| Metadata | Details |
|---|
| Publication Date | 2025-01-01 |
| Journal | The International Journal of Advanced Manufacturing Technology |
| Authors | Julian Polte, Toni Hocke, Kai ThiĂen, E. Uhlmann |
| Institutions | Technische UniversitÀt Berlin, Fraunhofer Institute for Production Systems and Design Technology |
| Citations | 2 |
| Analysis | Full AI Review Included |
- Novel Sensor Technology: A highly sensitive cutting edge temperature measurement system was developed using ion-implanted boron-doped single crystal diamonds (SCDs).
- High Accuracy and Speed: The system demonstrated a resolution accuracy (ar) between 0.29 °C and 0.39 °C, with a total measurement uncertainty (uM) of 0.098 °C in the process area. Reaction times (tR) were consistently fast, ranging from 420 ms to 440 ms.
- Localized Doping: Ion implantation enabled precise, partial boron doping close to the cutting edge (90 ”m distance, 150 nm depth), ensuring high sensitivity without compromising the SCD toolâs structural integrity or cutting edge geometry.
- Process Correlation: A direct correlation was established between measured cutting temperatures and chip formation mechanisms during ultra-precision turning of PMMA.
- Extreme Conditions Measured: Highest measured temperatures reached 50.18 °C (roughing parameters), correlating with simulated maximum cutting edge temperatures up to 183.12 °C.
- Material Versatility: The system proved suitable for measuring temperatures when machining both electrically conductive (metallic) and non-conductive (plastic) materials.
- Future Automation Basis: The technology provides the foundation for identifying complex temperature-induced wear behavior and developing self-optimizing and self-learning ultra-precision machine tools.
| Parameter | Value | Unit | Context |
|---|
| Sensor Resolution (ar) | 0.29 to 0.39 | °C | Ultra-precision turning process |
| Total Measurement Uncertainty (uM) | 0.098 | °C | Sensor accuracy in process area |
| Reaction Time (tR) | 420 to 440 | ms | Dynamic monitoring range |
| Doping Level (Sensing Area, dlev) | 1E15 | ions/cm2 | Ion-implanted boron doping |
| Doping Level (Contacting Area, dlev) | 2E16 | ions/cm2 | To achieve suitable electrical conductivity |
| Doping Depth (ddep) | 150 | nm | Isolation from environmental conditions |
| Distance to Cutting Edge (dc) | 90 | ”m | Distance of boron doping area |
| Diamond Thermal Conductivity (λ) | 2200 | W/(mK) | Input for FEM simulation |
| Diamond Density (Ï) | 3516 | kg/m3 | Input for FEM simulation |
| Highest Measured Temperature (ΞM,max) | 50.18 | °C | Roughing (vc=350 m/min, ap=35 ”m, f=35 ”m, γ0=-30°) |
| Highest Simulated Temperature (ΞS,max) | 183.12 | °C | Simulated maximum at cutting edge (same roughing parameters) |
| PMMA Glass Transition Temp (Ξg) | ~105 | °C | Critical temperature for chip modification |
- Sensor Fabrication via Ion Implantation: Single crystal diamonds were partially and specifically doped using a 100-keV implanter and a SNICS ion source. Boron ions were accelerated to achieve a precise penetration depth (150 nm) and concentration (1E15 ions/cm2) close to the cutting edge (90 ”m distance).
- Calibration and Characterization: The electrical resistance (Rel) of the boron-doped diamonds was calibrated as a function of temperature (20 °C to 140 °C) using a high-precision temperature-controlled WaferTherm chuck system (SP 74A).
- System Integration: The ion-implanted diamond sensor and micro-electronic components (including an Arduino Due microcontroller and an Analog-Digital converter) were fully embedded in a monolithic ceramic tool holder (Macor) for complete isolation from the machine environment.
- Ultra-Precision Turning Tests: Experiments were conducted on a Nanotech 350 FG machine tool using PMMA workpieces modified with individual web structures to minimize tool wear during testing.
