What is Cutter Location (CL) Data File?

A cutter location (CL) Data refers to the position to which a CNC milling machine has been instructed to hold a milling cutter by the G-code instructions. A neutral language file that helps to transfer instructions from CAM to a CNC machine. Each line of motion controlling G-code consists of two parts, first, the type of motion from the last cutter location to the next cutter location, e.g. "G01" means linear, "G02" means circular, and the next, the cutter location itself, the cartesian point (20, 1.3, 4.409), e.g. "G01 X20 Y1.3 Z4.409".

The fundamental basis for creating the cutter paths suitable for Computer- Aided Manufacturing are functions that can find valid cutter locations, and stringing them together in a series. There are two broad and conflicting approaches to the problem of generating valid cutter locations, in a CAD model and a tool definition. The contents of the cutter locations are:
(a) Cutter location by offsets
(b) Cutter location against triangles
(c) Z Map

Cutter location by offsets. It starts with a UV parametric point in a free form surface, the xyz point and the normal are calculated, and offset is taken from the point along the normal in a way consistent with the tool definition so that the cutter is now tangent to the surface at that point. It may collide with the model elsewhere and there is no indication to this happening until the full implementation of the triangulated approach.
Cutter Location by Offsets

Cutter Location Against Triangles. It starts with the XY component for a cutter location and loop across every triangle in the model. For each triangle which crosses under the circular shadow of the cutter, the Z value of the cutter location required for it is calculated to exactly touch the triangle, and find the maximum of all such values.

Problems. It requires a lot of memory to hold enough triangles to register the model at a tight enough tolerance, and it takes longer to program to get the initial cutter location values. However, they are at least guaranteed in all cases. This is how all major CAM systems do it these days because it works without failing, no matter what the complexity and geometry of the model may be. Reliability is far more important than efficiency. The above refers only to 3-axis machines and 5-axis machines need a special entry of their own.

Z Map. The Z Map algorithm is a regular array of Cutter Location values in the computer memory. The result is a model of the height map of cutter positions from which the values can be interpolated. Due to accuracy issues, this was generalized into an Extended Z Map, by the placement of "floating" points between the fixed Z Map points. The locations of the Extended Z Map points are found when the Z Map is created. Extended Z Map points are only placed where sharp edges occur between the normal Z Map points, completely flat source geometry will not require any Extended Z Map points.

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