Dimensional Tolerance Reallocation for Higher Part Assembly Fit
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Solution Overview
Problem
Conventional assembly methods can only assemble parts that meet specification tolerances, leading to high scrap rates for parts that do not meet these tolerances, thus necessitating a method to improve fit rates.
Innovation Solution
A part processing planning method and system that uses dimensional chain establishing technology to accumulate and re-allocate machining tolerances, ensuring that the size cumulative tolerance meets the specification tolerance, thereby allowing for the assembly of parts that initially do not meet the tolerance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional assembly methods are used to assemble parts that meet specification tolerances, then assembly quality is ensured, but scrap rate increases for parts that do not meet tolerances
Solution Approach 1:
The patent changes the tolerance parameters by establishing dimensional chains and re-allocating tolerances among multiple machining procedures. Instead of using fixed specification tolerances, the system calculates cumulative tolerances through dimensional chain analysis and adjusts individual procedure tolerances to achieve acceptable assembly fit, thereby reducing scrap of parts that would otherwise be rejected
Solution Approach 2:
The patent performs preliminary tolerance analysis and re-allocation before actual assembly. By pre-calculating dimensional chains and determining optimal tolerance distributions across machining procedures, the system prepares parts in advance to ensure they can be assembled successfully, preventing the need to scrap parts that might otherwise fail assembly requirements
2Manufacturing precision
If strict specification tolerances are enforced, then product quality is maintained, but manufacturing efficiency decreases due to high scrap rates
Solution Approach 1:
The system transforms the rigid specification tolerance parameter into a flexible cumulative tolerance parameter through dimensional chain analysis. By allowing individual machining procedure tolerances to vary while maintaining the overall cumulative tolerance within acceptable limits, the system improves manufacturing efficiency without sacrificing product quality
Solution Approach 2:
The patent introduces dynamic tolerance re-allocation where tolerance values are not fixed but are adjusted based on dimensional chain relationships. The system dynamically determines optimal tolerance distributions among machining procedures to maximize part utilization while ensuring assembly quality, thereby improving productivity
3Reliability
If parts are measured and selected to meet specification tolerances, then assembly fit is ensured, but fit rate decreases due to rejection of out-of-tolerance parts
Solution Approach 1:
The patent changes the acceptance criterion from individual part specification tolerance compliance to cumulative tolerance compliance through dimensional chain analysis. Parts that individually exceed specification tolerances can still be assembled if their cumulative tolerance, calculated through dimensional chains, falls within acceptable limits, thereby increasing the fit rate while maintaining assembly reliability
Data Source
AI summary
A part processing planning method includes the following steps. Firstly, a specific tolerance of a nominal size of a part is obtained. Then, a predetermined tolerance of each of processes is obtained. Then, using a process dimension chain establishing technique, at least one predetermined tolerance associated with the specification tolerance from the predetermined tolerances is obtained. Then, at least one predetermined tolerance associated with the specification tolerance is accumulated to obtain a size cumulative tolerance. Then, whether the size cumulative tolerance meets the specification tolerance is determined. Then, at least one predetermined tolerance associated with the specification tolerance is re-allocated when the cumulative tolerance does not meet the specification tolerance, such that the size cumulative tolerance is within the specification tolerance.