Diagonal Gear Machining Twist Control
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Solution Overview
Problem
Existing methods for machining helically toothed flank line crowned cylindrical gears in the continuous generating method often result in torsioned flanks, known as twist, which is difficult to avoid or control using conventional tools and techniques.
Innovation Solution
The method involves coordinating the crowning of tools, such as hobs or grinding worms, with the diagonal ratio to create a desired twist by superimposing additional crowning on the work piece, allowing for the selection of tools of varying lengths and adapting their crowning to achieve the required flank line crowning and twist, while simulating the machining process to optimize flank geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a volute tool with varying pressure angle is used to avoid twist, then the twist is avoided, but the tool becomes very difficult to produce and not flexible to use
Solution Approach 1:
The patent changes the parameter from pressure angle variation (volute tool) to lead modification of the worm tool. By modifying the lead of the worm instead of the pressure angle, the same twist control objective is achieved but with a simpler, more manufacturable tool geometry that can be produced using conventional machining methods
Solution Approach 2:
The patent applies local quality by modifying the lead of the worm only in specific regions (from one end toward the other end) rather than changing the entire tool geometry. This localized modification allows twist control while maintaining the overall simplicity and manufacturability of the tool
2Manufacturing precision
If a lead modified worm tool is used in diagonal method, then flank line crowning is created, but an additional unknown portion of offset is created that complicates twist control
Solution Approach 1:
The patent segments the twist into two distinct portions: one from the lead modified tool and another from the change of spacing between axes. By separating and independently controlling these two portions, the complex twist calculation is broken down into manageable components that can be coordinated to achieve the desired total twist
Solution Approach 2:
The patent employs feedback by calculating the twist from the flank line crowning and using this information to adjust the machining parameters (center distance changes, diagonal ratio) to achieve the desired twist value. This iterative adjustment allows precise control despite the additional offset portion
3Adaptability or versatility
If the sign of diagonal ratio D is changed for additional work piece, then flank line crowning and twist are created, but the twist has different amount and opposite sign relative to previous work piece
Solution Approach 1:
The patent applies dynamics by making the center distance between tool and work piece variable during the machining process. By dynamically adjusting the spacing while maintaining the diagonal method, the system can accommodate changes in diagonal ratio sign while keeping the twist consistent across different work pieces
4Manufacturing precision
If center distance is changed during axial carriage shift to generate crowning and twist, then desired values are created, but the method is complex requiring coordination of tool crowning and machine adjustment data
Solution Approach 1:
The patent applies preliminary action by pre-calculating the relationship between center distance changes and the resulting flank line crowning and twist. This allows the complex coordination to be performed in advance through calculation rather than during the actual machining process, simplifying the operational complexity
Data Source
AI summary
By coordinating the amount and course of the crowning of the tool and the diagonal ratio, a twist is created with a simple tool, and superimposed on the natural twist, thus resulting in the twist required for the work piece. Furthermore, an additional portion of the crowning is superimposed on the portion of the crowning of the work piece which is the result of the crowning of the tool during the machining in the diagonal method, thus resulting in the required crowning of the work piece, with the additional portion of the crowning being generated by changing the spacing between tool and work piece during the machining.