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Conversational Programming of Trochoidal Milling and Jog Grinding

HEIDENHAIN has incorporated new software into its TNC control systems, widely fitted by machine tool OEMs to their machining centres and mill-turn centres, that allows complex trochoidal milling routines to be programmed conversationally on the shop floor, without having to download the cycles from a CADCAM station. The OCM (optimised contour milling) functionality, which is a new option available for the company’s TNC640, TNC 620 and TNC 320 CNC systems, will be demonstrated for the first time in the UK at MACH 2020 (Hall 6, stand 275).


The OCM algorithm takes conventional ideas for trochoidal milling, traditionally used mainly to achieve high material removal rates when slotting, and considerably expands the range of application. In addition to the roughing of any open or closed pocket or island, the software also offers cycles for finishing the floors and side walls.

The milling tool’s wrap angle can be limited to reduce heat generation and prolong cutter life. As cutting forces are lower, delicate and thin-wall parts can be machined with greater accuracy and even spindles with low power and torque can be used successfully. Moreover, as the milling cutter occupies less of the area of a slot or pocket during machining, accumulation and re-cutting of chips is minimised. This is particularly important for features that are deep in comparison with their width.

The control automatically calculates the best tool paths for maintaining constant cutting parameters. The subsequent machining operation runs with continuously optimised cutting values, resulting in increased machining speed and a noticeable reduction in tool wear. A sample part produced recently in Germany showed just how effective the new milling strategy is. OCM lowered the machining time and raised tool life by a factor of three compared with conventional milling strategies.

Control of grinding in one-hit production

New grinding control capabilities have also been added by HEIDENHAIN to the TNC640 to extend complete machining possibilities. The CNC was already able to control milling and turning of components in a single set-up on prismatic machining platforms. However, the latter are increasingly adding grinding capability to extend the scope of one-hit production. At MACH 2020, HEIDENHAIN will show for the first time in the UK that this metalcutting process can also be programmed conversationally and controlled.

Having milling, turning and grinding on a single machine offers many benefits, particularly for quality-critical production such as mould making and medical prosthetics manufacture. These industries can now machine parts to exceptional surface quality in a single clamping. The new TNC functions enable jig grinding of any contour and in addition, easy-to-use standard dressing cycles can true grinding wheels inside the machine. Optimised tool management for each process supports the user.