Pallet Handling Research Articles

Development of an Automatic Pallet Handling System for Seeded Trays

The objective of this study was to develop an automatic pallet loading and unloading system for rice seeded trays, that receives three seeded trays in a stack from an automatic sowing line and arranges them orderly on a pallet. The loaded pallets will then be shipped out to a conditioning room for sprouting. The system can also reverse the former procedures to retrieve sprouted trays from pallets and arrange the trays to be sent to the nursery field, where the seeds in the tray keep growing to the seedling stage. A prototype was designed, constructed and subjected to performance testing and evaluation. Experimental results showed that the system worked satisfactorily at stacking 1416 trays h−1, with 95% pallet loading success rate. The unloading capacity was 1380 trays h−1, with 97·2% success rate.

A stochastic model for the analysis of a two-machine flexible manufacturing cell

This paper presents a stochastic model to determine the performance of a flexible manufacturing cell (FMC) under variable operational conditions, including random machining times, random loading and unloading times, and random pallet transfer times. The FMC under study consists of two machines, pallet handling system, and a loading/unloading robot. After delivering the blanks by the pallet to the cell, the robot loads the first machine followed by the second. Unloading of a part starts with the machine that finishes its part first, followed by the next machine. When the machining of all parts on the pallet is completed, the handling system moves the pallet with finished parts out and brings in a new pallet with blanks. A model with these characteristics turns out to be a Markov chain with a transition matrix of size 5 n +3, where n is the number of parts on the pallet. In this paper, we present exact numerical solutions and economic analysis to evaluate FMC systems, to determine optimal pallet capacity and robot speed that minimize total FMC cost per unit of production.

Ergonomic Analysis of Pallets and Drum Handling

This study investigates the effects of heavy pallet and drum handling on spinal loading at the L5/S1 region and surface electromyographic activity of the erector spinae muscles, and the associated risk of low back disorder (LBD). Ten field technicians at the Lawrence Livermore National Laboratory (LLNL) were asked to unstack plastic and metallic pallets and manipulate 55 gallon waste drums. Lifting the metallic and plastic pallets and lowering a 34 Kg drum induced the highest disc compression at the L5/S1 level, while manipulating the pallets and breaking up a 203 Kg drum induced the highest low back muscle activity. The major results showed that posture has a significant influence on disc compression force; however, the lowest muscle load may not be correlated with the lowest disc compression. The computed disc compression forces and EMG activities are most likely responsible for the elevated risk of back injury in waste management workers.

Prototype trailer‐loading robot

The Pallet Handling Device (PHD) is a five degree‐of‐freedom (dof) robot system under development by Stewart‐Glapat Corporation for autonomous loading of pallets into semi‐truck trailers at loading docks. The fully‐autonomous control is achieved using a programmable logic controller (PLC) and sensors. Ohio University has developed a one‐eighth‐scale prototype hardware system for PHD controls implementation and evaluation. This article describes the design and construction of this system, including the control architecture and PLC programming. The main objective of the scale hardware prototype is to demonstrate the autonomous control feasibility of the proposed full‐scale PHD system; this cannot be adequately performed in simulation.

Reliability analysis of a flexible manufacturing cell

In this study, mathematical models are developed to study and compare the operations of a fully reliable and an unreliable flexible manufacturing cell (FMC), each with a flexible machine, a loading/unloading robot, and a pallet handling system. The operation times, loading/unloading times, and material handling times by the pallet are assumed to be random. The operation of the reliable cell is compared to that of an unreliable cell with respect to utilization of the cell components, including the machine, robot, and pallet handling system. The unreliable cell is assumed to operate under random (machine and robot) failures with constant failure rates for the machine and the robot. The pallet handling system is assumed to be completely reliable.

Weighing, sack filling and pallet handling machinery

Pallet handling and conveying machinery made by Schaefer of Munich has been added to the range of equipment marketed by Medway in the UK. Schaefer are one of the market leaders in Europe and have hundreds of installations throughout the world, including many in British companies. Products include depalletisers, conveying equipment and palletisers. Systems are custom‐designed, manufactured and installed for each user.

Stochastic modelling and comparisons of two flexible manufacturing cells with single and double gripper robots

A stochastic model is presented for calculating the performance measures of a flexible manufacturing cell (FMC) which operates under stochastic environment and produces a variety of parts by utilizing a flexible production machine and a single or a double gripper robot for machine loading and unloading operations. The FMC is served by a pallet handling system which delivers blanks into the cell and moves finished parts out of the cell. By using the proposed model, an FMC utilizing a double gripper robot is compared with an FMC utilizing a single gripper robot. Comparisons which were based on cell performance measures, namely, production rate, machine utilization, robot utilization and pallet handling system utilization, show that use of a double gripper robot results in a substantial improvement in cell performance measures over a single gripper robot. The stochastic model developed in this study can be used to evaluate an FMC operating under different operational conditions.

A modular approach for the modelling of a class of zone-control conveyor system using timed Petri nets

Abstract In this paper, modeling of a programmable-control conveyor system or a ‘pallet handling system’ is described. The concept of zone control is introduced as traffic control for this type of conveyor. Timed Petri net (TPN) modules are presented as basic building blocks to model and analyse operational performance of the system. This modular approach facilitates an easy model construction, and provides an easy way to create or revise TPN models. Moreover, P-invariants are used to analyse the logical properties of the TPN model, i.e. boundedness, conservativeness, and liveness. T-invariants are used to find all possible pallet routeings. Finally, straightforward application of the modular approach is demonstrated in a case study.

Experimental field gantry for leaf vegetable production: Specification, design and evaluation

An experimental gantry for leaf vegetable production has been designed and built at AFRC Engineering and evaluated over two seasons. The objectives of the work are to develop and demonstrate practical gantry based systems of crop production. The machine has a 9 m wide working width between two hydraulically driven crawler track units. The upper surface of a 0·6 m deep space frame beam forms the working platform and the beam has a 0·9 m ground clearance. The gantry may be raised off its tracks by jacking down wheels at both ends, it then qualifies under the Road Traffic Regulations as a trailed agricultural appliance when towed on the road by a tractor. A pallet handling system for six pallets has been provided, and the gantry has the facility to carry and power conveyors for harvesting. Various standard or experimental implements may be mounted on a three-point linkage assembly which can be traversed along the beam. A commercial gantry based on the experimental machine has also been built. The cost of this was comparable with self-propelled wheel based field packhouses of similar load capacity. In its first season the farmer has demonstrated substantial advantages over the latter, largely due to reduced crop damage and improved vehicle flotation.