Experimental investigation of the machining characteristics in diamond wire sawing of unidirectional CFRP

At a Glance

Metadata	Details
Publication Date	2021-06-09
Journal	The International Journal of Advanced Manufacturing Technology
Authors	Lukas Seeholzer, Stefan Süssmaier, Fabian Kneubühler, Konrad Wegener
Institutions	ETH Zurich
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Wire Sawing of CFRP

This document analyzes the research findings on diamond wire sawing (DWS) of Carbon Fibre Reinforced Polymers (CFRP) and aligns the material requirements with the advanced capabilities offered by 6CCVD (6ccvd.com), an expert supplier of MPCVD diamond materials.

Executive Summary

The experimental investigation confirms that diamond wire sawing (DWS) is a highly effective, high-efficiency method for trimming unidirectional CFRP, offering significant advantages over traditional methods like AWJM, WEDM, and laser cutting.

High Efficiency & Quality: DWS achieved high feed speeds (up to 200 mm/min) while maintaining excellent surface quality, characterized by low roughness ($R_a$ down to 2.4 µm) and minimal Heat Affected Zone (HAZ).
Process Optimization: Key factors influencing process forces and temperature were identified as workpiece thickness, cutting speed ($v_c$), and feed speed ($v_f$). Fibre orientation ($\theta$) significantly affected surface quality and HAZ dimensions.
Material Wear: Wear on the fixed abrasive diamond grains was found to be very small, suggesting long tool life for this application.
Thermal Management: Process temperatures were manageable (Max 64.3 °C), but increased with higher cutting speed and material thickness, highlighting the need for robust thermal management in high-productivity systems.
Fixed Abrasive Requirement: The study relied on high-density, fixed abrasive diamond wires, confirming the necessity of high-quality diamond materials for successful CFRP trimming.
6CCVD Value Proposition: 6CCVD specializes in MPCVD Polycrystalline Diamond (PCD) and Single Crystal Diamond (SCD) materials, ideal for manufacturing next-generation, ultra-wear-resistant DWS tooling, guide rolls, and integrated sensors for advanced process control.

Technical Specifications

The following hard data points were extracted from the experimental plan and results:

Parameter	Value	Unit	Context
Workpiece Material	UD CFRP (MTM44-1/HTS)	N/A	Unidirectional Carbon Fibre Reinforced Polymer
Fibre Volume (by weight)	65	%	CFRP composition
Laminate Density	1.35	g/cm³	CFRP property
Wire Core Diameter	450	µm	Stranded electroplated wire used
Diamond Grain Size	50-100	µm	Fixed abrasive range
Cutting Speed ($v_c$) Range	25, 50	m/s	Varied process parameter
Feed Speed ($v_f$) Range	100, 200	mm/min	Varied process parameter
Workpiece Thickness ($t$)	7, 14, 21	mm	Varied material thickness (stacked plates)
Grain Density (GD)	50, 100	%	Tested wire types
Wire Tension ($F_s$)	25	N	Constant parameter
Lowest Mean Roughness ($R_a$)	2.4	µm	Achieved at $\theta = 90^\circ$ orientation
Max Workpiece Temperature ($T$)	64.3	°C	Highest recorded (Setting 19c, $t=21$ mm)
Min Mean Waviness ($W_a$)	1.5	µm	Achieved at $\theta = 0^\circ$ orientation

Key Methodologies

The experiments were conducted using a self-built single-loop diamond wire saw to analyze the effects of various parameters on CFRP machining.

Experimental Setup: Experiments utilized a 1.95m single wire loop led around five guide rolls, with one roll driven by a spindle and another hinged for wire tension control (fixed at 25 N).
Tooling: Two types of electroplated diamond wires (INSOLL Tools Technology) were used, characterized by a 450 µm core diameter and diamond grain sizes ranging from 50-100 µm, with Grain Densities (GD) of 50% and 100%.
Workpiece Preparation: Unidirectional CFRP sheets (MTM44-1/HTS) were prepared in 7 mm standard thickness. Larger thicknesses (14 mm and 21 mm) were achieved by mechanically stacking and clamping standard plates.
Parameter Variation: A full factorial design tested four fibre orientations ($\theta=0^\circ, 30^\circ, 60^\circ, 90^\circ$), two feed speeds ($v_f=100, 200$ mm/min), and two grain densities (GD=50%, 100%). Cutting speed ($v_c$) and thickness ($t$) were varied independently in subsequent tests.
Process Force Measurement: Feed force ($F_f$) and cutting force ($F_c$) were measured using a strain-gauge based force sensor, averaged over the last 20 s of the cut.
Temperature Measurement: Workpiece surface temperature ($T$) at the wire entrance was measured using an Optris PI 640 infrared camera (measuring range 0-100 °C, emissivity factor 1).
Surface Quality Analysis: Roughness ($R_a, R_z$) and waviness ($W_a, W_z$) were measured using a Taylor Hobson Form Talysurf tactile profilometer according to DIN EN ISO standards, using a cut-off filter ($\lambda_c = 2.5$ mm) and an evaluation length ($l_n = 60$ mm).

6CCVD Solutions & Capabilities

This research validates diamond wire sawing as a high-precision, high-efficiency method for advanced composite trimming. To replicate or extend this research into industrial production or next-generation tooling, engineers require diamond materials with guaranteed purity, dimensional accuracy, and superior wear characteristics—precisely the capabilities 6CCVD provides through its MPCVD technology.

Applicable Materials

Application Requirement	6CCVD Recommended Material	Rationale for Selection
High-Wear Tooling/Dies (Required for high-speed, abrasive CFRP cutting)	Polycrystalline Diamond (PCD)	Superior fracture toughness and isotropic wear resistance. Available in plates up to 125mm and thicknesses up to 500µm, ideal for manufacturing robust wire guides or dies.
Thermal Management/Sensors (Monitoring HAZ and process temperature)	Single Crystal Diamond (SCD)	Highest thermal conductivity (up to 2200 W/mK) for rapid heat dissipation in critical contact zones. Can be used as a substrate for integrated thermal sensors.
Electrochemical/BDD Applications (Potential future DWS process enhancement)	Boron-Doped Diamond (BDD)	Highly conductive material suitable for electrochemical process monitoring or specialized wire coating/plating applications requiring electrical conductivity.

Customization Potential

The study highlights the importance of precise tool geometry and material thickness. 6CCVD offers bespoke manufacturing services critical for DWS R&D and production:

Custom Dimensions: We supply SCD and PCD plates and wafers up to 125mm in diameter, and substrates up to 10mm thick, allowing for the creation of custom-sized wire guides, tensioning rolls, or specialized tooling components.
Ultra-Precision Polishing: While the CFRP surface roughness was in the µm range, the quality of the DWS tooling is paramount. 6CCVD guarantees ultra-smooth surfaces: $R_a < 1$ nm for SCD and $R_a < 5$ nm for inch-size PCD. This minimizes friction and improves the stability of the wire, directly impacting workpiece waviness ($W_a$).
Integrated Metalization: The use of force and temperature sensors is key to process control. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for bonding, electrical contact, or sensor integration directly onto diamond substrates, enabling advanced, real-time monitoring of cutting forces and thermal flux.

Engineering Support

The complexity of optimizing DWS across variables like fibre orientation ($\theta=0^\circ$ to $90^\circ$) and high speeds ($v_c=50$ m/s) requires expert material selection. 6CCVD’s in-house PhD team can assist with material selection and design consultation for similar CFRP Trimming and Advanced Composite Machining projects, ensuring the diamond material meets the extreme demands of high-productivity fixed abrasive processes.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1007/s00170-021-07146-8