The Absolute Basics
The feed unit advances the raw material into the press and die at a given distance, placing it in the right position to be stamped, cut or otherwise shaped. There are several different types of feed units available, each with advantages and drawbacks.
Mechanical Roll Feeds
Mechanical roll feeds are a good choice for high-speed applications. They use upper and lower conveyors to pinch the stock and roll it forward into the tool. They're low maintenance and have a high degree of accuracy. The biggest disadvantages to roll feeds or conveyors are the expense and the setup. Because they're tied to the machine crank, they can be limited in the type of part they can handle. Mechanical roll feeds also require precision adjustment to avoid misfeeds and damaged dies.
Air feeds are among the most popular type of feeds for material handling. They use a mechanical slide that clamps the material in place and moves forward and back. The advantages of air feeds include cost - they're considerably less expensive than other types of feed units - and versatility. They can be mounted to the tool or to the press and do not require a tie in to the press. They can either push or pull stock through the tool, and can easily be adjusted and retrofitted. Air feeds are dependable, and are generally very accurate. The biggest disadvantage to air is that they use shop air, which can be expensive, and can limit the speed of the press operation. They tend to be noisy and may require a lot of maintenance in a high volume production environment.
The fastest growing trend for many machining industries is the servo feed. Servo are extremely versatile and are capable of feeding material in any position of the ram stroke. This allows for longer feeds. Part geometry isn't an issue because they don't require half the stroke of the machine like mechanical roll feeds do. Because they're programmable, the unit can store and retrieve tooling information, reducing setup time. Newer servo feeds allow for higher speeds without risk of marking the material. The biggest disadvantages are cost and maintenance, and the fact that special operator training may be required.
When you work with metal stamping experts who have been in the business of providing fabrication equipment for years, you get the benefit of their knowledge and experience. They know what's likely to work best for your application, and more importantly, what definitely won't work. This can save you lots of trial and error, and get your production up and running much sooner.