Cycle 32 TOLERANCE for optimizing TNC path control

CNC machines are usually supplied with a “universal” configuration designed to suit a vast range of applications. If they have a TNC control, this universal configuration allows achieving good to excellent machining results. Cycle 32 TOLERANCE provides the possibility to further customize the machine to the task in hand. This is particularly useful, for example, when machining free-form surfaces with relatively long machining times. The cycle enables operators to achieve the ideal mix of accuracy and dynamic performance.

Each step in machining a workpiece would actually require a dedicated machine setup. For example, the setup for a finishing operation would be focused on a high contour accuracy and excellent contour smoothing. In a roughing operation, however, this setup would fail to take full advantage of the feed rate potential. The same applies the other way round. To achieve the best possible combination of accuracy and dynamics for all machining operations, operators need a way to fine-tune the predefined machine configuration—and thus also the TNC’s path control. The TNC controls offer this possibility with Cycle 32 TOLERANCE, which is available as standard.

The wider the path, the faster the corner speed

The path deviation T is usually set by the machine tool builder. It defines a default value for the maximum permissible contour deviation. Cycle 32 TOLERANCE enables operators to individually adapt the path deviation T to the specific machining operation by specifying the path width that is available to the control. In this way, operators can directly influence the maximum achievable machining feed rate—and thus the machining time. This is particularly useful for contour elements involving many direction changes, such as typical free-form surfaces.

An example from car racing illustrates the principle: The wider the track is, the faster the race car can go around a turn. The driver chooses the racing line that allows the highest speed through the turn. On a narrow track, in contrast, the driver has no choice of line and is forced to slow down.

Roughing operations, in particular, frequently support wider paths, and thus higher tolerances for the path deviation T. In this way the operator can also increase the maximum possible machining feed rate in narrow places. For finishing, the operator needs to reduce the tolerance value again or reset it to the value defined by the machine tool builder. This is done by programming Cycle 32 TOLERANCE once again with a low value or without a value.