Re: Calculation of toolpaths for milling

From: Bert VandenBerg (
Date: Tue May 12 1998 - 20:03:32 EEST

Jan Willem Gunnink wrote:
> Dear RP-people,
> A week ago I posted a mail concerning the calculation of millingpaths
> (see below) nobody could tell me anything (except from Mr. Ridder).
> Please take some time to help me when you know anything
> many thanks once again from a desperate milling-guy

You might try:
numerically controlled machine tools (Vickers, Ly & Oetter).

my thumb-nail version:
- a given milling strategy defines how the tool motions over the surface
are to be arrayed (parallel passes, constant Z height), and what
machining parameters are to be used (cutter size & shape, cutter
orientation relative to the surface or coordinate system, and cutter
spacing methods)
- a given trajectory has a start and end point. A cutter must be
positioned so that the tool contacts the surface, but does not 'gouge'
the surface. This calculation starts with the calculation of a point and
surface normal at the desired tool contact point. The tool position may
need to be adjusted to avoid 'gouging'. The tool is positioned for both
the start and end point. These two points are joined by a path (usually
in cartesian space, but possibly in machine axis space), and the path
swept by the cutter is checked against the surfaces of the part to be
cut. If the the tool is too close or far from the point intermediate
points are added until a point to point motion is calculated that
satisfies the tolerances specified. The processor then may fit arcs or
NURBS through these points for output. There are many variants on this
approach. Machining strategies are full of lots of special cases.

Bert van den Berg                   E-mail:
Hymarc Ltd.                 
35 Antares Drive                        Tel: (613) 727-1584
Ottawa, Ontario  K2E 8B1                Fax: (613) 727-0441

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