- Data Acquisition and Analysis: A full-factorial 25-1 test plan was executed, varying cutting speed (vc), depth of cut (ap), feed (f), and rake angle (Îł0) to analyze temperature development. Cutting forces (Fc) were measured using a dynamometer.
- Simulation and Validation: A 3D-Finite Element Method (FEM) thermal-transient analysis (using Ansys Mechanical) was developed and validated against measured temperatures to determine maximum cutting temperatures (Ξc,max) at the actual cutting edge (dc = 0 ”m).
- Chip Analysis: Chip formation mechanisms were analyzed using a Scanning Electron Microscope (SEM) to correlate structural changes (e.g., lamellar structures, melting effects, contraction) with measured and simulated cutting temperatures.
- Optical and Photonics Industry: Manufacturing high-performance and precision optics, including toric and multifocal lenses, fast steering mirrors, and space telescope components.
- Smart Manufacturing and Adaptive Control: Provides real-time, highly sensitive temperature monitoring necessary for self-optimizing and self-learning ultra-precision machine tools.
- Tool Wear Management: Enables fundamental research into complex temperature-induced wear behavior of single crystal diamonds, leading to increased tool life and economic efficiency.
- Material Processing Versatility: The sensor technology is validated for use with both electrically conductive (e.g., brass, aluminum, copper) and non-conductive (e.g., PMMA, PC, PSU) materials, expanding the scope of ultra-precision machining applications.
- Aerospace and Automotive: Production of components requiring high dimensional accuracies and low surface roughness values in these critical sectors.
View Original Abstract
Abstract Ultra-precision machining represents a key technology for manufacturing optical components in medical, aerospace and automotive industry. Dedicated single crystal diamond tools enable the production of innovative optical surfaces and components with high dimensional accuracies and low surface roughness values in a wide range of airborne sensing and imaging applications concerning space telescopes, fast steering mirrors, laser communication and high-energy laser systems. Despite the high mechanical hardness of single crystal diamonds, temperature-induced wear of the diamond tools occurs during the process. In order to increase the economic efficiency of ultra-precision turning, the characterisation and interpretation of cutting temperatures are of utmost importance. According to the state-of-the-art, there are no precise methods for online temperature monitoring during the process at the cutting edge with regard to the requirements for resolution accuracy, response time and accessibility to the cutting edge. For this purpose, a dedicated cutting edge temperature measurement system based on ion-implanted boron-doped single crystal diamonds as a highly sensitive temperature sensor for ultra-precision turning was developed. To enable highly sensitive temperature measurements, ion implantation was used for partial and specific boron doping close to the cutting edge of single crystal diamond tools. Within the investigations, a resolution accuracy of 0.29 °C †a R †0.39 °C could be proven for the developed cutting edge temperature measurement system. In addition, a total measurement uncertainty of u M = 0.098 °C was determined for the sensor accuracy a S in the investigated process area. For a rake angle range of 0° †γ 0 †â30°, reaction times of 420 ms †t R †440 ms were further determined. Using the developed cutting edge temperature measurement system enables a holistic view of the temperature development during ultra-precision machining, whereby a correlation between the measured cutting temperatures and the chip formation mechanisms depending on the applied process parameters could be identified. Within the investigations, the highest measured temperatures of Ï M = 50.18 °C and simulated maximum temperatures of Ï S,max = 183.12 °C were determined at a cutting speed of v c = 350 m/min, a cutting depth of a p = 35 ”m as well as a feed of f = 35 ”m using a rake angle of Îł 0 = â30°. The most uniform chips with the smoothest surfaces were identified within the chip analysis using a cutting speed of v c = 50 m/min, a cutting depth of a p = 5 ”m and a feed of f = 35 ”m with a measured temperature of Ï M = 21.30 °C and a simulated temperature of Ï S = 38.47 °C in the examined finishing area. According to the results, it was also shown that the cutting edge temperature measurement system with ion-implanted diamonds can be used for both electrically conductive and non-conductive materials. This provides the fundamentals for further research works to identify the complex temperature-induced wear behaviour of single crystal diamonds in ultra-precision turning and serves as the basis for self-optimising and self-learning ultra-precision machine tools.