Method of operation According to this criterion, the dies may be classified as : Single-operation dies or simple dies, compound dies, combination dies, progressive dies, transfer dies,and multiple dies.
Simple dies Simple dies or single action dies perform single operation for each stroke of the press slide. The operation may be any of operations listed under cutting or forming dies.
Compound dies. In these dies, two or more operations may be performed at one station. Such dies are considered as cutting tools since. Only cutting operations are carried out. Fig.215 sows a simple compound dies in which a washer is made by one stroke of the press. The washer is produced by simultaneous blanking and piercing operation. Compound dies are more accurate and economical in mass production as compered to single operation dies.
Combination dies. In this die also, more than one operations may be performed at one station. It differs from compound die in that in this die, a cutting operation is combined with a bending or drawing operation. Fig 2.16 explains the working of a combination
Tionblank and draw die. The die ring which is mounted on the die-shoe, is counterbored at the bottom to allow the flange of a pad to travel up and down. This pad is held flush with the face of the die by a spring. A drawing punch of required shape is fastened to the die shoe. The blanking punch is secured to the punch holder. A spring stripper strips the skeleton from the blanking punch. A knockout extending through the centre opening and through the punch stem ejects the part on the upstroke as it comes in contact with the knockout bar on the press. In operation, the blank holding ring descends as the part is blanked, then the drawing punch contacts and forces the blank into the drawing die which is made in the blanking punch.
Progressive dies. A progressive or follow on die has a series of stations. At each station, an operation is performed on a workpiece during a stroke of the press. Between stroke, the piece
In the metal strip is transferred to the nextstaion. A finished workpiece is made at each stroke of the press. A progressive die is shown in Fig 2.17. While the piercing punch cuts a hole in the stock , the blanking punch blanks out a portion of the metal in which a hole had been piered at a previonstation.Thus after the first stocke, when only a hole will be punched, each stroke of the press produces a finished washer
Thransfer dies. Unlike the progressive dies where the stock is fed progressively from one station to another dies the already cut blanks are fed mechanically from station to station.
Multiple dies. Multiple or gang dies produce two or more workpieces at each stroke of the press. A gang or number of simple dies and punches are ganged together to produce two or more parts at each stroke of the press.
2 7. Principle of metal cutting
The cutting of sheet metal in press work is a shearing process. The cutting action is explained with the help of Fig. 2.18. The punch is of the same shape as of the die opening except that it is smaller on each side by an amount known as"clearance'’. As the punch touches downward, it pushes the material into the die opening the material and travels die opening. The material is subjected to both tensile and compressive stresses as shown in Fig. 218(a). Stresses will be highest at the edges of punch and die and the material will start cracking there. The various steps in the rupture or fracture of the material can be
A Text Book of Production Engineering
written as stressing the materiel beyond its elastic limit, plastie reduction in area, fracturing starts m the reduced arc complete. If the clearance between punch and die is deformation, and becomes correct, the cracks starting from the punch and die edges will meet and the rupture is complete as shown in Fig. 218(b). If th clearance edg is too large or too small, the cracks do not meet and a results due to the material being dragged and torn through the die
This is explained in Fig. 2.19. Fig. 2.19 Improper clearance
Strip Layout. In the design of a blanking die set, the first step is to prepare blanking layout, that is, to layout the position of the workpieces in the strip and their orientation with respect to one another. While doing so, the major consideration is the economy of material. The direction of material grain may be another ration if the blanks have to undergo subsequent operationsuchas, bending or drawing. In Fig 2 20, the different ways ofarranging to blank the given workpiece are shown The ways ofement at Fig 2 20 (a) can be worked at . For can be worked at single row.Singlepuuch. Forarrangement Fig. 220(b), the strip would either have To be fed twice, once for each row, or double blanking will have to be employed. Fig 2.20 (c) shows asingle row, double-paee strip. Here the strip will have to be passed through the dies once, turned over, and passed through dies a second time. The strip layout with maximum material saving may not be the best strip layout, as the die construction may become more complex which would offset the savings due to material economy unless a large number of parts are to be produced
Another important consideration in strip layout is the distance between the nearest points of blanks and between blanks and the edges of the strip. To prevent the scrap from twisting and wedging between the punch and the die, this distance must increase with material thickness. A general rule of thumb is to keep this distance equal to from 1 to 1.5 times the material terms connected with strip layout are shown in Fig. 2.21.
