ward. If you want to show the firstform only, bends 2 and 3 can beturned off or suppressed. If youwant to show forms 1 and 2, bend 3would be the only one suppressed.For every line added to the familytable, an iteration of the part is creat-ed (Fig. 3); these will become usefulwhen creating the strip.

At the bottom of the family table,there is a row labeled “first formclosed”; this is the part drawn in the“tool closed” condition, completewith radius reduction to allow forspringback after forming. The insidebend radius (IBR) has been changedfrom 0.020 in. to 0.015 in. and theangle has increased accordingly.

By compiling this table, it be-

comes a very powerful tool. Howev-er, care must be taken to identifyeach bend. Remember that whenconstructing the table, refer to thedrawing of the finished part with thefeatures labeled (as in Fig. 1), as thiswill be of help.

Stage 3—Constructing the StripLayout, in Two Parts

With the flat-blank length and thematerial thickness determined, wenow can model a strip. This consistsof a rectangular part with length,width and thickness. We then inserta copy of the flat blank into the stripin order to make a multiple pattern,as shown in Fig. 4. The designer can

Various Stages of Design

Stage 1—Drawing Up the Piece PartFig. 1 shows a side view of the

sample part we will be working withto design a die. To draw this, Iworked out the developed length ofthe part, drawing the blank with thecorrect material thickness and goingback and adding each bend. Foreach bend added, you should createan “unbend” and a “bend-back” condition. A “bend-back” row automaticallywill be added to the fami-ly table. Pro E shows thedeveloped length of eachbend, which can be cross-referenced with yourmanual calculation. It’s

important that youthink of “design in-

tent” and askyourself thesetwo questions:

How am Igoing to makethis part? (cut-ting, form se-quence, etc.)

What possible changesmay take place once the die is

built? (strip width, progression, etc.)Notice that each bend on the part

has three elements to define it: bendnumber, inside bend radius and thebend angle. These will become veryimportant in the next stage of thedesign process.

Stage 2—Constructing the Family Table

The part is now easy to manipu-late. Pro E allows a family table to beconstructed that consists of the partin different iterations (Fig. 2). Howthis works is reasonably straightfor-

When I first started designingprogressive dies in the mid-1980s, most of it was done on

the drawing board; the 2D CAD revo-lution was just beginning. Then,making the change to the 2D systemwas as easy as giving up the pencilfor a mouse and a digitizing board.

More recently, I was faced withthe challenge of tackling the solid-modeling world. Having streamlinedthe 2D design process, I was skepti-cal at first about making this change.Now I regularly use Pro Engineer(Pro E) solid-modeling software fordesigning dies. I have used Pro E todesign complex and simple dies, andin doing so have learned a lot abouthow the software handles several is-sues of importance to die designers.

The following article examinessome of the features of solid model-ing in designing a progressive die,from construction of the piece part todesigning the die around the stripand detailing. The information willbe of interest to anyone in thefield of progressive-die de-sign and may addresssome of your questions.

Tailoring Your Bend Table

The Pro E packagecomes with three bendtables, taken from the Ma-chinery Handbook. These willsuffice if you are not working toclose tolerances on the finished part.If you are working with a toleranceof ±0.002 in. on a “rolled-up” diame-ter, you may experience problemsdue to blank lengths being too longor too short. Consequently, the partwill not meet the customer partprint. For this reason, I recommendthat you construct a bend table tosuit your specific application. It’swell worth the time to develop atable that will accurately calculatethe developed blank length of apart.

Solid Modeling forProgressive-DieDesign

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Bend #245°

R 0.140

R 0.020

75°

Bend #1

R 0.125

Bend #3

30°

Fig. 1—This side view of the sample part illustrates the three critical designelements—bend number, inside bend radius and bend angle.

Bend1 Angle IBR Bend2 Angle IBR Bend3 Angle IBR

Bendback Bendback Bendback

Generic Y* 75 0.02 Y 45 0.14 Y 30 0.125

1st Form Y 75 0.02 N* 45 0.14 N 30 0.125

2nd Form Y 75 0.02 Y 45 0.14 N 30 0.125

Flat Blank N 75 0.02 N 45 0.14 N 30 0.125

1st Form Y 82 0.015 N 45 0.14 N 30 0.125(closed)

*Y=Yes=Part formed N=No=Suppressed or in unbent form

Fig. 2—Using Pro E solid-modeling software, a designer can construct this family tablecontaining the critical dimensional data for each iteration of the part in a progressive die.

Solid Modeling forProgressive-DieDesign by Col Shepherd

Production Engineer, ADC

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Progressive Die Design

modify this pattern to show the dif-ferent number of parts, or vary theprogression to suit his needs.

Observe the cut between theparts, created by the use of a datumcurve. The designer can use thiscurve later to create the die, stripperand retainer openings as well as thepunch.

Insert the part in its different iter-ations into the strip to create thecomplete strip layout. These partscan be removed and replaced byother iterations if the designer wantsto modify the layout, such as whenadding idles or preforms. Fig. 5shows the completed strip used fordesigning the die.

Stage 4—Constructing the DieAround the Strip

With the strip designed, construct-ing the die becomes relatively easy.The edges of the strip are used toconstruct the punch and die insertsfor the cutting stations and also theform punch and die blocks (Fig. 6).The benefit of this will become ap-parent when die modification be-comes necessary. For example, if anoperator tries the tool and discoversthat one of the angles has too muchspringback on it, the modification isstraightforward. Rather than go intothe form punch and die block de-tails, as the designer would do whenusing a 2D system, he can simplymodify the angle in the family tablein the strip drawing and update themodel (Fig. 2). In turn, this will drivethe change to the form punch anddie as they were created using theedges of the strip.

