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  • Published on: 7th September 2019
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Learning Aim: Examine common engineering processes to create products or deliver services safely and effectively as a team.

Product: Hammer

Introduction

The hammer is the earliest tool of mankind. It is the most basic and essential tool for a number of everyday jobs inside the home and on the job. It is on every handyman’s tool belt and in the toolbox of every homeowner. The use of hammers can be dated all the way back to 2, 600,000 BC when several shaped stones were used to break or shape different materials. The earliest hammers with handles can be traced back to about 30,000 BC during the middle of Stone Age. As technology advanced in metallurgy, designers added new metals to the wooden handle, starting with the Bronze Age and developing to our modern age of metal alloys.

Processes

• Forming the head (Hot forging & Shot blasting)

• Forming the handle (Extrusion)

• Assembling the hammer

P1&P2: Explain the processes & explain how humans errors affect the production

The Head (Hot forging & Shot Blasting)

A process called hot forging is used to style the head. A steel bar is heated to about 1,250°C. This can be done with flame torches or by passing the steel bar through a high-power electrical induction coil.

Whilst the bar is hot, it can then be cut short (blanks), or it can continuously stay in a hot forge. The bar is then positioned between two shaped cavities called dies within the forge. One is held in a steady position, and the other is fixed to a movable ram. The ram forces the two dies together with a great deal of pressure, pushing the hot bar of steel into the shape of the two cavities. This process is repeated numerous times using different shaped dies to mould the hammer head slowly. The forging process line up the inside grain structure of the steel and delivers a much stronger and long-lasting piece.

The head is placed in the middle of two pruning dies, which are forced together to cut off any remaining flash. The head is then cooled, and any rough bits are smoothed out. To prevent the hammer head from chipping and breaking, the claws, the face and the poll are heated to strengthen them. This is done by heating those parts, with a flame or an induction coil, and then rapidly freezing them. This allows the steel near the surface to create a different grain structure that is a lot harder than the rest of the head.

The head is then cleaned with a process called shot blasting. This allows a stream of air holding small steel particles to clean the head. The head can then be painted. The claws, poll, and face are refined smooth which causes the paint in those areas to be removed. The slit in the claws is then smoothed using an abrasive disc as part of the process.

During this process human errors can occur. For example, if the bar is heated at a higher temperature, the steel will heat quicker and won’t mould properly. This will cause delay to the product and will cost manufacturers more money.  

Forming the Handle (Extrusion)

The handle of the Hammer can either be made from wood or steel.

The wooden handle of the hammer is formed on a lathe. A piece of wood is cut to the preferred size & length and secured on each side in the lathe. The wood must be positioned in the chuck tightly. The chuck key mustn’t be left in the chuck otherwise if the lathe is switched on, the chuck key may possibly fly out very fast and this could injure the operator.

As a result of this, operators must wear appropriate clothing for operating machinery or equipment. (Personal Protective Equipment at Work regulations 1992).

As the wood twists around the long part of the handle, a cutting device moves very quickly to cut the handle profile. The point of the cutting device is driven by a cam that has the same shape as the completed handle. As the cutting device goes along the length of the handle, it trails the shape of the cam and cuts the handle to size. The completed handle is fixed into a holding device and an opening is cut crossways through the top of the handle. The handle is finally polished to give it a smooth surface.

The steel-core handle is formed by a process called extrusion. It is made by heating a steel bar at 620°C until it becomes plastic. The plastic is then forced through an opening that has the chosen cross-sectional shape.

The steel-core handle can have a protective layer of plastic fitted around it to increase shock absorption.

Assembling the Hammer

Wooden Handle

The wooden handle is placed through the hole of the head. A piece of wood is put into the diagonal slot that is on top of the handle to make the two pieces go outwards to push against the head. This delivers enough contact to hold the head on the handle. The piece of wood is safeguarded in placed with two smaller steel pieces pierced through it diagonally.

Steel-core Handle

The handle is placed through the hole of the head. After, liquid epoxy resin is poured through the top of the hole to stick the handle in place. The handle is placed in a deep die and a rubber grip is shaped around its lower part.

After both metal and wooden handles are made, they can then be branded with an adhesive label to display the manufacturer, brand name, or other data.

General Health & Safety

As part of the Health & Safety at Work act, 1974 the following steps must be followed during the processes to ensure safety within the workplace.

If there is any damaged equipment, it must be reported and cannot be used until it has been repaired by a qualified person.  

All hazards, unsafe conditions and work practices must be reported.

Appropriately spot, identify and locate emergency stops so that they are easily seen and can be conveniently accessed by all operator locations.

A safe structure of work with any relevant health and safety representative and employees must be developed.

M1: Advantages and Disadvantages of the processes

Hot Forging Advantages & Disadvantages

The hot forged hammers contains increased ductility which makes them essential for a lot of structures. Furthermore, hot forging is more adaptable than cold forging, because modified parts can be manufactured. The surface quality also lets a range of final work such as: Painting or polishing to be tailored to customers’ specific wishes.

