Eight years ago, Kern came up with the plan to transfer the precision of the Micro HD five-axis machining center to larger dimensions. This approach is now being realized with the Kern Fortis HD. Delivery will start in mid-2026 and target groups include tool and mold making as well as parts production.

The Fortis HD is based on the Micro HD in terms of concept and operation, but has a completely new design. It processes blanks up to 565 mm in diameter and 350 mm in height with travel distances of 780 x 420 x 450 mm. Despite being almost twice the size, it achieves a similar level of precision: circle forming tests resulted in accuracies of less than 1 µm.

The machine processes large volumes of up to 1 l/min of steel. In addition to an HSK-40 spindle, an HSK-63 version is also available, designed for tools up to 200 mm in diameter and 390 mm in length. Both spindles, developed by Fischer, feature Compact Shaft Cooling, which eliminates run-in times and ensures thermal stability even under high loads. Precision and surface quality are ensured by Kern's patented micro-gap hydrostatics with direct drives on all linear axes. The system offers high rigidity and damping with low energy consumption - around 80 % less than conventional hydrostatic systems.

Stability through temperature management

Temperature management is a key element. As temperature fluctuations cause around 70 % of accuracy errors, the heat is dissipated directly at the point of origin. Linear motors and axes are temperature-controlled and integrated into the hydrostatic system. Structures such as swivel axes and spindles are controlled by a precise cooling system with a flow rate of up to 260 l/min. As a result, the temperature fluctuations in the machining area remain within ±0.05 K. The unit for hydrostatics and cooling is integrated into the machine housing to save space.

The axes are fully enclosed to increase productivity. A new chip handling system with scraper belt conveyors and belt filter system improves removal. The machine has a two-part access door to facilitate loading and set-up.

The Fortis HD is equipped with the Heidenhain TNC7 control system, which offers high stability and a familiar operating structure. Existing programs can be adopted with only minor adjustments. Extensive tests and customer applications prove the performance of the Fortis HD. Even after a short running-in period, it achieved results that exceeded those of established precision machines. The machine thus successfully transfers the Micro HD concept to larger dimensions and combines high accuracy with increased machining capacity.