1、21 世纪全国高校应用人才培养机电类规划教材 模具设计与制造专业英语 English for Die where Fland F2are the acting forces of the punch and die perpendicular to the blank respectively; F3and F4are the lateral pressures of the punch and die exerting on the blank respectively; F1, F2 are the frictions on the end surfaces of the punch an
2、d die acting on the blank respectively; F3, F4are the frictions on the lateral surfaces of the punch and die acting on the blank respectively. The directions of F1and F2 vary with the clearance between the punch and die. 1F 3F2F2 1 3M Fb 4F2F 4F1F3FtFig.1-3 Diagram of the blanking force 1-punch 2-bl
3、ank 3-die Analysis of the blanking forces shows that the lateral pressures F3and F4must be smaller than the perpendicular pressures F1and F2; and that the cracks occur and extend more easily in the area of small pressure. Therefore, the initial crack occurs on the side surface of the die in 8 模具设计与制
4、造专业英语 blanking. Observation on crack initiating and developing with scanning electronic microscope shows that when the depth of punch squeezing downward into the material reaches 20% of the blank thickness, the crack occurs on the side surface of the punch and die edges, and then the cracks at the t
5、op and bottom extend rapidly. When the two cracks meet, the blank is sheared and the process of fracture is ended. 1.2.3 Blanking Workpiece Quality The quality of the blanking workpiece mainly refers to the qualities of the cutting cross-section and workpiece surface, shape tolerance and dimensional
6、 accuracy. The cutting cross-section quality of the workpiece is an important factor to determine whether the blanking process is succeeded or not. As shown in Fig.1-4, the cutting cross-section can be divided into four regions: the smooth sheared zone, fracture zone, rollover zone and burr zone. Fr
7、acture zone Smooth sheared zone Burr zone Rollover zone Rollover zone Burr zone Smooth sheared zone Fracture zone Fig.1-4 Characteristic of the cutting cross-section of blanking workpieces When the punch edge cuts into the blank, the plastic deformation occurs due to extrusion between the material a
8、nd the side of the cutting edge, resulting in the forming of the smooth sheared zone. Due to the characteristic of extrusion, the surface of the smooth sheared zone is smooth and perpendicular, and is the region with highest accuracy and quality within the cutting cross-section of the blanking workp
9、iece. The thickness ratio of the smooth sheared zone to the cutting cross-section is about 1/21/3. The fracture zone is formed in the final stage of blanking, its the area where blank is cut off, and the fracture surface is formed with the cracks expanding continuously under tensile stress. The surf
10、ace of the fracture zone is rough and inclined, and is not perpendicular to the blank. The rollover zone is formed when the die presses into the blank. The material near cutting edge is embroiled and deformed. The better the plasticity of the material, the larger would be the Chapter 1 Stamping Form
11、ing and Die Design 9 rollover zone. The burr of the cutting cross-section is formed when micro-cracks occur during blanking. The formed burr is then elongated and remains on the workpiece. There are many factors affecting the quality of the cutting cross-section. The proportion of the thickness of t
12、he four zones (smooth sheared zone, fracture zone, rollover zone and burr zone) varies with blanking conditions, such as workpiece material, punch and die, equipment, etc. Fig.1-5 shows the main factors that affect the quality of the cutting cross-section of blanking workpiece. Fig.1-6 shows those f
13、actors affecting the dimensional accuracy of blanking workpiece. The research and analysis show that the clearance between the punch and die is the most important factor affecting the surface quality and the dimensional accuracy of the blanking workpiece. To increase the surface quality of the blank
14、ing workpiece, it is important to study the clearance influence mechanism, so as to find a method for calculating the optimal clearance between the punch and die. punch and die Quality of the cutting cross-section of blanding workpiece press machine clearance between the punch and die workpiece mate
15、rial properties state of the cutting edge surface state bland thickness accuracy rigidity Fig. 1-5 Factors affecting the quality of the cutting cross-section of blanking workpiece punch and die properties workpiece material press machine accuracy blank thickness clearance between the punch and die d
16、imension of the cutting edge error of the moving ditance surface state Dimensional accuracy of blanking workpiece rigidity Fig.1-6 Factors affecting the dimensional accuracy of blanking workpiece 10 模具设计与制造专业英语 1.2.4 Blanking and Punching Dies 1. Typical Structure of Blanking Die (1) Simple Die The
