Free-Form Surface Mode: Extension Function - Siemens SINUMERIK 828D Function Manual

B1: Continuous­path Mode, Exact Stop, LookAhead
3.3 Continuous-path mode
Limit conditions
Axis-specific feed stop/axis disable
Axis-specific feed stop and axis-specific axis disable are ignored by LookAhead.
If an axis is to be interpolated that should on the other hand be made stationary by axis-specific feed stop or axis
disable, LookAhead does not stop path movement before the block in question but decelerates in the block itself.
If this response is not wanted, an axis-specific feed stop can be transferred to a channel via the PLC to stop the
path immediately (see also "Clamping monitoring [Page 84]").
3.3.4.2

Free-form surface mode: Extension function

Function
The "Free-form surface mode: Extension function" is an extension of the LookAhead standard functionality and is
used to calculate the path velocity profile during free-form surface processing (see also "Free-form surface mode:
Basic functions [Page 193]").
Its use optimizes the continuous-path mode as follows:
• Symmetry between the acceleration and deceleration profiles
• Uniform acceleration process, even with changing jerk or acceleration limits
• Uniform acceleration process of target velocity profiles, irrespective of the degree to which they can or cannot
be started with the specified dynamic response limit
• LookAhead braking to lower setpoint velocities
Uniformity and compliance with the dynamic response limit guarantee that the setpoint velocity profiles are
smoothed to a homogeneous velocity profile on the part. This serves to minimize the effect of following errors on
the quality of the surface.
Therefore, the function offers the following advantages:
• Greater uniformity in the surface of the workpiece
• Lower machine load
Applications
The "Free-form surface mode: Extension function" is used to process workpieces which primarily comprise free-
form surfaces.
Note
As better results are not achieved for standard processing applications, standard LookAhead
functionality should be used in these cases.
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions