VTechWorks Repository :: Browsing by Author "White, Marshall S."

Browsing by Author "White, Marshall S."

Now showing 1 - 20 of 48

An assessment of manufacturing quality variation and an SPC handbook for the pallet and container industries
Gales, Teresa Leigh (Virginia Tech, 1988-09-01)
Today, American industries are in a highly competitive international market. To achieve the competitive edge, manufacturers are demanding excellence from their vendor/suppliers. The pallet and container industries are the suppliers to the other companies. Statistical Process Control (SPC) is one-way to prove to the buyer the quality level of their products. One part of the this thesis is a handbook, which explains a step by step process of implementing an SPC program for the pallet and container industry. In addition, the thesis examines the quality levels of materials that goes into the pallet including the finished product such as raw material, cut-stock, fasteners, and workmanship. The raw material proved quite variable from the different sawmills. The between board variation was greater than the within for both the thickness and width. The cut-stock had less size variation in thickness than width. The workmanship of the finished pallets showed that the number of nail splits and uniformity of deckboard spacing to be a problem. While the number of missing nails, protruding nail points and heads, and the "out of squareness." It was not a problem. The physical characteristics of the fasteners proved extremely variable from one characteristic to another. There are a number of fasteners being produced outside of the NWPCA criteria for wire diameters. The most popular fastener gauges are the 11 and 11.5. In addition, the most popular fastener length is 2.25 and fastener flute number is 4. The MIBANT angle variation is higher for the stiffstock fasteners then the hardened fasteners.
Case Study: The effect of pallet design on the performance of semi-automatic and fully-automatic warehouses
Mejias Rojas, Alina (Virginia Tech, 2020-06-05)
Pallets form the base of the unit load, which is the basis for global trade transportation. In order to achieve better performance, improve efficiency, and compete in much more versatile markets, industrial activities and pallet management service firms are becoming more automated than ever; they are adopting advanced manufacturing technologies and flexible manufacturing systems. This study focuses on the investigation of the most common compatibility issues between pallets and material handling systems in semi-automated and fully-automated warehouses. At the same time, it establishes an understanding of the downtime and frequency of problems caused by pallets in these types of facilities. This research was conducted in two phases. The primary phase was a mix mode questionnaire (phone interview and hard copy questionnaire) that was used to survey members of different industries, such as pallet manufacturers, equipment manufacturers, and pallet users. The secondary phase surveyed multiple general warehouses and storage facilities around the U.S., and surveyed warehouse professionals from manufacturing companies in the pharmaceutical, petroleum, dairy, beverage, chemical, and tobacco industries, to name a few. Results showed that 3% of the respondent warehouses are fully automated, and 20-30 % are semi-automated. Additionally, block class wooden pool pallets were identified as the most common pallet class used in semi/fully automated warehouses, followed closely by the use of stringer class recycled wooden pallets. Despite this, stringer class recycled wooden pallets were identified as the main pallet class involved in pallet related downtime in semi/ fully automated warehouses/ DC facilities. Further results present a guideline for improving automated warehouse performance, determine the pallet characteristics needed for this type of application, and expands the knowledge around downtime frequency cause by pallet related issues in these types of systems.
Comparison of the Different Hazards Experienced by Pallets During Material Handling
Sabattus, William Joseph-Clark (Virginia Tech, 2023-02-23)
Pallets play a crucial role in the supply chain with approximately 2.6 billion in circulation in the United States alone. Although often overlooked, pallets can become costly for a company if not designed correctly for their specific supply chain. Durability is an essential characteristic of pallets; it defines the expected life of the pallet in the supply chain. Forklifts are the dominant mode of material handling for palletized products, and they are responsible for the majority of damages experienced by pallets. Despite the prominence of forklifts in the supply chain and their importance in pallet design, there is a lack of research focusing on the dynamic nature of forklifts in the field. The objective of this research paper was to investigate the intensity of the vibrations and shock impacts that forklifts exert during material handling. Forklifts in multiple facilities were instrumented with Lansmont SAVER 3X90 and 3D15 data loggers to measure the acceleration peak, g of shock impacts, duration of impacts, random vibration intensity and RMS (g) values during forklift handling in the field. The highest vibration levels were observed for distribution facilities with an average acceleration (peak, g) of 0.353 g. Based on the results of the vibration data collection, the vibration profile for laboratory simulation was proposed. The results of the shock measurement showed that LTL facilities recorded the highest average shock impact of all the facilities investigated, with an average acceleration value of 4.74 g with an average shock duration of 7.42 msec. The intensity of shock events measured during the FasTrack procedure was slightly greater than what was observed for the LTL facility indicating that the FasTrack simulation is slightly harsher than the field handling of pallets. Based on the results of the shock measurement, new intensity levels were recommended for the incline impact test to better represent the harshness of handling in the field. The results of this study will be used to revise the durability testing procedures used in pallet testing standards in order to better represent the current material handling processes found in modern supply chains.
