly differentiated and assigned to their appropriate packages.


Reducing gaps, increasing throughput

Material handling companies are increasingly interested in systematically shrinking the gaps on the line as their conveyors and other handling equipment become faster and more precise. But distribution center throughput is limited by the inability to read codes in the gap.

At the same time, many older systems are still in use, and their gapping is much less controlled, also causing numerous barcode reading problems.

New approaches from Cognex enable high-speed material handling operations to dramatically shrink gaps while getting the full benefits of a 6-sided tunnel. The same Cognex technology can enable existing systems with inconsistent and unpredictable gapping to increase read rates while getting a few more years of use out of their investment.


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