Three-Part Axial Powder Compression Mold for Titanium Acetabular Cups
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Solution Overview
Problem
Current methods for molding complex geometries from metal or polymer powder, such as injection molding and isostatic pressing, are costly and often require additives that interfere with achieving fully dense parts and good surface quality, especially for two-dimensional shapes like hemispherical shells.
Innovation Solution
A three-part mold with independently moveable ram elements is used to compact titanium sponge powder, allowing for the formation of hollow hemispherical constructs without binding agents or flow-enhancing additives, enabling better surface quality and cost-effectiveness by varying compression pressures across different mold areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If injection molding is used to mold complex geometries from powder, then complicated shapes can be achieved, but mold and equipment costs increase significantly
Solution Approach 1:
The compression mold is divided into three separate parts: a stationary first part with a part-spherical inner surface, a second moveable part with a part-spherical outer impact surface, and a third moveable part with an annular impact surface. This segmentation allows each part to be independently designed and manufactured at lower cost while collectively achieving the complex hemispherical geometry without requiring expensive injection molding equipment.
2Shape
If injection molding is used to mold powder, then complicated shapes can be achieved, but powder additives are required which interfere with obtaining fully dense parts
Solution Approach 1:
The invention eliminates the need for powder additives (binders and flow enhancers) by using a compression molding process that relies solely on mechanical compression forces. The powder is compacted directly without requiring chemical binders, allowing the part to achieve full density while maintaining the complex hemispherical shape.
3Ease of manufacture
If isostatic pressing is used to mold powder, then tooling and equipment costs are reduced, but surface quality on the bladder-adjacent area deteriorates
Solution Approach 1:
The compression mold provides different compaction characteristics to different areas of the powder bed. The part-spherical impact surface of the second part and the annular impact surface of the third part create localized compression zones that achieve uniform density and high surface quality across the entire hemispherical part, including areas that would otherwise be problematic in isostatic pressing.
4Device complexity
If a single moveable ram is used in compression molding, then the mold structure is simple, but parts of different thicknesses cannot be molded uniformly
Solution Approach 1:
The compression mold is divided into three separate parts: a stationary first part with a part-spherical inner surface, a second moveable part with a part-spherical outer impact surface, and a third moveable part with an annular impact surface. This segmentation allows each part to be independently designed and manufactured at lower cost while collectively achieving the complex hemispherical geometry without requiring expensive injection molding equipment.
5Ease of manufacture
If binding agents are added to powder to enable compression molding, then the powder can be compacted, but the binder takes up space and causes dimensional change during sintering
Solution Approach 1:
The invention eliminates the need for powder additives (binders and flow enhancers) by using a compression molding process that relies solely on mechanical compression forces. The powder is compacted directly without requiring chemical binders, allowing the part to achieve full density while maintaining the complex hemispherical shape.
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
This method achieves fully dense, cost-effective, and high-quality acetabular cup shells with improved surface quality and reduced material costs, suitable for orthopedic implants, by compacting titanium powder to 50% of its original volume using pressures of 30-50 tons per square inch.
Implementation Method 1
The powder is compacted with the second part part-spherical outer impact surface and the third mold part annular impact surface... The powder is compacted to about 50% of its original volume by the mold parts... The second and third mold parts impact the powder to produce a pressure of 30 to 50 tons per square inch.
Data Source
AI summary
A method for manufacturing a titanium acetabular cup shell includes obtaining a titanium powder. A three part mold having a first part with a part-spherical inner surface, a second ram part with a part-spherical outer impact surface and a third ram part with an annular impact surface are provided to compact the titanium powder. The second and third parts are aligned along an axis within the first part. The second part is aligned along a center axis within the annular impact surface of the third part. The first mold part is filled with the titanium powder. The second mold part-spherical outer surface and the third part annular surface are moved towards the part-spherical inner surface of the first part into contact with the powder. The powder is compacted with the second part part-spherical outer impact surface and the third part annular impact surface to about 50% of its initial volume.