End Mill Contour Matching for Spiral Mold Machining
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Solution Overview
Problem
Current methods for machining molds with end mills are limited by the minimum radius of curvature of the mold, restricting machining efficiency while maintaining surface roughness at a predetermined value, especially for axially symmetric lens surfaces with varying curvature.
Innovation Solution
The method involves determining a spiral tool path for the end mill such that each point on the mold's contour is machined by a portion of the blade with a similar shape, allowing for increased radial interval and improved machining efficiency without compromising surface roughness, by varying the radius of curvature of the blade's contour to match the mold's curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a ball end mill is used for spiral tool path machining, then surface roughness can be maintained at or below a predetermined value, but machining efficiency is restricted by the minimum radius of curvature of the mold
Solution Approach 1:
The end mill blade is designed with a contour that has different radius of curvature at different locations along its length. Specifically, the radius of curvature of the blade contour is made larger than the minimum radius of curvature of the mold cross-section, allowing different portions of the blade to match different curvature requirements of the mold surface. This enables the use of a larger pitch while maintaining surface roughness requirements, thereby improving machining efficiency.
2Productivity
If the pitch of the spiral tool path is increased to improve machining efficiency, then productivity increases, but surface roughness exceeds the predetermined value
Solution Approach 1:
The invention changes the geometric parameters of the cutting tool (end mill blade) to match the workpiece geometry. By designing the blade contour with a radius of curvature that corresponds to the mold's minimum radius of curvature, the tool can maintain contact with the workpiece surface at optimal points throughout the machining process. This allows for a larger pitch while keeping surface roughness within acceptable limits, thus resolving the contradiction between productivity and manufacturing precision.
3Productivity
If the radius of curvature of the blade contour is increased to match the mold's minimum radius of curvature, then machining efficiency improves, but the tool design becomes more complex
Solution Approach 1:
The end mill blade is designed with a curved contour that has a radius of curvature matching the minimum radius of curvature of the mold cross-section. This curvature design allows the blade to maintain proper contact with the mold surface during spiral machining, enabling larger pitch values and improved machining efficiency. The curved geometry is achieved through standard tool manufacturing techniques, making the design practical despite the increased complexity compared to a straight-blade tool.
Data Source
AI summary
A mold machining method using an endmill, the contour of a cross section of the mold being concave and continuous in an area, a ratio of the maximum to the minimum of radius of curvature of the contour of a portion of the area (a first area) being 2 or greater, and a blade of the endmill having a second area where the contour of a cross section is similar to the contour of the first area, the method comprising the steps of determining a spiral path of the endmill such that each point of the first area is machined by a portion of the second area, corresponding to said each point in the similarity, and a radial interval between the spiral tool path is maximized while keeping surface roughness of the machined mold at or below a predetermined value; and machining the mold along the path.