Correlation of the Elastic Properties of Stretch Film on Unit Load Containment
Bisha, James Victor (Virginia Tech, 2012-05-24)
The purpose of this research was to correlate the applied material properties of stretch film with its elastic properties measured in a laboratory setting. There are currently no tools available for a packaging engineer to make a scientific decision on how one stretch film performs against another without applying the film. The system for stretch wrap comparison is mostly based on trial and error which can lead to a significant loss of product when testing a new film or shipping a new product for the first time. If the properties of applied stretch film could be predicted using a tensile test method, many different films could be compared at once without actually applying the film, saving time and money and reducing risk. The current method for evaluating the tensile properties of stretch film advises the user apply a hysteresis test to a standard sample size and calculate several standard engineering values. This test does not represent how the material is actually used. Therefore, a new tensile testing method was developed that considers the film gauge (thickness) and its prestretch. The results of this testing method allowed for the calculation of the material stiffness (Bisha Stiffness) and were used to predict its performance in unit load containment. Applied stretch film is currently compared measuring containment force, which current standards define as the amount of force required to pull out a 15.2cm diameter plate, 10.1cm out, located 25.4cm down from the top and 45.7cm over from the side of a standard 121.9cm width unit load. Given this definition, increasing the amount of force required to pull the plate out can be achieved by manipulating two different stretch film properties, either increasing the stiffness of the film or increasing the tension of the film across the face of the unit load during the application process. Therefore, for this research, the traditional definition of containment force has been broken down into two components. Applied film stiffness was defined as the amount of force required to pull the film a given distance off the unit load. Containment force was defined as the amount of force that an applied film exerts on the corner of the unit load. The applied stretch film was evaluated using two different methods. The first method used the standard 10.1cm pull plate (same plate as ASTM D 4649) to measure the force required to pull the film out at different increments from the center on the face of the unit load. This measurement force was transformed into a material stiffness and film tension (which were subsequently resolved into containment force). The second, newly developed, method involved wrapping a bar under the film, on the corner of the unit load, and pulling out on the bar with a tensile testing machine. This method allowed for the direct measurement of the containment force and material stiffness. The results indicated that while some statistically significant differences were found for certain films, the material stiffness and containment were relatively consistent and comparable using either method.The use of the Bisha Stiffness to predict the applied stiffness and containment force yielded a statistically significant correlation but with a very low coefficient of determination. These results suggest that while film thickness and prestretch are key variables that can predict applied stiffness and containment force, more research should be conducted to study other variables that may allow for a better. High variability of the predictions observed were caused by the differences in film morphology between the different method of elongation (tensile vs application). This study was the first that attempted to define and correlate the tensile properties of stretch film and the applied properties of stretch film. From this research many, terms have been clarified, myths have been dispelled, formulas have been properly derived and applied to the data collected and a clear path forward had been laid out for future researchers to be able to predict applied stiffness and containment force from the elastic properties of stretch film.
The development of a durability procedure for pallets with structural panel decking
Cao, Jiqiang (Virginia Tech, 1993-05-07)
The Pallet Design System (PDS) is a widely accepted engineering procedure for comparing the performance of competing pallet designs. As part of a new version of the PDS, the objective of this study was to develop a durability model for pallets with structural panel decking. An accelerated rough material handling test system, "the VPI unit-load material handling FasTrack" , was developed to simulate pallets used in the unit-load material handling environments. 100 pallets representing 14 different designs were tested in the "FasTrack." Damages to these pallets were recorded after each test cycle. A procedure relating damage to repair cost was developed. The effect of panel-deck pallet design on the resistance to damage was evaluated in terms of the total number of damaged parts and average damage cost or repair cost. Test results indicate that panel grade and type, species of related wood parts, size of stringer and deckboards, joints, and pallet configurations affect the resistance of panel deck pallet to damage. The plots of average total damage cost, Cu adjusted for repair as a function of test cycle, U, fit the equation: Ct = aU - 1. The equation provided good fits to all the pallet designs tested. Using the initial purchase prices, the average cost and the economic life were calculated for all the pallet designs. The VPI "FasTrack" was calibrated based on the number of physical handlings and the amortized life. Three typical in-field handling environments were compared with the VPI "FasTrack". It concluded that the 30-cycle test period in the VPI "FasTrack" simulates between 2 to 5 years of field uses depending on the field handling system being simulated. Thirty Canadian Pallet Council (CPC) pallets with known 7 years of amortized life in the field were tested in the VPI "FasTrack". The 30-cycle test in the VPI system simulated 6 years of use in the similar handling environment of the CPC pallet used by the grocery industry in Canada. The average total damage costs for different pallet designs were related to pallet structural characteristics using multivariate regression analysis. The shear resistance through the thickness of the top panel deck, bottom deck flexural strength, pallet flexural strength, fastener withdrawal resistance, and pallet configuration were used to predict the total damage cost. A multiple regression model was developed. The model was verified by comparing the predicted values with the tested values of 12 panel deck pallets representing 2 designs. The results indicated that the model is reliable for the future predictions.
