Pattern Making, Pattern Types, Core Making and Casting Processes for SS 3

Class: SS 3
Term: First Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Metal Fabrication and Joining
Previous Lesson: Casting Equipment, Sand, Die and Shell Casting
Topic: Pattern making
Subject Matter: Type of pattern; simple piece, split, flat back; core making; boxes, sand etc; processes; making pouring of ferrous and non ferrous metals, finishing

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Identify and describe different types of patterns used in casting.
• Explain the purpose and process of core making.
• Define and describe the stages of metal casting, including melting, pouring, gating, and finishing.

Affective Domain

• Appreciate the importance of accurate pattern making for quality castings.
• Recognise the safety precautions required during casting processes.

Psychomotor Domain

• Demonstrate the basic steps of core making using appropriate materials.
• Observe and describe the practical steps involved in casting a simple article.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Metal Work for Senior Secondary Schools textbook
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Examples of simple piece, split, and flat back patterns
• Core boxes and core sand
• Crucible and tongs (for demonstration or visual aid)
• Diagrams or charts illustrating casting processes (melting, pouring, gating, finishing)
• Video clips showing metal casting operations
• A simple cast article (e.g., a cutter)

Rationale for the Lesson

This lesson is important as it introduces students to the fundamental principles of pattern making, core making, and casting, which are essential processes in metal fabrication. Understanding these concepts provides a foundation for producing various metal components and appreciating the role of precision in manufacturing. It also highlights critical safety practices in the workshop environment.

Prerequisite/Previous Knowledge

Students should have basic knowledge of different types of metals (ferrous and non-ferrous) and their properties, as well as an understanding of workshop tools and safety rules.

Lesson Content/Board Summary

Pattern Making, Pattern Types, Core Making and Casting Processes

Types of Patterns

Patterns are replicas of the object to be cast, used to create a mould cavity in sand or other materials. Different types of patterns are used depending on the complexity and quantity of the casting required.

1. Simple Piece Pattern: This is the simplest type of pattern, made in one piece. It is used for castings with flat surfaces or simple shapes that do not have undercuts or complex internal features. It is easy to withdraw from the mould.
2. Split Pattern: This pattern is made in two or more pieces, divided along the parting line of the mould. It is used for castings with complex shapes, undercuts, or when the pattern cannot be easily withdrawn from the mould in one piece. The halves are typically doweled together for accurate alignment.
3. Flat Back Pattern: This type of pattern has one flat surface, which rests on the mould board during moulding. It is used for castings that have one flat side and is relatively easy to mould because the flat surface provides a stable base.

Core Making

Core making is the process of creating a sand core, which is used to form internal cavities, holes, or intricate passages within a casting that cannot be formed by the pattern alone.

1. Meaning of Core Making: It is the process of producing a sand shape (core) that is placed inside the mould cavity to create internal features in the final casting.
2. Materials for Core Making:
   1. Core Boxes: These are wooden or metal boxes that define the shape of the core.
   2. Core Sand: A special mixture of silica sand, binders (like linseed oil, resin, or cereal binders), and water. Binders give the core strength when baked.
   3. Core Vents: Small holes or passages in the core to allow gases to escape during pouring.
3. Process of Core Making:
   1. Mixing core sand with binders and water.
   2. Packing the core sand firmly into a core box.
   3. Removing the core from the core box carefully.
   4. Baking the core in an oven to harden it and improve its strength.
   5. Applying core washes (e.g., graphite) to improve surface finish and prevent metal penetration.

Casting Processes

Casting is a manufacturing process in which a liquid material is usually poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting.

1. Melting: This is the process of heating the metal (ferrous or non-ferrous) in a furnace or crucible until it reaches its liquid state, suitable for pouring. The temperature must be carefully controlled.
2. Pouring: The molten metal is carefully transferred from the crucible and poured into the gating system of the prepared mould. This must be done smoothly and continuously to avoid defects.
3. Gating: The gating system is a network of channels within the mould that directs the molten metal from the pouring basin to the mould cavity. It includes:
   1. Pouring Basin: A funnel-shaped opening on top of the mould where molten metal is poured.
   2. Sprue: A vertical channel connecting the pouring basin to the runner.
   3. Runner: A horizontal channel that distributes molten metal to the gates.
   4. Gate: The entry point through which molten metal enters the mould cavity.
   5. Riser: A reservoir of molten metal attached to the casting to compensate for shrinkage during solidification.
   6. Vent: Passages for gases to escape from the mould cavity.
4. Finishing: After the casting has solidified and cooled, it is removed from the mould, and several finishing operations are performed. These include:
   1. Fettling/Shakeout: Removing the casting from the mould and separating it from the sand.
   2. Cleaning: Removing adhering sand, scale, and other foreign materials.
   3. Trimming/Cutting: Removing the gating system (sprue, runners, risers) from the casting.
   4. Grinding/Filing: Smoothing rough edges and surfaces.
   5. Heat Treatment: Sometimes applied to improve mechanical properties.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Questioning/Recall

Teacher’s Activity: The teacher greets the students and asks questions about their previous knowledge of metals and their uses. The teacher then introduces the topic of pattern making and casting as fundamental processes in shaping metals.

Pupils’ Activity: Students respond to questions about metals and listen attentively to the introduction.

