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Savings made possible by Mitsubishi Electric automation products have enabled Omega Foundry Machinery to offer not only temperature compensation but also an enhanced user interface as standard.

Ambient temperature compensation, a desirable feature on sand mixers for foundry applications was, until recently, only available as an option at significant extra cost.

The ‘sand’ used for casting operations in foundries is, in fact, a mixture of sand, resin and catalysts that aid setting.

The proportions of the ingredients have to be accurately controlled in order to achieve the optimum setting qualities needed to ensure that sand moulds consistently produce high-quality castings.

The proportions of the ingredients required are, however, dependent on the ambient temperature.

Sand-mixer supplier Omega Foundry Machinery has for many years offered its customers the option of automatic compensation for this variation, but recently the company decided that it wanted to extend this benefit to all purchasers of new machines, without increasing its prices.

In order to do this, the engineers at Omega knew that it would be necessary to make savings in other areas, beginning with the automation system used on the machines.

At the time, this comprised a programmable controller (PLC) and several variable-speed drives, the exact number depending on the configuration of the machine.

To provide access to the drives for the purposes of changing operating parameters, they were mounted through an aperture in the front door of the control panel and covered with a lockable cover, an arrangement that involved complicated and expensive metalwork.

The machine’s user interface was principally made up of pushbuttons, switches and indicator lights, augmented by a small text-only message display.

All of the interconnection between the major components used conventional wiring.

Discussions with application engineers at Mitsubishi Electric suggested, however, that the company’s latest automation components – the GT1155 colour HMI terminals, FX-series PLCs and D700 inverters in particular – would make possible a more versatile and cost-effective design.

The key would be using the RS485 multi-drop connection feature supported by these devices, which would, in effect, allow them to be linked together with a single network cable, thereby eliminating much of the wiring in the control panel.

Further, the GT1155 HMI terminal, with its full graphical support and its associated keypad, would replace almost all of the pushbuttons, switches and indicator lights.

It could also be programmed to allow the operating parameters of the D700 drives to be accessed via its screen and keypad, so the expensive mounting arrangements required to allow direct physical access to the drives would no longer be needed.

Omega Foundry Machinery commented that the large memory capacity of the FX PLC and its convenient programming system had made it possible for it to develop one single program that could be used for all of its mixers.

With just one program to maintain instead of dozens, the company’s engineers could concentrate their efforts on upgrading performance and developing new features.

They also found loading the resulting upgrades into machines that are already in the field to be a quick and easy task, as the FX-series PLCs support standard Flash memory cards for program transfer.

The GT1155 HMI terminal used in the new machines has opened the door to further important benefits.

Its graphical display is intuitive for machine operators and provides them with detailed real-time information about machine status.

The display is also used to call the operator’s attention to alarm conditions, such as low air pressure or low sand levels and, in the event of a problem, it can be used to access detailed diagnostic information.

Mitsubishi Electric Automation Systems

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