CNC Lathe Turning Pass Strategy for Cutting Depth and Tool Wear

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Solution Overview

Problem

Existing methods for generating control command data for CNC-lathes in turning operations lack guidance for optimally selecting cutting depth, leading to suboptimal machining times, tool life, and chip breaking.

Innovation Solution

A method for generating control command data that includes selecting a turning tool and determining recommended and maximum cutting depths, with the option to adjust feed rates and tool paths to improve tool life and machining efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If cutting depth is increased to reduce machining time, then productivity improves, but tool wear increases and tool life decreases

Engineering Contradiction:
Improvemachining timeVSAvoidtool life
Core Design Contradiction:
ProductivityVSDuration of action of moving object

Solution Approach 1:

The patent segments the total material removal into multiple passes with different cutting depths. The first pass uses a limited cutting depth (less than the nose radius) to machine the outer surface, while subsequent passes use greater cutting depths (greater than the nose radius) to machine the inner surface. This segmentation allows optimization of each pass for its specific purpose, reducing overall machining time while preserving tool life by avoiding excessive wear during the critical first pass.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies different cutting depth strategies to different regions of the workpiece. The outer surface (peripheral surface) is machined with a more conservative cutting depth to account for the harder skin and uneven surface, while the inner surface is machined with greater cutting depths. This local quality approach optimizes tool life where needed while maintaining productivity overall.

Inventive Principle:
Principle #3Local quality

2Manufacturing precision

If cutting depth is increased to improve chip breaking, then manufacturing precision improves, but tool wear increases

Engineering Contradiction:
Improvechip breakingVSAvoidtool wear
Core Design Contradiction:
Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent divides the machining operation into two stages: a first pass with limited cutting depth focused on establishing the outer surface and initiating chip breaking, followed by subsequent passes with greater cutting depths that build on the chip breaking established in the first pass. This segmentation achieves effective chip breaking without subjecting the tool to excessive wear from consistently high cutting depths.

Inventive Principle:
Principle #1Segmentation

3Productivity

If cutting depth is set greater than nose radius to remove material efficiently, then productivity improves, but tool wear on outer surface increases

Engineering Contradiction:
Improvematerial removal efficiencyVSAvoidtool wear
Core Design Contradiction:
ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the material removal process into a first pass with cutting depth less than the nose radius for outer surface machining, and subsequent passes with cutting depth greater than the nose radius for inner surface machining. This segmentation allows efficient material removal in subsequent passes while protecting the tool from excessive wear during the critical first pass on the outer surface.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies different cutting depth parameters to different locations on the workpiece. The outer surface (where the tool first contacts the harder skin) receives more conservative cutting depth treatment, while the inner surface receives more aggressive cutting depths. This local quality optimization balances productivity with tool wear reduction.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP3702853B1Method for generating control command data for controlling a CNC-lathe
Publication Date: 2025.05.21 SANDVIK COROMANT
  • EP3702853B1 patent drawingFigure 1~2
  • EP3702853B1 patent drawingFigure 3~4
  • EP3702853B1 patent drawingFigure 5~6

AI summary

A method for generating control command data for controlling a CNC-lathe to perform a turning operation by means of a turning tool (7), the method comprises the steps of: generating control command data for: commanding the turning tool (7) to perform a first turning pass (52, 55) and a second turning pass (50), wherein a maximum cutting depth of a second turning pass (50) is greater than a maximum cutting depth (64) for the first turning pass (52, 55).