La pass with races “W” It is the main technique used in the process of parabolizzazione. Normally it runs with mirror above and below the tool, It can also be applied in some cases with inverted positions.
The position of the hands is the one with the palm which rests and pushes from the edge to "hours 8:20"And with the thumbs pointing towards the center to apply pressure , while the fingers to "hours 10:10"Exert traction , always by edge .
In mirror mode above, with tool and mirror of equal diameter latter must be pushed forward and backward with the pressure ( light or in some more substantial cases, ) located in the center.
During the large-and-fro longitudinal movement of the mirror, It is carried out at the same time a constant transverse displacement, whereby the center of the mirror describes a series of straight line segments in the shape of “W”. The extension of the races is delimited by the area inscribed in the concentric circle of the tool diameter not exceeding 3/4 the tool diameter the same, then the non-operating zone for the trajectory of the center of the mirror is the tool outer annulus amplitude 1/8 the diameter.
The operator performs the forward and backward strokes and simultaneously performs a slow and constant rotation around the tool. After some past ( yes 10 15) it makes a rotation of the mirror of an arbitrary value ( on average 30- 40 degrees ) in the direction opposite to that operator.
Among all the past is the one that most approximates the surfaces in contact to the parabolic shape.
SETTINGS AND ENFORCEMENT OF THE RACES WITH STROKES “W”
- Position: normally with mirror above, possibility of alternating mirror and the tool above / below
- Tool: Patina pitch.
- Pressure: weak and localized at the center,
- excursion: on segmented trajectory, the center of the mirror during the race describes a series of “W” inscribed in a concentric circle in the mirror, of up to amplitude 3/4 the diameter.
- racing Number: yes 5 10 , dependent on the diameter, for each series of “W” in one direction.
- times : circa 2 seconds between 'return stroke, time dependent variable to the dried mixture.
- Path: During the races the operator moves around the tool according to a slow and steady rotary motion and rotating the mirror ( 30-40 degrees) in the opposite direction after an arbitrary value racing. ( normally 10-15 )
- Grane used: the order of microns for abrasive polishing (cerium oxide, iron oxide, alumina and other …)
- Effectiveness: excellent for the purpose of approximation of the parabolic shape.
- Form produced: deepening at the center of the mirror surface with parabolic trend.
- Precautions: key is the verification or regeneration of the perfect tool operational status before each session ( adaptation, channels, hardness, etc… ).