Technology of subjection by empty: an option to the devices of standard subjection

In the first place, stand out some basic concepts about how work the systems of subjection by empty. An empty produces , according to the norm DIN 28400, when the density of the number of particles of a gas is lower that the density of the number of particles of the atmosphere in the terrestrial surface, or, in other words when the pressesure of a gas is lower that the atmospheric pressesure. It is precisely the difference of pressesure between the space evacuated under a piece and the natural atmospheric pressesure on a piece the one who uses a system of subjection by empty to attach pieces of work. In contrast with the belief that a piece is subjected to succión when subject by empty, in fact, the strength of subjection creates due to the fact that the pressesure of natural air presiona the piece of work of uniform way in all his surface on the plate of subjection.

Like norm in the area of the technology of subjection by empty, the values of empty give in terms of the difference between the pressesure acclimatise and subpresión, taking like point of reference the pressesure acclimatise and supposing that it is of 0 bar. The values of empty also carry always a sign less in front of them, for example, -0,3 bar (1 bar is the same by force of 10 N in a surface of 1 cm²). With the end to determine the strength of subjection (F) for a system of subjection by empty, the difference of pressesure (p) multiplies by the effective surface (To). If for a piece of 160 mm x 160 mm, evacúa a superficial area of 150 mm x 150 mm to -0,6 bar, the strength of retention (strength of succión) in the steering z is F = 6 N/cm² x 15 cm x 15 cm = 1350 N. The strength of retention and the subpresión have a proportional behaviour between himself. In contrast, the time of evacuation, as well as the necessary power increase disproportionately if the subpresión and the strength of retention increase . In the previous example, if the subpresión increased 1,5 times to -0,9 bar, the strength of retention increases proportionally to 2025 N. The necessary power and the time of evacuation increase disproportionately in a factor of 3.

When cutting metallic products, the systems of subjection by empty in shape of plates matrix, whose basic body consists in aluminium of high resistance, have showed to be the best. They can produce with dimensions normalised and dimensions of rejilla of different degrees of finura. The surface of subjection can expand by means of the connection of several plates matrix. In base to the geometry of the piece, can determine the mechanised and the horizontal strengths, the surface of succión and the dimensions of rejilla necessary. What finer was the rejilla, more complex can be the geometry of the pieces.

With the end to attach a piece of work, in the rejilla places one throws of calafateo that corresponds with the geometry of the piece. The topes rear mechanics of variable use facilitate the positioning and avoid that the piece displace horizontally, for example during the molienda in plane. Later, the piece of work places face down and activates the empty. In question of seconds, the piece remains subject in plane, of safe and precise form. The differences of height can compensate through the designated device of succión of the table of rejilla. With his help, the cut of the plates matrix also can produce without risk.

The plates matrix are the best to attach pieces of thin work. Even the metallic leaves can mount with precision and without risk of deformation. Attach the pieces in plane avoids that they produce vibrations and marks of rectified. It is true, however, that in comparison with the plates of magnetic fixation, the plates matrix have less strength of retention. However, can use in the mechanised of pieces no ferromagnetic, such like pieces of aluminium or of compound materials. With the help of plates matrix even can attach of reliable form thin plates or plates of metal, for which the magnetic field of the plates of magnetic subjection would not provide subjection. Because of his weight comparatively lower, the plates matrix can use like a solution of additional subjection. With help of blocks of subjection, supports of suje-ción or plates of magnetic subjection, can mount fast and easily in the table of mechanised. For his use like a system of fixation on the dot zero, come with threaded orifices of the factory for the vástagos of subjection.

To produce subpresión in the mechanised, use two methods. Nozzles Venturi of low cost that can integrate directly in the plates matrix. They are compact, light, of little wear, do not generate heat and allow to generate quickly the empty. However, have a capacity limited of succión, what means that only they can attach surfaces relatively small and entirely sealed. The liquids succionados only can delete with nozzles Venturi. Besides, the nozzles create a quite high noise. The users that require a big flexibility and reliability generally decide by units of empty of low maintenance, that are silent and with little vibration and can use with one or several plates matrix. With them can produce high subpresiones to volumetric flows simultaneously high. The units of empty with an integrated cheese cheese tank provide a strong impulse of succión and avoid a sudden fall of the empty. Ideally, the units have several components to supervise the system and interfaces for the integration in the system of control of the machine. With special functions of stop of emergency, the bomb of empty is protected of the damages caused by liquids succionados, or detains the machine if it produces a sudden loss of the strength of subjection.

A sophisticated solution to attach the piece in the zone of mechanised is the system modulate of subjection by empty Planes of Schunk, whose unit of empty has all these characteristics of hygiene. Apart from this, the pumps of empty lubricated with oil are instrumented with a separador of liquids, that also serves like a tank of empty. A centre of operation in empty makes possible goes-ciar automatically the unit during the execution of operations, if necessary, without interrupting the process. Like the bomb of empty activates only when the empty falls underneath of 85%, the units consume little power and are silent. In necessary case, the unit of control can desactivar, so that the bomb can work in way of continuous operation. The plates Flat matrix offer in the following sizes, 300 x 200, 300 x 400 and 400 x 600 mm with dimensions of rejilla of 12,5, 25 and 30 mm. The pieces of work with a tolerance of height of +/- 0,02 mm can attach in them. On request, the plates matrix can instrument with islands of friction patented. These activate automatically through the source of empty and allow greater strengths of shearing. In comparison with the plates matrix without islands of friction, the horizontal strengths subjection increase until in 30% with islands of friction. At the same time, this does not add strength on the piece of work. The islands of friction are resistant to the oil and to the ozone and can substitute individually if necessary. The plates matrix use often like a solution of additional subjection. Like part of the program modulate bigger all over the world to attach pieces of work estacionarias, can mount of fast and simple form on the devices of subjection already existent, in plates of magnetic subjection Magnos, for example, or in the system of fixation on the dot zero Vero-S.