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DIE DESIGN SIMPLE & PROGRESSIVE- Week 10

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ENGINEERING DESIGN

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DIE DESIGN SIMPLE & PROGRESSIVE- Week 10

  1. 1. Chapter 3 Design of Simple and Progressive Dies (week-10) DEPARTMENT OF PRODUCTION ENGINNERING PREPARED BY- KELIFA SEID 11/24/2014 1KELIFA SEID
  2. 2. Progressive die design • As already noted, the overall production requirements are the main factors in considering the size of a die and the number of finished products per stroke of the press. Let us consider a requirement for 1,000,000 washers per week, to be produced in a press capable of delivering 150 strokes per minute. • We may easily calculate that 150 hits per minute equals 9000 strokes per hour and 72,000 blows per workday. This means that if we run a strip through the die, producing one part with each blow, at the end of the week we will have 360,000 pieces. 11/24/2014 KELIFA SEID 2
  3. 3. Progressive die design… • For that reason we should increase the output of a press by producing more than one part at a single stroke. • To further shorten the length of production, we may want to build a die, producing four parts at a time, or a four-up die. • The output from such a tool will certainly satisfy the basic demand, and there will still be some time left. 11/24/2014 KELIFA SEID 3
  4. 4. Strip layout • With washers and other round blanks, the strip layout for a four-up die will look as shown below. • The punches are not mounted along a straight line, as their shanks and heads will never fit the distance in between, aside from the fact that such a crowded arrangement will considerably weaken the punch plate and the die shoe. • Instead, the tooling is spaced along an angular axis, the angle of inclination off the horizontal being either 19.5° or 30°, which is an industry standard.11/24/2014 KELIFA SEID 4
  5. 5. • Such an arrangement gives us a comfortable distance between the stations for placing punches and dies without any interference. It also provides for the strip engagement along its whole width at the same time. FIGURE a ---- Strip layout for a round washer, 19.5° inclination.11/24/2014 KELIFA SEID 5
  6. 6. FIGURE b --- Strip layout for a round washer, 30° inclination. 11/24/2014 KELIFA SEID 6
  7. 7. Sample examples Support bracket,first strip layout. 11/24/2014 KELIFA SEID 7
  8. 8. Support bracket, second strip layout. 11/24/2014 KELIFA SEID 8
  9. 9. Support bracket, third strip layout. 11/24/2014 KELIFA SEID 9
  10. 10. Support bracket, fourth strip layout. 11/24/2014 KELIFA SEID 10
  11. 11. • The 19.5° strip inclination is shown in Fig.a above. The formula to use for calculation of the feed, or progression is • The 30° strip inclination is shown in Fig .b above and the formula to use for calculation of the feed, is 11/24/2014 KELIFA SEID 11
  12. 12. Design or/selection of finger stops, automatic stops, pilots, stripper plate, punch, punch plate, pillar die set • Finger stops, or primary stops are used in progressive dies having two or more stations. They register the strip for performing operations prior to strip engagement by the automatic stop. • The number of finger stops used depend upon the number of stations in the die. For hand feeding it is always one less than the total number of stations but for automatic feeding only one finger stop is required. • Finger stops are made of cold rolled steel.11/24/2014 KELIFA SEID 12
  13. 13. • Finger stop A is in position to stop the strip for the piercing operation. 11/24/2014 KELIFA SEID 13
  14. 14. • Finger stop in pulled position allows strip to be moved to the automatic stop. 11/24/2014 KELIFA SEID 14
  15. 15. • Recommended front spacer thicknesses are tabulated which allows a minimum of 1/16 inch clearance between the top of the strip and the under side of the stripper plate to provide for possible curvature in the strip. 11/24/2014 KELIFA SEID 15
  16. 16. 11/24/2014 KELIFA SEID 16
  17. 17. 11/24/2014 KELIFA SEID 17
  18. 18. • Proportions of these fifteen finger stops enable ready selection for almost any die design and they assure positive stopping of the strip. • In both the forward and return positions the maximum thickness of the stops remain confined in the front spacer for strength. • For example ,if 3/32 inch thick strip is to be run, and the die hole contour is smooth and curved, it would fall in the second line: strip thickness A-1/16 to 1/8. and recommended front spacer is 1 ¼ inches ,and finger stop number 2 should be used . 11/24/2014 KELIFA SEID 18