The Effect of Load Stabilizer Selection on Load Shift Within Unit Loads
Bisha, James Victor (Virginia Tech, 2008-05-09)
Research on unit load stability aids manufacturing facilities in selecting the most efficient load stabilizer when shipping their products to market. This study's objective was to compare the performance a variety of different commonly used load stabilizers to stretch hooding. Stretch hooding is a method of load stabilization in which a tubular film is heat sealed at the top, stretched by four mechanical arms to a desired width, pulled down over the unit load. The film is slowly released as the arms descend, and is released under the pallet. 400ga stretch hooding, 80ga and 63ga stretch wrap and strapping were tested. Twenty unit loads for both vibration and impact testing were used, with 5 replications per load stabilizer. Container displacement and pallet-container displacement were measured, and the number of tares in the load stabilizer film, on the corners of the test units, after testing, was noted. Container displacement was significantly greater during impact testing than in vibration testing. Strapping was the most effective stabilizer during vibration testing because of its ability to restrict vertical displacement. The stretch hooding was the most effective stabilizer during impact testing because of its ability to restrict horizontal displacement.
Effect of Pallet Deckboard Stiffness and Unit Load Factors on Corrugated Box Compression Strength
Baker, Matthew W. (Virginia Tech, 2016-03-29)
Corrugated paper boxes are the predominant packaging and shipping material and account for the majority of packaging refuse by weight. Wooden pallets are equally predominant in shipping, transportation and warehousing logistics. The interaction between these two components is complex and unexplored leaving industry to compensate with outdated component specific safety factors. Providing a focused exploration of the box and pallet interaction will open the door for holistic design practices that will reduce cost, weight, damage, and safety incidents. This study was separated into four chapters exploring different aspects of the corrugated box to pallet interaction. The first chapter evaluates the support surface provided by a pallet consists of deckboards spaced perpendicular to the length of the pallet. The resulting gaps between deckboards reduce the support to the box. Gaps were limited to 55% of box sidewall length for practical reasons. The effect of gaps was significant and produced a nonlinear reduction in box strength. Small boxes were more susceptible to gaps than larger boxes. Moving the gap closer to the corner increased its effect while increasing the number of gaps did not increase the effect. A modification to the McKee equation was produced that was capable of predicting the loss in strength due to gaps. The equation is novel in that is modifies a widely used equation and is the first such equation capable of handling multiple box sizes. This study also has practical implications for packaging designers who must contend with pallet gap. Chapter 2 explores the relationship between deckboard deflection and box compression strength. Testing found that reducing the stiffness of the deckboard decreases the compression strength of the box by 26.4%. The location of the box relative to the stringer also had varying effects on the box strength. A combination of deckboard stiffness and gaps produced mixed with results with gaps reducing the effect of stiffness. It was observed that lower stiffness deckboards not only deflect but also twist during compression. The torsion is suspected to have a significant influence on compression but further exploration is needed. The third chapter tests the effect of box flap length on box compression strength under various support conditions. Variables included four flap lengths, gaps between deckboards, low stiffness deckboards, column stacking and misaligned stacking. The results show that the box flaps can be reduced by 25% with no significant effect of box strength under any support condition tested. Furthermore, the box flap can be reduced by 50% with less than 10% loss in compression strength under all scenarios. These results have significant sustainability implication as 25% and 50% reduction in box flap reduce material usage by approximately 12% and 24%, respectively. In the fourth and final chapter, the theory of beam-on-elastic foundation is applied to deckboard bending and corrugated boxes. In this model the corrugated box acts and the foundation and the deckboard is the beam. Rotational stiffness, load bridging, and foundation stiffness changes required the development of novel testing solution and model development. The model was capable of predicting the distribution of force along the length sidewall but was not capable of predicting the ultimate strength of the box. The model developed in the study will be applicable in determining potential weakness in the unit load in addition to optimizing those that are over designed. These four chapters represent a considerable contribution of applicable research to a field that relied on outdated safety factors over thirty years. These safety factors often lead to costly over design in an industry where corrugated box and pallets volumes make event the smallest improvements highly beneficial. Furthermore, this research has opened the door for significant additional research that will undoubtedly provided even greater economic and sustainability benefits.
