Tool & Die Overview

Stamping tooling and stamping dies are detailed here, including, progressive dies, one-hit dies and transfer dies. We will also discuss tool steels and tool coatings in addition to in-die sensors, in-die welding and in-die tapping. Die design is also discussed.

Sheetmetal stamping, incorporating bending, piercing and other processes, depends on a various types of tooling to get the job done. In a metal-stamping operation, the die, or tooling, is where the action is. Located within the stamping-press window, tooling uses the energy created by press movement to produce a sheetmetal part. The tooling can cut sheetmetal and perform many other part-producing functions such as piercing, bending and trimming. With the addition of specialized modules or other equipment, tooling can even perform tapping, welding and inserting (of nuts or other pieces of hardware).

What is a die? 

In simple terms, a die set contains two halves, the die punch and the die cavity, with all of the components needed to cut and form a stamped part resting upon a metallic plate called a die shoe. Two die shoes (usually an upper die shoe and a lower die shoe), with components included, form the die set. The size of a die set depends on the size and type of part to be stamped, and the type of work that must be done to produce that part. Some dies, such as those used to create tiny electronic components, may be as small as a few inches across and few inches high. Other dies, such as those used to produce automotive panels, can stretch to more than 10 ft. long and 6 ft. high. A limiting factor in die size is the size of the window opening on a stamping press. 

What is the material makeup of a die? 

Though most sheetmetal stamping is considered a cold-forming process, stresses and forces encountered during the process generate heat. Combating heat, and also combating wear and tear associated with working various types of part material, demands the use of specialized materials in creating dies and tooling components. These materials, collectively referred to as tool steels, are specified primarily according to the type of part material to be stamped and the number of hits required per part run. The introduction of unique steels, driven by automotive-industry needs for high-strength, lightweight parts, have spurred development and use of unique die materials and tool coatings. These materials and coatings allow tooling to hold up while working on these new, high-strength steels.

How are dies classified? 

With a single hit of the press, stamping dies can form complete parts or certain features of a part.  One-hit dies, representing the simplest form of tooling, produce complete parts with a single press hit, or at least a shape that travels to secondary machinery for completion or to another one-hit die in another press. Progressive dies contain multiple stations—think of a series of one-hit dies connected together. Dies of this type add features to a part with each press hit as the base material travels along the die in a strip. In this manner a part is progressively formed. Transfer dies have characteristics of one-hit and progressive dies. With transfer dies, a material blank travels from die to die, eventually forming a complete part. Unlike with a progressive die, parts in a transfer die do not travel from station to station attached to a carrier strip. Rather, mechanisms located outside of the tooling physically lift a part from one die station and deposit it into the next. This is accomplished through the use of a transfer press—essentially a specialized mechanical press—or via a transfer system attached to an existing stamping press. 

How are dies made? 

Design and construction of dies are time-consuming and costly processes. Development of die-design software that simulates the forming process and allows specialists to design tooling on computers has enabled shortened lead times for die delivery. Using such software—once general design programs such as SolidWorks, but now available in various programs tailored for stamping-die design--also can eliminate problems that at one time only showed themselves during tryout after the stamping die was built. Using such software has reduced costs. Also, in some cases die lead time—the time period between die design and production of quality parts in a stamping press using that particular die—has shrunk from months to days.

Dies typically are machined, with components such as pins, punches and springs fastened to the die base. Die components such as punches are particularly susceptible to wear and breakage. Problems with these types of components can cause press shutdowns while tooling is repaired, slowing production and adding cost to the stamping process. To combat this, tooling suppliers have developed methods to change out components quickly. Also, stamping tooling can undergo special coating processes to enhance tool life and ensure production of precision, quality parts even after hundreds of thousands of press hits. 

High-tech tooling replaces costly secondary processes 

As a capital-intensive process, sheetmetal stamping can be quite costly. To remain competitive, metal stampers must employ process efficiencies. One method to improve efficiency is to perform as many processes as possible within the press. Secondary processes that take place away from the stamping press are costly and time-consuming. But performing more and more work within the press—actually, within the tooling—can result in more complicated, and costly, dies. Given this fact, die design, maintenance, protection and utilization are so important to the stamping process that a manufacturer will have personnel dedicated to tooling issues.

The high cost of stamping dies, and the care required to allow these dies to produce part after part to rigid specifications, demand attention to detail in this area. To protect tooling, a die designer or stamper will incorporate various press controls and sensors into the stamping process. Often, sensors will be embedded into tooling to ensure presence, and correct orientation and shape of the part material. These are referred to as in-die sensors. Many stamping operations, especially those tasked with performing multiple jobs on a single press line, incorporate quick-die-change (QDC) equipment. Such equipment—rolling bolsters, die carts, clamps, etc.—allow rapid changeout of tooling from one job run to the next in order to keep presses running.

The right forming fluids can spell stamping success 

Stamping lubricants aid tooling and dies in creating quality parts, while bringing longer tool and die life. Lubricants are available in many formulations depending on factors such as the material to be stamped and the stamping process to be employed. Lubricant-delivery systems ensure that forming fluids reach into critical areas of the tooling and material, without hampering the performance of sensitive components such as in-die sensors.