One of the keys to the success of CDs as a medium for data and picture storage is their low cost. With billions of CDs being manufactured each year, though, it would be impossible to maintain the necessary output rate and product quality by conventional methods. Therefore, the entire manufacturing process-from the supply of granulate to the molding, labeling and quality control of the finished CDs-is fully automated.

Once the plastic disk has been injection-molded, it is a precision part that is easily damaged, yet it still has to be moved accurately from one station to the next in the production process. This cannot be done easily with conventional mechanical-pneumatic transport and handling devices. Mechanical grippers can distort and damage the CDs. In many cases they are not fast enough for the short machine cycles. Vacuum-assisted handling of the parts, on the other hand, is fast, reliable and safe.

Germany's Messrs STEAG company uses Schmalz (Raleigh, NC) suction pads to assist in its CD manufacturing, including round, flat suction pads and ring-shaped, or annular, pads. Schmalz's type SGA 7 SI flat pads and type SGR 31 SI annular pads were designed specifically for handling CDs. STEAG also employs an assortment of other vacuum components, including vacuum generators, vacuum switches and monitoring devices. Together the Schmalz components are used in the transfer stations that connect the various modules that make up STEAG's production process.

Suction pads made of silicone are used for the safe handling of CDs, because silicone is more resistant to the high temperature associated with CD production. Nitrile pads, for example, are more sensitive to temperature.

The use of either round suction pads or special annular pads depends on the specific application. Groups of flat suction pads are sufficient for some handling sequences. But in cases requiring a higher suction force, annular pads are better, with their ring-shaped suction cups gripping the disks centrally around the center hole. Higher suction forces and fast reaction times-requiring mere fractions of a second to engage and disengage-allow production to be carried out at the maximum possible speed and with very dynamic movements.

To ensure that the suction cups operate at the top end of their performance range, STEAG uses vacuum switches such as the type VS-V-A-PNP to continuously monitor the vacuum values.

For more information on vacuum transport devices, call 919-713-0880 or visit www.schmalzinc.com.