Clearance
As is clear in the previous article, the die opening must be metal. This larger than the punch to permit a clean fracture of the sufficiently between the mating members difference in dimensions between the mating members of a die set is called ‘clearance'. This clearance is applied in the following manner
(i) when the hole has to be held to size, t.e., the hole in the sheet metal is to be accurate Punching operation), and slug is to be discarded, the punch is made to the size of hole and the die opening size is obtained by addin clearance to the punch size, Fig. 222(a)
(ii) In blanking where the slug or blank is the operation desired part and has to be held to size, the die opening size equals the blank size and the punch size is obtained by ting the clearance from the di"ize, Fig. 2.22(b).
In Fig 2.22 c, is the amount of clearance per side of he die opening the clearance is a function of the kind, thickness and
Section through Blanking Die
temper of the work material, harder materials requiring larger clearance than soft materials, the exception being Aluminium. The usual clearances side of the die. forvarioms metals. are given below in terms of the stock thickness, t
For brass and soft steel, c= 5% of t
For medium steel o c=6% of t
For hard steel, c= 7% of t
For aluminium c= 10% of
The total clearance between punch and die size will be twice these figures. These clearances are for blanking and piercing operation
The reason behind the appliontion of clearance in the manner us given above, is explained below
The diameter of the blank or punched hole is determined by the burnished area. On the blank, the burnished area is produced by the walls of the die Therefore, the blank size will be equal to the size of die-opening (neglection a slight expansion of the blank due to elastic recovery after the cutting operation is completed). Slimilarly, in punching operation, the burnished area in the hole is produced by the punch, therefore, the size of the will be the produced by the punch, therefore, the size of the hole will be the
วิธีการดำเนินการตามเงื่อนไขนี้ การตายอาจแบ่งเป็น: เดียวดำเนินการตาย หรือตายง่าย ตายผสม รวมตาย ตายก้าวหน้า โอนย้ายตาย และตายหลาย ตายง่ายตายง่ายหรือตายการดำเนินการเดียวในจังหวะกดภาพนิ่ง การดำเนินการอาจมีการดำเนินงานอยู่ภายใต้การตัด หรือขึ้นรูปตาย ผสมตาย สอง การดำเนินอาจทำที่สถานีหนึ่งในเหล่านี้ตาย ตายดังกล่าวถือเป็นเครื่องมือตัดตั้งแต่ เฉพาะการดำเนินการตัดทำ Fig.215 sows ตายผสมอย่างที่ทำเครื่องซักผ้าตามจังหวะหนึ่งกด เครื่องซักผ้าที่ผลิต โดย blanking และเจาะดำเนินการพร้อมกัน ผสมตายจะยิ่งถูกต้อง และประหยัดในการผลิตโดยรวมเป็น compered การดำเนินการเดียวตายรวมกันตาย ในนี้ตาย ยัง การดำเนินการที่มากกว่าหนึ่งอาจทำงานที่สถานีหนึ่ง มันต่างจากตายผสมที่ในชีวิตนี้ พร้อมดำเนินการตัดกับการดัด หรือรูปวาด ฟิก 2.16 อธิบายการทำงานของชุดTionblank and draw die. The die ring which is mounted on the die-shoe, is counterbored at the bottom to allow the flange of a pad to travel up and down. This pad is held flush with the face of the die by a spring. A drawing punch of required shape is fastened to the die shoe. The blanking punch is secured to the punch holder. A spring stripper strips the skeleton from the blanking punch. A knockout extending through the centre opening and through the punch stem ejects the part on the upstroke as it comes in contact with the knockout bar on the press. In operation, the blank holding ring descends as the part is blanked, then the drawing punch contacts and forces the blank into the drawing die which is made in the blanking punch.Progressive dies. A progressive or follow on die has a series of stations. At each station, an operation is performed on a workpiece during a stroke of the press. Between stroke, the piece In the metal strip is transferred to the nextstaion. A finished workpiece is made at each stroke of the press. A progressive die is shown in Fig 2.17. While the piercing punch cuts a hole in the stock , the blanking punch blanks out a portion of the metal in which a hole had been piered at a previonstation.Thus after the first stocke, when only a hole will be punched, each stroke of the press produces a finished washerThransfer dies. Unlike the progressive dies where the stock is fed progressively from one station to another dies the already cut blanks are fed mechanically from station to station.Multiple dies. Multiple or gang dies produce two or more workpieces at each stroke of the press. A gang or number of simple dies and punches are ganged together to produce two or more parts at each stroke of the press.2 7. Principle of metal cutting The cutting of sheet metal in press work is a shearing process. The cutting action is explained with the help of Fig. 2.18. The punch is of