Construction of the die plates, dieset and other components takes get-ting used to and care should betaken when assembling them aroundthe strip. Creating a library of stan-dard components helps minimizedesign time. These parts can bepulled from the library and renamedto suit each new die number. As allmodels are dimension-driven, chang-ing a die block from a 1-by-6-by-12in. to 0.75-by-4-by 8 in. requires justa few mouse clicks and keyboard

Springback

1st form (tool closed)

Generic (fully formed)

1st form

2nd form

Flat blank

Fig. 3—For every row added to the family table of part dimensions (Fig. 2), Pro E generates a drawing illustrating the progression of the part through the die. This becomes very useful when the designer begins to create the strip.

Fig. 4—Once the designer has determined the flat-blank length and materi-al thickness, he’s ready to model the strip. Using Pro E, he inserts a copy ofthe flat blank into the strip and the software generates a multiple pattern,shown here, which easily can be modified to show the number of parts orvary the progression. The datum curve is used for creating the die, stripperand retainer openings as well as the punch.

Flat blank inserted into strip andcopied to create progression

Datum curve to create cut

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strokes, and, most importantly, nodrafting time.

Stage 5—Detailing the DieFig. 7 shows an exploded view of

the die; some components havebeen removed for clarity. It’s nowready for detailing. The typical dieassembly will consist of a series ofsolid models, used to create individ-ual details.

Evolving from a 2D-design pro-

gram to solid model-ing, a designer can’t help butsee huge differences. Each detailwill be brought into the drawingmode, enabling the designer to se-lect their orientation. Once he’splaced the first view of the detail, hecan add additional views by clickingin the approximate position—again,no drafting required.

The dimensions used for con-structing the details need to beswitched on or off, dependingupon which ones arerequired, using theshow/erase com-mand. Additionalnotes are addedmanually. Theprogram thenautomaticallycreates a bill of ma-terials (BOM) as itlogs each compo-nent. The compo-nents can be renum-bered or reordered atany time in the BOM.

The die is now com-plete and ready tohand off for manu-facture.

Solid Models Have High IQs

Having designedthe die, the de-signer will noticemany differ-ences between2D and solidmodeling, themain one beingthat the solidmodel containsintelligence—all

of the components in the design arereferenced from some other part ordatum. This can have a positive ornegative affect. For example, if thereis a die insert assembled to an open-ing in a die block which the design-

er moves, the die block will fol-low the opening. But, if he

deletes the die block,the insert has lost

its referencesand the modelwill fail. Thepart needs

new referencesand the new userinitially will haveproblems with this.

Part failure is to beaccepted, and fixing

these failures must be-come routine.

The built-in intelligenceof the solid model will helpwhen it comes to modify-

ing a die. For example,if a stamper wants tochange the position of a

hole on the partand if the tool hasbeen properly

constructed,the part modelshould be theonly detailthat needs tobe changed.The strip, fullyp a r ame t r i c ,will completelyupdate along

Fig. 5—The completed strip, shown here,is used for designing the die.

Fig. 6—The designer uses the edges of the strip to construct thepunch and die inserts for the cuttingstations, and the form punch and die blocks.

Punch and dieprofiles are created usingthe edges of the previously constructed strip

Fig. 7—Pro E generates an explodedview of the die, now ready for detailing.

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the die components. With a 2Dsetup, the designer may forget tomodify one of the components.

With some complex dies, a de-signer may struggle when trying toconceptualize the form sequence. Ithelps to sketch the form out first, be-fore attempting to develop the solidmodels, as would be done in 2D.There are three different ways to dothis:

1) Use the sketcher mode withinPro E (somewhat limited in capability);

2) Use a 2D CAD system and im-port the geometry;

3) Use Pro Desktop.It also is worth considering file

size and processor speed, particular-ly if the die is complex and may con-tain 100 or more details. Part regen-eration and real-time motion of the

part, therefore, become an issue. Inmy experience, a 700-MHz PentiumIII PC with 512 MB of RAM workswell, but you can get by with a less-er system.

ConclusionAs with any new software pack-

age, it takes some time to becomefully competent in its use. The chal-lenges encountered can be vast, butif the designer takes care when con-structing the strip layout, he’ll likelyavoid many problems in the designstages. The design sequence is muchthe same as in a 2D system; howev-er, more time must be spent in thebeginning when constructing thepiece part and strip.

Overall, initial comparisons showthat solid-model design can takelonger to complete than 2D, al-though experience continually re-duces the design time. Also, the ad-

dition of third-party software writershas led to more of an emphasis onprogressive dies.

The transition between the use of2D systems and solid-modeling soft-ware for progressive-die design willcontinue, I expect, in order to pre-vent customers from facing longerlead times on their dies. Companiesneed to decide if they can absorbthe cost of retraining employees. Weall, however, are aware of the pres-sures of keeping abreast of customerrequirements and newer, more com-plex systems may be necessary,which in turn continue to challengethe designer. MF

Col Shepherd received his educa-tion in mechanical engineering inScotland, and has worked as a diedesigner for several years. ADC,Shakopee, MN, manufactures net-work equipment enabling high-speed Internet, data, video and voiceservices to homes and businesses.

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