17、die that only one process is carried out in one press stroke is called simple die. Its structure is simple (see Fig.1-7), so it can be easily manufactured. It is applicable to small batch production. 111 73 2 4 695 8101213Fig.1-7 Simple die 1-stop pin 2-guide bushing 3-guide pin 4-bolt 5-dieshank 6-
18、pin 7-fixed plate 8-upper bolster 9-punch 10-stripper 11-stock guide 12-die 13-lower bolster Chapter 1 Stamping Forming and Die Design 11 (2) Progressive Die The die that several blanking processes are carried out at different positions of the die in one press stroke is called progressive die, as sh
19、own in Fig.1-8. In the operation, the locating pin 2 aims at the locating holes punched previously, and the punch moves downwards to punch by punch 4 and to blank by punch 1, thus the workpiece 8 is produced. When the punch returns, the stripper 6 scrapes the blank 7 from the punch 4, the blank 7 mo
20、ves forward one step and then the second blanking begins. Above steps are repeated continually. The step distance of the blank is controlled by a stop pin. 38452 9 671 Fig. 1-8 Progressive die for blanking and punching 1-blanking punch 2-locating pin 3-blanking die 4-punching punch 5-punching die 6-
21、stripper 7-blank 8-workpiece 9-waster (3) Compound Die The die that several processes are carried out at the same die position in one press stroke is called compound die, as shown in Fig.1-9. The main characteristic of the compound die is that the part 1 is both the punch and the die. The outside ci
22、rcle of the punch-die 1 is the cutting edge of the blanking punch, while the inside hole is a deep drawing die. When the slide moves downwards along with the punch-die 1, the blanking process is done first by the punch-die 1 and the blanking die 4, the blanked workpiece is pushed by deep drawing pun
23、ch 2, and then the deep drawing die moves downwards to carry out deep drawing operation. The ejector 5 and the 12 模具设计与制造专业英语 stripper 3 push the deep drawn workpiece 9 out of the die when the slide returns. The compound die is suitable for mass production and high accuracy blanking. 2 6 7 5 341 598
24、1011 Fig. 1-9 Compound die for blanking and deep drawing 1-punch die 2-deep drawing punch 3-press plate (stripper) 4-blanking die 5-ejector 6-strip blank 7-stop pin 8-blank 9-deep drawn workpiece 10-finished part 11-waste 2. Punch and Die (1) Punch There are three kinds of standard punches with circ
25、ular form in the National Standard, as shown in Fig.1-10. Which kind of punch should be selected is determined by the dimension d in the working portion. A type circular punch is adopted for d = 1.130.2 mm, B type for d = 3.030.2 mm, quick-change circular punch for d = 529 mm. To fix the circular pu
26、nch on the punch plate, the hole-base transition fit h6 is adopted for A and B types of circular punches, and the hole-base clearance fit h6 for the quick-change circular punch. The length L of punch should be determined by the die structure. When using the fixed stripper and stock guide (see Fig.1-
27、11), the length L of punch is: L = H1+ H2+ H3+ H where, H1is the thickness of the fastening plate in mm; H2is the thickness of the stripper in mm; H3is the thickness of the stock guide in mm; H is the additional length mainly determined by the depth of punch entering into the die (0.51 mm), the tota
28、l wearing repairing amount (1015 mm) and the safe distance between the stripper and punch plate when the die is in the shut state (1520 mm). Chapter 1 Stamping Forming and Die Design 13 (b) (c)(a) H3d L dd(a) A type circular punch (b) B type circular punch (c) quick-change circular punchH2H1Fig.1-10
29、 Standard punches Fig.1-11 Determination the punch length The non-standard punches and their fastening patterns are shown in Fig.1-12. When the distance between punches in the same die is very small, a riveting structure can be used for the circular punch (Fig.1-12(a); a jacket structure is usually
30、used for the small hole punching (Fig.1-12(b); the quick-change type is used for the small punch which is vulnerable to damage during blanking (Fig.1-12(c); for the non-circular punch, if its size is a bit large, it can be fastened to the die bolster directly by bolts, pins or bolts and location gro
31、ove instead of the fastening plate (Fig.1-12(d); if the working portion of punch is non-circular, a circular step structure is used in the fastening portion, and a stop gauge should be added (Fig.1-12(e). (b) (e) (d) (c)(a) Fig.1-12 Non-standard punches and their patterns 14 模具设计与制造专业英语 For the smal
32、l punch, it can also be fastened to the punch plate by low-melting alloy, inorganic or epoxy resin adhesive, as shown in Fig.1-13. H(1/31/4)H0.30.5 35 0.10.3 or 11.25 (a) by epoxy resin (b) by low melting point alloy (c) by inorganic adhesive Fig.1-13 Other methods to fix the punch (2) Die The patte
33、rns of the die cutting edge are illustrated in Fig.1-14. Fig.1-14(a) and Fig.1-14(b) are the dies with the straight wall cutting edge. The strength of the cutting edge is high, the dimension of its working portion keeps unchanged after mending and its manufacture is convenient. It is suitable for st
