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Integrated servo drives square up for a packaging battle

01 February, 2007

Integrated servo drives square up for a packaging battle

At the recent SPS/IPC/Drives show, two German companies were touting rival integrated servo motor drives that, they claim, will deliver substantial savings in cabling and other costs, especially in applications such as packaging machines.

Bosch Rexroth says that its IndraDrive Mi drive, which places a complete drive including motion and logic control on top of a servo motor, will need half the space of traditional servo drives and could cut cabling by 75%.

Meanhwile, the packaging specialist Elau has developed a servo motor with an integrated amplifier that is connected to a separate motion and logic controller using a hybrid cabling system which, it says, will cut the amount of cabling needed by up to 70%.

Rexroth`s system (shown above) uses the motor case as a heatsink. By mounting the electronics on top of the motor, it needs 30% less space than integrated motors that attach the electronics to the back of a motor. A single cable carries both power and Sercos communications.

Several of the drives can be daisy-chained to each other using prefabricated connectors, thus avoiding the need to run two cables from a control cabinet to each axis, as is needed in most conventional set-ups. The drive and all connections are protected to IP65.

Rexroth says that the integrated design of the IndraDrive Mi will eliminate the need to replace wearing parts such as fans, electrolytic capacitors and relays. There will be six models delivering peak torques up to 30Nm, at 3,400 rpm.

The packaging machinery giant KHS helped Rexroth to develop the integrated drive and is one of the first users of the new technology. Last month, it delivered its first machine to incorporate the integrated drives — a shrinkpacker — to a customer.

Dirk Langanki, manager of KHS` electrical engineering department, reckons that the new technology could cut cabling lengths for a typical ten-drive machine by as much as 85%, while reducing overall costs by about 15%. He cites other benefits including fewer components, easier troubleshooting, and smaller cabinets needing less cooling.

Schneider-owned Elau is claiming similar benefits for its integrated drive which, it calculates, will cut per-axis hardware costs by about 15%. The company`s chief executive, Dr Thomas Cord, predicts that the iSH servo drive (shown above) "will revolutionise drive technology in the packaging industry".

The Elau technology uses a centralised power supply with a single hybrid cable carrying the motion bus, power, brake control, I/O signals, and safety functions, to each servo module.

Elau argues that locating a shared power supply away from the drive electronics reduces heat generation and boosts efficiency because the supply can be sized according to the sum of the individual motor currents, averaged over time. Individual power supplies, it points out, must each be sized for the maximum current that each motor may draw.

The Elau servo drives are available with 70 or 100mm flange dimensions, with peak outputs up to 28.3Nm. Up to 16 of the drives can be powered by one supply, and they can be linked in line or tree structures — or a combination. The drives are compatible with Elau`s SH servo motors and MC-4 servo amplifiers, and can be linked into the same synchronised drive network. Option modules can add I/O and safety functions to the iSH drives.

Elau says that with installations of up to three drives, it will usually be more economic to stick with standard motors and amplifiers. Larger installations will benefit from the integrated technology.

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