Difference between capstan and turret lathe

Capstan and Turret lathes are the advancements of the Engine lathes and centre lathes in which the tailstock is replaced by a hexagonal turret tool head with 6 different tools in the turret where the turret tool is rotated according to process requirements in each operation. The capstan and turret lathe although appear to be identical in the first sight but a lot of differences in construction, operation, and use. In this article, you can check it out some difference between these two lathe machines. 

Capstan lathe :

  • Lightweight machine.
  • These are usually horizontal lathe. 
  • Turret head is mounted on a slide called ram which is mounted on the saddle.
  • Suitable for bar work.
  • The saddle is locked at a particular point and the ram is moved to provide feed to the tool.
  • Only a limited amount of feed and depth of cut are provided for machining.
  • The cross slide is mounted on a carriage which rests on bed ways between the headstock and the ram.
  • The turret tool head is indexed automatically.
  • Feed stop screws are used to control the distance of tool movement which is at the rear side of the turret.
  • No such facility to moving turret at right angles.
  • Feed rod gives for longitudinal feed.
  • Used for mass production of small size equal part.
  • It has hand-operated collet chucks.
  • Heavy cuts on workpiece can't be given because of non-rigid construction. 

Turret lathe :

  • Heavyweight machine.
  • Turret tool head is directly fitted on the saddle and both of them appear like one unit.
  • Suitable for heavier chucking work.
  • The saddle is moved to provide feed to the tool.
  • They are heavy and durable.
  • More feed and depth of cut are provided for machining.
  • Some turret type lathes are equipped with side hung type carriage.
  • To index the turret tool head, a clamping lever is released and the turret is rotated manually.
  • Limit dogs are used to control the distance of tool movement.
  • Some turret lathes have the facility of moving the turret at right angles to the lathe axis.
  • Feed rod does not give for longitudinal feed.
  • Used for mass production of large size equal part.
  • It is accommodated with power chucks.
  • Heavy cuts on a workpiece can be given because of the rigid construction of a machine. 
  • These are available in the horizontal and vertical lathe. 

Press forging advantages and disadvantages

Press forging defined as the process of shaping a metal that is placed between two dies by applying mechanical or hydraulic pressure. so now let us understand the key pros and cons of press forging to understand more about it. 

Advantages of press forging :  

  • It deforms the workpiece completely. 
  • The compression rate of the workpiece can be controlled automatically. 
  • More economical for high volume productions. 
  • Any size and shape can be created. 
  • Requires less draft and produces lesser scrap so better dimensional accuracy. 
  • Greater accuracy in terms of tolerance within 0.01 to 0.02 inch. 
  • This operation is completed in a single squeezing so save the time. 
  • The plastic deformation goes deep into the center of the workpiece provides uniform deformation. 
  • The capacity of presses ranging from 500 to 9000 tons and the number of working strokes per minute can be high as 40 or even 50. 
  • It is suitable for mass production of nuts, bolts, rivets, screws, brake levers, valves.
Disadvantages of press forging : 
  • The initial cost is higher because the cost of the crank press is always higher than of an equivalent hammer. 
  • The difficulty of descaling the blank. 
  • It is economical when the equipment is efficiently utilized. 

Drop forging advantages and disadvantages

Drop forging is a process that using the die with high strength, a metal blank on forging press will be plastic-deformed, then we will obtain the required shape, size, and internal quality. Now let us discuss the pros and cons of drop forging to understand more about it. 

Advantages of drop forging : 
  • The production efficiency is higher. 
  • Complex shaped metal parts can be forged with this process, and the distribution of metal flow line is more reasonable. 
  • Improve the serving life of parts. 
  • Achieve better surface quality, and smaller machining allowance and the size of this process is accurate. 
  • Reduce machining work so save metal. 
  • It will reduce the cost of spare parts. 
  • The production operation is easy, so force or work is low. 
  • Improved microstructure. 
  • Finer grain size. 
  • Continuous grain flow. 
Disadvantages of drop forging : 
  • For short runs, this process is not very economical due to the high cost of die production.
  • Drop forging presents a dangerous working environment.

