Roll Embossing of Curved Surfaces for Coating Adhesion
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Solution Overview
Problem
Current methods for machining curved workpiece surfaces, such as those in engine construction, face challenges in efficiently and cost-effectively preparing surfaces for thermal spraying, particularly in ensuring reliable adhesive strength and minimizing material removal while maintaining surface integrity.
Innovation Solution
A machining method employing roll embossing with a processing tool featuring a rolling element with a rough surface structure, which deforms the workpiece surface under controlled contact pressure to create a specific rough embossing structure, enhancing adhesive strength and reducing material removal, allowing for subsequent thermal spraying without significant cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional machining methods (sandblasting, laser structuring, jet roughening) are used to prepare the workpiece surface for thermal spraying, then the surface can be roughened to improve coating adhesion, but additional work steps are required which increase processing time and costs
Solution Approach 1:
The invention combines the surface roughening operation and the thermal spraying operation into a single integrated process. The thermal spray tool itself is used to create the rough surface structure while depositing the coating material, eliminating the need for separate pre-treatment steps and significantly improving processing efficiency
Solution Approach 2:
The rough surface structure is created as a preliminary action during the coating deposition process itself. The thermal spray particles mechanically interlock with the base material while forming the coating, simultaneously achieving both surface preparation and coating application in one operation
2Reliability
If sandblasting is used to roughen the surface, then coating adhesion is improved, but sand particles may remain embedded in the workpiece surface causing harmful effects
Solution Approach 1:
The invention converts the thermal spray particles, which would normally be waste material, into a useful function by using them to mechanically roughen the surface and create anchoring structures for the coating. The same particles that form the coating also serve to prepare the surface, eliminating the need for separate abrasive blasting that leaves harmful residues
Solution Approach 2:
The thermal spray process serves dual functions: it deposits the coating material while simultaneously preparing the surface for optimal adhesion. The process is self-sufficient, using its own spray particles to create the rough surface structure without requiring external abrasive materials that could contaminate the workpiece
3Reliability
If significant material removal is performed to prepare the surface, then the surface can be adequately prepared for coating, but material loss increases and processing costs rise
Solution Approach 1:
The invention changes the approach from material removal to material deposition. Instead of removing material to create surface structure, thermal spray particles are deposited to build up the coating while simultaneously creating mechanical interlocking features. This parameter change from subtractive to additive manufacturing eliminates material loss while achieving adequate surface preparation
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 method effectively enhances the adhesive strength of coatings on workpiece surfaces, reduces material removal and processing costs, and enables efficient surface preparation for thermal spraying, improving the tribological properties of machined surfaces.
Implementation Method 1
The contact pressure is adjusted in such a way that when the rolling element rolls on the curved workpiece surface, a rough roll embossing structure is produced by local deformation of workpiece material
Data Source
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AI summary
The invention relates to a machining method for machining a curved workpiece surface (210) of a workpiece (200), in which a roll forming operation is carried out. At least one roller element (180A, 180B, 180C) of a machining tool (100) is rolled under a contact pressure against a segment (198) of the curved workpiece to be machined. An outer surface of the roller element comprises a rough surface structure in at least one working segment (190A, 190B, 190C) intended for rolling contact with the workpiece surface. The contact pressure is set so that a rough roll-formed structure is generated when rolling by locally deforming the workpiece material without removing material in the area of the workpiece surface being machined. The machining method can be used, for example, for machining the inner surface of a hole in a workpiece, in particular for roughening the workpiece surface for subsequent coating. The invention further relates to a machining tool and to a workpiece thus produced.