step in designing any die is to make a careful study of the part print because the information given on it provides many clues for solving the design problem.
Figure 1.1 A typical part drawing.
Figure 1.2 A complete die drawing.
1.1.2 Die Drawing
Figure 1.2 is a complete die drawing ready to be printed in blueprint form. To the uninitiated it might appear to be just a confusing maze of lines. Actually, however, each line represents important information that the die makers must have to build the die successfully. In illustrations to follow, we will remove the individual parts from this assembly and see how they appear both as three- and as two-view drawings, and as pictorial views, to help you to visualize their shapes. As you study further, keep coming back to this illustration to see how each component fits in. When you are through, you should have a good idea of how the various parts go together to make up a complete die.
1.1.3 Blueprints
After a die has been designed on tracing paper using traditional techniques or AutoCAD, blueprints are produced for use in the die shop where the dies are actually built by die makers. This is how a blueprint of a die drawing appears. From such prints, die makers build the die exactly as the designer designed it. The drawing must be complete with all required views, dimensions, notes, and specifications. If the die maker is obliged to ask numerous questions, the drawing was poorly done. Figure 1.3 shows a typical blueprint.
Figure 1.3 A typical blueprint.
1.1.4 Bill of Material
The bill of material (Figure 1.4) is filled in last. This gives required information and specifications for ordering standard parts and for cutting steel to the correct dimensions. This material is cut and assembled in the stock room, then placed in a pan, along with a print of the die drawing. When filled, the pan must contain everything the die maker will require for building the die, including all fasteners and the die set.
Figure 1.4 A typical bill of material.
Figure 1.5 A pictorial view of an entire die.
1.1.5 Die Assembly
Figure 1.5 is a pictorial view of the entire die as shown in Figure 1.2. The die pierces two holes at the first station, and then the part is blanked out at the second station. The material from which the blanks are removed is a cold-rolled steel strip. Cold-rolled steel is a smooth, medium-hard steel, and it gets its name from the process by which it is produced. It is rolled, cold, between rollers under high pressure to provide a smooth surface. The strip A is shown entering the die at the right.
1.1.6 Scrap Strip
A scrap strip (Figure 1.6) is designed as a guide for laying out the views of the actual die. Figure 1.6a shows a typical scrap strip. This illustration shows the material strip as it will appear after holes have been pierced and the blank has been removed from it. We would first consider running the blank the wide way as shown at A. When blanks are positioned in this manner, the widest possible strip is employed and more blanks can be removed from each length of strip. In addition, the distance between blanks is short and little time is consumed in moving the strip from station to station. However, for this particular blank there is a serious disadvantage in this method of positioning. Because the grain in a metal strip runs along its length, the grain in each blank would run across the short width; the blanks would be weak and lacking in rigidity. This defect is important enough for the method to be discarded. Instead, the blanks should be positioned the long way in the strip as shown at B. The grain will then run along the length of each blank for maximum stiffness and strength.
Figure 1.6 Scrap strips: (a) Typical scrap strip layouts and (b) Three views of the scrap strip.
Three views of the material strip are shown in Figure 1.6b exactly as they appear in the die drawing in Figure 1.2. In addition, a pictorial view is supplied at the upper right corner to help in visualizing the strip. In other words, this is the way you would imagine the strip if you were to draw it in three views. The top or plan view shows the strip outline, as well as all openings. This would be made actual size on the drawing. The holes are represented by circles at the first station, and the blanked opening is shown at the second station. At the lower left, a side view of the strip is drawn. It is shown exactly as it would appear at the bottom of the press stroke, with the pierced slugs pushed out of the strip at the first station and the blank pushed out of the strip at the second station. The narrow end view at the lower right corner is shown as a section through the blanking station, and the blank is shown pushed out of the strip. The strip in many instances is often drawn shaded to differentiate it from the numerous lines that will represent die members. In the upper plan view, shading lines would appear on the surface of the metal. In the two lower views, the lines are shown in solid black to further differentiate the strip from the die members.
1.1.7 Stampings
Stampings are parts cut and formed from sheet material. Look around you! Wherever you may be, you will find stampings. Many are worn on your own person; the ring on your finger is probably a stamping. Most of the parts in old-fashioned wrist watches are stampings, including the wristband. Your belt buckle, the metal grommets through which your shoe laces pass, eyeglass frame, the clip on your ball point pen, and zipper—all these are stampings.
Look around the room, any room, and you will find products of the pressed-metal industry. Most of the parts in the lighting fixture are stampings; so are threaded portions of light bulbs, door knobs, and the radiator cover. The list is a long one indeed. In the home we find stampings by the score: pots and pans, knives, forks, and spoons, coffee pot, canister set, pie plates and muffin pans, cabinet handles, kettle, can opener, and more.
The refrigerator is almost entirely made of stampings. So are the stove, toaster, and other appliances. And each single part in all these requires an average of three to six dies to produce.
Every automobile contains hundreds of stampings. The largest are the roofs, hoods, quarter-panels, doors, etc. Even the wheels are stampings. There are hundreds of smaller parts, many of which are covered and seldom seen. For example, even the points require very complex dies with multiple stations each, costing thousands of dollars to build, in addition to assembly dies for joining the components.
Office machines and computers provide another big stamping field. So do adding machines, calculators, and dictating machines. We could go on and on; the list is