Difference between drop forging and press forging

Drop forging is when half of the die is dropped from a height onto the other half of the die, that will contain the hot metal workpiece to be formed and is more suitable for mass production. Press forging is instead of dropping half the die onto the other half the two halves are put together and pushed together under a large pressure to forming the object. 

Main difference : 

The difference is that drop forming leaves the center of the metal not so hard as the outside, but the press forming gives more uniform hardness for larger components. We could also differ forgings from its temperature, such forgings are named cold forging, warm forging, and hot forging. 

Difference :

  • The metal is shaped by means of a series of blows in drop forging while in press forging, the metal is shaped by means of a single, continuous stroke. 
  • The pressure applied is impacted, and in multi-stroke in drop forging, while the pressure applied is slow, steady and continuous in a single squeezing action in case of press forging. 
  • The deformation of metal is more at the surface layers than that of a center of the metal in case of drop forging, while it is uniform, simultaneous and deep penetrating at the center of the metal part. 
  • The jarred impressions are obtained in drop forging while impressions obtained in press forging are clean. 
  • The draft angles used are more in case of drop forging than that of press forging. 
  • Tong holds are normally required for manipulating dies in drop forging whereas in press forging tong holds are not required. 
  • The initial cost of drop forging is less as compared to press forging. 
  • The drop forging is suitable for almost all types of medium size forgings and press forging is recommended when machine utilization is quite high. 
  • The drop forging is a relatively slow process and has moderate production rates where press forging is a faster and higher production rate. 

Closed die forging application

Due to its high precision, closed die forging is preferred for small critical parts with consideration for safety. It is mainly used to produce small products like forged fittings, forged lifting and rigging hardware, forged automotive parts, etc. Now let we check the applications of closed die forging one by one below. 

Applications of closed die forging : 

  • According to the advantages of closed die forging, it has become the main metal forming process in modern manufacturing. It can be used for lots of metal components for cars, aeroplane, heavy trucks, shipbuilding, etc. 
  • The motivation that encourages many manufacturers to change the production process into closed die forging because it offers better surface finish with good quality, also the price is competitive so we could use this process in below application. 
Automotive application: Connecting rod, control arm, rock arm, axle shafts, axle beams, axle arms, steering yokes. 

Construction machinery applications: Bucket teeth, excavator. 

Agriculture applications: Shafts, spike harrow teeth, tie rod ends, gears. 

Oilfield applications: Elbow, hammer union nuts, cross, tee. 

Mining applications: Ground foundation and auger bits. 

Open die forging application

The differences between open and closed forging process make the end product look different and the major difference in application lies in the size of the product. Now let we understand and applications of open die forging.

Applications : 
  • It is the rough process of forging as it does not involve a fixed die size so this process does not use in precision. 
  • This process is best suited for forging bigger and heavier metal parts like forged shafts and rollers that find their application in railways because not required much surface finishing machining and create ultra-finished products. 
  • The advantages of this process range from better microstructure as the grain size are fine and have a continuous flow this the products in forging method include forged long shafts, forged rollers, and forged cylinders which mostly used for the application of many industries. 

Closed die forging advantages and disadvantages

When it comes to shaping a metal part, forging is the one used to shape the metal in a controlled manner using plastic deformation while there are different types of forging methods, one of the most common is closed die forging. This technique involves the pressing of hot round bars and their net shaping in closed dies. This process provides the desired shapes and is being wide applications for all industries, including engineering, construction, aerospace, power generation, defence, oil, and gas, etc. Let us now have a look at some of its major pros and cons to understand more about it.

Advantages of closed die forging : 

  • The forging process of closed die creates net shapes or near-net shapes. 
  • This process offers superior mechanical properties, higher product strength, and toughness.
  • Closed tolerance can be achieved through this process close to + / - 0.3 mm. 
  • It is suitable for steel brass and aluminium as well as some other alloys too so no material limitation. 
  • Better surface finish so saves the cost of machining. 
  • It is a cleaner and greener process as compared to casting so it is environmentally protected. 
  • Good reproducibility and high production rate. 

