DÜSSELDORF, GERMANY (Dec. 10, 3:25 p.m. EST) — Sandretto Industrie SpA has developed a hybrid injection molding press — dubbed “electro-hydraulic” by a company official — that uses electric motors to run fixed-displacement hydraulic pumps.
Shown during K 2001 in Dusseldorf, presses with the ES injection unit clearly do not qualify as “all-electric” machines. But Tony Firth said the term “hybrid” has become too squishy, since just slapping an electric screw drive on a hydraulic press qualifies as hybrid.
“It's a mistake to describe this as a hybrid, as it's defined by the current use of the term,” said Firth, vice president and general manager of Sandretto USA in Freedom, Pa. He said the word hybrid implies blending the two technologies into something new — such as Sandretto's use of electric motors with a fluid drive train.
Typical all-electric presses use mechanical means, such as belts, to transmit the spinning motion of an electric servomotor to the linear motion of an injection press. Instead of belts, Sandretto ES uses what it terms FluiDrive technology.
When motion is required, the pumps run. But the pumps stop — along with the electric motors — when the press does not have to move. An inverter-driven system controls the electric motors to produce the rotation speed and pressure required at each moment. That means the ES boasts energy savings of 50 percent, compared with standard hydraulically driven injection molding machines.
The ES does, of course, have hydraulic oil — but Firth said the machine is just 15 percent more expensive than a standard hydraulic press. The price premium of all-electrics can range from 15-20 percent for smaller presses, up to 40-50 percent for larger machines.
Firth also said that the electro-hydraulic method handles load and pressure better than exclusively using electric motors, for example, on pack-and-hold and clamping.
Very large tonnage presses have presented a roadblock to current electric servomotor technology, since there are limits on the size of electric motors and ball screws now available. One way to get around this is to synchronize two electric motors together. But Firth said FluiDrive presents a much simpler solution, since Sandretto can attach multiple combinations of motors to the hydraulic system. The hydraulic fluid evens out any differences in output between the motors.
At K 2001, Sandretto used ES technology to mold car motor covers on a press with 1,320 tons of clamping force.
Firth said Sandretto can use the system on both its toggle-clamp presses and machines with straight hydraulic clamp.
The standard electric motor on the ES is air-cooled. As an option, Sandretto offers a quieter, water-cooled motor.