Asymmetrical Gear Hobbing Tool to Prevent Undercut and Material Loss
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Solution Overview
Problem
Conventional hobbing machines are unable to effectively cut gearwheels with pronounced asymmetrical teeth, particularly those with a concave secondary flank, due to the production of undercuts and material removal issues when using standard rotating cutting tools.
Innovation Solution
A rotating cutting tool with an asymmetrical configuration, featuring a first convex active flank and a secondary concave flank, where the pitch between the cutting edges is constant for the active side and variable for the secondary side, allowing for the generation of asymmetrical teeth with a helical development that avoids undercutting and material loss during the cutting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional hobbing machine with a standard rotating cutting tool is used to cut gearwheels with pronounced asymmetrical teeth, then the productivity and simplicity of manufacture are improved, but the cutting process produces undercuts and removes material from the tooth profiles
Solution Approach 1:
The cutting tool is designed with an asymmetrical configuration where the first side (CA) has a convex active flank and the second side (CS) has a concave secondary flank. This asymmetry allows the tool to generate the corresponding asymmetrical tooth profiles in the gearwheel without producing undercuts or removing excessive material, while still using a conventional hobbing machine for high productivity cutting.
Solution Approach 2:
Different sections of the cutting tool have different geometric properties: the first side (CA) has a constant pitch suitable for generating the active flank, while the second side (CS) has a variable pitch greater than P1 suitable for generating the secondary flank. This local differentiation of tool geometry enables precise generation of both convex and concave tooth flanks simultaneously.
2Length of moving object
If the cutting tool has a high tool height (more than 4 times the normal module) to generate the full tooth height, then the complete tooth profile can be cut, but the concave secondary flank combined with high tool height causes material to be cut and subsequently removed by different sections of the tool
Solution Approach 1:
The cutting tool employs asymmetrical flank configurations where the concave secondary flank on the second side (CS) is specifically designed to match the required gearwheel tooth geometry. This asymmetrical design, combined with variable pitch, prevents the undercutting problem that would otherwise occur with high tool height conventional tools.
Solution Approach 2:
The pitch parameter is differentiated between the two sides of the cutting tool: the first side (CA) has a constant pitch P1, while the second side (CS) has a variable pitch P2 greater than P1. This parameter change along the axial direction enables each side to independently generate its corresponding tooth flank without interfering with or removing material from the other flank.
3Ease of manufacture
If a conventional symmetrical cutting tool is used, then the tool design and manufacture are simple, but it cannot generate the concave secondary flank of asymmetrical teeth
Solution Approach 1:
The cutting tool is designed with asymmetrical flanks (convex active flank on first side CA, concave secondary flank on second side CS) to generate the required asymmetrical gearwheel teeth. Despite this increased geometric complexity, the tool can still be manufactured using standard production machine tools and techniques, maintaining reasonable ease of manufacture while achieving the required adaptability.
Data Source
AI summary
A rotating cutting tool to cut asymmetrical teeth in a gearwheel in which each tooth (21) has an active flank (A) with a convex profile meshing with the profile of a tooth of an opposing gearwheel meshing with the gearwheel and a secondary concave flank (S), provided with teeth (11) on a generally helical path which extends from one side to the other with respect to a median cross-section (M-M) of the tool which is intended to be intersected by the radius Rp of the gearwheel which is at right angles to the axis of rotation of the tool working on the gearwheel to cut its teeth. The helical teeth have a first flank (CA) which is intended to cut the said active flank (A) of the gearwheel teeth and a second flank (CS) intended to cut the secondary flank (S), the pitch (P1) between the first flank (CA) of the helical teeth being constant and the pitch (P2) of the second flank of the teeth being smaller than the pitch (P1).