Hybrid Laser-Mechanical Machining of OX-OX CMC
Project challenges
Ceramic matrix composites (CMCs) are a revolutionary material suitable for a vast range of applications. They are often used in the aerospace sector due to their excellent properties. Current standalone machining methods have weaknesses when processing these advanced materials. For example, mechanical machining results in high tool wear and has low process speeds, whilst laser processing results in large thermal damage and delamination.
Business challenge
Process Innovation
Sector
Aerospace
Technology or capability
Laser Processing
The MTC investigated a hybrid laser-mechanical machining technique for Ox-Ox ceramic matrix composite. The hybrid machining approach demonstrated the possibility of overcoming challenges associated with the standalone machining processes.
The Challenge
Ceramic matrix composites (CMCs) are a revolutionary material suitable for a vast range of applications. They are often used in the aerospace sector due to their excellent properties. This includes being very light-weight, capable of withstanding high temperatures with no impact on performance, and high resistance to corrosion and other harsh environments.
Standalone machining methods have weaknesses when processing advanced materials such as CMCs.
- Laser processing (cutting, drilling, machining) results in large thermal damage and delamination.
- Mechanical machining results in high tool wear and has low process speeds.
MTC's Solution
- A two-stage hybrid machining approach which utilised a high-speed laser followed by mechanical milling has potential to reduce or even eliminate these weaknesses, creating an improved solution for processing advanced materials.
- The MTC conducted trials using a 6 mm thick Ox-Ox CMC to evaluate the concept of hybrid laser-mechanical machining and demonstrate its performance for processing advanced materials.
- A comparison between using standalone laser, standalone milling, and hybrid laser-mechanical processes to machine the CMC was performed. Key performance indicators were cutting speed, surface roughness, and tool wear.
The MTC managed this project with its usual professionalism and technical expertise. The outcomes were very interesting and showed that there are benefits to be gained by combining laser and mechanical machining of CMCs. Quality and speed of machining were both improved, along with reduced tool wear.
Stuart Lee, AR&T Manager, Parker Meggitt
The Outcome
- Laser processing offers the highest processing speeds but results in high dross formation and surface roughness.
- Mechanical machining suffers from very high tool wear, with quality degrading as the process continues. However, surface roughness is low.
- Hybrid machining significantly improved standalone mechanical machining process speeds and tool wear, whilst maintaining a similar surface quality.
- Peak machining forces were reduced by 81% through Hybrid machining compared to milling, resulting in a 192% increase in tool life.
Benefits to the Client
- Demonstrated a technique for machining CMCs that overcomes the challenges associated with the standalone machining processes.
- Achieved a surface quality comparable to that of mechanical machining at a process speed 2.5 times faster
This work provides a useful bridge between initial demonstration and the process optimisation that is needed before real industrial application.
Dr Katy Voisey, Associate Professor, University of Nottingham
