Surface Quality, Velocity, Accuracy - Siemens SINUMERIK 828D Manual

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Basic information
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Surface quality, velocity, accuracy

Special attention must be paid to the CAD -> CAM -> (postprocessor) -> CNC process chain
when machining three-dimensional geometries, e.g. free-form surfaces. CAM systems generate
NC programs for free-form surface machining. The CAM system receives the workpiece
geometry from a CAD system. The CNC machine has to process the NC data generated and
convert it into axis movements.
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G1
G1
© Siemens AG All rights reserved SINUMERIK, Manual, Mold-Making with 3- to 5-Axis Simultaneous Milling
In CAD systems, surfaces
are constructed (free-form surfaces).
For example, in order to be able to mill an
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entire surface - or for collision checking - the
CAM system generally converts the CAD free-
form surface into a polyhedron.
This means that the smooth design surface is
approximated
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small planes.
This produces deviations from the original
free-form surface.
The CAM programmer overlays this
polyhedron with tool paths. From these, the
postprocessor generates NC blocks within the
specified error tolerances. These usually
G1
comprise many short straight line elements,
G1 X Y Z.
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G1
Thus, the machining result is no longer a free-
form surface, but a polyhedron. The small
planes of the polyhedron can be visibly
mapped on the surface.
This can result in undesirable remachining.
of higher orders
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by a number of individual
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