MEASUREMENT AND ANALYSIS OF DISTRIBUTION ENVIRONMENTS
To: MADE Members
From: Jorge Marcondes, San Jose State University
Paul Russell, HP Corporate Packaging Program
This phase was performed with the objective of establishing and validating guidelines for data collection and analysis. Eight shipments (round-trip) were measured for impacts and temperature using self-contained data recorders. Shipments covered distances across the USA, between companies in the west and the east coasts. Three recording units were mounted on wood blocks (two units to measure shock and temperature, and one unit to measure only temperature). The weight of the total assembly was 20 lb. The recording units were hard mounted on the wood structure to simulate a typical shipment within the high tech industry. Figure 1 shows a picture with the two recording units in place.
Figure 1. Recorders mounted on a wood structure for phase alpha.
The recording units were set to record impacts and temperature. The wood structure containing the recorders was cushioned with corner pads and placed in a corrugated fiberboard box to be sent via small parcel distribution systems. The recording units were set to record the most serious 100 events during the entire trip, and temperature every 30 minutes. Before shipment, the entire assembly was subjected to calibration by performing free fall tests from 12, 24, 36 and 48 inches, on faces, edges and corner of the package, and comparing the reading results with the actual drops. In situations when a unit reported an event with less than 95% accuracy, a correction factor was established, to be used to adjust the results obtained from the field. All three units tested showed satisfactory performance for phase alpha.
RESULTS OF PHASE ALPHA
a. Trips details
Phase alpha consisted of eight round trips, with the following trip codes and other details, as per test plan guidelines (Table 2):
Table 2. Phase alpha details
|Trip Code||Sender||Receiver||Carrier (out/return)||Notes|
|HP San Diego
HP San Diego
HP San Diego
HP San Diego
HP San Diego
(d) (e) (f)
(a) At HP-San Diego, someone along the way put "fragile" stickers on all 4 sides of the box.
(b) Data from 1st. half of trip (San Diego to Andover) is invalid because the unit was not properly packed.
(c) Was mistakenly returned via UPS Ground on return trip
(d) FedEx service was unavailable from IBM Research Triangle Park, NC, so Airborne Express was used instead.
(e) Error reading acceleration data from EDR3 - only temperature data was recorded on disk and sent for analysis
(f) One week delay in return due to UPS strike
b. How the analysis was made
At the end of each trip, raw data files were send to SJSU for analysis. The files were analyzed using the software provided by the data recorders manufacturers (Lansmont and IST), along with recommended software setup. After the initial analysis of all data files at SJSU, it was noticed some differences in the results. Lansmont and IST agreed to do the analysis of the files separately, therefore the respective raw data files, along with details of the package used were sent to them.
Some errors occurred in reading or processing files (two files, one from EDR3 and one from SAVER) presented errors and their data could not be analyzed:
HP061F10 for SAVER - at the end of the processing, it returns a "General Error" fault and then reports that there are no events in the file, and HP061F12 for EDR3 - when uploading data from unit to computer, it showed an error in reading acceleration data from unit, and only temperature data was recorded.
c. "e values used for analysis
Before the units were sent out for data acquisition, the package system was calibrated at SJSU (as per test plan). The raw data files were also sent to IST and Lansmont, separately. The following are the "e" values they found in the calibration files and used in the analysis of data: SAVER, according to Table 3. For EDR3, values of "e" were determined as: 0.375, 0.47, 0.43, and 0.52. The average was 0.44
Table 3. SAVER "e" (coefficient of restitution) values
|Drop height (inches)||Orientation||e|
d - How the shock comparison tables were constructed and what they show:
Initially, for each pair of files to be compared, the events that had equivalent drop height above 10 inches were selected, and listed for each unit. The events date and time were used as a basis for comparison.
The clocks disagreed slightly (the EDR clock was slightly faster than the SAVER, for the recording units used in the phase: two SAVERs and two EDR3s). No study was done to determine which one was more accurate. This issue was important for phase alpha because it was the basis for event comparison, but it should not be a problem for phase Beta.
Most events observed were not free fall. They were impacts, in basically all orientations. The highest equivalent drop height found in all six round trips was 38.8 inches.
There was still some disagreement between the results given by the units. Most of these were found to be caused by the fact that the analysis was being performed in different parts of the same event. This occurred because the "window" recorded did not always agree completely between units (although the units were triggered by the same event, the recorded waveforms started and ended at slightly different times, sometimes missing important parts of an event). This issue will be addressed in phase beta by extending the recording window well beyond the triggering time, and by minimizing the dead time (time just after one event, when unit does not record the waveform - or "event storm").
e. Temperature results
There were no significant differences between temperature recorded in all trips. Temperature values ranged between 70oF and 95oF.
a. How data is to be presented
If a large number of replications of same trip, package size, etc. will be conducted, than it may be better to present results in a statistical distribution format. If conditions will change from trip to trip, it is more appropriate to present actual results (example, events higher than 10 inches, 5 largest drops, etc.). The user can then determine what statistical analysis is more appropriate depending on the applications.
b. Package and trip documentation form:
Minor changes are required: 1) change from "shipper" to "sender", 2) include date and time of turn around (or make two forms, one for each leg of the trip)
c. Recording unit orientation:
Units should be positioned in the package according to their designated orientation, no matter what orientation the axes are (the software is set to report impact direction as per the units designated orientation). This was an issue in phase alpha because the units were side by side, but should not be a problem for phase Beta.
d. Data base
Results of phase beta will be added to the database as they are collected and analyzed. After a certain amount of data has been collected, several statistical analysis will be performed on the data to better understand its distribution and the influence of controllable variables such as package size and weight.
The goal of the task force is to provide a web site where users would log on and request information by entering some basic information about their products and packages, such as:
and information about the following parameters would be retrieved from the database:
The measurement and analysis of distribution environments aims to provide packaging designers with accurate and updated information about distribution hazards, such as drops, impacts, humidity and temperature. The task group is a joint effort between ISTA and IoPP and has open participation. Companies willing to join the task group can do so by contacting the authors. Members can participate in the study by contributing with engineering time, loaning data recorders, and sharing information.