Pressing obkatnaya processing by a roller
The rotational extract (RE) is understood as receiving a hollow axisymmetric detail from the flat or volume, hollow, rotating preparation deformed by one or several rollers on the rotating mandrel. Characteristic of process of RV is the local center of deformation and the set regulated considerable reduction of thickness of a wall of initial preparation.
Scheme of a shaping
RV is made from the preparation fixed on the rotating mandrel, the rollers satellitno rotating from preparation which move along the forming mandrel with the necessary set gap. At contact of rollers with preparation in the place of their contact there is a big specific pressure under the influence of which preparation metal plastically flows in a gap between a roller and a mandrel, forming a detail. The internal surface of a detail takes the form of an external surface of a mandrel, and the external contour of a detail repeats a trajectory of movement of a working edge of a roller.
On modern camps of a rotational extract it is possible to conduct expansion by one, two or three rollers. Presence of the stretching forces in the formed preparation site throughout all process of an extract and the fact that the formed part of preparation all the time is on a mandrel reduces a possibility of a longitudinal bend of a detail even in the presence of a small beating of a mandrel or a small raznostennost of preparation.
Ways of a shaping
Distinguish two main ways of the Rotational extract:
Straight line at which the direction of a current of material coincides with the direction of movement of a roller
The return, at which the direction of a current of material to an opposite direction of movement of a roller
At a rotational extract in the direct way the external contour of a mandrel has to repeat an internal contour of the extended detail with technological allowances therefore length of a mandrel has to be more than length of a detail that complicates a mandrel design, does it heavy and expensive, and adjustment of more labor - consuming.
The direct way of a rotational extract is recommended for a shaping of thin - walled and lengthy cylindrical details, and also all types of details of conic and ozhivalny forms. At RV on the return way the mandrel has to correspond to an internal contour of preparation therefore the mandrel can be several times shorter than a detail. The return way is admissible to be applied to a shaping of rather thick - walled and short exact preparations of cylindrical details or preparations of details.
At expression without thinning for several consecutive passes of the tool thickness of a wall does not change or slightly decreases. Receive more or less considerable reduction of the maximum diameter of preparation when processing without thinning. When processing with thinning and expansion outer diameter for cooking (or the internal diameter of pipes) and the received detail remains invariable, and wall thickness more or less considerably decreases; thanks to it length of the received detail along a rotation axis increases.