Asymmetric Indexable Insert for Shoulder Milling
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Solution Overview
Problem
Existing indexable inserts with a rhombic shape face difficulties in achieving sufficient clearance and rake angles when used in shoulder milling cutters, leading to limited feed and weakened cutting edges due to their rectangular shape and symmetrical design, which complicates the production of suitable contact surfaces and support for the inserts.
Innovation Solution
An indexable insert with a non-rectangular parallelogram shape, featuring two diagonally opposite corners at a greater distance from an intermediate plane, with triangular surfaces forming the top and bottom, creating longer and shorter cutting edges, allowing for a wedge angle of less than 90° and enabling a positive clearance angle for secondary cutting edges, and providing stable main cutting edges that are parallel to the milling cutter axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rhombic indexable insert with symmetrical design is used, then the insert can be manufactured with standard geometries, but the clearance angle and rake angle are insufficient leading to weakened cutting edges
Solution Approach 1:
The patent applies asymmetry by designing the indexable insert with a non-rectangular parallelogram shape where diagonally opposite corners are at different distances from the intermediate plane. This asymmetric geometry enables sufficient clearance angles and positive rake angles for the cutting edges, resolving the contradiction between manufacturability and cutting edge strength by creating a geometry that is both manufacturable and mechanically effective for cutting operations
2Ease of manufacture
If a rectangular indexable insert is used, then the contact surfaces are easy to produce, but the feed is limited and the cutting edges are weakened
Solution Approach 1:
The non-rectangular parallelogram shape with asymmetric corner positioning creates longer cutting edges that enable higher feed rates while maintaining ease of manufacture. The asymmetric geometry allows the cutting edges to engage the workpiece more effectively, increasing material removal rate without complicating the manufacturing of contact surfaces
3Manufacturing precision
If the corners are raised diagonally to create clearance, then the clearance angle is improved, but the upper and lower sides become helically twisted making support difficult
Solution Approach 1:
Instead of raising corners diagonally which creates helical twisting, the patent uses asymmetric positioning of corners at different distances from the intermediate plane. This approach achieves the necessary clearance angles while keeping the upper and lower sides planar and parallel, maintaining simple and effective support surfaces that are easy to manufacture and provide stable insert support
4Ease of operation
If a positive rake angle is maintained, then the cutting action is improved, but the cutting edges become weakened
Solution Approach 1:
The asymmetric parallelogram geometry allows different corners to be positioned at different distances from the intermediate plane, enabling the creation of cutting edges with positive rake angles that maintain sharp cutting action. The asymmetric design distributes the geometric constraints differently across the insert, allowing optimal rake angles without compromising cutting edge strength through proper corner positioning and support surface design
Data Source
Figure 1
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Figure 6~6c
AI summary
The present invention relates to an indexable insert (10) comprising an upper side (1) and an underside (1'), which are connected by a peripheral lateral surface consisting of a plurality of sub-surfaces, (2a, 2b, 2c, 2d), wherein at least a part of the section lines between the sub-surfaces (2a, 2b, 2c, 2d) and the upper side and the underside form equivalent cutting edges (3a, 3b, 3c, 3d). The indexable insert has, in a plan view onto the upper side and the underside (1, 1'), the shape in each case of a non-rectangular parallelogram with a nearly rhombic basic shape and has an imaginary intermediate plane (Z) which is spanned by four corners of an imaginary rhombus, the sides (z1, z2, z3, z4) of which run at a distance away from the upper side and the underside along the peripheral lateral surface in a plane such that each of the equivalent cutting edges (3a, 3c; 3b', 3d') of the upper side and the underside has the same variation of distance and angle from the intermediate plane (Z). According to the invention, in order to create an indexable insert which provides four equivalent, stable main cutting edges, effects a sufficient clearance angle for the front-side secondary cutting edge and has a rake angle of less than 90° at the main cutting edge, two diagonally opposing corners (4a, 4c) of the upper side and two diagonally opposing corners (4a', 4c') of the underside each have a greater distance (D) from the intermediate plane (Z) than do the respective diagonally opposing corners (4b, 4d; 4b', 4d') of the upper side and the underside lying therebetween, and the diagonally opposing corners (4a, 4b, 4c, 4d) of the upper side and the diagonally opposing corners (4a', 4b', 4c', 4d') of the underside are shifted parallel to the intermediate plane Z and, as viewed in a plan view onto the intermediate plane Z, in mutually opposite directions away from the associated diagonals (d1, d2) of the rhombus spanning the intermediate plane.