  19. 19. • Automatic stops, or trigger stops used to register the strip at the final die station, they differ from finger stops in that they stops in that they stop the strip automatically ,the operator simply keeping the strip pushed against the stop in its travel through the die. 11/24/2014 KELIFA SEID 19
  20. 20. • All necessary dimensions are given for making automatic stops ranging from number one to six . From this table the designer can apply dimensions, or the automatic stop can be specified by number. 11/24/2014 KELIFA SEID 20
  21. 21. 11/24/2014 KELIFA SEID 21
  22. 22. Proportions for six standard automatic stops 11/24/2014 KELIFA SEID 22
  23. 23. 11/24/2014 KELIFA SEID 23
  24. 24. pilots • Every strip design should begin with an assessment of the location of pilot holes. These openings must be pierced at the first station, because they serve afterward as guides and locating arrangements for the strip on its way through the die. • Pilot holes may be extra openings placed beside the parts, or they may be holes included within the part itself and serving at the same time as the strip guidance. • The location of pilot holes should always be at the far opposite sides of the strip, with the greatest possible gap in between. This is to secure the best fixation and positioning of the strip, once the pilots engage in their respective openings. • Pilot holes may not be necessary where producing complete parts from the strip in a single station of the die, as with production of washers. 11/24/2014 KELIFA SEID 24
  25. 25. • The frequently used shoulder pilot A is retained in blanking punch B by socket pilot nut C. pilot holes are pierced at the first station. The strip is then located by pilots at the second and succeeding stations. • The automatic stop is positioned so that the strip is stopped with a previously pierced hole 0.010 inch past its final location. The pilot moves the strip back this amount to bring it into correct register. • This over travel prevents possible cramping of the strip between pilot and automatic stop as shown below ,the pilot is just contacting one side of the hole in the strip preparatory to bringing it back to true position. 11/24/2014 KELIFA SEID 25
  26. 26. • The shoulder pilot is used for holes A from ¼ to ¾ inch diameter ,and it has the following general proportions straight engagement length B should be from 1/3 to 2/3 of stock thickness ,engagement D is made three times pilot diameter C. clearance relief diameter E is usually 1/32 inch larger than body diameter C of the pilot. 11/24/2014 KELIFA SEID 26
  27. 27. 11/24/2014 KELIFA SEID 27
  28. 28. Punch plates… 11/24/2014 KELIFA SEID 28 • Punch plates hold and support piercing, notching and cut off punches. They are usually made of machine steel, but can be made of tool steel, and ranges from small simple blocks for holding single piercing punches to large precision- machined plates for holding hundreds of perforator • Important design considerations are:- 1. Adequate thickness for proper punch support. 2. Good dowelling practice to insure accurate location. 3. Sufficient screws to over come stripping load.
  29. 29. 11/24/2014 KELIFA SEID 29
  30. 30. Compound and Combination dies • Some compound dies are used just for trimming, others are specialized for blanking. • There may be compound dies with interchangeable inserts, which can produce several different products just by switching between them. • Several compound dies can be involved in production of a single part, which, during the manufacturing process, is transferred as in progression from one die to another. 11/24/2014 KELIFA SEID 30
  31. 31. • There are many variations of compound dies, all of them having one feature in common ,with each stroke of the press, a minimum of one operation is being performed. • Combination dies combine at least two operations during each stroke of the press. Otherwise these two types of dies are so similar in their construction and application that their names are often considered interchangeable. • Some shops, however, are making a distinction between the two types calling any cutting and forming die a combination die, while the compound die is considered only a cutting die. 11/24/2014 KELIFA SEID 31
  32. 32. • Compound dies produce very accurate parts, but their production rate is quite slow. • These dies consist of a single station where the part is most often blanked out and either formed, embossed, pierced, or otherwise adjusted in a single stroke of the press. • No progression of the strip is involved, as each stroke of the press produces a single, complete part. 11/24/2014 KELIFA SEID 32
  33. 33. FIGURE – Compound/combination die, producing a pierced cup. 11/24/2014 KELIFA SEID 33
  34. 34. FIGURE 3-1 Compound die. 11/24/2014 KELIFA SEID 34

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