Servo-proportional valves optimise roller performance

Intelligent Moog hydraulic valves are adding brain to muscle at metalworking company Bronx Manufacturing, which builds high-quality, specialist mechanical equipment for a diverse range of industries, from automotive to construction and from security to mining.

The company, which has particular experience in metal forming and finishing within the steel industry, is fitting Moog's Digital Interface Valve (DIV) to a new machine that levels coiled high-strength, low-carbon steel strip. This is the first application of the DIV in the UK.

Fundamentally the levelling machine is still based on a set of rollers, but the way those rollers apply deflections to the material has improved significantly and, in Bronx Manufacturing's new Completely Automatic Levelling Machine (CALM), the hydraulics are the primary flattening control element.

Depending on their output, the controlling pressure of each of the seven hydraulic axes can be altered using the Moog DIV. Bronx has built a test rig to verify the feedback mechanism, and has proved that it can position to an accuracy within five microns.

New control philosophy

Tim Brown, chairman of Bronx Manufacturing, explains: "We go about position control in a slightly different way because we calculate exactly where to position the rollers from the hydraulic cylinders using the Moog valves.

"The currently available systems for positioning rollers are quite crude. Our system is quite sophisticated in that the operator can select the level of plasticity, which is the ratio of the cross-section that has been plastically deformed, or bent beyond its elastic limit, to that which has not. Dependent on the plasticity, the material will be permanently deformed, unless it is bent back the other way."

A Digital Interface Valve is a DDV Direct Drive Valve with microprocessor-based electronics and a CANopen fieldbus. These servo-proportional valves are parameterised and monitored using the built-in CANbus interface.

Brown states: "In effect, the versatility of the valve itself enables a programmable machine. The Moog valves are fully programmable and accessible via CAN fieldbus. Moog provides an application program that allows you to configure the valve and to communicate with a PLC or PC acting as a fieldbus master.

"If you have a material that does not behave like ordinary materials, you have the flexibility to program it. When you are dealing with high-strength, low-carbon steel, it is very important to match the roller size and spacing accurately. Another advantage of the Moog Valve is that when you change rollers to another diameter, you may have to change the setpoints, and that can now be programmed. Previously, you would have had to recalibrate the machine, which could be a long-winded process.

"We are claiming that you can change the rollers in our machine at the touch of a button. We would have used hand-cranked jacks to do in the past what we are doing now with Moog Digital Interface Valves, or wedges that would be pushed in by jacks driven by geared motors. Now we can go fully automatic with load-sensitive control, or we can use position control derived from basic operator inputs calculated from where to place rollers."

Rick Steele, Business Development Manager at Moog, adds: "This is the first application of the DIV technology in the UK and it was fantastic to find one that would really highlight its capabilities. It is a good example of where digital hydraulic valve technology can be used to co-ordinate axis and change the dynamic parameters of the valves to optimise machine performance. Tim really knows what he is talking about when it comes to achieving machine performance, having undertaken a significant portion of the design work himself, so I am delighted that he chose Moog technology to complement the systems he had already developed in house."