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6 Mode 1 : Continous rolling milling mode
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This method may be carried out ONLY after spacewidth rough machining!
 (fig.02A)
(fig.03U)
, better if followed by a proper root undercut made
with rounded mill.
(fig.12A)
(fig.13U)
show innest position layout.
(fig.15A)
(fig.16A)
show start and arrive conditions.
In this machining mode milling tool center moves along X over a plane tangent
to base cylinder, while gear on the table turns, according to
rolling law shown before, with a simple NC
command from (X1,B1) to (X2,B2) with Z=base radius.
In case the gear is not exactly centered on the table, the movement
must involve also Z-axe and must be shared into n partial positions,
each of them with properly re-calcoulated X-B intermediate values
according to value and current direction of center desplacenment vector; in
this case some form error occours since a continue formula is
linearized into n steps.
Extreme positions may be easily calculated according to tip diameter
and (for example) active profile starting diameter.
Both these values may be modified according to milling path width
and tool angle:
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[9] Extra radius = path width / 2 * TAN(beta0)
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In enclosed example this extra is considered only for multi-cut planning.
Form error: both values of path width and tool diameter lead to
a first value F1 representing the arrow operated by milling tool movement
in local tangent plane
(fig.19U)
.
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[10] F1 = Rtool - ( SQR ( Rtool ^ 2 - (path width / 2) ^ 2 ) )
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This value and minimum curvature radius lead to the true form error F2
(fig.20U)
(fig.27A)
:
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[11] F2 = rcurv -( SQR ( rcurv ^ 2 - F1 ^ 2 ) )
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(tabled in
(fig.20U)
with entrance in column 1)
For example, for Dtool=250 mm and pathwidth=60 mm you have F1=4,50 mm.
In case of minimum curvature radius = 75 mm you may have a form error
= 0,122 mm , that lowers to 0,017 mm for radius=500 mm .
Although these are good values, they may be easily reduced:
if you operate an extra-position of tool along Z, UNDER the level
of tangent plane and equal to 1/2 of F1 value (2,24 mm in example),
then real error F2
lowers very much, since the true value F1 to be considered is the
half (
(fig.20U)
with entrance in column 2):
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[12] F2 = rcurv -( SQR ( rcurv ^ 2 -( F1 / 2 ) ^ 2 ))
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leads to better values:
: rcurv = 75 form error 0,030 mm instead of 0,112 mm
: = 517 form error 0,004 mm instead of 0,017 mm
A further improvement may come from insert cutting edge, in case
it offers a flat front edge.
In any case form error
(fig.04U)
(fig.05U)
lowers when tool diameter increases
or path width reduces
(fig.18A)
.
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