Lobed Dolly Profile for Uniform Friction in Extrusion
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Solution Overview
Problem
Existing continuous extrusion processes face challenges in achieving uniform frictional surface drag and minimizing shear forces during the extrusion of metals, leading to inconsistent wall thickness in the final product.
Innovation Solution
The use of a lobed, mushroom-shaped dolly with a central spacing stem and profiled lobes in the extrusion mandrel assembly ensures that the paths from discharge ports to the annular extrusion gap are equal in length, providing uniform frictional surface drag and reducing shear forces, allowing for even merging of flows and uniform wall thickness in the extruded cylindrical tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional extrusion tooling is used with simple exit apertures, then the device complexity is low, but the manufacturing precision of wall thickness is inconsistent
Solution Approach 1:
The extrusion mandrel assembly is segmented into multiple functional components: a body with multiple exit apertures, a lobed dolly with profiled surfaces, and a collar with an annular extrusion gap. Each component performs a specific function in controlling material flow, and the segmentation allows independent optimization of each part to achieve uniform wall thickness while maintaining manageable complexity through modular design.
Solution Approach 2:
The lobed dolly features non-uniform local geometry with profiled surfaces that create equal path lengths from different exit apertures to the annular extrusion gap. This local quality variation in the dolly's surface profile compensates for the inherent non-uniformity of multi-aperture configuration, ensuring uniform frictional drag and consistent material flow distribution across all apertures, thereby achieving uniform wall thickness.
2Stability of the object's composition
If equal path lengths are achieved through profiled lobes, then the frictional surface drag becomes uniform, but the device complexity increases
Solution Approach 1:
The lobed dolly employs asymmetric profiling of its surfaces, with each lobe having a specifically contoured shape that creates equal path lengths from the exit apertures to the annular extrusion gap. This asymmetric geometry is deliberately designed to compensate for the radial distribution of apertures, ensuring that material flowing from any aperture experiences the same frictional drag regardless of its position, thereby achieving uniform flow distribution.
3Productivity
If multiple exit apertures are used to increase productivity, then the extrusion rate increases, but the wall thickness consistency deteriorates
Solution Approach 1:
The lobed dolly creates equipotential flow conditions by ensuring equal path lengths from all exit apertures to the annular extrusion gap. This equipotential design equalizes the flow resistance experienced by material from each aperture, creating a balanced flow distribution that maintains consistent wall thickness even though multiple apertures are operating simultaneously to increase productivity.
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 configuration results in the production of cylindrical tubes with substantially uniform wall thickness by minimizing shear forces and ensuring uniform frictional drag, enhancing the extrusion process efficiency and product consistency.
Implementation Method 1
each of the lobes being profiled such that frictional surface drag on extruding material is substantially uniform around the lobed dolly
Data Source
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AI summary
An extrusion mandrel assembly for continuous extrusion apparatus has a lobed, mushroom shaped, dolly (28) formed with a central spacing stem (30) located in the chamber (16) adjacent a pair of discharge ports (27) connecting respective exit apertures (10) into an internal cavity in the chamber (16) and a pair of shaped lobes (32) having rear faces (34) extending from the central spacing stem (30), outer edge portions (36) and front faces merging inco a collar (38) around a neck (40) co-acting with an annular shoulder (42) on the extrusion die body (20) to form an annular extrusion gap (44), with each of the lobes (32) being profiled such that frictional surface drag on extruding material is substantially uniform around the lobed dolly (28). Individual paths between the discharge ports (27) and the annular extrusion gap (44) are substantially equal in length as measured on the respective surfaces of the rear faces, edge portions and front faces of the profiled lobes (32). An extruded aluminium cylindrical tube of up to 150mm diameter and wall thickness in the range from lmm to 4mm may be formed avoiding discontinuities.