Planetary Carrier Opening Machining to Prevent Green Compact Chipping
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Solution Overview
Problem
The challenge is to form openings in a green compact without chipping the sidewall surfaces, as the particles are brittle and prone to chipping due to their mechanical entanglement rather than strong bonding, unlike sintered bodies.
Innovation Solution
A machining method using a first milling tool to form the first sidewall surface from the acute angle to the obtuse angle, leaving a cutting allowance on the second sidewall surface, and then using a second milling tool with reversed cutting edges to form the second sidewall surface from the acute angle to the obtuse angle, minimizing chipping by cutting in a direction that reduces stress on acute angle corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a milling tool cuts through the green compact to form an opening, then the opening is created, but the sidewall surfaces become chipped due to the brittle nature of the green compact particles
Solution Approach 1:
The cutting process is divided into two separate stages: pre-machining that creates the opening with rough sidewalls, and post-machining that precisely forms the final sidewall surfaces. This segmentation allows each stage to be optimized independently, preventing chipping while achieving the required opening
Solution Approach 2:
The pre-machining step performs preliminary cutting to create the opening and leave a cutting allowance, preparing the workpiece for the subsequent precise post-machining operation. This preliminary action removes the bulk material while setting up conditions for accurate final machining
2Ease of operation
If the milling tool cuts from the obtuse angle corner to the acute angle corner, then the cutting path is straightforward, but the acute angle corner becomes chipped due to stress concentration
Solution Approach 1:
The cutting direction is inverted from the conventional approach: instead of cutting from the obtuse angle corner to the acute angle corner, the tool cuts from the acute angle corner to the obtuse angle corner. This reversal prevents stress concentration at the acute corner, eliminating chipping while maintaining operational simplicity
3Device complexity
If a single milling tool is used to machine both sidewall surfaces, then the process is simpler, but the second sidewall surface cannot be properly finished without chipping
Solution Approach 1:
The single milling tool is segmented into two functional versions: the first milling tool with cutting edges oriented for pre-machining, and the second milling tool with cutting edges reversed for post-machining. This segmentation enables each tool to perform its specific function optimally, achieving high precision on both sidewall surfaces
Solution Approach 2:
The cutting edge orientation parameter of the milling tool is changed between the two machining stages. The first milling tool has cutting edges configured for one direction, while the second milling tool has cutting edges reversed to cut from the acute angle corner to the obtuse angle corner, optimizing the cutting action for each sidewall surface
Data Source
AI summary
A machining method for forming an opening through a workpiece, serving as a green compact, by moving a milling tool in a radial direction relative to the workpiece is provided. The milling tool includes a first milling tool and a second milling tool. The method includes a pre-machining step of using the first milling tool, and forming the first sidewall surface by rotating the first milling tool so as to cause cutting edges of the first milling tool to cut the workpiece from the acute angle corner to the obtuse angle corner, while leaving a cutting allowance on the second sidewall surface; and a post-machining step of using the second milling tool whose cutting edges are reversed from the cutting edges of the first milling tool, and forming the second sidewall surface by rotating the second milling tool so as to cause the cutting edges of the second milling tool to cut the cutting allowance from the acute angle corner to the obtuse angle corner.