3D-Printed Bone Screw Structure for Fatigue Strength
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Solution Overview
Problem
Existing 3D printing processes for bone screws result in surface roughness and micro-notches that negatively impact fatigue strength, and the process is inefficient for large-scale production due to the need for manual removal of cantilever elements.
Innovation Solution
An additive manufacturing process using laser or electron beam melting with defined geometric features and post-processing steps, including heat treatments and abrasive processes, to produce screw elements with improved fatigue strength and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 3D printing is used to manufacture bone screws, then manufacturing flexibility and cost efficiency are improved, but surface roughness and micro-notches are generated that reduce fatigue strength
Solution Approach 1:
The patent applies preliminary action by performing stress relief heat treatment immediately after 3D printing while the component is still in the build plate, preventing micro-notch formation during cooling. This preliminary intervention eliminates the harmful surface roughness before the component is removed and subjected to further processing or use.
Solution Approach 2:
The patent utilizes parameter changes by controlling the cooling rate and temperature gradients during the 3D printing process through adjusted laser parameters, build plate temperature, and layer thickness. These parameter modifications minimize thermal stress and prevent micro-notch formation, thereby maintaining fatigue strength while preserving manufacturing flexibility.
2Productivity
If screw elements are manufactured upright in 3D printing, then production efficiency is improved, but manufacturing precision and surface finish are compromised
Solution Approach 1:
The patent applies dimensionality change by rotating the build plate orientation during the 3D printing process. Critical surfaces that require high precision are printed in optimal orientations (horizontal or inclined) rather than upright, while maintaining overall production efficiency through automated build plate rotation and multi-level build strategies.
Solution Approach 2:
The patent implements local quality by applying different printing orientations and support structures to different regions of the screw element. Critical surfaces such as the thread flanks and bearing surfaces are printed with high precision orientations, while non-critical areas can be printed upright for efficiency. This localized approach maintains both precision and productivity.
3Manufacturing precision
If inclined placement is used in 3D printing, then surface finish quality is improved, but production cost efficiency decreases due to reduced build space utilization and manual support removal
Solution Approach 1:
The patent applies universality by designing self-supporting geometric features that serve multiple functions: they provide structural support during inclined printing, enable automated support removal, and maintain surface finish quality. This eliminates the need for manual support removal and allows inclined printing to be used for all components, improving both quality and cost efficiency.
Solution Approach 2:
The patent implements self-service through self-supporting geometries that automatically remove themselves during or after printing without manual intervention. The design includes features that break away cleanly or are easily detached by automated systems, eliminating the labor-intensive manual support removal that reduces productivity and increases costs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process enables cost-effective, high-quality production of bone screws with enhanced fatigue strength and reduced micro-notches, suitable for clinical use under high bending loads.
Implementation Method 1
additive building of the screw element (1) by means of a 3D printing process, which joins the raw material particles together in three dimensions
Implementation Method 2
additive manufacturing process using laser or electron beam melting
Implementation Method 3
a stress relief heat treatment is conducted on the screw element (1) at a temperature of at least 500° C., but not greater than 840° C., with a hold time of at least one hour, but less than 6 hours
Implementation Method 4
different heat treatments are proposed to counteract this material behavior
Implementation Method 5
incompletely joined raw material particles are removed by means of an abrasive process
Data Source
AI summary
A screw element and a process for manufacturing of the screw element for the fixation of bone components and bone fragments are disclosed including a shaft with a bone thread, and a longitudinal central axis extending along the shaft defining a distal direction and a proximal direction. The screw element further includes a head, and a neck area, and a tool attachment point is provided in the head. At least three cantilever elements are attached to the proximal end of the head and said cantilever elements extend in proximal direction beyond the proximal end of the head and are positioned mainly along the longitudinal central axis.