die design simple & progressive- week 10

Chapter 3Design of Simple and Progressive Dies

(week-10)

DEPARTMENT OF PRODUCTION ENGINNERING

PREPARED

BY- KELIFA SEID

11/24/2014 1KELIFA SEID

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

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.


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

• Such an arrangement gives us a comfortable distance between the stations forplacing punches and dies without any interference. It also provides for thestrip 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

FIGURE b --- Strip layout for a round washer, 30° inclination.11/24/2014 KELIFA SEID 6

Sample examples Support bracket,first strip layout.


Support bracket, second strip layout.


Support bracket, third strip layout.


Support bracket, fourth strip layout.


• 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 usefor calculation of the feed, is


Design or/selection of finger stops, automatic stops,pilots, stripper plate, punch, punch plate, pillar dieset

• 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

• Finger stop A is in position to stop the strip for the piercing operation.


• Finger stop in pulled position allows strip to be moved to the automatic stop.


• Recommended front spacer thicknesses are tabulated which allows aminimum of 1/16 inch clearance between the top of the strip and the underside of the stripper plate to provide for possible curvature in the strip.


• 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 .


• 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.


• All necessary dimensions are given for making automatic stops rangingfrom number one to six . From this table the designer can applydimensions, or the automatic stop can be specified by number.


Proportions for six standard automatic

stops


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 theyserve afterward as guides and locating arrangements for the strip on its waythrough the die.

• Pilot holes may be extra openings placed beside the parts, or they may beholes included within the part itself and serving at the same time as thestrip guidance.

• The location of pilot holes should always be at the far opposite sides of thestrip, with the greatest possible gap in between. This is to secure the bestfixation and positioning of the strip, once the pilots engage in theirrespective openings.

• Pilot holes may not be necessary where producing complete parts from thestrip in a single station of the die, as with production of washers.


• The frequently used shoulder pilot A is retained in blanking punch B bysocket pilot nut C. pilot holes are pierced at the first station. The strip isthen located by pilots at the second and succeeding stations.

• The automatic stop is positioned so that the strip is stopped with apreviously pierced hole 0.010 inch past its final location. The pilot movesthe strip back this amount to bring it into correct register.

• This over travel prevents possible cramping of the strip between pilot andautomatic stop as shown below ,the pilot is just contacting one side of thehole in the strip preparatory to bringing it back to true position.


• 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.


Punch plates…


• Punch plates hold and support piercing, notching and cut off punches. They areusually made of machine steel, but can be made of tool steel, and ranges fromsmall 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.

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.


• There are many variations of compound dies, all of them having one feature incommon ,with each stroke of the press, a minimum of one operation is beingperformed.

• Combination dies combine at least two operations during each stroke of thepress. Otherwise these two types of dies are so similar in their constructionand application that their names are often considered interchangeable.

• Some shops, however, are making a distinction between the two types callingany cutting and forming die a combination die, while the compound die isconsidered only a cutting die.


• 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.


FIGURE – Compound/combination die, producing a pierced cup.11/24/2014 KELIFA SEID 33

FIGURE 3-1 Compound die.


die design simple & progressive- week 10

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