NC Verification

In material-removing manufacturing, ``gouging'' (over-cutting) usually refers to any contact between the tool and the part to be machined that causes the tool to penetrate the part beyond some specified threshold value. Gouging is generally considered to be the worst defect which an NC tool path can exhibit, since it results in the machined part becoming scrap. Serious gouging may also inflict substantial damage on the cutting tool and on the NC machine. This is particularly true if the tool bumps into the part at high speed during a rapid-feed move.

Under-cutting is less problematic than gouging in the sense that there is no implied risk of damage of the machine tool. However, small amounts of under-cutting may be hard to spot visually, and they may be even harder to correct by applying an additional machining pass.

The detection (and elimination) of both over-cutting and under-cutting is the task of NC verification. For given geometric models of input stock, of goal shape, and of a cutting tool, the problem of determining if a given tool path results in removing the appropriate material from the input stock, while avoiding gouging is of paramount importance in verifying a tool path prior to production machining. Whether the tool path was generated manually, automatically, or semi-automatically, it is essential to check the path for deficiencies prior to making a potentially costly and wasteful error.

In joint work with Jim Klosowski and Joe Mitchell, the GougeChek system was developed to solve this problem, based on the underlying technology provided by QuickCD. Financial support for this project was provided by Bridgeport Machines.

The following images show some of the datasets on which we ran GougeChek. (Click on an image icon in order to see the full-size image. The full-size images have 800x800 pixels.) Typically, the (static) environment is shown in yellow and the flying object is shown in either green or blue. When the flying object makes contact with the environmental obstacles, the contact region is highlighted in red.

This picture shows a polyhedral conical-shaped tool interfering with a "mold" representing a real-world digital elevation terrain, Moab-W. (The part surface consists of 178,802 triangles, and the tool has 1,230 triangles.) A close-up of the tool is available, too.

This picture shows a polyhedral ball-nose tool interfering with an industrial mold. (The part surface consists of 1,634 triangles, and the tool has 1,148 triangles.) A close-up of the tool is available, too.

This picture shows a zoomed-in view of a polyhedral ball-nose tool interfering with the same industrial mold. (The part surface consists of 1,634 triangles, and the tool has 1,148 triangles.) A close-up of the tool is available, too.

This picture shows another zoomed-in view of a polyhedral ball-nose tool interfering with the same industrial mold. (The part surface consists of 1,634 triangles, and the tool has 1,148 triangles.) A close-up of the tool is available, too.

This picture shows the swept volume (cylinder) of a ball during a check for gouging on an industrial mold.

file last modified: Thursday, 27-Feb-2020 07:29:07 CET
held@cs.sbg.ac.at