Producing Pattern, Corebox or Model Components using Flexible Composite Materials — EAL Occupational Qualification Construction & Building Services Revision
This subtopic focuses on the practical skills and knowledge required to produce patterns, coreboxes, and models using flexible composite materials such as
Topic Synopsis
This subtopic focuses on the practical skills and knowledge required to produce patterns, coreboxes, and models using flexible composite materials such as silicone rubbers, polyurethane resins, and epoxy systems. Learners will apply techniques for mould preparation, material mixing, casting, and finishing to create durable and dimensionally accurate tooling components for foundry applications, ensuring compatibility with sand moulding and core making processes.
Key Concepts & Core Principles
- Interpretation of engineering drawings and specifications, including symbols, tolerances, and material requirements.
- Selection and preparation of timbers, plywoods, and composite materials, considering grain direction, moisture content, and stability.
- Use of hand tools (e.g., chisels, planes, saws) and machine tools (e.g., bandsaws, planers, routers) to shape and finish components.
- Pattern construction techniques, including core boxes, loose pieces, and split patterns, with allowances for shrinkage and draft angles.
- Quality assurance methods, such as checking dimensions, surface finish, and fit, and making adjustments to meet tolerances.
Exam Tips & Revision Strategies
- Always reference manufacturer’s technical data sheets (TDS) and safety data sheets (SDS) in your portfolio evidence to demonstrate compliance with COSHH.
- Provide step-by-step photographic evidence of each stage, from mould preparation to finished component inspection, to show process control.
- Explain in your witness testimony or written account why a specific flexible composite was chosen over rigid alternatives (e.g., for deep draws, undercuts, or high production runs).
- Include a dimensioned sketch or CAD drawing with tolerances, and record actual measurements after curing to prove accuracy.
- Highlight how the finished component interfaces with foundry tooling systems (e.g., pattern plates, core boxes) to demonstrate understanding of the full manufacturing chain.
Common Misconceptions & Mistakes to Avoid
- Students often neglect surface preparation, leading to poor adhesion or silicone not releasing from the pattern.
- Inaccurate ratio mixing (e.g., catalyst-to-base) results in soft or tacky finishes that fail to cure properly.
- Introducing air bubbles during mixing or pouring without vacuum degassing, causing porosity in the final component.
- Moving or disturbing the mould before full cure time, causing warping or dimensional inaccuracies.
- Overlooking the need for post-curing or conditioning of the composite before use in a foundry environment, reducing heat resistance.
- Choosing an excessively stiff composite for a deep-draw pattern, leading to breakage during withdrawal from sand moulds.
Examiner Marking Points
- Award credit for demonstrating correct selection of flexible composite material based on pattern/corebox requirements (e.g., tear strength, shore hardness, heat resistance).
- Award credit for accurately measuring and mixing composite components by weight or volume as per manufacturer’s instructions, with evidence of thorough blending to avoid uncured spots.
- Award credit for preparing mould surfaces/patterns appropriately using release agents and ensuring a dust-free, dry environment before application.
- Award credit for applying the material using proper techniques (pouring, brushing, or spraying) to minimise air entrapment and achieve uniform thickness.
- Award credit for monitoring and controlling curing conditions (time, temperature, humidity) as specified for the material to achieve full mechanical properties.
- Award credit for demoulding carefully and inspecting the finished component for defects such as bubbles, incomplete cure, or distortion, and undertaking corrective actions if needed.
- Award credit for finishing the component to required dimensional tolerances using trimming, sanding, or patching, and verifying against specifications (e.g., using gauges or CMM).