Servo drives provide versatility to machine builder

A new machine design for the building of car radiator cores is using AC drives and motion control software to provide precise servo motion control, writes Dean Palmer

"We set out to rethink the approach to core building machines," explained Mike Evans, managing director at Equipment Building Systems (EBS) a company that builds machines for making car radiator cores. He continued: "The traditional approach to resetting the machine for another product involves tool resetting and the time consuming changing of fixtures. "With this [new] machine, it's a simple matter of changing over quick-release tools, plugging in identification modules and resetting the software - all of which takes just a matter of minutes, compared with a couple of hours for a conventional machine." Evans is describing his company's new 'Semi-Automatic Servo Driven Core Builder', a radical new concept, with the objective of simplifying and cutting tool changeover times. The machine uses an intelligent servo drive system, with automatic selection of the correct 'recipe' when tooling is swapped over. Cores can be of variable sizes so the operator can set the part number on the display interface, which automatically selects the programme in the drives. The part number is also compared with the electro-mechanical plug-in identification for the tooling that is fitted, before the controlling PLC allows the programme to proceed. The two drives on the machine are Unidrive SP units supplied by Control Techniques (CT). The two, 5.5kW Unidrive SP AC drives, coupled with Unimotor servomotors, are linked to the machine by 101 gearboxes and safety clutches, provide the motive power for the two key servo movements on the core making machine. The drives are both fitted with CT's 'EZMotion' on-board PLC modules that contain all of the programming for the motions. They also have modules to provide DeviceNet networking with the machine's PLC, providing overall supervisory control and the operators man-machine interface (MMI). The EZMotion modules give straightforward, logical programming of speeds, positioning and limits as well as a 'first time correct' programming capability. EZMotion is basically a motion controller that clicks into one of the Unidrive SP's option slots, taking up no extra cubicle space. It uses its own internal processor, offering users one-and-a-half axis motion synchronised to a reference encoder. The motion controller is backed up by CT's free 'PowerTools Pro' programming software that can be used by experienced control engineers or by someone who is new to servo systems. The operator of the EBS core builder machine adds sub-components - up to 62 tubes - using tube locators to keep the gaps constant. Then, on pressing a foot pedal, the first of the servo drives brings down a pressure plate to hold the tubes, compress the core and create the correct pitch, while the pneumatically-operated tube locators are moved away and down. The second servo drive brings in the header nests from both sides, securing them by means of folding tags. The servos return to the start position and the operator removes the completed core with a c-clamp to provide extra support. "The Unidrive SP provides us with the versatility we need for these machines," explained Evans. "As well as powerful on-board PLCs, the drives incorporate DeviceNet, which significantly simplifies the wiring and have proved very reliable in operation. This is the third such machine we have built, the first was delivered just over a year ago and we've never had a call-out." EBS designs and manufactures special purpose machines, mainly assembly and test machines, for the automotive, consumer, pharmaceutical and general industrial sectors.