Powerful TNC functions for perfect molds
In tool and mold making, dimensional and contour errors need to be so low as to be barely measurable and must certainly never be visible. These requirements are increasingly at odds with demands for higher productivity and lower costs. Many powerful TNC functions of HEIDENHAIN controls offer possible solutions to the key questions that arise between the conflicting demands of a production process that is highly precise and at the same time highly efficient. The user can take advantage of these functions that bring out the best of a machine in any machining scenario while efficiently meeting workpiece accuracy requirements.
How can I optimally tune my machine to the given machining conditions?
Cycle 32 TOLERANCE and the ADP function of the TNC result in perfect molds, thanks to a milling machine that has been perfectly tuned to the respective machining scenario.
In Cycle 32 TOLERANCE the TNC user can precisely tune the machine setup by adapting the contouring deviation T to the task at hand, thus individually specifying the path width that is available to the control. The user can so directly influence the maximum attainable contouring feed rate and thus also the machining time, in particular for contour elements with numerous changes in direction—a common characteristic of free-form surfaces.
Some machine tool builders also offer their own cycles based on Cycle 32. These are often designated Cycle 332. In addition to the contouring deviation T that the TNC user enters, these cycles make further modifications to the machine setup that the OEM had programmed for specific machining operations, such as roughing, finishing, or pre-finishing.
The Advanced Dynamic Prediction (ADP) function offers another possibility for optimizing the machining process. It starts with the data quality of the NC program and enables optimized motion control for feed axes in three- and five-axis milling. An insufficient quality of data frequently causes poor motion control, leading to inferior surface quality of the milled workpieces.
With ADP, the TNC control can dynamically calculate the contour in advance and adapt the axis speeds in time for contour transitions using acceleration-limited and jerk-smoothing motion control. As a result, clean surfaces can be milled in short machining times even for contours with highly irregular point distributions in neighboring tool paths. The strengths of ADP are apparent, for example, in the resulting symmetrical feed behavior on forward and reverse paths during bidirectional finish milling and in the form of particularly smooth feed-rate curves on parallel milling paths.
How can I take full advantage of a milling machine’s dynamics?
The Dynamic Precision package of functions for the TNC controls perfectly combines a high level of accuracy with dynamic motions.
The Dynamic Precision package of functions for the TNC controls is a collection of functions that combine high accuracies with dynamic motions. These functions minimize not only forces that affect the mechanics of a machine tool during operation, but also the resulting deviations at the tool center point.
The Cross Talk Compensation (CTC) function compensates for forces that are introduced by dynamic acceleration processes and that briefly deform parts of the machine, leading to deviations at the tool center point. Regardless of the actual acceleration, CTC makes either more precise production with better surfaces possible, or it significantly reduces the machining times by increasing the jerk.
Active Vibration Damping (AVD) suppresses dominant low-frequency vibrations and permits fast, vibration-free milling. This makes it possible to set high jerk values. Machining times can be reduced without compromising surface quality. In particular, the combination of CTC and AVD helps reconcile the contradictory requirements of accuracy and speed. In practice, this functionality provides greater efficiency during the milling of high-quality, free-form contours.
The Load Adaptive Control (LAC) function continuously determines the current mass for linear axes, or the mass moment of inertia for rotary axes, and adapts the feed-rate control to the values measured at any given time. This improves the dynamic accuracy of the axis for every situation under load, enabling the use of optimized jerk values for the feed axes on the workpiece side. The result is a shorter machining time, since the feed axes reach the desired positions sooner. In addition, LAC compensates for all changed friction values and therefore ensures higher contour accuracy.
How can I implement the accuracy requirements of a workpiece efficiently?
KinematicsOpt and 3D-ToolComp make it possible to efficiently create a highly accurate workpiece using the true accuracy of the machine and tool.
Accuracy requirements are becoming ever more stringent, particularly in the realm of 5-axis machining. Complex parts must be manufactured with both precision and reproducible accuracy, including over extended periods of time. During machining, however, machine components are subjected to relatively high temperature fluctuations. The kinematic transformation chain should therefore be adapted correspondingly. The KinematicsOpt software option not only handles the re-calibration, but also saves all data regarding modifications to the kinematic configuration.
A triggering 3-D touch probe is used to measure the position of a precise calibration sphere at various rotary axis settings. The result is a report providing the current actual accuracy during tilting. If desired, KinematicsOpt also automatically optimizes the measured axes simultaneously, and requisite modifications to the machine data are also automatically implemented. The user needs no detailed knowledge about the kinematic configuration of the machine and can re-calibrate his milling machine in just a few minutes. If the calibration sphere is permanently mounted on the machine table, then this procedure can even be performed as an automated step between the individual machining processes.