Coated Pit Bore Cutting Tool Lubricant Retention
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Solution Overview
Problem
Existing bore cutting tools experience accelerated tool wear and reduced performance due to inefficient lubrication during metal machining, leading to poor hole reproducibility and increased friction, which is exacerbated by the difficulty in achieving sufficient film thickness between the tool and workpiece surfaces.
Innovation Solution
A bore cutting tool with a plurality of pits on its surface, coated with a wear-resistant coating, which retains lubricant and increases film thickness, transitioning from boundary to hydrodynamic lubrication by forcing fluid into the pits during contact, thereby reducing friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pits are formed in the tool substrate and coated with tool coating, then lubricant retention is improved and tool wear is reduced, but manufacturing complexity increases
Solution Approach 1:
The pits are formed in the tool substrate before applying the tool coating. This preliminary action allows the coating to be deposited over the pit surfaces, ensuring complete coverage and integration of the coating with the pit structure, which maximizes lubricant retention while maintaining a consistent coated surface
Solution Approach 2:
The pit structure creates a porous or cavitated surface topology on the tool substrate. These pores or cavities act as lubricant reservoirs, trapping and retaining lubricant during the machining process, thereby reducing friction and tool wear without requiring excessive lubricant application
2Reliability
If pits are formed after coating by laser etching, then lubricant retention is improved, but coating damage and cracking occur
Solution Approach 1:
The pits are formed in the tool substrate before the tool coating is applied, rather than etching into the coating after deposition. This preliminary formation of pits avoids subjecting the coating to laser etching processes that cause cracking and damage, while still achieving the desired lubricant retention through the coated pit structure
3Reliability
If lubricant film thickness is increased between tool and workpiece, then friction and tool wear are reduced, but lubricant consumption increases
Solution Approach 1:
The pit structure creates localized regions of increased lubricant film thickness at the pit locations, while maintaining thinner film regions elsewhere on the tool surface. This local quality variation allows effective lubrication at critical contact points without requiring a uniform increase in lubricant consumption across the entire tool surface
Solution Approach 2:
The pits act as self-contained lubricant reservoirs that automatically supply lubricant to the tool-workpiece interface during machining. As the tool rotates or moves, the pits periodically release trapped lubricant, creating a self-sustaining lubrication system that maintains adequate film thickness without continuous external lubricant application
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coated pit structure effectively retains lubricant, reduces tool wear, and improves hole reproducibility and tool performance by maintaining a smooth, consistent surface and optimizing lubricant usage, even with minimal quantities, leading to reduced torque and improved productivity.
Implementation Method 1
a bore cutting tool with a plurality of pits on its surface, coated with a wear-resistant coating, which retains lubricant
Implementation Method 2
the lubrication reduces the 'μ' value (coefficient of friction) between the surfaces of contact, i.e. tool and workpiece. Reducing the value of μ leads to a reduction in friction between the contactable surfaces, which consequently leads to a reduction in tool wear
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Bore cutting tool (2), particularly for cutting metal workpieces, comprising a tool substrate (4) and a tool coating (8) on a surface of the tool substrate wherein the bore cutting tool comprises a plurality of pits (6) in the surface of the tool substrate and wherein the tool coating extends over the pits such that the pit surface comprises the tool coating. In this way, the pit dimensions can be retained over prolonged tool life and the pits, with their coated surface, are particularly effective at retaining lubricant so that the thickness of a lubricant film can be increased as compared to a tool without the coated pits. In embodiments the pits are formed by laser etching and are present only on the cylindrical land. Average pit depth is suitably in the range 8μm to 25μm, average pit width and pit length is independently selected from 40μm to 250μm and average pit density is 20 to 30 pits/mm2.