Energy-Saving Hydraulic Press Varies Pump Speed and Volume

Processors from around the world got a close look at a new series of energy-efficient hydraulic injection machines at an open house recently held by Negri Bossi in Milan, Italy. They are said to use a unique combination of a digital variable-volume pump driven by a variable-speed electric motor. Negri Bossi, with U.S. offices in Newark, Del.  also showcased new high-speed compression molding machinery for caps and closures and a versatile stretch-blow molding machine from parent company Sacmi of Imola, Italy (U.S. office in Des Moines, Iowa).

In injection molding, Negri Bossi’s two highlights were the VS line, which the company described as an “entry-level” series priced to compete with low-cost Chinese machines; and the VSE series, which features novel hydraulic technology said to offer a combination of energy savings close to that of an all-electric machine and superior performance vs. hydraulic alternatives. Both machine lines fall under Negri Bossi’s Canbio Series of presses. Both are offered in clamp sizes of 120, 145, 200, 275, 365, and 475 tons with shot capacities from 3 oz to more than 70 oz.

Standard features of the Canbio VS include a quick-barrel-change system using a bayonet coupling of the screw directly to the screw motor, permitting changeover times on the order of 15 min. Dual-cylinder injection units are offered in six sizes ranging from 28 to 80 mm diam. In the clamping system, flexibility is enhanced by a quick-coupling ejector system and T-slots. Sealed bushings for tiebar lubrication and sealed bearings on the platen slides are designed to keep the mold area clean. The frame of the machine is open on each side to facilitate part removal.

The line also features a new Columbia Canbus Network PC closed-loop control system. Patented wireless communication with a central Amico PC LAN workstation permits on-line troubleshooting.

NOVEL HYDRAULICS

The Canbio VSE series is distinguished by “smart-pump” technology coupled with a “smart-energy” drive system from Bosch Rexroth. Like some other “hybrid” pump systems on the market, the pump is driven by a variable-speed motor, in this case an AC variable-frequency type. But Negri Bossi adds a unique twist. “The current industry standard for a variable-speed ‘hybrid’ hydraulic pump unit is a fixed-volume pump,” explains Liam Burns, general manager of Negri Bossi USA. “Our solution uses a variable-volume pump, which offers faster and more consistent machine performance.” As Burns explains it, the variable-volume pump provides a quicker ramp-up in speed, as it can move its swash plate to generate more volume at lower rpm. Moreover, as the drive system arrives at the set speed, the variable volume can more consistently control the speed by small adjustments of the swash plate without requiring the pump drive system to “hunt”—continually slowing and speeding up.

Negri Bossi says this system uses 15% and 45% less energy than conventional hydraulic presses—savings said to be close to those of all-electric machines—and up to a 20% gain in performance over other hydraulic types. Burns says the VSE series is aimed at “a market that prefers the hydraulic solution—mostly because of the maintenance associated with all-electric machine ballscrews and drives—but is looking for all-electric-like performance.” Burns says a 365-ton version has been sold to a molder an Indiana. The VSE series is priced about 10% above Negri Bossi’s standard hydraulic line.

FASTER COMPRESSION MOLDING

Sacmi, meanwhile, treated visitors to its recently unveiled CCM 80 continuous compression molder for high-volume production of caps and closures.  The machine, which debuted last year at the K 2010 fair in Dusseldorf, produces more than 2000 pieces/min with a cycle time of 2.1 sec. The machine joins the CCM 48 and 64 models. It’s the latest salvo in the battle between injection and compression molding for caps and closures. Sacmi maintains that compression technology will continue to make inroads as bottling lines continue to speed up.

The CCM 80 features a new “variable-consumption” extrusion control system, which adjusts energy consumption based on speed—which, in turn, depends on cap type and geometry.
In blow molding, Sacmi displayed a rotary stretch machine for PET that incorporates what the machine builder calls a 1B=2b system. With this technology, the press can be used in either single- or dual-mold mode. In single-mold mode, the machine can produce one large bottle up to 3.5 liters. In dual-mold mode, it can produce two smaller ones of up to 75-mm diam. The stretching block has three rods, the central one for single-mode configuration, and the two lateral ones for dual-mold configuration. Switching from 1B to 2b is by a simple mechanical adjustment.