The Effect of Pallet Top Deck Stiffness on the Compression Strength of Asymmetrically Supported Corrugated Boxes
Quesenberry, Chandler Blake (Virginia Tech, 2020-03-18)
During unitized shipment, the components of unit loads are interacting with each other. During floor stacking of unit loads, the load on the top of the pallet causes the top deck of the pallet to bend which creates an uneven top deck surface resulting in uneven, or asymmetrical support of the corrugated boxes. This asymmetrical support could significantly affect the strength of the corrugated boxes, and it depends on the top deck stiffness of the pallet. This study is aimed at investigating how the variations of pallet top deck stiffness and the resulting asymmetric support, affects corrugated box compression strength. Pallet top deck stiffness was determined to have a significant effect on box compression strength. There was a 27-37% increase in box compression strength for boxes supported by high stiffness pallets in comparison to low stiffness pallets. The fact that boxes were weaker on low stiffness pallets could be explained by the uneven pressure distribution between the pallet deck and bottom layer of boxes. Pressure data showed that a higher percentage of total pressure was located under the box sidewalls that were supported on the outside stringers of low stiffness pallets in comparison to high stiffness pallets. This was disproportionately loading one side of the box. Utilizing the effects of pallet top deck stiffness on box compression performance, a unit load cost analysis is presented showing that a stiffer pallet can be used to carry boxes with less board material; hence, it can reduce the total unit load packaging cost.
The Effect of Pallets and Unitization on the Efficiency of Intercontinental Product Movement Using Ocean Freight Containers
Hagedorn, Alexander (Virginia Tech, 2009-07-20)
Global industrialization was developed in response to both consumers and manufacturers demand for lower product prices and availability of goods and services. As a result, products are transported greater distances. Shipping constitutes the majority of costs in the export/import supply chain. Shippers and buyers commonly attempt to offset these costs by maximizing the capacity of ocean freight containers (cube or weight). Boxes (usually constructed of corrugated fiberboard) containing consumer grade products are commonly floor loaded into containers to maximize capacity. Boxes that are not floor loaded are likely to be unitized on pallets in containers. Beyond maximizing a container with cargo, a defined decision to determine which method of loading is most efficient in regard to cost and time does not exist. For this research, field studies were conducted and questionnaires were distributed to identify the variables that influence efficiency. A method to make an efficient decision was developed by incorporating the variables into a model. The model compares the overall export/import supply chain efficiency for boxes that are floor loaded to boxes that are unitized on pallets in containers. The recommended decision is determined by comparing the shipping and handling costs and the receiving dock door capability for the two loading methods. The results of this research reveal that floor loading boxes can provide a higher value per container due to increased capacity. Increased capacity by floor loading often reduces the number of containers needed to meet daily demand. However, since manual labor is utilized for the loading/unloading process, more time is required, which results in higher labor costs and restricted product throughput. Unitized boxes loaded in containers on pallets can limit container capacity, but allows for faster loading/unloading times (if no incompatibilities between product and pallet or pallet and/or material handling equipment exist), reduced labor costs, and the potential for increased product throughput. Importing boxes unitized on pallets commonly requires more containers to meet demand, but fewer receiving dock doors. Utilizing fewer dock doors allows otherwise occupied doors to be available to receive additional product. The decision to floor load or unitize exports/imports needs to be made on a SKU basis meeting daily demand, not only per container capacity. Labor cost, pallet cost, the magnitude of box variation between loading methods, and the ability of the receiver to process containers are all influencing factors in determining which loading method is most overall efficient. Given the current cost for containerized shipments and considering all costs, most consumer goods are more efficiently shipped floor loaded. When additional containers would be needed to meet demand for product unitized on pallets, floor loading will be more efficient. When there is only a small difference in box count between floor loading and palletizing, palletizing product will be more efficient. This will often occur when loads will meet container weight capacity before it reaches volume capacity. If the product is too heavy to move manually it will be palletized.
The Effect of the Stiffness of Unit Load Components on Pallet Deflection and Box Compression Strength
Phanthanousy, Samantha (Virginia Tech, 2017-06-08)
Currently, pallets are designed assuming that the load is distributed evenly on the top of the pallet. When pallets are loaded with packages such as corrugated boxes or returnable plastic containers, due to their physical shape, packages, are not capable of deforming freely with the pallet and a bridging phenomenon occurs. During this load bridging phenomenon, a portion of the vertical forces are redistributed as horizontal forces which causes the redistribution of the vertical compression stresses on the pallet towards the support. As a result, the deflection of the pallet can decrease and the load capacity of the pallet can increase significantly. The second chapter of this paper investigates the effect of package content on pallet deflection. The study concluded that package content did not have a significant effect on pallet deflection within the boundary conditions of the experiment. The third part of this paper considers how a specific pallet characteristic could affect the way a corrugated box performs. Standard box design procedures include adjustments of estimated compression strength for relative humidity, overhang on pallets, vibration, and alignment of boxes. However, there is no adjustment factor for pallet stiffness. The objective of the study described in this thesis is to find an answer for how the compression strength of a box is affected by pallet stiffness and top deckboard twist. The study concluded that the pallet stiffness and top deckboard twist do not have an effect on the compression strength of the box until less than 12% of the area box is supported.
