- Despite a great application of force, the air actuators are impressively durable
- Tappet counterweight considerably reduces energy requirements
- Air actuators enable controlled power transmission and clean machines
The core of a forming press is the "tappet." It moves up and down within a frame and holds the upper part of the mold for the pressing process. The lower part of the mold lies firm in the press equipment. After the sheet metal is inserted, the movement of the tappet presses both parts together and the sheet is shaped. The forming presses work at up to 80 strokes per minute. To make the tappet move, the large carrier mass must be put into motion and a lot of power is needed for this to generate up to 400 kN. This is mostly done using an engine. In order to minimize the need for energy as much as possible, modern forming presses have a tappet counterweight for which ContiTech's air actuators are also used. "For this reason, tappets mostly rely on multiple air actuators which bear the static weight," explains Dr. Olaf Kluth, segment head at ContiTech Air Spring Systems. "This design means that engine output is not necessary in the central position. The drive is only needed for the loading and unloading of the tappet. This allows energy to be saved and likewise mechanical components can be protected."
In this application, the air actuators work as an air spring. They do not have an air supply and produce a spring effect by compressing air using movement. Air actuators with large diameters of 600 to 700 millimeters are generally used to create the enormous power needed to bear the tappets.
As opposed to conventional pneumatic cylinders with sliding seals, ContiTech air actuators have considerable advantages. Sliding seals can quickly wear at approximately 80 strokes per minute. Downtime is necessary for servicing and replacing them, which means loss of production. ContiTech air actuators are different: they operate without sliding seals, are practically maintenance-free, and provide pressing companies with a long-lasting and energy-saving solution.
Controlled power and clean machines
In forming presses, air actuators can also be used within the tappet bolster. They sit directly in the tappet and cushion the affixed tool against impacts. For example, this can be molds like those used in the automotive industry to manufacture body parts. "The tools used can be fed in a controlled manner," says Kluth. "The power exerted can be individually adjusted. This achieves optimal results."
Another possible use for air actuators in forming presses is contained in the area above the tappet, where the tappet's upward and downward movement takes place. The mechanical components are set in a greasy medium which enables frictionless movement. The common sliding ring seals cannot, however, fully prevent liquid from leaking. As a result, the machine becomes increasingly dirty. To prevent this process, ContiTech has developed sealing bellows which are modified from an air actuator. "In practice, we have noticed that the sealing bellows also withstand high stroke rates and therefore the enormous loads in the forming press," explains Kluth.
ContiTech has decades of practical experience with the different uses of air actuators in forming presses. For years the air spring specialist has successfully worked together with leading manufacturers in the supply industry to develop individual solutions according to their needs. New developments are extensively tested in simulations and designed for practical application. The result? ContiTech air actuators make forming presses even more effective, cleaner, and more energy efficient.