Coated Bore Cutting Tool Pits for Lubricant Retention

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Solution Overview

Problem

Existing bore cutting tools experience reduced tool life and poor hole reproducibility due to inefficient lubrication, particularly in boundary lubrication conditions during metal machining, where the lubricant film thickness is difficult to increase effectively.

Innovation Solution

A bore cutting tool with a plurality of pits on its surface, coated with a wear-resistant coating that follows the contour of the pits, retains lubricant and increases the lubricant film thickness, thereby reducing friction and wear, and is manufactured using laser etching and vapour deposition techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pits are formed in the coating after coating is applied (e.g., by laser etching into the coating), then the coating structure is modified to retain lubricant, but the coating is damaged in the area around the pit causing cracking and premature tool failure

Engineering Contradiction:

Improvetool lifeVSAvoidcoating damage and cracking

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The pits are formed in the tool substrate before the coating is applied, rather than etching into the coating after it is applied. This preliminary action allows the coating to be deposited over the pre-formed pits, avoiding damage to the coating structure while still creating lubricant retention features.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The conventional sequence is inverted: instead of coating first then etching pits, the pits are formed in the substrate first, then the coating is applied. This reversal prevents the harmful side effect of coating damage while achieving the desired lubricant retention function.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If pits are formed in the coating by laser etching, then lubricant retention is improved, but uneven and inconsistent pit dimensions are produced

Engineering Contradiction:

Improvelubricant retentionVSAvoidpit dimension consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Pits are pre-formed in the tool substrate with precise dimensions using laser etching or other methods before coating application. This ensures consistent pit dimensions are achieved in the substrate, and the subsequent coating process preserves these dimensions rather than creating variations through post-coating etching.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If pits are formed in the substrate and coated, then the coating properties are retained on the surface between pits and in the pits, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvecoating integrityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pits are formed in the substrate before coating, allowing a single continuous coating process to cover both the pit surfaces and the areas between pits. This approach maintains coating integrity throughout while avoiding the need for separate coating operations for different surface regions.

Inventive Principle:

Principle #10Preliminary action

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 enhances tool performance by maintaining consistent pit dimensions, reducing tool wear, and achieving improved hole quality and extended tool life, even with minimal lubricant usage, while optimizing the use of lubricant in areas of hydrodynamic lubrication.

Implementation Method 1

the pits are formed in the tool substrate prior to forming the tool coating. For example, laser etching systems used for marking metal components can be applied to bore cutting tools to produce the desired plurality of pits

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

coating the pitted surface of the tool substrate to form a tool coating... manufactured using laser etching and vapour deposition techniques

Methodology Applied

Scientific EffectVapour deposition: Physical Vapour Deposition

Implementation Method 3

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

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS11524345B2Bore cutting tool and method of making the same

Publication Date: 2022.12.13 SANDVIK INTELLECTUAL PROPERTY AB

AI summary

A bore cutting tool for cutting metal workpieces includes a tool substrate and a tool coating on a surface of the tool substrate. The bore cutting tool includes a plurality of pits in the surface of the tool substrate and wherein the tool coating extends over the pits such that the pit surface includes 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 the embodiments, the pits are formed by laser etching and are present only on the cylindrical land. Average pit depth is suitably in the range 8 μm to 25 μm, average pit width and pit length is independently selected from 40 μm to 250 μm and average pit density may be 20 to 30 pits/mm2.