Die Basics 101: Intro to Stamping
July 18, 2018Comments
When I conduct conferences, it isn't unusual to have one or two attendees who are new to the stamping die and pressworking world.
When I conduct conferences, it isn't unusual to have one or two attendees who are new to the stamping die and pressworking world. Some are young new hires trying to learn about stamping, and others are individuals who have been transferred from a different department and thrown to the wolves in the stamping department.
This article is the first in a series intended to introduce beginner toolmakers, die maintenance technicians, engineers, and press technicians to stamping. The series will define a die as well as a stamping operation. It will also discuss cutting and forming operations, components and functions, and different methods used to stamp parts.
What Is a Stamping Die?
A stamping die is a special, one-of-a-kind precision tool that cuts and forms sheet metal into a desired shape or profile. The die's cutting and forming sections typically are made from special types of hardenable steel called tool steel. Dies also can contain cutting and forming sections made from carbide or various other hard, wear-resistant materials.
Stamping is a cold-forming operation, which means that no heat is introduced into the die or the sheet material intentionally. However, because heat is generated from friction during the cutting and forming process, stamped parts often exit the dies very hot.
Dies range in size from those used to make microelectronics, which can fit in the palm of your hand, to those that are 20 ft. square and 10 ft. thick that are used to make entire automobile body sides.
The part a stamping operation produces is called a piece part (see Fig. 1). Certain dies can make more than one piece part per cycle and can cycle as fast as 1,500 cycles (strokes) per minute. Force from a press enables the die to perform.
There are many kinds of stamping dies, all of which perform two basic operations—cutting, forming, or both. Manually or robotically loaded dies are referred to as line dies. Progressive and transfer dies are fully automated.
Cutting clearances change with respect to the type of cutting operation being performed, the metal's properties, and the desired edge condition of the piece part. The cutting clearance often is expressed as a percentage of the metal's thickness. The most common cutting clearance used is about 10 percent of the metal's thickness.
Very high force is needed to cut metal. The process often introduces substantial shock to the die and press. In most cutting operations, the metal is stressed to the point of failure, which produces a cut edge with a shiny portion referred to as the cut band, or shear, and a portion called the fracture zone, or break line (see Fig. 2).
Blanking—A dual-purpose cutting operation usually performed on a larger scale, blanking is used in operations in which the slug is saved for further pressworking. It also is used to cut finished piece parts free from the sheet metal. The profiled sheet metal slug removed from the sheet by this process is called the blank, or starting piece of sheet metal that will be cut or formed later (see Fig. 5).
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