the same shape as of the die opening except that it is smaller on each side by an amount known as"clearance'’. As the punch touches downward, it pushes the material into the die opening the material and travels die opening. The material is subjected to both tensile and compressive stresses as shown in Fig. 218(a). Stresses will be highest at the edges of punch and die and the material will start cracking there. The various steps in the rupture or fracture of the material can beA Text Book of Production Engineering written as stressing the materiel beyond its elastic limit, plastie reduction in area, fracturing starts m the reduced arc complete. If the clearance between punch and die is deformation, and becomes correct, the cracks starting from the punch and die edges will meet and the rupture is complete as shown in Fig. 218(b). If th clearance edg is too large or too small, the cracks do not meet and a results due to the material being dragged and torn through the dieThis is explained in Fig. 2.19. Fig. 2.19 Improper clearanceStrip Layout. In the design of a blanking die set, the first step is to prepare blanking layout, that is, to layout the position of the workpieces in the strip and their orientation with respect to one another. While doing so, the major consideration is the economy of material. The direction of material grain may be another ration if the blanks have to undergo subsequent operationsuchas, bending or drawing. In Fig 2 20, the different ways ofarranging to blank the given workpiece are shown The ways ofement at Fig 2 20 (a) can be worked at . For can be worked at single row.Singlepuuch. Forarrangement Fig. 220(b), the strip would either have To be fed twice, once for each row, or double blanking will have to be employed. Fig 2.20 (c) shows asingle row, double-paee strip. Here the strip will have to be passed through the dies once, turned over, and passed through dies a second time. The strip layout with maximum material saving may not be the best strip layout, as the die construction may become more complex which would offset the savings due to material economy unless a large number of parts are to be producedAnother important consideration in strip layout is the distance between the nearest points of blanks and between blanks and the edges of the strip. To prevent the scrap from twisting and wedging between the punch and the die, this distance must increase with material thickness. A general rule of thumb is to keep this distance equal to from 1 to 1.5 times the material terms connected with strip layout are shown in Fig. 2.21.Clearance As is clear in the previous article, the die opening must be metal. This larger than the punch to permit a clean fracture of the sufficiently between the mating members difference in dimensions between the mating members of a die set is called ‘clearance'. This clearance is applied in the following manner (i) when the hole has to be held to size, t.e., the hole in the sheet metal is to be accurate Punching operation), and slug is to be discarded, the punch is made to the size of hole and the die opening size is obtained by addin clearance to the punch size, Fig. 222(a) (ii) In blanking where the slug or blank is the operation desired part and has to be held to size, the die opening size equals the blank size and the punch size is obtained by ting the clearance from the di"ize, Fig. 2.22(b).In Fig 2.22 c, is the amount of clearance per side of he die opening the clearance is a function of the kind, thickness andSection through Blanking Dietemper of the work material, harder materials requiring larger clearance than soft materials, the exception being Aluminium. The usual clearances side of the die. forvarioms metals. are given below in terms of the stock thickness, t For brass and soft steel, c= 5% of t For medium steel o c=6% of tFor hard steel, c= 7% of t For aluminium c= 10% of The total clearance between punch and die size will be twice these figures. These clearances are for blanking and piercing operation The reason behind the appliontion of clearance in the manner us given above, is explained below
The diameter of the blank or punched hole is determined by the burnished area. On the blank, the burnished area is produced by the walls of the die Therefore, the blank size will be equal to the size of die-opening (neglection a slight expansion of the blank due to elastic recovery after the cutting operation is completed). Slimilarly, in punching operation, the burnished area in the hole is produced by the punch, therefore, the size of the will be the produced by the punch, therefore, the size of the hole will be the
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