The Effectiveness of Splicing Notched Pallet Stringer Segments With Metal Connector Plates
Tong, Chao (Virginia Tech, 1997-08-01)
Notched stringer segments spliced with metal connector plates (MCPs) and pallets with spliced stringer(s) were tested in static bending in order to determine the relative effectiveness of different stringer splicing methods and under what conditions the process is or is not effective. The species tested were oak, southern yellow pine, yellow-poplar, and two combined species - oak and yellow-poplar, and oak and southern yellow pine. The metal connector plates used were 3 x 4-inch, 3 x 6-inch truss plates, and a 3 x 4-inch plug plate. The splice methods tested were a vertical splice (VS), a 45° angle splice (AS), and a vertical splice with -inch gap between segments (VSG). The results of bending tests of these specimens were compared to non-spliced whole stringers and pallets containing whole stringers. Multiple comparison, statistical methods were used to analyze all test data. An analysis of the failure locations and types of specimens was also used to analyze test results. Vertical spliced stringers with 3 x 4 and 3 x 6 inch truss plates were the best designs of those tested. Spliced stringers were an average of 112% and 74% bending strength and stiffness of new non-spliced stringer. These plates were an average of 26% stronger and 13% stiffer than the 3 x 4 inch plug plate splice stringer. There was no difference between the performance stringers spliced with 3 x 6 and 3 x 4 inch truss plate. An angle splice design and the addition of 1.25 x 6 inch truss plate on the tension side of spliced stringer did not appear to improve the strength and stiffness. A gap between segments significantly reduces splice strength and stiffness by an average of 35% and 16% respectively. When mixing stringer segment species, the performance is determined by the weaker segment. The average strength and stiffness of pallets containing spliced stringers were similar to that of pallets with whole stringers, however the variation in performance was greater when notched stringer pallets contain splices.
Evaluating vacuum and steam process on hardwood veneer logs for export
Chen, Zhangjing; White, Marshall S.; Mack, Ronald (2017-11)
There is an immediate need to develop and adopt new treatment technologies for eliminating insect pest and tree pathogens from veneer logs moved in trade. This is largely due to the current phase-out of methyl bromide and the uncertainty associated with the efficacy of potential alternatives. Vacuum and steam in combination has a proven and reliable record for commercially sanitizing a variety of commodities, including cotton, spices and textiles among others. This study was designed to evaluate basic parameters of vacuum and steam application on five high value hardwood veneer log species in an effort to ascertain the feasibility of continued treatment development. Relative heating rates to log center, damage and value loss assessment due to treatment, and overall energy used during treatment were recorded for logs treated individually in a flexible polymer chamber. At 200 mm Hg vacuum, time to reach 56 A degrees C for 30 min to core ranged from 17 to 29 h, depending on density and log diameter. End checking varied by species, but veneer sawn from logs was largely unaffected in terms of yield and value. Energy used during treatments ranged from 54 to 205 kWh for individual logs. Results suggest that vacuum and steam as a phytosanitary treatment for hardwood veneer logs has potential and should be explored further.
Evaluation of metal connector plates for repair and reinforcement of wood pallets
Clarke, John W. (Virginia Tech, 1992-07-05)
Pallet repair and reinforcement with metal connector plates (MCPs) may reduce wood waste while providing pallet users with quality, economical pallets. The study objectives were to evaluate the effect of MCP repair and reinforcement on pallet performance, and to evaluate preliminary standards for repair and reinforcement of pallets with MCPs. Whole pallets and pallet components were tested. Stringers and notched segments were tested in static bending, while end feet were tested for resistance to fork tine impact. Whole pallets were evaluated with a test protocol that simulated the effects of long-term handling. Stringers, repaired at notch corners, had greater strength, but less stiffness than the original stringers. Notch reinforcement with MCPs resulted in stringers with greater strength and stiffness than equivalent unreinforced stringers. No consistent species-width effect was found for strength of plated stringers. MCP-repair of above-notch failures did not restore the original strength or stiffness of notched segments. However, these repairs may be satisfactory since above-notch failures are secondary in frequency of occurrence. No differences were found between performance of plates used to repair stringers and notched segments. Both repaired and reinforced end feet had greater impact resistance than the equivalent original or unreinforced end feet. Wood species, rather than stringer width, had a greater influence on MCP performance. In general, tests of whole pallets supported the results from component tests which suggests that component testing may be a practical means of assessing the effect of repair and reinforcement techniques on pallet performance.
