Ambient temperature compensation on sand mixers for foundry applications was, until recently, only available as an optional extra. But Mitsubishi Electric automation products are making savings possible by allowing Omega Foundry Machinery to offer not only temperature compensation but also an enhanced user interface as standard on all of its machines, with no price penalty for the end user
The ‘sand’ used for casting operations in foundries is, in fact, a mix 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.
Supplier of sand mixers, Omega Foundry Machinery has for years offered customers the option of automatic compensation for this variation, but recently it decided to extend this benefit to all purchasers of new machines, without increasing prices.
In order to do this, Omega engineers knew it would be necessary to make savings in other areas. They turned their attention to the automation system used on the machines.
At the time, this comprised a programmable controller and several variable speed drives, the exact number depending on the configuration of the machine. To provide access to the drives for 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 the company’s latest automation components – in particular, the GT1155 colour HMI terminals, FX-series PLCs and D700 inverters – would make possible a more versatile and cost-effective design. The key would be the use of the RS485 multi-drop connection feature supported by these devices, which would, in effect, allow them to be daisy-chained together with a single network cable, thereby eliminating much 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.
“Presented with the potential benefits, it was an easy decision to redesign our automation system around the latest Mitsubishi products,” says Mark Lewis, technical director of Omega Foundry Machinery. “And the savings we made, combined with the attractive pricing of the products, made it possible for us to achieve our objective of offering temperature compensation as a standard feature on our machines. In fact, the power and versatility of the equipment allowed us to do much more.
“For example, the large memory capacity of the FX PLC and its convenient programming system allowed us to develop one single program that we use for all of our mixers – we simply enable and disable blocks of software according to the machine’s requirements. With just one program to maintain, we can concentrate our efforts on upgrading performance and developing new features,” says Lewis
For Omega engineers, loading the resulting upgrades into machines that are already in the field is also a quick, easy task, as the FX-series PLCs support standard Flash memory cards for program transfer.
The GT1155 HMI terminal in the new machines has an intuitive graphical display for machine operators, and provides them with detailed real-time information about machine status. The display calls 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 access detailed diagnostic information.
“Our objective is to manufacture the very best in foundry equipment that gives our customers decisive operational advantages while allowing them to benefit from the keenest of pricing. Our new machines meet this objective, thanks to the convenience, versatility and performance of Mitsubishi Electric automation products,” says Lewis.
