Clamped-Ring Cutter Assembly for TBM Weight Reduction
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Solution Overview
Problem
Tunnel boring machine (TBM) cutter assemblies face high costs and maintenance challenges due to the use of expensive tool steel and complex fabrication processes, leading to frequent replacement and downtime, especially when dealing with mixed ground conditions and extreme stress.
Innovation Solution
A clamped-ring cutter assembly design that reduces the amount of tool steel required by using a disc subassembly with a first and second hub member, where the cutter ring is clamped between the hub members with bolts, allowing for a simpler and lighter construction that can be easily disassembled and replaced, and optionally using segmented or layered materials for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigidly-mounted spikes or massive cutter rings are used, then the cutter assembly has sufficient strength to handle extreme stress, but the cost and weight increase significantly
Solution Approach 1:
The cutter ring is divided into multiple segments that can be independently replaced, eliminating the need for a single massive cutter ring. Each segment is smaller and lighter, but collectively they provide the necessary cutting capability while reducing overall weight and cost.
Solution Approach 2:
The cutter ring segments are nested within a hub structure that provides structural support. The hub members contain L-shaped channels that receive and position the cutter ring segments, allowing the cutter ring to be lighter while the hub provides the necessary strength.
2Reliability
If expensive tool steel is used for the entire cutter assembly, then durability and strength are improved, but the cost increases significantly
Solution Approach 1:
Tool steel is applied only to the cutter ring segments where cutting action occurs, rather than the entire cutter assembly. The hub members can be made from less expensive materials since they provide structural support rather than direct cutting function, reducing the quantity of expensive tool steel required.
Solution Approach 2:
The cutter ring segments are designed as replaceable wear components that can be discarded when worn, while the expensive hub structure is retained and reused. This allows the expensive tool steel to be concentrated in the segments that experience wear, rather than the entire assembly.
3Stability of the object's composition
If a solid integrated cutter ring design is used, then structural integrity is maintained, but fabrication complexity and cost increase
Solution Approach 1:
The cutter ring is segmented into multiple smaller pieces that are easier to manufacture and assemble than a single large integrated ring. Each segment can be fabricated independently using simpler processes, then assembled into the complete cutter ring structure within the hub.
Solution Approach 2:
The hub members are designed with L-shaped channels that integrate the support function and the cutter ring retention function. This merging of functions into the hub structure simplifies the overall fabrication process compared to creating a single complex integrated component.
Data Source
AI summary
A cutter assembly includes a disc subassembly rotatably mounted on a shaft with bearing assemblies, and end retainers. The disc subassembly includes a first hub member having a tubular portion that houses the bearing assemblies and an outer flange portion, a second hub member that slidably engages the tubular portion, and an annular cutter ring, preferably formed from a tool steel, and optionally formed in a plurality of segments. The first and second hub members define a channel that receives and clampingly engages a rectangular inner base portion of the cutter ring. The clamping force is provided by a plurality of bolts that join the first and second hub members, while the flange portion of the first hub member remains separated from the second hub member by a gap (S). In an embodiment the cutter ring includes a carbide core.