3D Printed Threaded Fastener Geometry for Support-Free Threads
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Solution Overview
Problem
Standard threaded fasteners with thread angles of 60 or 55 degrees are difficult to additively manufacture without support members due to overhang angles exceeding 45 degrees, requiring special shapes and extensive data creation for different diameters, leading to ambiguity in thread engagement and increased labor.
Innovation Solution
A method involving data generation steps: enlarging, duplicating, and aligning threaded portion data to create a double-start thread with overhang angles less than 50 degrees, allowing smooth manufacturing without support members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If standard threaded fastener data is used with thread angles of 60 or 55 degrees, then the thread strength and standard compliance are improved, but the overhang angle exceeds 45 degrees making smooth additive manufacturing without support members difficult
Solution Approach 1:
The threaded portion is segmented into multiple individual threads along the axial direction. By controlling the pitch and depth of each thread segment, the overhang angle of each ridge is reduced to 45 degrees or smaller, enabling smooth additive manufacturing without support members while maintaining overall thread functionality
Solution Approach 2:
The thread geometry parameters are modified by controlling the pitch (distance between adjacent threads) and depth (height of ridges). This parameter optimization ensures that the overhang angle of each thread ridge remains at 45 degrees or smaller, allowing direct additive manufacturing without support structures while preserving thread engagement capability
2Ease of manufacture
If special-shaped external thread portions are created for additive manufacturing, then the overhang angle is reduced to enable smooth manufacturing, but the shape becomes entirely different from standard threaded fasteners requiring extensive data creation for different diameters
Solution Approach 1:
A universal data generation method is established that can produce threaded portion data for various nominal diameters using the same fundamental approach. The method universally applies pitch and depth control principles across different sizes, enabling standardized data creation processes for multiple fastener specifications without requiring entirely new designs for each diameter
Solution Approach 2:
Instead of creating entirely new geometric shapes for each diameter, the invention adjusts specific parameters (pitch, depth, and ridge angle) of a standardized thread design. This parameter-based adaptation allows efficient generation of size-varied threaded portions while maintaining the optimized overhang angle characteristic that enables support-free additive manufacturing
3Ease of manufacture
If special-shaped external thread portions with different nominal diameters are developed, then the overhang angle is optimized for manufacturing, but the direction of engagement between external and internal threads becomes unambiguous causing troubleshooting issues
Solution Approach 1:
The thread ridges are designed with asymmetric flank angles where the leading flank (in the screw-in direction) has a smaller angle and the following flank has a larger angle. This asymmetric geometry creates a self-guiding effect that ensures proper alignment and unambiguous engagement direction between external and internal threads, preventing incorrect assembly while maintaining the optimized overhang angle for additive manufacturing
Data Source
AI summary
A three-dimensional data generation method of a threaded fastener for three-dimensional additive manufacturing includes: a step of generating first threaded portion data by enlarging three-dimensional data of a threaded portion of a standard threaded fastener along the axial direction of the threaded portion by a factor of 1.0 to 2.5; a step of generating second threaded portion data by duplicating the first threaded portion data; a step of generating third threaded portion data by disposing the first threaded portion data and the second threaded portion data on the same axis such that one ridge in the second threaded portion data is located between two ridges in the first threaded portion data; and a step of generating fourth threaded portion data by extracting a portion with a length from a part in which the first threaded portion data and the second threaded portion data overlap in the third threaded portion data.