Threading Cutting Insert Geometry for Rigidity and Accurate Positioning
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Solution Overview
Problem
Existing cutting inserts with negative rake lands face issues of increased cutting forces and unwanted movement during threading operations, leading to reduced tool life and accuracy.
Innovation Solution
A cutting insert with a negative rake land and a dovetail abutment mechanism that securely holds it within a tool holder, preventing shifting and maintaining accurate positioning, using a hard, wear-resistant material like tungsten carbide, and featuring a clamping mechanism to ensure rigidity and stability during threading operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a negative rake land is used in the cutting insert, then tool strength and resistance to plastic deformation are improved, but cutting forces and pressure increase causing unwanted movement of the insert
Solution Approach 1:
The cutting insert is divided into distinct functional zones: a negative rake land portion for strength and a positive rake angle portion for reduced cutting forces. This segmentation allows each zone to perform its optimized function independently, resolving the contradiction between strength and cutting forces.
Solution Approach 2:
Different portions of the cutting insert have different rake angles tailored to their specific functions. The negative rake land is located at the cutting tip where strength is critical, while the positive rake angle portion is positioned where chip removal and reduced cutting forces are priorities. This local differentiation resolves the contradiction by applying the appropriate geometry where needed.
2Strength
If a negative rake land is used in the cutting insert, then tool strength is improved, but positioning accuracy deteriorates due to insert shifting or rotation
Solution Approach 1:
The cutting insert combines a negative rake land portion for strength with a positive rake angle portion for stability. The positive rake angle portion acts as a stabilizing element that prevents unwanted movement and rotation, thereby maintaining positioning accuracy while the negative rake land provides the necessary strength.
Solution Approach 2:
The cutting insert features an asymmetric geometry with the negative rake land positioned specifically at the cutting tip area while the positive rake angle portion extends in a different orientation. This asymmetric arrangement allows the negative rake land to provide strength without causing rotational instability, as the positive rake angle portion counterbalances the asymmetry.
3Ease of operation
If an acute-angled positive rake land is used, then chip removal is improved, but heat concentration increases and tool life decreases
Solution Approach 1:
The cutting insert separates the chip removal function from the heat resistance function by using a negative rake land portion for heat resistance and a positive rake angle portion for chip removal. This segmentation allows acute-angled geometry to be used for chip removal without the detrimental heat concentration effects, as the negative rake land portion is positioned to handle thermal loads.
Data Source
AI summary
Disclosed is a cutting insert having a generally polygonal primary body having a primary body base connected to an opposing and similarly-shaped body face through a plurality of primary flank portions extending there between. The cutting insert further includes at least one cutting protrusion extending away from at least one of the primary flank portions, and merging therewith. The cutting protrusion includes a rake face coplanar and extending away from the adjacent primary flank portions, and an edge portion extended towards a cutting flank portion. The cutting protrusion further includes a tip flat extending between a rake front from a protrusion tip towards a rake root portion, adjacent one of the primary flank portions.