Evaluation of Methods to Control Mold on Hardwood Pallets
Blount, Thomas Richard (Virginia Tech, 2013-06-14)
The objectives of this project were:
1.ï¿½ï¿½ï¿½ï¿½To compare the drying cost and drying time for oak and poplar pallets for the following mold mitigation strategies for hardwood pallets: air drying, forced air drying (fan shed), kiln drying to 25% moisture content and chemical treatment, and
2.ï¿½ï¿½ï¿½ï¿½Develop and evaluate a procedure for preventing and controlling mold growth on heat treated hardwood pallets
Twenty red oak pallets and twenty yellow-poplar pallets were tested for each drying method to compare costs and to determine drying times. ï¿½Additional pallets were obtained to conduct a more thorough air drying procedure. ï¿½Drying data was extrapolated to allow estimates of the drying time from green (83% moisture content for poplar and 64% moisture content for oak) to 25%. ï¿½
After the pallets reached the desired 25% moisture content, they were placed in a 40ï¿½" enclosed trailer, inoculated with mold (Aspergillus, Stachybotrys, and Penicillium) and were left undisturbed for a period of 14 days. ï¿½After the 14 day incubation period, the pallets were inspected for mold using the ASTM D-4445 Standard Test Method for Fungicides for Controlling Sapstain and Mold on Unseasoned Lumber. ï¿½
A comparison of drying costs was then conducted to determine which method was the most cost efficient based on the data obtained in this study. ï¿½The cost to treat the pallets with each treatment was calculated including electrical cost, labor, and tax values. ï¿½In addition to the cost comparison, a Net Present Value (NPV) was calculated to determine which method produced the best outcome over a longer period of time.
Two heat treatment and drying schedules were then developed to meet both IPPC-ISPM #15 requirements and achieve the desired 25% moisture content with minimal degrade. ï¿½This was accomplished by testing several HT/drying schedules on green yellow-poplar and white oak pallets until the pallets met the criteria for being heat treated and had minimal degrade. ï¿½The schedules developed are a modified oak HT/KD schedule that required 30 hours to complete and a modified poplar HT/KD schedule that required 16 hours to complete.
The results demonstrated that that mold would not grow on the pallets stored in an enclosed container when the dew point is not reached. Air-drying pallets, chemical application in conjunction with air-drying pallets, fan shed drying pallets and kiln drying pallets to a 19-24% moisture content was demonstrated to prevent mold growth on oak and yellow poplar pallets. Estimates for the time required to dry yellow-poplar and oak pallets to 19% and 25% moisture content were developed for air-drying, forced air-drying and kiln drying for the conditions experienced in Blacksburg, VA between 7/30/2008 and 11/10/2008. Air-drying pallets was found to have the lowest daily operational cost but not the lowest total drying cost. ï¿½Fan shed drying had the lowest drying cost to achieve 25% moisture content. ï¿½Kiln drying was the most expensive daily and total cost, but yielded the fastest method of drying pallets to 25% moisture content. A NPV cost comparison showed that over a 3 year (36 month) time period, fan shed drying is the most cost effective method of drying pallets based on the values used in this study. Given the environmental conditions experienced between 7/30/2008 and 11/10/2008, no mold grew on the air-dried, fan shed, and kiln dried pallets during the drying process.
Evaluation of the Ability of Adhesives to Substitute Nails in Wooden Block Pallets
Alvarez, Gloria Amelia (Virginia Tech, 2019-02-01)
The most common fastening technique that is used to connect the components of wooden pallets together are helically or annularly threaded pallet nails. Pallet nails create a strong durable connection and increase manufacturing efficiency for a low cost. However, nails can also cause iron staining, wood splitting, and when exposed can cause product damage or personnel injury. Using adhesives could be a solution to these problems, but only if the adhesives' strength and durability is comparable or higher than nails. The objective of the study was to investigate the tensile and shear strength of pallet connections secured using commercially available wood adhesives and compare their performance to pallet connections secured using common pallet nails. The lowest pre-compression pressure resulted in the best tension and shear performance for a solvent based construction adhesive (SBCA). The pre-compression pressure did not have any practical effect on the performance of the two-part emulsion polymer isocyanate (EPI) adhesive. Samples made with the solvent based construction adhesive (SBCA) had greater strength and energy at failure than nailed samples. Meanwhile, the samples made with the two-part emulsion polymer isocyanate (EPI) adhesive had equal or greater strength than nailed samples, except for during the tension parallel to the grain tests in which they had equal or lower strength.
