Drives stack up to steel handling requirements

A purpose-built machine for the handling and stacking of steel blanks of any shape and size for use in the car industry features the new Unidrive SP "solutions platform" AC drives.

A purpose-built machine for the handling and stacking of steel blanks of any shape and size for use in the car industry features the new Unidrive SP 'solutions platform" AC drives from Control Techniques, chosen for their unique combination of features - Profibus connection, onboard programmability, secure disable safety function and ease of programming from a PC.

A conventional stacker drops blanks onto a stacking pallet, with the possibility of edge or surface damage to the blanks.

This stacker, designed by Specialist Stacking Systems (SSS) of Kingswinford carefully handles blanks, preventing damage, whilst simultaneously boosting handling speed by an estimated 50%.

"There's no other drive on the market that meets all our requirements for this particular job", says Dave Caple of Transicon, the company tasked by the SSS with designing and building the complex control system for the machine.

"It was essential that we had complete flexibility over every aspect of the drives" performance from the outset.

I was impressed that whatever we needed was there as a standard item on the drives, from communications to preset speeds and independent ramps and secure disable for complete confidence when we were working on the machine - and they were very straightforward to program too", he says.

"Perhaps most important of all", he adds, "was the high resolution speed loop within the new Unidrive SP, which gives us +/-1mm accuracy on all the drives and this precision of control was maintained and was entirely predictable even at very low speeds".

The stacking machine, designed by Dave Mardel at SSS, has to meet the particular requirements for side stacking in an area with a space of just three metres.

The machine also has to traverse so that operators can access and change dies on the press.

A four-strand magnetic indexing belt for the initial handling of the panels, a feature rarely seen in the UK, brings the panels into the machine, where pneumatic fingers push the blanks onto a loading conveyor that loads a stacking table, the orientation of which is adjustable +/-90 degrees to suit subsequent automatic loaders.

As the stack builds, the table moves down by degrees to accommodate new blanks and, when full, the stack is unloaded by conveyor.

All movements of the machine are controlled by Unidrive SP AC drives in closed loop vector mode, with feedback from 560pulse/rev encoders to the controlling PLC, which, in turn, transmits a speed or position signal to the drives.

All motors on the machine are vector motors from sister company Leroy Somer.

1.1kW Unidrive SP drives control the indexing magnetic feed conveyor, the loading conveyor, the stacking table rotation, the ball-screw positioned tamper guide drives, the and the unloading conveyor and the traverse drive is 2.2kW.

"The drives are all preprogrammed using selectable preset speeds and ramps", explains Dave Caple.

"Using CTSoft it was very easy to program and other changes were programmed in using the removable keypad - we only needed the one for all seven drives", he says.

"We have used the secure disable capability of the Unidrive SP's extensively during the development process", says Caple, "and this is a good safety feature for the end user".

Safety relays monitor all of the gates on the machine with outputs to the drives, to initiate the secure disable feature preventing drives running whilst gates are open.

"We have used the features of the Unidrive SP extensively on this project", concludes Caple.

"The drive's flexibility and wealth of standard features have met all of our needs and more, giving us great confidence from the outset that it would meet all eventualities - and it has.

An excellent product".

Transicon, based in Telford, specialises in multitechnology monitoring and control systems aimed at achieving process optimisation.

The company, provides programming and application of Scada and PLC systems and designs and builds drive control systems to control process lines such as cut-to-length, slitting, multiblanking, coiling and coating processes with the ferrous and nonferrous strip, bar and tube industries.

Specialist Stacking Systems produces a wide range of machines for stacking ferrous and nonferrous blanks and sheets of virtually any size or shape in different multiples either in width or length.

The company confidently predicts a 50% increase in productivity against any conventional stacking system and additionally offers more careful handling, particularly important in the white goods and automotive industries.

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