Disadvantages of closed die forging : 

  • This process involves higher tolling cost that makes it expensive. However, it can be suitable for mass production. 
  • Closed die forging may not be helpful for complex and large products.
Thus, this process is overall a cost-effective process when used for mass production and to gain higher product strength and toughness.

Advantages and disadvantages of open die forging

Open die forging is only suitable for simple shapes for its less dimensional accuracy, and high skill operators are required, the dies of this process are simple and less expensive which is the simplest process of all the forging process. In this article, you can check it out the pros and cons of open die forging to understand more about it. 

Advantages of open die forging : 

  • Better fatigue resistance and improved microstructure.
  • A continuous flow of grain and finer size of the grain.
  • Increased strength and prolonged part life.
  • Less material waste.
  • Reduced chance of voids.
  • Cost savings are valuable.

Disadvantages of open die forging : 

  • Close tolerance and higher precision parts cannot be formed.
  • To achieve the desired dimensions, machining is often required.

Difference between open die forging and closed die forging

The method of deforming a piece of metal between various dies that does not fully enclose the material is open die forging. The metal is modified by a sequence of movements as the dies "hammer" or "stamp" material until the required shape is achieved. 

Let us have a deep insight into the difference between open and closed die forging.

Difference between open and closed die forging : 

  • Open die forging is also known as free forging, meaning metal billets compressed under the external compressive force and deformed to desired dimensions in a freeway without forging dies while closed die forging is also known as impression die forging, is a process that heated by medium frequency induction heating furnace to high temperature and forced between upper and lower dies to get expected shapes like the drawing.
  • Both forging processes are also different in the side of their processes. Moulding dies are firstly made for closed die forging, and then forged steel bars are placed on the dies and drop forged to desired shapes. In open-die forging, it involves enormous compressive force imposed by the continuous strike of a hammer to make the metal billets deformed. 
  • Open die forging will require further rough machining due to its free forging and imprecise dimensions may be reached by second precision machining while closed die forging is more common in small parts for its high precision used to make forged fittings, forged flange and forged automotive parts. 
  • The open die metal forged parts are more suitable for larger parts in a number of tons whereas for small parts closed die forging is preferred as high precision is obtained in closed die forging. 

Difference between hot rolling and cold rolling

One of the important processes in metal manufacturing is rolling, but there are two methods available for rolling one is hot rolling and another is cold rolling. It is a common misconception that these processes relate to a specification of metal or grade of metal instead, they refer to how metal is processed at the mill. Now in this article, you can check it out the hot rolling vs cold rolling and some key difference between them. 

What is hot rolling?

Hot rolling is the process in which rolling the steel at a high temperature which is higher than the recrystallization temperature of steel.

What is cold rolling?

Cold rolling is a similar process to hot rolling, the steel is subjected to further cooling process at room temperature in cold reduction mills after being rolled. 

Main difference :

The main difference between these two processes is the temperature in which they are performed. Hot rolling is under high temperature also called as above recrystallization and the cold rolling is under room temperature also called as below recrystallization. 

Some more difference between hot and cold rolling process is explaining below. 
  • Hot rolling is the father of cold rolling which follows hot rolling. 
  • Hot-rolled metal does not show work hardening effect whereas it shows in cold roller metal. 
  • Co-efficient of friction between two rolls is higher in hot rolling it may even cause shearing of metal in contact with rolls and co-efficient of friction us lower in cold rolling. 
  • Experiment measurement is difficult in hot rolling while it can be carried out easily in cold rolling.
  • Heavy reduction area of a workpiece can be obtained in hot rolling whereas heavy reduction is not possible in cold rolling. 
  • The radius of rolls is generally higher for hot rolling and it relatively smaller in cold rolling. 
  • The very thin section is not obtained by a hot rolling process vice versa in the cold rolling process. 
  • Hot rolling does not allow partial buckling of cross-section while cold rolling is allowed to have local buckling. 
  • Mechanical properties are improved by beaking cast structure thus toughness increases in hot rolling and cold rolling increases the tensile strength and yield strength. 
  • The hot-rolled surface is not good it has metal oxide on it while the cold-rolled surface is smooth and oxide-free.