CIM Bulletin, Vol. 1, No. 2, 2006
N. Shi and T.G. Joseph
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Electric cable shovels are the most extensively used highvolume excavators in open pit mining. The design of dippers for cable shovels has essentially remained unchanged for the last 100 years. Previous work to improve the production capability of these units focused on updating mechanical and electrical components, and optimizing utilization and operational approaches. Little work has been done to improve dippers and their ground interactions. With the trend of higher production forcing the development of ever bigger, faster, and smarter cable shovels, there is a need to move beyond the aging geometry of dippers. In the past 10 years, shovel manufacturers have started taking another look at dipper design, resulting in changes that have borne models from the major manufacturers that address some of the wear conditions and material retention problems that dominate maintenance and operational costs. However, with the exception of added lateral curvatures to the front and corners of the dipper, most base features, including geometry and mechanism, are essentially unchanged.
This paper looks at the criteria that will lead to a better cutting dipper design, and suggests an alternative design approach for use in ground conditions where cutting virgin ground rather than scooping blasted material is required. The criteria include digging force, friction force, trajectory, fill time, fill factor, etc., which may be integrated into three basic considerations: power (energy consumption); volume delivered (production); and lifespan (wear and strength) as indicators of dipper performance. The approach basically consists of 3D solid modelling and the simulation of a shovel’s duty cycle, in which shovel kinematics, dynamics, and ground-dipper interactions are primary considerations. The research first aims at a revolutionary geometry which will improve performance considerably without changing any configuration of the current shovels.
The design is based on kinematic considerations, reflected in a revolutionary geometry that matches the range of motions of the shovel, designed to minimize wear, impact loading and power required to dig, thus maximizing productivity for a minimum energy requirement. The shape configuration is such that the weight of the dipper through wall thickness is reduced, enabling a larger capacity dipper to be conceived for the same shovel. Benefits are reflected in reduced operational and maintenance costs, and increased productivity.
To prove the new design further, a 3 yd3 dipper was fabricated to match a Dominion 500 cable shovel. This shovel was identified as having the same operating action and geometric orientation as modern ultra class shovels at 1/20th of the dipper scale. Both the new and original dipper will be tested in the field, allowing the relative performance data to be compared.
One of the ultimate objectives of this research is to build the biggest dipper in the world for ultra class shovels currently employed without changing shovel structure and power drive systems. Several options have been proposed according to the working scenario in which it would be applied. A typical design is illustrated in the figure.