Evaluation of the Pallet Deflection that Occurs Under Forklift Handling Conditions
Huang, Yu Yang (Virginia Tech, 2021-09-24)
Industrial forklifts consist of one of the most common handling methods for pallets in warehouses and distribution centers. Pallets deflect while they are being transported by forklifts due to the weight of the unit load. Thus, most of the deflection is observed to occur on the outside edges and corners of the pallet. Several international standards are used in order to define the maximum deflection for pallet bending, including ISO 8611 and ASTM D1185. However, there is still a lack of understanding on the accuracy of these deflection limits and the exact performance of a pallet during a forklift support condition. Understanding pallet bending during forklift support condition and how it affects the stability of a unit load helps create an industry accepted deflection limit that will help to design safer and more cost-effective pallets. For this study, two chapters were proposed in order to assess pallet deflection and unit load stability. The first chapter consisted of measuring and analyzing the vibration levels for three different industrial forklifts affect by factors such as the speed, the payload of the unit load carried, sensor location, forklift type, and road conditions. The results obtained showed that the highest vibration intensity occurred at 3-4 Hz, while the highest overall Grms value observed was 0.145 G2/Hz (between 1-200 Hz). An increase in the forklift speed caused an increase in vibration intensity. In contrast, an increase in the unit load weight carried by the forklift caused a decrease in vibration intensity. Among the three forklifts studied, the gas-powered forklift had the highest vibration intensity, and all forklifts, when driven on asphalt, experienced more vibration. The second chapter of the research project consisted of evaluating pallet deflection under forklift handling conditions. These conditions included fork tines configuration (leveled and 4° angle), unit load condition (bound and unbound), pallet orientation (across width and across length), and type of handling condition (static and dynamic). The results showed that when unit loads were handled in a static condition, they survived the throughout the entire testing. However, when they were tested under a dynamic condition, and specifically, with the unbound unit loads, they did not survive the entire testing. Moreover, unit loads that were tested with the 4° angle forktines configuration tended to survive longer during the dynamic testing. For this particular case, the unit load capacity obtained based on the ISO 8611 standard was too conservative.
Evaluation of Unit Load Stability Under Dynamic Forklift Handling Conditions
Capizzi, Seth (Virginia Tech, 2024-06-12)
A vast amount of goods and products are transported in bulk as palletized unit loads, where the pallet is the base of the unit load. Material handling systems represent the physical environment in which unit loads are transported through supply chains. Material handling systems include different transportation modes and storage conditions, many of which are well researched. While industrial forklifts are paramount to material handling systems, the physical effect they have on load systems is not well understood. The weight of the unit load causes the pallets to deflect, and previous research has revealed that forklift vibration amplifies pallet deflection. The effects of forklift vibration on pallet deflection are not considered in international standards used to determine pallet load capacities. Standards such as ISO 8611 and ASTM D1185 provide deflection limits that are used to determine pallet load capacities, yet there is a lack of understanding and justification on these deflection limits related to forklift support conditions. A comprehensive understanding of the effects of forklift vibration on unit load performance is necessary to produce accurate and safe load capacity ratings. In this research, two studies were completed to gain further understanding on unit load performance and stability in forklift handling conditions. The first study evaluated pallet deflection and unit load stability of unbound unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). Common forklift handling factors were investigated and included fork tine angle (level and 4-degree incline) and pallet orientation (racked across the width and across the length). The results showed that the dynamic environment of forklift handling created unstable unit loads. The second study of this research project investigated unit load performance against unit load design factors of load capacity (500 lbs., 750 lbs., 900 lbs.) and box size (8 in., 12 in., 16 in.). The results showed that unit load instability occurred at all load levels and all box sizes. Additionally, an increase in box size decreased load bridging for unit loads under fork tine support conditions. Furthermore, the time to instability was used to calculate projected forklift travel distances that can be used to further optimize material handling systems.
Exploration of plastic pallets using various fillers on graphite nanoplatelets/polypropylene composites
Lee, Soohyung (Virginia Tech, 2023-01-26)
In this study, composite system was developed to enhance mechanical properties of plastic pallets. The potential of graphite nanoplatelets (GnP)/PP composites for the application in packaging was scrutinized by examining mechanical properties, thermal properties, flow properties, and morphology as a function of GnP loading and by comparison of two mixing methods: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Incorporation of the GnP into PP resulted in a significant enhancement in the mechanical strength (tensile, impact, and flexural strength) and thermal decomposition temperature compared to the neat PP specimen. The CPC process clearly shows good exfoliation and better distribution on the PP matrix compared to the PMC method based on morphological evaluation measured by SEM. The impact test at low temperature revealed that the composites made by the CPC process showed 64% higher impact strength than neat PP due to higher even-distribution of GnP molecules into the PP matrix. We attempted to discover the degree of dispersion of natural fiber (kenaf) and graphite nanoplatelets (GnP) into the polypropylene (PP) polymer matrix and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (graphite nanoplatelets (GnP)/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. The impact strength of composite samples, containing 1wt% of GnP and mCaCO3 nanoparticles, increased up to 64% compared to neat PP. Among all tested samples, the highest tensile strength was found at 1wt% of mCaCO3 nanoparticles regardless of the presence or absence of GnP addition. There was no significant difference in flexural strength regardless of any nano-filler addition. However, both the flexural modulus and Young's modulus increased significantly when 10wt% of mCaCO3 nanoparticles were added. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. It may be contributed by thermal degradation of polymeric structure by double heat processing. This study can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobile, where carbon-based nanomaterials are more affordable.
