G10 Board Properties and CNC Machining Guide

G10 epoxy glass fiber laminate sheets (standardized under NEMA LI-1 Grade G10 and equivalent to IEC 60893 EP GC 201) are high-strength composite materials constructed from continuous woven fiberglass cloth impregnated with a non-brominated epoxy resin binder. Cured under elevated temperature and hydraulic pressure, G10 delivers exceptional mechanical shear strength, extremely low moisture absorption (< 0.10%), and excellent dielectric strength across cryogenic to 130°C thermal environments.

This technical guide from RDS Composite provides a concise engineering reference for Grade G10, including standard sheet dimensions, manufacturing thickness tolerances, CNC machining protocols, precision machined components, and material performance boundaries.

1. Standard Dimensions & Sheet Thickness Tolerances

RDS manufactures G10 epoxy laminates in standard raw panel sizes of 1020 x 1220 mm (40" x 48") and 1220 x 2440 mm (48" x 96") across a full thickness range from 0.5 mm to 100.0 mm.

2. Technical Datasheet (TDS): Mechanical & Electrical Properties

The table below summarizes key standardized test performance criteria for NEMA Grade G10 laminates:

3. CNC Machining Guide for G10 Components

Due to the high abrasiveness of glass fibers bonded in cured epoxy, machining G10 requires specific tooling and cutting parameter adjustments to maintain tool life and tight dimensional tolerances (±0.05 mm):

Tooling Selection

• Cutting Tools: Standard HSS (High-Speed Steel) tools wear out almost immediately. High-grain Solid Carbide tools or PCD (Polycrystalline Diamond) router bits are strongly recommended.
• Flute Geometry: Use 2-flute or 3-flute diamond-cut router bits or compression cutters to prevent top and bottom glass layer delamination during high-speed profiling.

Machining Parameter Recommendations

• Milling Feeds & Speeds: High spindle speeds (12,000 – 18,000 RPM) paired with moderate chip loads (0.05 – 0.12 mm/tooth). Avoid dwell time in cuts to prevent thermal resin scorching.
• Drilling Protocols: Use specialized 118° to 130° carbide drill points. Use peck-drilling cycles for deep holes to clear abrasive dust and prevent heat buildup. Back up the exit side of the plate with sacrificial backing material to eliminate exit breakout/burrs.
• Dust Extraction: Dry machining with high-vacuum dust extraction systems is mandatory. Glass dust particles are hazardous and highly abrasive to CNC linear guides and ball screws.

4. Custom Machined G10 Parts & Structural Applications

RDS's in-house CNC facility processes custom-fabricated G10 components directly from customer CAD files (.STEP / .DWG / .DXF):

• Electrical Switchgear Insulation: Busbar support blocks, terminal spacers, insulation baffles, and arc chute structural plates.
• Cryogenic Engineering: Liquid nitrogen/helium tank insulation supports, thermal isolation bushings, and structural pump components (G10 maintains impact strength down to -196°C).
• Precision Mechanical Components: Wear plates, structural link arms, gear blanks, and test fixtures for electronics testing.

5. Engineering Limitations: When NOT to Specify G10

While Grade G10 offers superior mechanical strength, engineers should consider alternate laminates under the following conditions:

• Fire Resistance / Self-Extinguishing Requirement: G10 uses a non-brominated resin matrix and meets only UL 94 HB flammability. If UL 94 V-0 flame retardancy is required by electrical safety codes, specify Grade FR4 instead.
• Operating Temperatures Above 130°C: For continuous thermal exposure between 150°C and 180°C (Class H), specify Grade G11 (EP GC 203) or GPO-3 / Glastic.
• Extreme High Voltage Arc Resistance: Where high tracking resistance (CTI ≥ 600V) and arc quenching under continuous AC arcs are required, polyester-glass GPO-3 is preferred over epoxy G10.