Roll grinding made easy with Ethernet

26 March 2013

A control system is helping machine-tool expert Halifax Numerical Controls (HNC) to achieve success in the competitive market for roll grinders for rubber-coated rollers.

Among the many benefits offered by the new control system, which includes components supplied by Omron, are complete integration of machine functions, an intuitive graphical operator interface, simple menu-based roll type selection, almost unlimited expandability to add new roll types, and powerful integrated diagnostics.

The first of the new HNC RG300 machines has been operating for several months at a site in Wales, and its benefits have proved so convincing that HNC has already received orders for a further machine to be used in the UK, and no fewer than four machines that will be used in the far east.

Rubber-coated rollers must be accurately ground with a profile to suit their ultimate application. For some applications, the profiles are parallel, but for the majority a precise convex or concave profile is needed. Designing a machine that will consistently and accurately grind these profiles is a difficult task, especially when end-users typically expect the machines to handle rollers up to 5m long, 600mm in diameter and weighing up to a quarter of a tonne.

After carefully evaluating the available control technologies for the new roll grinder, HNC’s engineers concluded that using a CNC system may not offer the most flexible and customisable platform for their machine. They felt that they needed a solution that would allow them to easily tailor the control system to suit the specific application.

After further investigating control options the HNC engineers decided that the best option would be to design a new control system based on Omron products, which would allow them to produce a fully customisable solution.

There were several reasons why HNC selected Omron equipment for this important project. These included Omron’s ability to supply all of the major control items needed, its ability to demonstrate Ethernet connectivity to third-party equipment, the global availability of service and support for its products, and HNC’s previous excellent experience of working with Omron.
The control solution developed for the new RG300 roll grinder includes a four-axis machine controller, of which only two axes are currently used; two 600W servo axes with absolute encoders; two inverter drives, one for the workhead drive, the other for the grinding wheel drive; a colour touchscreen operator interface panel; a safety relay and a safety locking switch. All of these components are linked by an EtherCAT network.

Using EtherCAT in this project delivered several important advantages – the control wiring was simplified, reducing wiring time, saving space in the control panel and reducing the risk of wiring errors, which resulted in faster testing and commissioning.

In addition, EtherCAT allows direct access to the key operating parameters for all of the inverters and servo drives, which means that they can all be set up and controlled from the HMI panel.

The Ethernet support offered by the Omron machine automation controller made it possible to connect a third-party wheel balancer direct to the control system via the controller’s built-in Ethernet/IP port. As a result, the wheel balancer can be monitored and controlled from the machine’s main HMI panel, eliminating the need for it to have its own separate user interface.

For configuring and programming the control system, HNC made use of Omron’s Sysmac Studio Integrated Motion and Logic programming platform.

With the new control system, profiles for each type of roller are prepared off-line, and are loaded into the control system with the aid of a standard SD memory card. The operator then choose the required recipe via a hand-held barcode scanner. The selected product is confirmed on the HMI’s display, and the control system does the rest.

In addition, the graphical display minimises the amount of text used in the operator interface, making it readily adaptable to international markets. In fact, HNC has programmed the interface so that the small amount of text it was essential to use can be displayed in any one of sixteen languages, with instant switching between languages. In addition, the operator interface can be easily and inexpensively customised to suit specific user requirements.

During the development of the control system for the new RG300, the HNC engineers discovered many additional benefits. For example, to accommodate the need for a manual handwheel control option for the grinding operation, it was only necessary to add an encoder interface to connect the handwheel to the EtherCAT network – no other hardware was needed. And it was also possible to use a spare analogue input on one of the inverter drives as a general purpose analogue input instead of purchasing an additional analogue module.
“The Omron control solution gives us everything we were looking for in terms of performance, versatility and reliability,” explained Mike Diskin, managing director of Halifax Numerical Controls, “It I also good value. In fact, compared with other control systems we investigated it gives us much more functionality for our money.”

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