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Figure 1.13 A piercing punch.
1.2.5 Punch Plate
The punch plate (Figure 1.14) is a block of machine steel that retains punches by keeping the punch heads against the punch holder of the die set. The punches are held in counterbored holes into which they are pressed. Four screws and two dowels retain the punch plate to the punch holder of the die set. The screws prevent it from being pulled away from the punch holder. Dowels, which are accurately ground round pins, are pressed through both the punch plate and punch holder to prevent shifting. Locate the front view and plan view of the punch plate in the die drawing Figure 1.2.
Figure 1.14 A punch plate.
Figure 1.15 A pilot.
1.2.6 Pilot
Pilots (Figure 1.15) are provided with acorn-shaped heads, which enter previously pierced holes in the strip. The acorn shape causes the strip to shift to correct register before blanking occurs.
1.2.7 The Back Gage
The back gage (Figure 1.16) is a relatively thin steel member against which the material strip is held by the operator in its travel through the die. The front spacer is a shorter component of the same thickness. The strip is fed from right to left. It rests on the die block and is guided between the back gage and front spacer. The distance between the back gage and front spacer is greater than the strip width to allow for possible slight variations in width.
Figure 1.16 The back gage.
Figure 1.17 A finger stop.
1.2.8 The Finger Stops
The finger stop (Figure 1.17) locates the strip at the first station. In progressive dies having a number of stations, a finger stop may be applied at each station to register the strip before it contacts the automatic stop. Finger stops have slots machined in their lower surfaces to limit stop travel.
1.2.9 Automatic Stops
Automatic stops (Figure 1.18) locate the strip automatically while it is fed through the die. The operator simply keeps the strip pushed against the automatic stop toe, and the strip is stopped while the blank and pierced slugs are removed from it, then it is automatically allowed to move one station further and stopped again for the next cutting operation.
1.2.10 The Stripper Plate
The stripper plate (Figure 1.19) removes the material strip from around blanking and piercing punches. There are two types of stripper plates: spring-operated and solid. The one illustrated is solid. The stripper plate has a slot A machined into it in which the automatic stop operates. Another slot B at the right provides a shelf for easy insertion of a new strip when it is started through the die.
Figure 1.18 An automatic stop.
Figure 1.19 The stripper plate.
1.2.11 Fasteners
Fasteners hold the various components of the die together. Figure 1.20 shows the commonly used socket cap screw. These fasteners are available from various suppliers, and all have a threaded portion and a larger round head provided with an internal hexagon for wrenching. As you have been doing for previous illustrations, pick out the fasteners shown in the die drawing, Figure 1.2. Note that in section views, screws are shown on one side and dowels on the other.
Figure 1.20 Socket head cap screw for use as a fastener.
Let us now consider the steps taken in designing, building, and inspecting a representative die. At the same time, you will gain an insight into the operation of press shops, tool rooms, and manufacturing plants so that your understanding of tooling and manufacturing will be better than average.
1.3.1 The Product
First, we will consider the product to be manufactured. The product engineering department designs the product. In most plants, the work consists in improving the product from year to year to meet changing styles and changing requirements of customers.
After management has decided upon the final form of the new or improved product, a directive is sent to the process planning department to route the various parts through the appropriate manufacturing departments. The process or methods engineers then plan the order of manufacturing operations and decide what operations will be used. They request that the tool design department produce designs of all jigs, fixtures, cutting tools, and dies needed for efficient production of the parts.
After a product designer has prepared layouts and assembly drawings of the product to be manufactured, the engineering department prepares detail drawings of each component the shop has to produce. These drawings contain all required views, dimensions, and explanatory notes to represent all detail features of the objects.
The part which is to be machined, formed, pressed, or inspected is called by one of the following terms:
•Part
•Work
•Workpiece
Part is the preferred term, but workpiece or, simply, work are often employed as alternate names; all three terms will be used interchangeably throughout this book.
The print on which this part, work, or work-piece is represented is called a part print. In designing a die for producing a stamping, the die designer works from a part print.
1.3.2 Process Planning
Prints of detail drawings are sent to the process planning department. When stampings are required, it is the function of this department’s employees to determine how the stampings are to be made. They decide how many operations will be required and what presses will be employed to make them. This department thus assumes the responsibility of determining the sequence of manufacturing operations. The information is noted on a series of forms:
a)
