Stamping is an invaluable process for many manufacturers. It shapes metal sheet into a wide variety of parts in a consistent manner. It grants producers a highly specific method of controlling the production process, and because of the many options available it can fit nearly any need.
This versatility implies that manufacturers have a great deal of knowledge about the different methods of stamping, so partnering with an experienced materials supplier makes a lot of sense. When working with metals like aluminum or stainless steel, it’s important to understand an alloy’s application in each process, and that’s true of stamping as well.
Two of the most common methods of stamping are progressive die stamping and transfer press stamping.
What is stamping?
Stamping is a process that involves placing a flat sheet of metal onto a press. The starting material can be in blank or coil form. A stamping die is then applied to form the metal into the desired shape. There are many different types of stamping that can used with metal sheet, including punching, blanking, embossing, bending, flanging, piercing and coining.
In some cases, the stamping cycle is performed only once, with that operation sufficient to create the finished form. In other instances, the stamping process might take place in several stages. The process is normally performed on a cold metal sheet using a precision machined die manufactured from high performance tool steel to ensure the uniformity and reliability of the stamping process.
Simple metal forming dates back thousands of years and was originally performed manually using a hammer, awl or other such tool. With the advent of industrialization and automation, the stamping process has grown increasingly complex and diversified over time, with several options to choose from.
What is progressive die stamping?
One of the most popular types of stamping is known as progressive die stamping, which employs a sequence of stamping operations in a single linear process. The metal is fed through using a system that pushes it forward through each of the stations, where each necessary operation is progressively performed until the part is completed. The last action is commonly a trimming operation, separating the work piece from the rest of the material. Coil stock is commonly employed as raw material in progressive stamping operations, as they are often used in high volume production runs.
Progressive die operations can be elaborate processes involving numerous steps prior to completion. It’s critical that the sheet be advanced in an extremely precise manner, often within a few thousandths of an inch. Bullet-shaped or conical pilots have been added to the machines, which conjoin with previously pierced holes in the sheet metal to ensure the proper alignment during the feeding process.
The more stations involved, the more expensive and time consuming the process; it’s advisable to design the progressive die with as few stations as possible for reasons of economy. It’s important to note that when the features are close together, there may not be enough clearance for the punch. Likewise, problems can arise when the cuts and protrusions are too narrow. Most of these issues are worked out and compensated for with the use of CAD (computer assisted design) software in both part and die design.
Examples of applications that use progressive dies include beverage can lids, sporting goods, automotive body parts, aerospace components, consumer electronics, construction, food packaging and more.
What is transfer press stamping?
Transfer press stamping is like progressive die stamping, except that the work piece is physically transferred from one station to the next rather than pushed through continuously. This is the recommended method for complicated pressing operations that involve several complex steps. An automated transfer system is used to move the part from station to station and hold the component in place during the operation.
Each die is tasked with shaping the part in one particular manner, until the final dimensions are achieved. The transfer press allows for a single machine to operate multiple tools all at the same time. In fact, as the workpiece progresses through the press, each closing of the press will involve all the tools acting simultaneously. Transfer presses, with modern automation, can now perform the actions of what might have previously involved several different operations in one single press.
Because of their complexity, transfer presses will often operate more slowly than a progressive die system. However, for complex parts, the inclusion of all the steps in one process allows for a faster production process overall.
Transfer die systems are commonly employed for larger parts than would be suitable for the progressive die process, including frames, enclosures and structural components. It will generally be found in all the same industries that employ progressive die stamping technology.
How to choose between the two processes
Choosing between the two generally comes down to the application. Factors that must be considered include the intricacy of the parts involved, their size and their quantity. Progressive die stamping is ideal when working with a larger number of small parts in a short amount of time. The larger, more complex the parts involved, the more likely a transfer press will be required. Progressive die stamping is fast and economical, whereas a transfer press allows for greater versatility and variety.
There are a few other disadvantages of progressive presses that manufacturers need to be aware of. Progressive die stamping normally requires greater raw material input. The tools are more expensive as well. They also cannot be used to perform actions that need the part to leave the process. This means several operations, such as beading, necking, flange curling, thread rolling, or rotary stamping are all better off with transfer presses.
At Clinton Aluminum, our team understands the various metal forming processes, including progressive die stamping and transfer press stamping. Contact one of our friendly and knowledgeable customer service representatives today to learn more.