Tuesday 13 April 2010

Innovative vacuum generator module features energy-efficient air-saving function

Festo has launched a highly innovative vacuum generator module equipped with a host of built-in energy-saving and condition monitoring functions. One of the key features of the new OVEM vacuum generator is an integrated vacuum sensor, which continuously monitors the output; the module will operate until a user-defined vacuum threshold has been reached, and then automatically switch off, resulting in significant energy savings. A built-in non-return valve ensures that in normal use, vacuum loss is limited to air leakage between the suction cup and the workpiece; the generator will automatically turn on again if the vacuum drops to a second user-defined vacuum threshold.

Their OVEM vacuum generators use the venturi principle to create a vacuum, employing a de Laval nozzle to accelerate airflow across the top of the evacuation tube. They are designed for use with standard 40 µm filtered compressed air supplies, with efficiency-optimised flow characteristics to reduce energy consumption. The generators are available in high vacuum and high suction rate versions, and offer a choice of 5, 7 and 10 mm de Laval nozzles to accommodate a variety of vacuum flow rate requirements and different porosities of workpiece materials.

As well as helping to save compressed air, the OVEM generator’s vacuum sensor provides continuous system monitoring and diagnostic functions. Any gradual or sudden loss of vacuum, or any lengthening of vacuum evacuation time, is detected automatically and an electrical signal fed back to the system’s controller. This information can be used for preventive maintenance purposes, to minimise machine downtime and ensure process reliability.

All user-defined operating parameters – including upper and lower vacuum thresholds, normal vacuum evacuation time and overall system cycle time – are set up using the pushbuttons and LCD screen on the front face of the vacuum generator module. The 4-character alphanumeric LCD is backlit and features analogue and numeric displays which enable the relative pressure, or vacuum, to be seen at a glance. Users can choose to display the vacuum level in inchHg, inchH2O or bar – whichever is most meaningful for their application.

The OVEM vacuum generator module features two fully integrated solenoid control valves – one for switching its compressed air supply on and off to generate the vacuum, the other for activating an ejector pulse. The ejector pulse helps speed cycle time by quickly dissipating the vacuum when the generator is turned off, enabling the workpiece to be released using a quick ‘blip’, instead of having to let the suction cup and associated air pathway slowly come back up to full atmospheric pressure. A flow control screw is provided for adjustment of ejector pulse flow.

Festo’s OVEM vacuum generators are very easy to install and maintain. All pneumatic connections employ push-in QS fittings, and all electrical connections are made via a single 5-pin M12 plug. The solenoid valve for vacuum on/off can be controlled by a normally-closed or normally-open switch, and there is a choice of six different configurations for the vacuum sensor’s electrical switching output, to further simplify system integration. The generators require very little in the way of maintenance; an open silencer and integrated air filter prevent internal contamination, and a built-in viewing window facilitates filter inspection without having to remove the module from the system.

Venturi based vacuum generators can be extremely effective, speeding up cycle times and operating reliability. To ensure that they are energy efficient they need to be selected according to the demands of the application; the size, mass and porosity of the item to be picked, as well as the forces resulting from the planned movement, are all factors which influence this choice. Festo’s vacuum selection software is now available free of charge, to shorten the calculation time in selecting the right unit for each application.

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