Outsourced Logistics Com Images Archive Dimens Inline

Dimensioning Takes Shape

June 18, 2007
"Carriers have always said if customers want to go to a density-based system that didn't have a class element, we would do that. ABF introduced a density-based

"Carriers have always said if customers want to go to a density-based system that didn't have a class element, we would do that. ABF introduced a density-based tariff ten years ago and customers were not interested in it," says Chris Baltz, senior vice president Yield Management and Strategic Development, ABF Freight System, Inc. (www.abf.com)

Coupled with distance charges that reflect mileage and lane density, carriers feel density-based systems that look at the weight and dimensions of a shipment provide a better reflection of their actual costs. Shippers often complain that the charges are inaccurfate or difficult to understand and compute.

With the recent decision to eliminate antitrust immunity for rate bureaus (see "The End is Near," page 34), there are questions about the future of the longstanding freight classification system or the methods that may be used in the future to determine transportation base rates. Should the density system begin to supplant class rates, shippers and carriers will need an accurate and trusted method to determine shipment characteristics.

Kartik Damany, program manager for Accu-Sort Systems Inc. (www.accusort.com), offers an overview of dimensioning and weighing systems and how they can improve rate accuracy and operations efficiency.

Carriers and forwarders typically calculate truck loading or storage volume requirements based on package and shipment size and weight provided by shippers. In addition, warehouse managers often devise storage schemes based on the same data about inbound shipments.

If the actual shipment size and weight vary significantly from what is provided, the result can be lost revenue for the carrier or warehouse operator or, on the flip side, it could lead to higher costs for shippers depending on which way the inaccuracy trends.

Automated, in-line dimensioning and weighing systems can provide accurate data to calculate shipping and storage costs. The systems can be located at the end of the pick/pack operation on the outbound side for shippers or along the receiving line at carrier hubs and terminals. In both cases, the system can provide an automatic update to the shipment record reflecting the actual load characteristics as shipped or received.

Except on rare occasions, carriers cannot afford to spot check package size and weight because measuring packages by hand is time-consuming and interrupts workflow. As a result, carriers and warehouses often seek a way to verify package dimensions and weights automatically. The challenge is to devise a fast, accurate and efficient system that does not interfere with workflow.

In-line, automated dimensioning and weighing equipment, coupled with a bar code scanning system can verify package size and weight without stopping package movement through a facility. This combination assigns dimension and weight data to a specific package, enabling shippers or carriers to calculate shipping costs more accurately and helping warehouse managers plan storage patterns better.

Generally, there are two reasons to use a dimensioning system:

  • To determine the volume of packages that can be placed into a trailer or shipping container, shippers, forwarders, and carriers need accurate package dimensions. This also helps determine how many containers or trailers may be needed for a particular shipment or group of shipments.
  • To calculate accurate shipping costs (revenue recovery for the carrier, overcharge avoidance for the shipper). Every unit of volume has an associated shipping cost. If a package is actually larger than indicated by the customer, a carrier can bill for the added shipping cost. If it is smaller or lighter, the shipper may overpay for the transportation.

In-line dimensioning and weighing offers several benefits:

  • Parcel and LTL carriers gain the ability to recover revenue on improperly measured parcels.
  • Warehouse managers receive an instant indication of package size, allowing them to use warehouse space effectively and bill accordingly.
  • Carriers have clear understanding of volume (cube) requirements needed to ship packages.

Ideally, dimensioning and weighing are done before the load is shipped, so package size is determined before it enters the carrier's system. It can also be performed at the sortation hub or terminal to verify what has been received.

Automated dimensioning systems consist of a dimensioner, a weigh scale, a bar code scanning device, and one or more photo detectors to signal the presence of a package. These so-called Dimensioning/ Weighing/Scanning (DWS) systems provide a complete solution by integrating bar code scanning, dimension, and weight data into a single message that can be generated at sortation.

Several factors must be considered when designing DWS, including:

  • Typical package size
  • Package shape—cube or irregular
  • Package placement on the conveyor—singulated vs. nonsigulated
  • Conveyor speed
  • Weigh scale capabilities

Package size dimensioners are typically mounted above the conveyor flow and project a laser beam down onto the package. The dimensioner then senses the reflected beam to determine package length, width and height. Generally, the closer the dimensioner can be mounted to the package flow, the smaller the coverage angle and the more accurate the measurement.

Side and angle mounting also are possible, but these schemes require more space and are not as accurate. In addition, any mounting other than vertical will not provide volume data unless the packages are "justified" (positioned) to one side of the conveyor.

Package shape dimensioners provide the highest accuracy when measuring cube-shaped packages. Irregularly shaped objects are dimensioned using a bounding box approach in which the package is assigned approximate cubic dimensions—a virtual box.

Package placement dimensioners work best when only one package at a time is in the field of vision—called singulated flow. To differentiate between two or more packages, the system must employ photo detectors to indicate to the dimensioner that more than one box is in the field of view. Special algorithms in the dimensioner help sort out the signals to measure each package separately.

Generally, the slower the conveyor speed, the better the accuracy. Adding a scale to the conveyor system provides accurate weight data; however, it also limits the top speed of the conveyor.

Gathering dimensional and weight data for packages is just the start. The carrier must recover the actual shipping cost by billing the customer. To do this, however, the dimensioner must be certified by a government agency—National Type Evaluation Program (NTEP) in the U.S., Measurement Canada in Canada, and the International Organization of Legal Metrology (OIML) in Europe.

NTEP is a cooperative program between the National Conference on Weights and Measures (NCWM), the National Institute of Standards and Technology (NIST), the states and the private sector. Through twelve participating laboratories, NTEP evaluates the performance, operating characteristics, features, and options of weighing and measuring devices against the requirements of NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. Devices meeting NTEP requirements receive a Certificate of Conformance indicating that they meet applicable requirements for commercial weighing and measuring equipment in the US.

Measurement Canada is an agency of Industry Canada that oversees programs and services to evaluate and certify the accuracy of measuring equipment.

The U.S. and Canada have signed a Mutual Recognition Agreement for certain weighing devices and recognize each other's type evaluation results for:

  • Electronic weight indicating elements (except those that are software based, i.e. programmed by downloading parameters).
  • Electronic computing and noncomputing bench, counter, floor and platform scales up to 1,000 kg (2,000 lb) capacity
  • Weighing/load receiving elements with capacities up to 1,000 kg (2,000 lb)
  • Mechanical scales with capacities not exceeding 10,000 kg (20,000 lb)

Each agency issues its own document upon successful completion of testing.

OIML is a worldwide organization whose aim is to harmonize the regulations and metrological controls of its member states. It oversees the implementation of OIML R, which specifies the metrological and technical requirements for measuring instruments that determine the dimensions or volume of an object in order to calculate charges for postage, freight, or storage.

The dimensioning instruments can be used in conjunction with a weighing instrument. In this case, the volume is usually calculated. A conversion factor is applied, and the resulting dimensional weight compared to the actual weight to determine charges. OIML R also includes approval, verification and test procedures.

The requirements of NTEP, Measurement Canada and OIML differ slightly; so a dimensioner or weigh scale meeting the requirements of one certifying body may or may not meet the requirements of the others.

Equipment meeting the applicable requirements is certified as being best in class for any "legal for trade" applications, and the data they generate can be used for billing purposes.

A typical in-line automated dimensioning and weighing system contains a dimensioner, bar code scanner and scale.

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