Trecnología de Vacío

Introducción La tecnología de vacío hace uso del diferencial de presión entre la presión atmosférica y un vacío parcial para realizar el trabajo Si un vacío completo se creara, el diferencial de presión máximo sería 1 atmósfera (alrededor de 1013mbar) The larger the surface area over which this differential is acting the higher is the force

Unidades de medida de Vacío Atmósfera std

Factores de Conversión 1 Torr = 1mm Hg at 00C 1mm H2O = 9.81 Pa 1 Pa = 1 N/m2

Importante El tamaño físico de un generador del vacío no se rige por la condición de aire inducido, en el nivel de vacío que alcanzará

Tipos de generadores de Vacío Simple etapa Ventajas Bajo costo No emite calor compacto Desventajas Alto nivel de ruido Flujo alto o vacío alto Cuando el aire entra en el difusor y su diámetro aumenta el aire se expande y aumenta su velocidad, el aire que se encuentra en el puerto de vacío es inducido en direccion del flujo y es succionado aumentando así el caudal de salida y creando el vacío.

Tipos de generadores de Vacío Multi etapa Ventajas Bajo nivel de ruido No genera calor Vajo consumo de aire (4-1) Diseño compacto Rapida respuesta Desventajas Alto costo Funcionamiento similar al de simple etapa, pero se usan mas difusores para crear mas vaío.

Diseno de sistemas Centralizado decentralizado

Sistema de diseño. Descentralización La energía usada es proporcional al volumen de evacuación por lo que se debe considerar la descentralización. Si varios puntos son equipados para vacío, una mayor economía se obtiene si se coloca a cada punto de aplicación un generador de vacío. Mínimo Volumen de Vacío Mayor seguridad Maximiza el desempeño del sistema Conclusión – siempre trate en lo posible de obtener le menor cantidad de volumen a evacuar.

Capacidad del generador Material no poroso Una vez asegurado el componente, el flujo de vacío es cero. Requiere bajo caudal Material poroso Para obtener un adecuado nivel de vacío, el generador debe tener suficiente capacidad de evacuación te aire, que esta en constante fuga dentro del sistema Alto Flujo General Copa con sello perfecto = bajo flujo, alto vacío Material poroso = alto flujo, menos vacío

Comparación de flujo. Comparación de flujo de vació l/min.

Copa de Vacio FUELLE Flat

Materiales de Copas Nitrile Silicon

Consideraciones Velocidad: Considerar los momentos generados por la alta velocidad de transferencia y los movimientos de carga. Cup distortion in certain designs and materials will occur. Component release: Ordinarily the workpiece would be released when the air supply is removed and the vacuum level drops. In high speed automation a separate system can be used to eject the workpiece by adding momentary pressure to the vacuum line. Filtration: The ingress of dust, lint or moisture can have a detrimental effect on the efficiency of the venturi. Where ingress is likely fit a vacuum filter. Fittings: Conventional design push in fittings are acceptable, although push on fittings are more suitable. Avoid 90 degree bends, preferably swept. Tube: Conventional nylon or polyurethane

Ejection circuit Valves can be air or direct acting solenoid 2/2 or 3/2 with a pulse signal to the eject valve

Applications Packaging machines Electronics Automotive Evacuating the vessel of air speeds up liquid filling Bellows suction cups are ideal for picking up and opening all kinds of bags Labels can be applied quickly and efficiently to particularly soft or uneven products Box and carton forming Electronics Printed Circuit Board test fixtures Vacuum forceps Automotive Body panel transfer Glass component handling And many more…..

Porosity (fixed) To maintain the desired vacuum level a generator must have the capacity to account for the leaking air. If leakage occurs via a known aperture, flow can be established by using the table

Porosity (unknown) When leakage occurs through a porous material, or in an unknown way, the flow can be established by a test with a vacuum generator. It is connected to the system and the achieved vacuum level read (at least 40%). The flow that occurs at this vacuum level can be seen in the data against each generator. This roughly corresponds to the leaking flow.

Sizing suction cups When sizing a suction cup it is the required lifting force that is crucial. As the weight of the object being handled is often known and the diameter of the cup is required, a simple equation can be used, dependent on the type of lift taking place. Horizontal contact lift Vertical contact lift

Sizing suction cups F Horizontal contact lift Where : F = lift force (N) p = vacuum (bar) d = suction cup dia. (mm) n = number of suction cups s = safety factor F

Sizing suction cups F Vertical contact lift Where : F = lift force (N) p = vacuum (bar) d = suction cup dia. (mm) n = number of suction cups s = safety factor m = friction coefficient F

Suction cup selection Select the right type of cup for the application Use a safety factor of 2 or 4, depending on type of lift Consider additional dynamic forces Bear in mind positioning accuracy Consider the effect of black rubber on bright surfaces No silicon on pre-painted surfaces Distribution and number of cups in relation to centre of gravity Choose accessories to give the best performance

Example Task A glass plate measuring 2500mm x 1250mm is to be lifted from a machine. The weight of the glass is 200kg. (2000 N) The internal volume of the vacuum line on the lifting frame is V1 = 2.71 litres. An evacuation time of t = 3 seconds is required. The working vacuum level is 60% at 6 bar operating pressure. Specify Suction cup type. Number and size of suction cups. Total volume to be evacuated. A suitable vacuum generator.

Example (checklist) Weight of object to be lifted 200kg (2000 N) Horizontal or vertical lift Horizontal Flat or curved surface Flat Porous, yes or no No Operating pressure 6 bar Working vacuum level 60% Centralized or localized system Centralized Number of suction cups 6 (due to size of plate) Suction cup type / material Flat, nitrile Suction cup positioning Evenly distributed around center of gravity Particle ingress None Non return valve No Pressure switch type None Level compensation None Eject circuit Not required Evacuation time 3 second Tube length / dia. or volume 2.71 liters

Example (calculation) Suction cup d= 118 mm Nearest standard dia. = 150 mm Part Number - M/58312/01 p ´ = 6 0.6 2 2000 d 40

Example (calculation) System capacity Total system capacity (V) is the sum of the internal volume of the vacuum line (V1) and that of the suction cups (VC). Thus: V = V1 + VC V1 is given as 2.71 litres VC is obtained from product data sheets. For M/58312/01 VC = 177cm3 x 6 = 1062 cm3 = 1.06 litres Therefore: V = 2.71 + 1.06 = 3.77 litres

Example (calculation) Evacuation time The time to evacuate a volume of 1 litre (t1): From the vacuum generator technical data refer to the table ‘Time (sec) for evacuation of 1 litre volume to vacuum’ in the column ‘p = -0.6 bar’. Select a generator with a lower figure than that calculated. We find 0.58 s/l for M/58102/30

Vacuum products Single stage generator Multi stage generators

Vacuum products Flat and bellows type suction cups Level compensators Flexible connectors

Vacuum products Pneumatic, electronic and electrical pressure switches Vacuum filters and gauges Cylinders with hollow piston rods

Modular vacuum management Sensing, logic and local analogue control AVAILABLE OCTOBER 2000

Complex integration Internal silencer High performance jet modules Modular construction Switchable vacuum and blow-off Reduces installation time LED function indicators Reliable check valve design Optional remote control Internal sensor with 4-20 ma output

Removable/replaceable jet modules

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