34、amping the workpieces with complex shape or high tolerance demand. But the waste or the workpiece in such circumstances is prone to be accumulated inside the hole of the cutting edge, so increasing the expanding force, the ejecting force and the wearing of hole wall. The worn cutting edge forms the
35、shape of inverse cone, which may induce the workpiece jumping from the opening-mouth of the hole to the surface of the die, and cause difficulty in operation. The Fig.1-14(a) type cutting edge of die is suitable for the non-circular workpiece, and Fig.1-14(b) type is suitable for the circular workpi
36、ece, the die which the workpiece or waste needs to be ejected, or the compound blanking die. Fig.1-14(c) and Fig.1-14(d) show the die with conical shape cutting edge. The workpiece or waste is easy to fall down from the die hole. The workpiece or waste wouldnt accumulate easily inside the hole of th
37、e cutting edge. The friction and expanding force exerting on the hole wall are small, therefore the wearing of the die as well as the mending amount of the die per operation are small. But the strength of cutting edge is a bit lower. The dimension of cutting edge increases after mending, but in gene
38、ral its influence on the workpiece dimension and the die life is weak. The dies with conical shape cutting edges are suitable for stamping thin workpieces with simple shape and low tolerance demand. Chapter 1 Stamping Forming and Die Design 15 0.51 Hh (a) (b) (c) (d) 0.51 h H HH h Fig. 1-14 Shapes o
39、f the die cutting edge 1.2.5 Blanking Tools Depending on the type of guidance for the shearing elements with respect to one another, the tools are divided into free, plate-guided, and pillar-guided blanking tooling. The structure of a free blanking tool is similar to the one shown in Fig.1-15. The s
40、hearing elements of the tooling are not guided with respect to one another; the guidance of the tooling is generally controlled by the press ram guides. For a good-quality press and its ram guides, the tools can be expected to be well guided under load. Spigot Punch plateStripperPunchDieBaseplateFig
41、.1-15 Free blanking tool setup The free blanking tool is the cheapest type of blanking tooling based on the simplicity of design. It is therefore used for smaller batch sizes. It is difficult to adjust the clearance all around uniformly at the time of initial setup of the tooling. This can lead to l
42、arger wear, especially for 16 模具设计与制造专业英语 small thickness as s1 mm, when the clearance can be as small as 0.01 mm. In the case of a plate-guided tool setup (Fig.1-16) the blanking punch is guided by the guide plate. In setting up the tooling a positional error can thus be avoided. The effects of poo
43、r guidance of the press guides due to bearing clearances and the angular deflection of C-frame presses are reduced by guiding the punch. Another advantage of punch guidance is the resistance of long punches to buckling. The guide plate is also used as a stripper. The use of a blanking element as a g
44、uiding element may pose some disadvantages. If proper measures are not taken, the material particles sticking to the punch or to the punch shoulder will cause a faster wear of the guide plate. Also, the manufacture of large accurate guidance holes for large complicated tooling is difficult and expen
45、sive. In the case of pillar-guided blanking tooling (Fig.1-17) the functions of guidance and shearing are separated from each other. The pillar guides make this tooling accurate, with the corresponding design of the other elements reducing the tool wear. The errors in bearing clearances of the press
46、 need not be taken care of during setting up because of the excellent accuracy of guidance by the pillar die set. Setting the tooling is simple and less time-consuming. The pillar-guided tooling, like the plate-guided tooling, can contribute to the reduction of defects due to bearing clearance and a
47、ngular deflection of the press on load. Basically the pillar guides are to be viewed as tools to help in setting up and manufacturing accurate tools. Normally used pillar guides are not stiff enough to take the strong side thrusts caused by noncentral loading on the tools and the tilting movement in
48、 G-type presses without allowing large displacements. Hence the pillar guides are not substitutes for inaccurate press guides and less rigid presses. SpigotGuide plate Punch plate PunchBaseplate DiePillar guide Stripper Punch Upper part Lower part Die Fig.1-16 Plate-guided blanking tool setup Fig.1-
49、17 Pillar-guided blanking tool setup Chapter 1 Stamping Forming and Die Design 17 There are different types of pillar guides. Guidance can be accomplished with either bush- ings or ball bearings (Fig.1-18). Guides with ball bearings are very rigid under load. They have little friction, and are hence used in fast-stroking presses or in cases where sufficient lubrication is not possible. Guidance bush
