Mechanical Technology February 2015

⎪ Local manufacturing and beneficiation ⎪

automatically released. The press comes down to the ideal height for that particu- lar die, and the support platform slides forward on moving bolsters. The new die is then loaded and, once the platform is back inside the press, hydraulic clamps automatically latch onto the two halves. “Typically, we would change over every four hours, although a long run might take an entire shift to complete. We are currently doing trial pressings of a steer- ing wheel airbag housing and mounting bracket using a 2,8 m die, but the machine can accept a 4.0 m by 1.8 m die just as easily,” he adds.

In addition to metal press- ings, the Schuler press also of- fers value added fastening options including: in die tapping; nut welding; and riveting of nuts and studs into pressed parts, as well as the ability to inspect parts

Above: The progression die process keeps flat side strips of material attached to the set of parts being formed. These strips are used to advance the parts from die to die through each successive pressing operation and are cut off just before the finished parts leave the press. Right: A test component used for machine com- missioning, a steering wheel airbag housing and mounting bracket pressed using a 2,8 m die.

in cycle without significantly reducing the cycle time of the press. “The fences, doors and die and coil loading systems make this press one of the safest in the country. With its automatic lubrication system and its hydraulic die release ram, it is also well protected against common incidents that might cause downtime. “This is one of the most modern transfer and progression die presses to be installed in South Africa for many years. It places us in an ideal position to take advantage of the growing local and export automotive market and the new model releases that are due in the coming years.” Gunter concludes. q

is the first to be used to power the servo motors,” he explains. This system im- proves the net energy efficiency of the press and it can be used to reduce peak demand from the grid. To take full advantage of the speed of this 630 t press, particularly in the relatively low-volume South African automotive market, changeover times become a key productivity factor. “This is a 15-minute system,” Gunter reveals.” It has a quick die changing system, which enables a die to be removed and replaced within 15 minutes.” On changeover, the die is closed in the press and the hydrau- lic clamps for the dies and punch are

before straightening it and draping a buffer loop immediately in front of the powerful main feeder. Both transfer and progressive die pressing processes can be accommo- dated. Gunter explains the difference: “When using the ‘prog die’ process, flat strips of material remain attached at either side to the set of parts being formed. These strips are used to advance the parts from die to die through each successive pressing operation and are cut off just before the finished parts leave the press. “The transfer die process involves cut- ting the material to the size required as it entered the press. Between each opera- tion, the parts are systematically lifted and placed in the subsequent position. While the progressive process is much faster − up to 60 strokes per minute − the transfer process wastes much less material. And since it can still achieve 30 strokes per minute, sometimes it can be more cost effective,” he informs. The servo press also offers very low energy consumption – much less than that drawn by traditional flywheel-based machines. In a cavity below the new Schuler press, Gunter points out the ca- pacitor bank for energy recovery. “Instead of using brakes to decelerate the press, the power flow is switched to connect to this capacitor bank instead of the mains supply, changing the servo motor into a generator and recovering some of the electrical energy. When the press again needs to accelerate, this stored energy

The servo drives and controllers enable the slide motion curve for each part being formed to be individually programmed to the speeds and forces required. These settings are automatically set when the die for a new part is inserted.

Mechanical Technology — February 2015

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