Factors influencing pallet material substitution by the U.S. grocery distribution industry
Engle, Catherine Anna (Virginia Tech, 1994-05-05)
Persons involved in pallet decisions at U.S. grocery distribution centers were surveyed to investigate the degree of material substitution, assess factors influencing pallet material substitution, and quantify consumer perceptions of wood pallets compared to substitutes. A total of 444 questionnaires were mailed nationwide. Underlying reasons for material substitution were investigated through in-depth interviews with 20 respondents. Cost per use was considered by grocery distributors to be the Persons involved in pallet decisions at U.S. grocery distribution centers were surveyed to investigate the degree of material substitution, assess factors influencing pallet material substitution, and quantify consumer perceptions of wood pallets compared to substitutes. A total of 444 questionnaires were mailed nationwide. Underlying reasons for material substitution were investigated through in-depth interviews with 20 respondents. Cost per use was considered by grocery distributors to be the most important factor when choosing a pallet to be sent downstream to their customers. Common advantages of solid wood pallets reported by respondents included: availability, low initial cost, durability/stability (the ability of the pallet to be racked and hold the necessary weight with little deflection), industry standard, ability to exchange, ease of repair. Common disadvantages of solid wood pallets reported by respondents included: easily damaged, short life, high repair and replacement costs, heavy, inconsistent construction, and damages product. Advantages of plastic pallets reported by respondents included: light weight, durability, longer life, true four-way entry, and ability to nest. Plastic pallets were perceived to be superior to wood pallets in terms of overall performance, durability, and recyclability. Although 100 percent of the responding companies use solid wood pallets to ship goods to customers, approximately 20 percent of the companies also use plastic pallets (the dominant substitute pallet material) for this purpose. The common plastic pallet used by respondents was of the twin sheet thermoform type. The primary reason for switching to plastic pallets was perceived overall cost savings resulting from long pallet life.
Identifying Success Factors in the Wood Pallet Supply Chain
Sanchez, Leslie Scarlett (Virginia Tech, 2011-05-02)
Pallets are a critical component of logistics infrastructure. Approximately 1.9 billion pallets are used each year in the United States for transportation of goods, from raw materials to finished products. Solid wood pallets represent 90% to 95% of the pallet market. To run their operations, wood pallet companies deal with suppliers, customers, and other supply chain components. Each of the steps is important to deliver the right products, with the required quality, and in a timely fashion. However, there is little research about the industry's supply chain practices. The objective of this research is to increase the understanding of the U.S. wood pallet manufacturing industry, its supply chain management practices, and factors affecting the supply chain management processes. To accomplish the research objectives, a nationwide mail survey of wood pallet manufacturers was carried out. In total 1,500 companies were sent questionnaires and the response rate was 14%. A model for supply chain success factors was developed based on previous research and was analyzed using the results from the survey. Results of the survey provide an up-to-date profile of the US wood pallet industry. It was found that pallet production per company was 727,229 units on average during 2009. Out of the 1500 respondents, 38.6% indicated they were medium-sized companies (20 to 99 employees) and 53.9% small companies (1 to 19 employees). Thirty five percentage of respondents indicated that their sales were less than one million dollars and 43% from one to five million dollars. Also, 45% of respondents were involved in pallet recycling or repair, and these companies indicated that, on average, 42% of the material in a recycled pallet is, in fact, new material. Regarding Supply Chain practices, close to three-quarters (73.1%) of respondents sold their products directly to customers and the order lead time for raw materials to shipment was 1 to 10 days for 81.9% of companies. The most important factors for purchasing decisions are availability, cost, and reliability of supplier (all rated 4.4 in an importance scale from 1 to 5, respectively). Respondents' answers suggest a preference to work with domestic materials (rated 4.3); however, respondents also indicated that there is currently a high level of competition for raw materials (rated 4.3). Results also indicated that information technology (IT) appears to receive little attention from wood pallet manufacturers, given that the importance of items in this area were rated relatively low, especially the use of internet for purchasing and training in IT (rated 2.2 and 2.1, respectively). Lastly, 86.0% of respondents did not believe that their customers would be willing to pay a premium for environmentally certified pallets, citing cost as the major barrier for a higher demand of these products. Also, a theoretical framework of supply chain management was designed, developed, and tested with factor analysis, allowing identification of seven factors in the wood pallet supply chain: (1) environmental uncertainty, (2) information technology, (3) supply chain relationships, (4) value-added process, (5) supply chain management performance, (6) business management, and (7) customer satisfaction. Relationships between factors were tested using multiple linear regression. Results show that value-added process positively affects supply chain relationships, and these in turn are positively correlated to supply chain management performance and customer satisfaction. Results from this research are useful for the industry to formulate a well-informed supply chain management strategy by understanding the connections between the different supply chain management practices and the business performance and customer satisfaction. The information presented is also useful for organizations supporting the wood pallet industry to design more effective assistance and educational programs.

Browsing by Author "White, Marshall S."

Results Per Page

Sort Options