Learning Point: Introduction to casting processes

Step 2: Types of Patterns

Time: 8 minutes

Teaching Skill: Explanation/Demonstration

Teacher’s Activity: The teacher explains the concept of patterns and their importance in casting. Using actual examples or clear diagrams, the teacher describes and shows the simple piece, split, and flat back patterns, highlighting their characteristics and applications.

Pupils’ Activity: Students observe the patterns, ask questions, and take notes on the different types.

Learning Point: Identification of pattern types

Step 3: Core Making

Time: 10 minutes

Teaching Skill: Explanation/Demonstration/Guided Practice

Teacher’s Activity: The teacher explains the purpose of core making and the materials involved (core boxes, core sand). The teacher then demonstrates the process of preparing core sand and packing it into a core box to form a simple core. Students are encouraged to observe closely and ask questions.

Pupils’ Activity: Students watch the demonstration, identify core making materials, and discuss the steps involved. Some may assist in handling materials if safe to do so.

Learning Point: Core making process

Step 4: Casting Processes – Melting and Pouring

Time: 6 minutes

Teaching Skill: Explanation/Visual Aid

Teacher’s Activity: The teacher explains the first two stages of casting: melting and pouring. The teacher describes how metals are melted in a crucible and then poured into the mould, emphasising temperature control and safety. Diagrams or video clips may be used.

Pupils’ Activity: Students listen to the explanation, observe the visual aids, and understand the initial stages of casting.

Learning Point: Melting and pouring stages

Step 5: Casting Processes – Gating and Finishing

Time: 6 minutes

Teaching Skill: Explanation/Illustration

Teacher’s Activity: The teacher continues by explaining the gating system (sprue, runner, gate, riser) and its role in directing molten metal. The teacher then describes the finishing processes (fettling, cleaning, trimming, grinding) that occur after the casting has solidified. The teacher uses diagrams to illustrate the gating system.

Pupils’ Activity: Students listen, study the diagrams of the gating system, and grasp the final stages of casting.

Learning Point: Gating and finishing steps

Step 6: Demonstration of Casting a Simple Article

Time: 5 minutes

Teaching Skill: Demonstration/Observation

Teacher’s Activity: The teacher uses a pre-prepared simple mould and, if feasible and safe, performs a simplified demonstration of pouring molten metal into a mould (or shows a detailed video) to cast a simple article like a cutter. The teacher highlights the practical application of patterns and core making.

Pupils’ Activity: Students observe the demonstration intently, noting the practical application of the concepts learned. They may ask questions about the process.

Learning Point: Practical casting demonstration

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Mention three types of patterns used in casting.
2. What is the purpose of core making?
3. List the main stages of the casting process.
4. Briefly explain what a “gating system” is.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Understanding of casting processes

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on pattern types, core making, and casting processes into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson information

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Reinforcement

Teacher’s Activity: The teacher summarises the key points of the lesson, reiterating the importance of pattern making, core making, and the casting process in metal work. The teacher encourages students to continue exploring metal fabrication techniques.

Pupils’ Activity: Students listen to the summary and prepare for the next lesson.

Learning Point: Consolidation of casting knowledge

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook.

1. Draw and label a simple piece pattern and a split pattern.
2. Describe the materials used for core making and their functions.
3. Outline the steps involved in the finishing stage of a casting process.
4. Research and write a short paragraph on the safety precautions to observe when working with molten metals.

Lesson Keywords

• Pattern – A replica of the object to be cast, used to create a mould cavity.
• Core – A sand shape used to form internal cavities or holes in a casting.
• Mould – A cavity into which molten metal is poured to form a casting.
• Melting – The process of heating metal to its liquid state.
• Pouring – Transferring molten metal into a mould.
• Gating System – Channels that direct molten metal into the mould cavity.
• Finishing – Operations performed on a casting after solidification to prepare it for use.
• Ferrous Metals – Metals containing iron (e.g., cast iron, steel).
• Non-ferrous Metals – Metals that do not contain iron (e.g., aluminium, copper).

Differentiation

Support for struggling learners: Provide simplified diagrams and step-by-step instructions for core making. Pair them with more capable students for observation and discussion. Focus on identifying the main pattern types and the basic stages of casting.
Extension for advanced learners: Challenge them to research different types of core binders or advanced casting techniques like die casting. They can also be asked to design a simple pattern for a specific article and explain their choice of pattern type.

Suggested Lesson Videos

For visual demonstrations of pattern making, core making, and casting processes, search on YouTube for: metal casting process for students SS3

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have prepared or sourced examples of the different pattern types (simple piece, split, flat back), core boxes, and core sand. Visual aids such as charts or video clips illustrating the melting, pouring, gating, and finishing stages of casting will greatly enhance understanding. Begin by activating students’ prior knowledge of metals. When explaining pattern types, use the physical examples to make the concepts concrete. The demonstration of core making should be clear and step-by-step, allowing students to observe the process closely. Emphasise safety during any discussion or demonstration involving molten metal or hot equipment. Encourage students to ask questions throughout the lesson. After the main teaching points, use the evaluation questions to check comprehension. Guide students to copy the Board Summary notes accurately into their notebooks before concluding the lesson. For practical involvement, consider a follow-up session where students can try packing core sand or identifying parts of a simple mould.