21-04-2012, 01:28 PM
die design and punch presses.
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INTRODUCTION
A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create. Products made with dies range from simple paper clips to complex pieces used in advanced technology. An important cost cutting method of expediting tooling program evolved over years is precision of casting, die and mold components. Substaintial reduction in time, labour and material can be realized when compare to other methods of manufacturing. Many parts may be rapidly produced to almost excat shape and size, thus minimizing the need for machining.
In addition to cost saving that can be realized , cast tool and dies have physical properties which are uniform in all directions. Such omni-directional properties permit the tools to withstand high stress in several direction in same time. These properties also reduce directional distortions during heat treatment.
High emphasis on mass production calls for dies which can perform multiple operations in lesser time. Dies generally used in mass production are compound dies, combination dies and progressive dies.
Commercial Practice for producing washer by die
A die press comprises a bolster and a ram which are held in rigid alignment to each other, plus some way to apply pressure to the ram. The bolster provides the means to secure the die so that a punch attached to the ram is correctly aligned with it. Material is placed between the two and pressure applied to the punch via the ram forces the work material to extrude into the die in the shape of the punch. Depending on the clearance between the punch and die and the material itself, the work will either draw into the die, or shear in the shape of the punch.
NEED FOR DESINGNING OF PROGRESSIVE DIE
Die design, a large division of tool engineering is a complex, fascinating subject. It is one of the most exciting of all areas of the general field of tool designing. The die designer originates designs of the die employed to stamp & form parts from sheet metal, assemble parts together & perform variety of other operations,
Today `s industrial era demands something that is simple and economical .in this regard the progressive die will play a very important role. A progressive die is a die which can perform a number of operations at each press of ram and hence will be the brightest future in the mass production area.
METHOD OF DESIGNING A PROGRESSIVE DIE
• The first step of designing a progressive die is to study the piece pat drawing carefully and to plan the operations to be carried out in different stations.
• The drawing of the stock strip is laid out as it will appear after it as gone through all stations, till a finished piece part is removed from it.
• It should be dimensioned and should carry all information’s necessary to start with the tool design like the feed direction, the amount by which the strip advances after each stroke of the press.
• The blank must be positioned in the strip so that a maximum area of the strip is utilized for the production of the stepping.
• The existence of numerous die stations having many punches tends to weaken the over all die. Than one or more idle stations, where now operations or performed should be included. The addition of an idle station is also called for when the punches from two active stations are too close to each other.
ADVANTAGES AND DISADVANTAGES OF PROGRESSIVE DIE
Advantages:
• If the pierced holes are too near to the outer edge of the piece part, the blanking punch of a compound die which accommodates the piercing dies will be come very weak.
• The posses a very big disadvantage of punch breakage either during manufacturing or during the course of the die life. For such piece parts the best solution is always a progressive die.
• Compound dies generally uses more than one press along with secondary press. Where as progressive die needs only one press even for to work stations.
• Progressive dies increases the annual production to a high volume(thus high scale production only through progressive die)
Disadvantages:
• Parts produced from compound die are very accurate and identical as all operations are carried out in a single station. this is made possible because the accuracy the part does not
• Depend on the accuracy of the advance of the strip or the accuracy of the layout of the stations as in the progressive die.
• Scrape stocks from other dies can be economically employed to produce piece part in a compound die whereas progressive die always need stock strip sheared to size.
• In a compound die burrs resulting from piercing and blanking are on the same side of the piece part. Piece parts produced by a progressive die have the burrs on the opposite sides.
• Die cost incurred in manufacturing a compound die is lesser then that of a progressive die made for the same component because of its smaller size and easier manufacturing methods warranted.
Thus we need to design a progressive die for better scale of production and effective use