Used Forging Machines for Sale — 793

History of Forging

Metal forging is a bulk deformation process which can be defined as the controlled deformation of metal into a specific shape by localized compressive forces. It is the oldest of the metal working process known. The forging process dates back to 4000 B.C. and evolved from the manual art of simple blacksmithing. From simple drop hammers and anvils which were operated manually water, air and steam powered hammers came into use after the industrial revolution. Later, the smiths of those days started using hammers driven by transmission shafts to produce a wide range of forged parts for the railways, for the car industry and for agricultural machinery. Modern forging uses machine driven impact hammers or presses which deform the work piece by controlled pressure.

Hot and Cold Forging

Hot forging is defined as working a metal above its recrystallization temperature while in cold forging the metal is worked far below its recrystallization temperature. In simple terms, hot forging is carried out at fairly elevated temperatures while cold forging is done at room or near room temperatures. Cold forging requires heavier forces and stronger equipments but the dimensional accuracy and surface finish produced on the part will be excellent. Even though lighter forces perform the function in hot forging, the precision on tolerance is less due to thermal contraction and warping from uneven cooling. Also undesirable reactions between the metal and the surrounding atmosphere and contaminations take place at higher temperature which are minimized during cold forging.

Forging Machines and Forging Tools

There are basically two types of forging equipment namely: forging hammers and forging presses. Hammers can be further divided into two types as drop hammers and counter blow hammers. The main variations among drop hammers is in the way that the hammer is powered: by air, gravity, friction or steam. Drop hammers are usually operated in vertical position. To overcome some of the limitations of drop hammers like high noise, requirement of a large foundation impact or counter blow hammers were used. In a counterblow machine both the hammer and anvil move and the work piece is held between them thereby the excess energy becomes recoil which allows for the machine to work horizontally and consist of a smaller base. Forging presses can be sub-divided based on the powering mechanism as mechanical presses and hydraulic presses. Mechanical presses function by using cams, toggles and cranks to give pre-determined force. Hydraulic presses employ fluid pressure and a piston to generate force. Mechanical presses are very faster than their hydraulic counterparts. But hydraulic ones are more flexible with greater capability. The initial set-up cost for a hydraulic press is relatively higher than the same for the mechanical press.

Types of Forging Machines

Forging metal can be classified into three types according to the degree to which the flow of the metal is constrained by the dies:

• Open die forging 
• Impression die forging Ž
• Flashless forging

Open die forging also known as upsetting involves compression of a work between two flat dies, or platens with the absence of any lateral constraints which there is very less restriction to metal flow. It basically reduces the height of the job by increasing the diameter. Open die forging is performed on ingots, billets, or a pre-formed shape. Graphite based lubricants are used during this type of metal forging process. Pancaking or barreling can occur during upsetting due to the frictional forces present at the die-work piece interface or due to the thermal differences. Closed die or impression forging is done in one or in a series of die impressions or die cavities. Simple shapes may be forged in a single stroke while more complicated pieces may pass through several strokes and die cavities before achieving their final form. During the final forging, a thin layer of excess material flows radially outward around the periphery of the die metal, which is termed as the flash. The flash is subsequently trimmed off manually or by using specialized dies. Press forging and drop forging are two popular methods in closed die forging. Both open and closed die forging processes are carried out at room temperature as well as in hot state. In flashless forging as the name suggests, the die tooling is designed in such a way that the cavity does not allow the formation of a flash. The work material is completely surrounded by the die cavity during compression and hence no flash is formed. Control over the process is more demanding than impression die forging. Most important requirement in flashless forging is that the work volume must equal the space in the die cavity to a very close tolerance.

Advantages and Applications of Forging Machinery

All metals and their alloys with a very few exception can be forged. Many metals are forged cold, but iron and its alloys are almost always forged hot. Forging results in metal that is stronger than cast or machined metal parts. This can be attributed to the grain flow caused through forging process. As the metal is pounded the grains deform to follow the shape of the part, thus the grains are unbroken throughout the part. Therefore some modern parts take advantage of this for a high strength-to-weight ratio. Forge equipment is now capable of making parts ranging in size of a bolt to a turbine rotor. Typical parts: bolts, rivets, engine crankshafts, connecting rods, turbine shafts, coins, gears, hand tools, structural components of machinery or aircraft, jet engine parts. Also, basic small scale industries use forging processes to establish basic shape of large parts that are subsequently machined to final geometry and size.

Forging Manufacturers

FAGOR, SCHULER, AIDA, FICEP, KOMATSU, DEYI, AEM3, DIMECO, Bliss-Bret, Beckwood, WANZKE, MHG and MECOLPRESS are some of the well-known brands in the world involved in the production of forging presses.