Rotary Cutting Insert Geometry for Long-Reach Finish Machining
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Solution Overview
Problem
Conventional indexable rotary cutting tools face challenges in achieving accurate finish machining on side surfaces and bottom surfaces of workpieces, particularly when the tool protrusion length is long (L/D ratio of 4 or more), due to tilting issues and reduced cutting conditions required to prevent chattering and chipping.
Innovation Solution
An indexable rotary cutting tool with a specific cutting edge configuration, including a peripheral cutting edge, bottom cutting edge, and corner R cutting edge, featuring a negative axial rake angle, positive twist angle, and a radial rake angle that minimizes cutting resistance and enhances edge strength, allowing for point-contact biting and improved chip discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a long tool protrusion length (L/D ≥ 4) is used for finish machining, then the tool can reach deep cavities and complex geometries, but machining accuracy deteriorates due to tool tilting
Solution Approach 1:
The invention changes the geometric parameters of the cutting edge, specifically setting the axial rake angle to negative values (first axial rake angle: -5° to -15°, second axial rake angle: -10° to -20°) and the twist angle to positive values (5° to 15°). These parameter changes optimize the cutting edge strength and chip evacuation, allowing accurate finish machining even with long tool protrusion lengths where tool tilting occurs
2Reliability
If cutting conditions are decreased to prevent chattering and chipping, then cutting edge durability is improved, but productivity decreases
Solution Approach 1:
The invention optimizes the cutting edge geometry parameters including axial rake angles, twist angles, and the relationship between first and second axial rake angles. This geometric optimization allows the cutting edge to maintain durability while enabling higher cutting conditions (cutting speed, feed rate, depth of cut) to be used, thereby improving productivity without sacrificing reliability
3Manufacturing precision
If a solid type end mill is used for finish machining, then machining accuracy is maintained, but tool cost increases significantly for tools with outer diameter φ10mm or more
Solution Approach 1:
The invention segments the end mill into two parts: a reusable tool body and replaceable inserts. The insert contains the cutting edge portion that can be detached and replaced when worn. This segmentation allows the expensive solid type machining accuracy to be achieved while reducing overall tool cost, as only the insert needs replacement rather than the entire solid end mill
Solution Approach 2:
The invention implements a system where the insert with the cutting edge is discarded (removed from the tool body) and recovered (repositioned in another groove or replaced with a fresh insert). This allows continuous operation without discarding the entire tool, significantly reducing tool cost for finish machining applications
4Quantity of substance
If an indexable radius end mill is used with long tool protrusion, then tool cost is reduced, but chattering vibration occurs requiring decreased cutting conditions
Solution Approach 1:
The invention changes the cutting edge geometry parameters to suppress chattering vibration. Specifically, the negative axial rake angles and positive twist angles create a cutting edge that is more resistant to vibration, while the relationship between the first and second axial rake angles optimizes chip flow and reduces vibration-induced chattering, allowing higher cutting conditions to be used
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In an indexable rotary cutting tool (6) of the present invention, a cutting edge portion (4) of an insert (5) includes a peripheral cutting edge (9), a bottom cutting edge (11), a cutting edge (13) of a corner R, and a chamfered surface (15), a radial rake angle (δ) of the cutting edge (13) of the corner R has a negative value in an entire edge length region of the cutting edge (13) of the corner R, and the radial rake angle (δ) becomes a minimum value at an intermediate portion located between a pair of boundary points (P, Q) in the cutting edge (13) of the corner R.