Background
CMP Engineers was engaged by a specialist manufacturer that produces replacement components for large mining equipment. The client develops engineered alternatives to OEM parts used on machines such as draglines and rope shovels.
Many draglines currently operating in mines have been in service for decades. Critical structural and drivetrain components on these machines are commonly manufactured as large castings. Over extended service periods, these components can experience fatigue cracking, particularly where geometric details in the original designs create stress concentrations.
The client initiated a program to replace several legacy cast components with redesigned forged alternatives. The components included dragline drum spiders, walking spiders, and walking eccentrics; all large load-bearing components subjected to significant cyclic forces during operation.
Due to the scale and structural importance of these parts, the client engaged CMP Engineers to perform detailed engineering analysis, redesign the components, and validate the structural performance of the proposed forged replacements.
Many draglines currently operating in mines have been in service for decades. Critical structural and drivetrain components on these machines are commonly manufactured as large castings. Over extended service periods, these components can experience fatigue cracking, particularly where geometric details in the original designs create stress concentrations.
The client initiated a program to replace several legacy cast components with redesigned forged alternatives. The components included dragline drum spiders, walking spiders, and walking eccentrics; all large load-bearing components subjected to significant cyclic forces during operation.
Due to the scale and structural importance of these parts, the client engaged CMP Engineers to perform detailed engineering analysis, redesign the components, and validate the structural performance of the proposed forged replacements.
Challenge
The original OEM components were manufactured as castings. While casting allows complex shapes to be produced, the existing designs contained several geometric features that resulted in elevated local stresses during operation.
These stress concentrations, combined with the high cyclic loading experienced during dragline operation, contributed to fatigue cracking over time. In addition, casting geometry can restrict the ability to optimise load paths or remove problematic features once the design is established.
The challenge was therefore to redesign these large structural components so they could be manufactured as forgings, while significantly improving their fatigue performance and structural reliability.
Given the complexity of the load transfer between interacting components within the dragline mechanism, simplified loading assumptions were insufficient. The engineering analysis needed to replicate realistic load paths through the machine to accurately assess stresses within the components.
These stress concentrations, combined with the high cyclic loading experienced during dragline operation, contributed to fatigue cracking over time. In addition, casting geometry can restrict the ability to optimise load paths or remove problematic features once the design is established.
The challenge was therefore to redesign these large structural components so they could be manufactured as forgings, while significantly improving their fatigue performance and structural reliability.
Given the complexity of the load transfer between interacting components within the dragline mechanism, simplified loading assumptions were insufficient. The engineering analysis needed to replicate realistic load paths through the machine to accurately assess stresses within the components.
Solution
CMP Engineers developed detailed 3D CAD models of the existing components based on available engineering information and reconstruction of the component geometry.
Finite element analysis was then performed to simulate the operational loads experienced by the components. In order to accurately represent the real load transfer within the machine, interfacing components were also modelled, and the contact faces between components were included in the analysis. This allowed realistic boundary conditions and load paths to be applied within the simulations.
The analysis identified several locations where stress concentrations occurred within the original casting designs. These areas were examined to understand the failure mechanisms and to guide the redesign process.
The components were then completely redesigned to suit forged manufacture. The forging process removed many of the geometric constraints associated with casting and allowed the components to be optimised for structural performance.
Stress-raising features present in the original designs were removed, transitions between sections were improved, and radii were increased to reduce localised stresses. In some areas, material thickness was increased to reduce stresses, while in other areas, material was redistributed to improve overall load transfer.
The redesigned forged components were then validated through further finite element analysis to confirm the improvements in structural performance.
CMP Engineers also produced the full set of manufacturing drawings and specifications required for the client to manufacture the components. This included detailed engineering drawings as well as forging process requirements and associated specifications.
Finite element analysis was then performed to simulate the operational loads experienced by the components. In order to accurately represent the real load transfer within the machine, interfacing components were also modelled, and the contact faces between components were included in the analysis. This allowed realistic boundary conditions and load paths to be applied within the simulations.
The analysis identified several locations where stress concentrations occurred within the original casting designs. These areas were examined to understand the failure mechanisms and to guide the redesign process.
The components were then completely redesigned to suit forged manufacture. The forging process removed many of the geometric constraints associated with casting and allowed the components to be optimised for structural performance.
Stress-raising features present in the original designs were removed, transitions between sections were improved, and radii were increased to reduce localised stresses. In some areas, material thickness was increased to reduce stresses, while in other areas, material was redistributed to improve overall load transfer.
The redesigned forged components were then validated through further finite element analysis to confirm the improvements in structural performance.
CMP Engineers also produced the full set of manufacturing drawings and specifications required for the client to manufacture the components. This included detailed engineering drawings as well as forging process requirements and associated specifications.
Outcomes
The redesigned forged components demonstrated a significant reduction in peak stresses compared with the original cast designs.
From a fatigue perspective, the improved geometry and load distribution resulted in an estimated doubling of the components’ relative fatigue life.
By eliminating several stress-raising features present in the original castings and optimising the geometry for forged manufacture, the redesigned components provided improved structural robustness and reduced the risk of fatigue crack initiation.
These improvements contributed to increased machine reliability, reduced risk of unplanned shutdowns, longer inspection intervals, and lower long-term maintenance costs.
The project demonstrates CMP Engineers’ capability in applying advanced engineering analysis and structural redesign techniques to improve the performance and reliability of large-scale mining equipment components.
