April 2021

38 n MACHINE BUILDING April 2021 www.drivesncontrols.com Multi-VSD turret design cuts machining times by at least 40% J afs Machines of Colombia designs and builds machining systems including one that allows simultaneous machining of components via seven individually controlled spindles in an indexable turret. In addition to drilling, some of the spindle tools need to thread components, so reversible movement is required. The spindles rotate individually on the turret powered by 1.5hp (1.12kW) 220V three-phase motors. But they have to rotate at different speeds, and to stop and start, depending on the station and tool being used, as well as being reversible. To achieve the required flexibility, it was decided to use a separate VSD for each spindle. Two local companies – Inginieria OL and Fanauto – worked together on the project. “The difficulty with the process was that because of the indexable turret and its movements, it was not easy to connect to the drives using individual wiring,” recalls Juan Carlos Figueredo of Faunauto, which supplied the VSDs for the project, built by the Welsh drives-maker Invertek. “We needed to use eight Invertek Optidrive E3 VSDs to accurately control the speed of the spindles and the indexing rotation of the turret,” he continues. “They were connected through a Modbus RS-485 communications network to avoid wiring the drives individually, which would have been impossible because of the movement of the turret. “Using this type of connection means only two signals are sent to the eight drives (RS- 485+ and RS-485–) via slip-rings,” Figueredo explains. “The drives are configured to be controlled through Modbus communication, via a PLC.” Not only were the IP20-protected 2hp (1.5kW) drives able to control the multiple motors on the moving turret, but they also helped reduce machining times by 40%. “We managed to achieve excellent response speed which also allowed changes in the rotation of the threading stations without damaging the tapping tool,” Figueredo reports. “The response in speed, on and off, and change of rotation, met all of the requirements of the process.” The Jafs machines – which the company calls Octo-Unit Drilling Machines – are a key product in its strategy to penetrate the US market. They can be used to machine a variety of materials including carbon steels, bronze, alloy steels and engineering plastics. Their ability to cut machining times by 40% means that the VSD-equipped machines has attractions over Jafs’ rivals. “Our customers can not only produce more products in a shorter time,” says a representative of the company, “but they know they also have a product that is reliable, cost-effective and, more importantly, providing greater opportunities for profit.” n A Colombian machine-builder has slashed machining times in a complex seven-station drilling machine by more than 40% by introducing UK-manufactured VSDs into the process. The seven spindles in Jafs’drilling machine are controlled by individual VSDs The Jafs machine can perform eight separate machining operations simultaneously