Metals. Shaping Techniques

The manufacture of metal products, or components for assembly into products, takes many forms. There are different techniques to shape metals depending on the kind of metal and the object that we want to make. some of the more common industrial processes are describe below.

Blanking: This is one of the simplest pressing operations also called punching. A hardened punch is used to stamp sheet metal through a die, The metal is stamped cold. This method is used to form hollow objects like washers and bearings.

Press Forging: the heated unprocessed metal is placed between two dies, one fixed and the other mobile. The dies are the shape of the object that we want to make. They are pressed together to make the required shape. Press-formed panels for domestic radiators and motor cars panels (wings, doors, roofs, etc.) are among the numerous components which are press forging.

Forging: It's the shaping of metal using compression forces. The force may be applied by hammer, press, or rollers. The metal is usually hot, but some operations are carried out cold. Forging at temperature increases the plasticity of a metal and reduces the forces needed to work it. Drop forging is the forming of a component from a metal bar between two half dies, tongs and an anvil. The metal is placed on an anvil. The hammer repeatedly rises and falls on the metal. This is powered by a pneumatic or hydraulic force. Forgings can be made to very close tolerances, hence very little finishing is required. Materials used in drop forging include: mild and medium carbon steel, aluminium and copper alloys. Motor car crankshafts, some G-clamps, and other tools , door handles, are among the numerous products which are drop forged.

Rolling: The heated metal is passed through a series of rollers that compress it, reduce it thickness and increase its length. It's used to make sheets and bars.

Thread rolling: This is a method of applying a thread to machine bolts produced by cold heading. Other parallel-sided components can be threaded in this way too. Knurled patterns, spline shafts and worm gears are just a few of the many other forms  which can be produced by roll forming.

Cold heading: This is the process of forming cold wire into components by squeezing the metal into a die cavity. This is a quick and cheap method of changing the shape and diameter of a metal bar to produce products. Brass, stainless steel, mild steel and medium carbon steel are the materials commonly used in this process. It's used for making bolts, screws, rivets and nails.

Extrusion: the heated metal is pushed through a die of a required shape by a hydraulic ram, using compression. It's used to make long objects, e.g. bars and tubes. In addition, an almost infinite of solid cross-sections can be produced in this way. Products made from extruded sections include: door and window frames, hinges, components for locks, edging strips. By far, the largest number of sections produced are made from aluminium and brass.

Bending: This method is used to make objects with angles. a metal sheet is subjected to force to make a curved shape with a specific curve radius.

Casting: This is the shaping of metal by pouring molten metal into a mould. A mould is a cavity which has the shape of the required object. Sand is a particulary good material for making moulds. It can withstand very high temperatures and can be moulded into complex shape. The mould can also be made from steel or cast iron. The moulds are made into pieces so they can be separated. Another type of mould uses a wax model of the object that we want to make.

First, the metal is heated to melting point.  Then, the liquid metal is poured into the mould.  After that, the mould and metal are left to cool until the metal has solidified and finally, the solidified piece is extracted from the mould.

The casting method used depends on the type of objects that we want to make:

Sand casting: is a quick method of producing complex shapes. Motor car engine blocks and cylinder heads, bases for heavy machinery, manhole covers and the body of a mechanic's vice at school workshops are examples of sandcast products.

Die casting is employed where many items of the same form are to be manufactured. It is a very fast production method which can produce extremely complex precision parts due to the injection of metal under pressure. The products have a high quality surface requiring very little secondary finishing. Many thousands of different die cast products are manufactured. These include: the case of some electric hand tools: drills, jig-saws, sanders, components parts for washing machines, food mixers and lawn mowers and many motor car components. Die casting is limited to non-ferrous metals whose molten temperatures won't damage the dies.

Wax casting: the wax is first burn away to make the hollow space before the metal is poured in. It's used for ornaments, jewellery, dental prosthetics and sculptures.

Centrifugal casting: this method uses a mould which rotates when the liquid metal is poured inside. The centrifugal force makes that the liquid sticks to the walls of the mould. It's used to make pipes and objects that are composed of various layers of material.

Wire drawing: a wire is pulled through a hole that has the required dimensions. A rotating drum is used to pull it through the hole to increase its lenght while reducing its diameter. It's used to make strings and wires.

Spanish terms

Blanking - impresion

Punching - punzonado

shape - dar forma

stamp - estampar

bearing - cojinete

washer - arandela

forging - forja

die - matriz/troquel

roller - rodillo

carry out - llevar a cabo

Drop forging - estampado

tongs - tenacillas

anvil - yunque

crankshafts - cigueñales

clamps - abrazaderas

Rolling - Laminación

thickness - espesor

Thread rolling - Laminado de roscas

knurled patterns - patrones estriados

spline shafts - ejes estriados

worm gears - engranajes helicoidales

squeezing - apretar

bolts - pernos

screws - tornillos

rivets - remaches

nails - clavos

frame - marco

edging strip - ribete

hinge - bisagra

lock - cerradura

string - cuerda

wire - cable

wire drawing - trefilado