Unboxed: Mastering Transit Testing
Introduction
The primary function of packaging is to safeguard its contents throughout the journey from the production site to the customer's hands. This journey can include various stages such as conveyor transport, secondary and tertiary packaging, storage in warehouses, transport in trucks, and even instances of mishandling. Balancing the demands of cost efficiency, sustainability, and effective packaging performance can pose challenges, especially when the forces experienced by the package during transport are hard to quantify, making it tricky for designers to make the right design choices.?
H. James Harrington, an author and management mentor, once said, "Measurement is the first step that leads to control and eventually to improvement. If you can’t measure something, you can’t understand it. If you can’t understand it, you can’t control it. If you can’t control it, you can’t improve it.�
Loads Experienced by Packages
The standard test?protocols covers a range of situations that packages may encounter in their actual distribution environment. Measuring transit loads allows for a more tailored approach to testing, reflecting the specific conditions your packages will confront. This is achieved by using data and testing methods to provide a comprehensive view of your packaging's performance. Examples of these situations might include non-unitized shipments during the rainy season, e-commerce shipments via various vehicles, or large unitized shipments with high volume to weight ratio.
Through careful observation, several types of loads have been identified, such as:
- Static Load: This refers to stacked packages in the warehouse.
- Temperature and humidity changes: These occur across the distribution stages from the factory to the customer.
- Pressure changes: These are due to altitude differences, which can cause panelling issues on bottles due to a discrepancy between internal pressure and altitude-based external pressures.
- Accelerations: The package experiences these during various stages of transit. For example, a long trailer truck driving on a smooth road may induce a slow rocking motion, or a short wheelbase truck on a rough road might induce a low-frequency vibration. Other potentially damaging road scenarios include sudden braking/acceleration, sharp cornering, or high-speed driving on a moderately rough road for an extended period.
- Package drops: These can be due to accidental drops or multiple small height drops due to the defined process. The damage depends on the height of drop, orientation, weight of the dropped unit, and the package's characteristics and structural strength.
Measurement Systems
To understand these loads, it is critical to employ the right measurement tools, such as sensors, processors, storage devices, and batteries. Some key components include:
- Accelerometers: These sensors measure the vibration levels during the transit phases of the distribution. They capture vibrations in X, Y, and Z directions, providing a comprehensive view of the various vibratory loads acting on the package.The high G load and high data version is used for shock sensing ( around 200G at 2000samples/sec per Axis) while low G at lower rate for vibration sensing ( around 50G at 1000 Samples per second)
- Pressure Sensors: These measure changes in atmospheric pressure during transit, which is especially useful when the shipment travels through landscapes of varying altitudes.
- Temperature Sensors: These record temperature changes experienced by the product and the packages.
- Humidity Sensors: These help understand the humidity levels in the vicinity of the sensor, which is critical for packages sensitive to changes in humidity.
- Geolocation (GPS): GPS data provides location context to the events and anomalies detected by the sensors and can also aid in route planning.
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- Battery Unit: The battery technology and capacity are chosen based on the duration and rate of data collection.
- Memory Storage: The storage capacity is selected based on the total journey, total number of sensors, and the data capture rate.
Several companies provide high-quality instrumentation for data collection. For example, our team at Axiom has developed a customized system called Memoir, used in several initiatives.
Data Analysis
Analyzing this data is a complex process, but in broad strokes:
- Humidity/Temperature/Pressure: The analysis typically outputs maximum and minimum values for each journey segment. The analysis can also be customized to determine parameter changes and importantly, track their rates of change.
- Accelerometer: The data from accelerometers can be processed in numerous ways. One common approach involves using statistical methods to understand intensity through histograms and other statistical parameters. The data is often converted to a frequency domain using Fast Fourier Transforms (FFT), which allows for the determination of Power Spectral Density (PSD). PSD refers to the evaluation of a signal's power distribution in relation to its frequency, which is a critical parameter for packaging test engineers as shaker tables used for vibration testing accept PSD as input.
The information from these sensors, when combined with GPS data, provides useful spatial correlation of physical phenomena, pinpointing where changes occurred.
Use Cases?
Some of the Use cases are shown in image below
Pathway to Modeling and Simulation (M&S)
These measurements and analyses also pave the way for modeling and simulation. Our Modeling & Simulation team has spent nearly a decade refining approaches for modeling the various scenarios that a package might encounter during distribution. We've created detailed virtual models to represent either an ISTA test sequence or a custom test sequence. The data capture and analysis have been instrumental in defining the loads and boundary conditions for these custom sequences, along with the necessary detailed material and geometry details to create a realistic virtual model. This has now become a streamlined consulting practice that helps to identify and address potential distribution issues using a digital model early in the design cycle.
Look forward to hearing your views and comments!
Great Piece Chandra!!