Experimental investigation of the machining characteristics in diamond wire sawing of unidirectional CFRP
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-06-09 |
| Journal | The International Journal of Advanced Manufacturing Technology |
| Authors | Lukas Seeholzer, Stefan SĂŒssmaier, Fabian KneubĂŒhler, Konrad Wegener |
| Institutions | ETH Zurich |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis experimental study investigates the characteristics of diamond wire sawing (DWS) applied to unidirectional Carbon Fiber Reinforced Polymers (UD CFRP), validating DWS as a high-quality, high-productivity trimming alternative.
- Process Suitability: DWS is confirmed as a suitable method for trimming UD CFRP, achieving high surface quality (low roughness and waviness) and minimal heat-affected zones (HAZ), addressing major drawbacks of laser cutting and WEDM.
- Dominant Factors: Process forces ($F_f$, $F_c$) and workpiece temperature ($T$) are primarily influenced by feed speed ($v_f$), cutting speed ($v_c$), and material thickness ($t$). Increasing $v_f$ (100 to 200 mm/min) significantly increases both forces and temperature.
- Grain Density Effect: The difference between 50% and 100% diamond grain density was found to be negligible regarding process forces, temperature, roughness, and waviness, suggesting that the higher density wires used do not increase the number of kinematically active cutting edges.
- Fibre Orientation Impact: Fibre orientation ($\theta$) critically affects surface quality and temperature. The lowest roughness ($R_a$ 2.4-3.4 ”m) and waviness are achieved at $\theta = 90°$ (cutting along the fibre axis). HAZ dimensions are largest at $\theta = 0°$ and decrease as $\theta$ approaches 90°.
- Productivity vs. Quality: Increasing the cutting speed from 25 m/s to 50 m/s leads to an overall reduction in process forces and potentially lower surface roughness and waviness, despite causing higher surface temperatures.
- Thickness Scaling: Both feed force and cutting force increase in a nearly linear trend with increasing material thickness (7 mm to 21 mm).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| CFRP Material Type | MTM44-1/HTS(12K)-134-35%RW | N/A | Unidirectional (UD) Laminate |
| Fibre Volume (by weight) | 65 | % | Material Composition |
| Laminate Density | 1.35 | g/cm3 | Material Property |
| Tensile Strength | 2159 | MPa | Along Fibre Axis |
| Wire Core Diameter | 450 | ”m | INSOLL Diamond Wire (Stranded) |
| Diamond Grain Size Range | 50-100 | ”m | Fixed Abrasives |
| Wire Tension (Constant) | 25 | N | Process Parameter |
| Cutting Speed (vc) Range | 25, 50 | m/s | Tested Process Parameter |
| Feed Speed (vf) Range | 100, 200 | mm/min | Tested Process Parameter |
| Material Thickness (t) Range | 7, 14, 21 | mm | Tested Workpiece Dimensions |
| Fibre Orientation ($\theta$) Tested | 0, 30, 60, 90 | ° | Experimental Variable |
| Lowest Mean Roughness (Ra) | 2.4 | ”m | Achieved at $\theta = 90°$ |
| Temperature Measurement Range | -20 to 900 | °C | Optris PI 640 IR Camera |
| Force Measurement Sample Rate | 20 | Hz | Data Acquisition Rate |
Key Methodologies
Section titled âKey Methodologiesâ- Experimental Setup: Experiments were conducted on a self-built diamond wire saw utilizing a single wire loop (1.95 m length) with constant wire tension (25 N).
- Tooling: Two types of electroplated diamond wires (INSOLL Tools Technology) were used: EL-MS-045D-50 (50% grain density) and EL-MS045D-100 (100% grain density).
- Workpiece Preparation: UD CFRP plates (7 mm standard thickness) were tested, with stacked plates used to achieve 14 mm and 21 mm thicknesses. The feed path length was constant at 130 mm.
- Process Force Measurement: Feed force ($F_f$) and cutting force ($F_c$) were measured using a strain-gauge based force sensor (ME K3D40-20N). Mean force values were derived by averaging the signals over the last 20 s of the cut (steady-state period).
- Workpiece Temperature Measurement: An infrared camera (Optris PI 640) measured the maximum surface temperature ($T$) at the wire entrance side. The emissivity factor was set to 1.0. Temperature analysis excluded the initial run-in period, averaging the signal over the last 20 s of the cut.
- Surface Quality Analysis: Roughness ($R_a$, $R_z$) and waviness ($W_a$, $W_z$) were measured using a Taylor Hobson Form Talysurf tactile profilometer.
- Filtering and Evaluation: A roughness cut-off filter ($\lambda_c$) of 2.5 mm and a form cut-off filter ($\lambda_f$) of 20 mm were applied. A total evaluation length ($l_n$) of 60 mm was used to ensure robust averaging and comparability across specimens.
- Experimental Design: A full factorial design tested four fibre orientations, two grain densities, and two feed speeds. Additional tests varied cutting speed (25 m/s vs 50 m/s) and material thickness (7 mm, 14 mm, 21 mm).
Commercial Applications
Section titled âCommercial ApplicationsâThe findings support the adoption of diamond wire sawing in sectors requiring high-precision trimming of composite materials with minimal material damage.
- Aerospace Manufacturing: Trimming near net shape CFRP components for aircraft and rotorcraft (as mentioned in the introduction), where high quality standards, low kerf loss, and absence of thermal damage (HAZ) are critical for structural integrity.
- Automotive and Motorsport: Precision slicing and finishing of high-performance CFRP parts used in lightweight construction, demanding high form accuracy and surface finish.
- Precision Composite Slicing: Applications requiring the separation of thick composite materials (up to 21 mm tested) with high productivity, where traditional methods like AWJM may result in non-uniform cuts or excessive kerf loss.
- Manufacturing of Sensitive Composites: Machining operations where thermal degradation of the matrix material must be avoided, making DWS a superior alternative to laser cutting or wire electric discharge machining (WEDM).