Hot forged works contain less precise dimensional lenience compared to works that are cold forged. If the cooling process isn’t done under special conditions, there is a high risk of damage to the hammer. Additionally, the forged metal’s grain structure can fluctuate and there is also a very high possibility of the air and the hammer reacting.

Shot Blasting Advantages & Disadvantages

Shot blasting excludes the use of vicious chemical compounds. Shot blasting lets the creation of a lasting bond between the protective coat (zinc, paint or epoxy) and the shot blasted hammer head. Additionally, it helps to identify surface faults or defects. Shot blasting increases durability and sturdiness of protective floor coats because it sticks better to the shot blast cleaned and scale free surface.

No disadvantages could be found.

Extrusion Advantages & Disadvantages

Extrusion is very cheap compared to other moulding processes such as, thermoforming and powder metallurgy. This is because of the efficiency of the process. Extrusion uses a lot of thermoplastics that can continually be melted and hardened. Materials that are left over which are usually disposed of in other processes can be used again. This lowers the cost of raw materials and disposals. With the exception of mechanical failure or scheduled stoppage, plastic extrusion machines are always in operation. This therefore reduces the possibility of a shortage in inventory and also allows 24 hours manufacturing per day.

Hot plastic usually expands when it leaves the extruder. This is called die swell. Because it comes from different factors in the process, calculating the exact degree of expansion continues to be a huge problem. Due to this, manufacturers always have to take major levels of alterations from the dimensions of the product. Although there are methods that can control the problem, the problem of tolerance excludes extrusion as a process for accurate parts manufacturing.

D1: Explain why processes are used

Hot Forging

Hot Forging is a process used to form the hammer head. It involves shaping metal using restricted compressive forces.

Hot forging is performed at very high temperatures. For steel, temperatures can go as high as 1150°C, for aluminium alloys 520°C and for copper alloys 800°C. These temperatures are essential to avoid metals from being under too much pressure during deformation.

Shot Blasting

Shot blasting is the method that is used to polish, clean & strengthen the hammer head. It is used in virtually every industry that handles metal. This includes automotive, construction, shipbuilding rail and many more.

Extrusion

Extrusion is a process that is used to make objects with a fixed cross-sectional shape. The material is forced through a die of the wanted cross-section.

D1: Consider alternative processes

Cold forging

Cold forging is an alternative process to hot forging. The two are similar in results, but use different steps. Cold forging is achieved at lukewarm temperature. The piece of work is forced between two dies until it takes shape. To provide a finished piece, techniques such as pressing, rolling, drawing and extruding are also used.

Sand blasting

Sandblasting is a processes wherein abrasives are quicker by steam from dense air through an outflow from blasting nozzle. Sand blasting is often used in cleaning rubble and rust on surfaces that need painting or layering. Sand or any type of chisel is used to scrape particles from the surface.

Pultrusion

Pultrusion is a constant process for manufacturing compound materials with continuous cross-section. Contrasting to extrusion, which pushes the material, pultrusion pulls the material.

D1: Compare and Contrast processes with their alternatives and decide which one is better and why

Hot forging & Cold forging

Hot forging preserves resources from permanently deforming so as to increase its resistance to additional deformation at high temperatures. Although this causes the materials to be strong, it results in low resistance and high flexibility. On the other hand, cold forging increases the strength of a metal through permanently deforming so as to increase its resistance to additional deformation at a room temperature.

Manufacturers might choose cold forging over hot forging because cold forged parts need little work which reduces the end cost. Another reason is that the material savings attained through accurate shapes. The financial advantages plus high production rates and extended die life are enough to persuade manufacturers that cold forging is the best selection for them.

In contrast to this, subject on the manufacturer’s requests, some of the cold forging features could be disadvantages. For example, only simple shapes in high volumes can be moulded. As a result, if the client is looking for a precise modified component, then hot forging would be better suited. Furthermore, another disadvantage of cold forging is that cold forged metals are less malleable which makes them useless for certain structures. Also, residual stress may arise as a result of the grain structure that provides the material its strength.

Extrusion & Pultrusion

Pultrusion is less known than extrusion as a moulding process. Both the processes are alike as they both allow countless lengths of a set and a fixed shape to be produced. The major difference between the two is that extrusion can be used for other materials such as: thermoplastics, aluminium and wood compounds, while pultrusion is used in producing compounds that use long threads of fibre as support.

Pultrused plastics demonstrate an improved variety of physical properties that is an advantage to both engineering and design applications, as they give the durability of metals with the benefits of low weight and resistance to rust and corrosion. Pultrused work pieces are very durable and are very much like metals.

Although pultrusion is resourceful in its usage of materials, the process is completely mechanical and needs a frequently heated die. This endless use of electricity and heat that is needed to fuel the process makes pultrusion less energy efficient than other processes such as extrusion. Furthermore, the restricted kind of materials that can be pultrused are not often recyclable.

This could push manufacturers to choose extrusion over pultrusion.

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