Using vacuum technology to improve material handling
June 22, 2012
By J. Schmalz GmbH
The requirements of the automotive and sheet metal industries are increasing in complexity, and a large part of this is due to the fact that increases in efficiency and reductions in costs are of critical importance to the competitiveness of a company.
But new vacuum suction pad technology can help manufacturers reduce costs and improve productivity when handling sheet metal. Recent servo press generations that handle metal parts with vacuum can deliver 16 – 18 stokes per minute, depending on the type of press and complexity of the component.
Still, that’s not always enough. Whether you can take maximum advantage of the efficiency of the machine also depends on the capability of the vacuum system and the suction pads in particular. The ability of the vacuum suction pad to hold the workpiece, absorb lateral forces, adapt to the workpiece and resist wear is ultimately responsible for process reliability and transport speed when working with metal sheets.
That’s where new vacuum suction pad technology can help. When done right, a good suction pad will have a large stroke that allows them to adjust optimally to workpieces with complex contours. The suction pad geometry can provide all the features required for the highly dynamic handling of metal sheets: minimal pick-up times, high intrinsic stability while suction is applied and the absorption of extreme holding and lateral forces, especially on oily surfaces.
Improved dynamic handling, decreased costs
Until now, it was a simple rule of three: the faster the press, the more suction pads required. The more suction pads used, the more tooling work required. The more complicated the tooling work, the heavier and the more expensive it becomes.
But suction pads can redefine those laws of vacuum handling. The special structure of the suction pad interior and the additional friction disc allow the pad to absorb several times the lateral forces as compared to metal suction pads. This has a positive effect on the costs and output. On the one hand, the number of suction pads and thus the tooling expenses can be reduced, while maintaining the speed of the press. On the other hand, the speed of the press can be increased while maintaining the same number of suction pads.
When using a single cavity tool, an increase of just one stroke per minute – when applied to a production year comprised of 250 working days with 20 hours of operation and three shifts per day – can result in an increase of 300,000 parts per year.
Adaptability and flexibility
Workpieces such as doors, fenders and valence panels have projecting edges and gaps that restrict the areas where the suction pad can be used. The advantages of new suction pad technology are two-fold. These new pads provide a stroke that is twice as high as that of common flat suction pads, which allows it to adjust considerably better to the three-dimensional contour of the workpiece.
In addition, the suction pads provide a high level of lateral force absorption while keeping the suction pad diameter comparatively small. This allows for more flexible positioning on the contoured metal sheet when space is limited versus other common metal suction pads with larger diameters.
Long-lasting and environmentally-friendly
Constant exposure to ozone, such as from welding auto body parts, can cause suction pads to become brittle over time. Contact with aggressive drawing oils, such as those used in presses during forming operation, can cause suction pads to swell. Both can result in vacuum system leakage and increasing energy costs. In the worst case, they can even cause system failure and machine downtime.
But new materials can help with this problem as well. New suction pads are made of the innovative material Elastodur, which neither ozone nor drawing oils negatively affect. The increased service life that the material makes possible results in further advantages:
the low amount of wear not only increases the reliability of the system, it also reduces purchase costs and general costs. The long lifetime brings about less machine downtimes, in which worn suction pads have to removed and new ones installed.
Schmalz is one of the world’s leading suppliers in automation technology, handling technology and clamping technology. The company offers a wide range of individual vacuum component products, from suction pads and special grippers to vacuum generators and switches. Learn more at www.schmalz.com.