ROBBI PLC control delivers CNC performance

By Simon Rood - Tuesday 2nd April 2013 Italy-based grinding machine manufacturer ROBBI has introduced a new PLC control for its range of Omicron cylindrical grinders. A move that delivers enhanced performance, improved cycle times and greater ease of use that take their performance to near CNC control level, but at a considerable price advantage. The new T6 control system is being introduced to the UK through ROBBI’s long-term sole distributor, RK International Machine Tools and Sales Director Dick Aldrich hails the development as a milestone in grinding machine control technology. “We have worked with ROBBI for 15 years and the success of their machines in the UK is testament to the quality of manufacture and their ability to meet the demands of the market. This latest development continues that tradition as we are finding that the vast majority of cylindrical grinding in the UK is relatively straightforward, with the main requirement being for plain diameters, such as bearing journals. Therefore, we find that demand for full CNC control of a cylindrical grinding machine is not that great a priority for customers. However, they do we the advantage of having some of the benefits that CNC can bring, and the T6 control meets those completely.” The development of the T6 control is such that it delivers as close as you will get to full CNC performance from a PLC control system, with the added benefit of a price advantage over CNC and simplicity of use for customers producing low to medium volume components. One of the key features of the T6 control is the ability to create up to eight diameter pre-sets, including setting grinding tolerances. These diameters can then be ground in an automatic cycle. The wheel dressing function is also simplified using the control’s teach facility. The operator uses the machine’s hand wheel to the dressing diamond, the position of the dresser is then memorised in the x and z axes. The operator then simply inputs the dressing width and feed and the control takes over. Once set the dressing can be done in cycle with automatic compensation for the changes that occur to the wheel during the process. Other benefits of the control are its control of key aspects of the grinding process including the easy integration of wheel balancing, anti-crash, probing and side flagging systems. The latter simplifies the grinding of shoulders, and when active the machine will stop at that point in the cycle, allowing the operator to manually grind the shoulder. Once done, the cycle is restarted and the machine moves on to the next diameter in the sequence. When combined with the in-built plunge and traverse cycles that control rapid grinding wheel approach, rough and finish grinding, spark out and wheel retraction, the T6 can significantly improve productivity. “The advantages that the T6 control brings, in terms of functionality and simplicity of operation make it ideal for those companies that have been reluctant to move from manual grinding to CNC,” says RK International’s Dick Aldrich. “The T6 control will help to reduce non-grinding time making the overall process much more efficient. At the same time it marries the skill of an experienced operator to the technical ability of a modern control to provide automation of laborious operations, allowing the move from manual operations to near CNC control for minimal investment.” That said, machines fitted with the T6 control can still be used in manual mode and one addition that ROBBI has included is an automatic stop at size function, a feature that has long been absent on full CNC machines with electronic handwheels. The ease of use of the T6 control is emphasised by the fact that operator training can be completed within four hours and with the full range of ROBBI Omicron cylindrical grinding machines being fitted with the new control users have the ability to enhance the productivity of grinding operations to cover between centre distances of 600 mm to 12,000 mm.

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