Deforming and reforming (AQA GCSE Design and Technology): Revision Notes
Deforming and reforming
What is deforming and reforming?
Metal materials can have their form altered and reshaped while remaining in their solid state. This means we can change the appearance and structure of metals without needing to melt them down first. These processes are essential in manufacturing and allow us to create complex shapes and functional objects from basic metal materials.
These metal forming processes are fundamental to modern manufacturing, enabling everything from simple household items to complex automotive components to be created efficiently from raw metal materials.
Bending and folding methods
There are several different techniques used to bend and fold metals, each suited to different applications and desired outcomes. Understanding the appropriate method for each application is crucial for achieving quality results.
Beaten metal work
Beaten metal work involves using various mallets and hammers to gradually shape metal into the required form. This traditional technique requires several specialised processes:
Hollowing stretches copper material into a bowl-like shape. The metal is worked using a bossing mallet while positioned in the hollow of a sand-filled leather bag. This provides support while allowing the metal to be formed into curved shapes.
Planishing smooths out any imperfections left from the hollowing process. A highly polished planishing hammer is used alongside a mushroom-shaped planishing stake. This creates smaller, more even indentations that give a refined finish to the metalwork.
Sinking stretches the metal further and creates a defined edge. The edge of the metal is positioned against a block, and the metal is forced into the desired shape using controlled hammering techniques.
Raising creates tall-sided shapes by striking the metal above a stake. This forces the metal into shape without making it thinner, but causes the edge of the metal to become thicker as material is compressed.
Worked Example: Creating a Copper Bowl
- Hollowing: Start with a flat copper sheet and use a bossing mallet to gradually work the metal into a shallow bowl shape while it rests in a sand-filled leather bag
- Planishing: Use a polished planishing hammer against a mushroom stake to smooth out hammer marks and create an even surface
- Sinking: Define the bowl's edge by positioning it against a block and using controlled strikes to create the final shape
- Raising: If deeper sides are needed, strike the metal above a stake to compress and thicken the rim while maintaining wall thickness
Critical Point: The sequence of beaten metal work processes must be followed correctly. Attempting to planish before proper hollowing, or skipping the sinking stage, can result in uneven thickness and poor structural integrity in the final piece.
Forging
Forging requires heating metal in a hearth, forge, or furnace until it becomes soft and malleable. The hot metal is then shaped by hammering. Drop forging uses machinery designed for larger-scale production, employing much greater forces with a stationary die and a dropping part called a hammer.
Sheet metal work
Sheet metal work is ideal when creating more defined shapes from flat sheet materials. For smaller scale projects, metal can be forced into shape using folding bars or a vice. Larger scale operations use folding machines for straight lines, while rollers create curved shapes and bends.
Tube bending
Tube bending uses specialised formers or rollers to bend tubes into curved shapes. The key advantage of this method is that it prevents the material from buckling or collapsing during the bending process, maintaining the tube's structural integrity.
Stamping or press forming
Stamping (also called press forming) uses cold forming techniques to shape metal sheets into three-dimensional forms. This process is commonly used for creating car body panels and other complex curved components.
Cold forming processes like stamping work the metal at room temperature, which can increase the material's strength through work hardening, but also increases the force required for forming.
Extrusion process
Extrusion creates products with a defined cross-sectional shape by forcing a metal billet (the piece of metal to be formed) through a specially shaped opening called a die. This process is particularly valuable for creating consistent, repeatable shapes with precise dimensions.
How extrusion works
Worked Example: The Extrusion Process
Step 1: Create a die with a shaped opening that matches the desired final cross-section
Step 2: Position the metal billet correctly at the die entrance
Step 3: Use a ram to push the billet through the die with tremendous force
Step 4: The extrusion emerges with the exact shape of the die opening
Step 5: Cut the extrusion to the desired length and allow it to cool
Applications of extrusion
Complex extrusions are commonly used for products like aluminium window frames, while simpler extrusions can create basic shapes such as metal tubes. The process can be performed with either hot or cold metal, depending on the relative softness required and the complexity of the desired shape.
Equipment components
Key Components of Extrusion Equipment:
- Die: Contains the shaped opening that determines the final cross-section
- Billet: The piece of metal being formed
- Ram: Provides the force to push the billet through the die
- Die holder: Keeps the die securely in position
- Container: Houses the billet during the process
Real-world examples
Understanding these processes becomes clearer when we consider practical applications. For instance, when creating a copper bowl, hollowing stretches the material into the basic bowl shape, followed by planishing to create a smooth, professional finish.
In industrial applications, extrusion might be used to create steel sections with specific shapes for construction or manufacturing purposes. The ability to produce consistent cross-sections makes extrusion particularly valuable for creating components that need to fit together precisely.
Real-World Application: Automotive Manufacturing
In car production, stamping/press forming is used extensively to create body panels. A flat steel sheet is placed over a shaped die, and tremendous pressure forms it into complex curves that match the vehicle's design. This process can create everything from door panels to hood sections in a single operation.
Key Points to Remember:
- Metal deforming and reforming allows shape changes while keeping the material in its solid state
- Beaten metal work uses a sequence of processes: hollowing, planishing, sinking, and raising
- Forging requires heating the metal to make it more workable before shaping
- Extrusion pushes metal through a shaped die to create consistent cross-sectional shapes
- Different methods are suited to different scales of production and types of final products