What are Transfer and Progressive Dies? Basic Metal Stamping Concepts
Metal stamping is an essential part of modern industry. A single machine can produce tens of thousands of parts per day. Companies can then use these parts to fabricate everything from headphones to airplanes.
The two most common types of dies are known as “transfer” and “progressive” dies. There are important differences in how each operates. These differences impact the parts they can produce, their speed, and the complexity of constructing the die itself.
This article provides an overview of transfer and progressive dies. It focuses on the critical differences between transfer and progressive dies and what to consider when selecting a type of die.
What is a Transfer Die?
Transfer dies begin with a blank. A blank is a piece of sheet metal cut into a particular shape. Usually blanks are a square, circle, or rectangle, but it can be more complicated shapes depending on the application.
Blanks are fed into the machine one by one. The die then stamps them in a step-by-step fashion, where specific modifications occur at each stage. The blanks are carried between stages by transfer machinery. Once the blank has passed through each step of the press, the piece can undergo any finishing steps that are necessary.
Transfer dies are substantially slower than progressive dies. After each press, the transfer machinery must reach to grab the part, move it to the next stage of the die, and then retract again before the next press can occur. Stages of the die are also generally several inches apart, meaning the pieces have longer to travel between stages.
Altogether, this means the transfer machinery has to go through many motions between the presses of the die. The speed of the transfer arms generally controls the productivity of the die. Transfer dies can produce up to 25 parts per minute, though larger pieces are often slower.
While constructing any die assembly is complicated, transfer dies are straightforward compared to progressive dies. Each stage of the process is semi-independent, meaning the construction is more flexible.
Initial die assembly for transfer dies is generally less expensive than progressive dies. For this reason, transfer dies are often preferred for parts that only need a limited production run.
What is a Progressive Die?
Progressive dies work with sheet metal rather than blanks. As sheet metal is fed into the machine, it is precisely positioned inside the die, then stamped. Once the stamp is complete, the metal is moved forward by one stage. The press then repeats, adding a new alteration.
Understanding this process is easiest with an illustration. Below is a picture of a piece of sheet metal as it is fed into a progressive die. The machine makes brackets with a 90’ angle and two holes for screws or nails on each wing. First, the metal has holes punched. It then moves forward by one stage. The metal is then cut and moves forward again. Next, it is bent, then moved forward. Finally, the bracket is cut free from the sheet metal.
As the metal moves through the die, new features are added to the sheet at each stage. When the piece reaches the end of the die, it is complete. A new bracket will be released with each press of the machine.
It is important to note that the piece is cut free from the sheet during the final stage. Cutting is the last step in every progressive die, since the parts need to be separated from the sheet metal. This is a critical limitation of progressive dies. Each piece must stay connected to the sheet metal until the end. Transfer dies use blanks, which allows greater flexibility in processing. Some parts that can be made with a transfer die cannot be made with a progressive die.
The main advantage of progressive dies is the speed of production. The continuous feed of sheet metal means a new part is made with each stamp of the die. Moving the sheet between presses only takes a fraction of a second. Progressive dies can produce as much as 100 parts per minute!
Higher speeds also mean lower costs. Presses are expensive pieces of equipment, so time spent on the press represents a substantial cost. There are also millwrights and machinists who are paid by the hour to attend to the machine. A faster pressing process means lower equipment and manpower expenses.
Progressive die design and construction are extremely complicated. All of the components of a progressive die need to be perfectly aligned with each other for the die to work properly. If the stages are not perfectly aligned, then a small error in spacing can grow to a larger error over the stages of the die. The parts produced will then be defective.
Progressive dies are also generally designed to make only one part. It is rare that a progressive die can be reconfigured to make another piece. Transfer dies are more flexible, as the different components are more easily retooled.
While it is uncommon to repurpose a progressive die, it is possible to reuse the same die later. Suppose the press makes parts faster than you can use them. Once you accumulate a backlog of parts, you can remove the die from the press. If you start to run out of parts months later, you can reattach the die and easily restart production. For a transfer die, the whole apparatus needs to be reassembled, meaning a longer set-up time and higher manpower costs.
What Kind of Die Should I Use?
Choosing between a progressive and a transfer die can be challenging. There are many concerns to consider. What is the design of the part you need? How many parts do you need? How quickly do you need them? What is your target price point? To answer these questions, you need to work with a team of skilled engineers, millwrights, and machinists.
Gold Precision are experts in both progressive and transfer die assembly and operation. Our team of has over 20 years of experience in the metal stamping industry. With almost 2 acres (8,000 m2) of factory space, we have tools and equipment suited for a wide range of stamping procedures.
Want to learn more about our process? Contact us today to get a free consultation.