For years, customers have been asking for larger components in Kern quality. With the new five-axis machining center Kern Fortis HD, manufacturing companies with the highest precision requirements will have a new machine available starting in spring 2026. While the outer dimensions will only grow about one and a half times compared to the Kern Micro HD, the generous machining area allows for approximately double the travel paths.
Eight years ago, the dream began for the Kern team to achieve the incredible accuracy of the five-axis machining center Micro HD in other dimensions that are up to twice as large. Now it has become a reality and has a name: Kern Fortis HD. First presented to a broad professional audience at EMO 2025, delivery will be possible from mid-2026. This will bring industries such as tool and mold making as well as various parts manufacturing into focus.
Kern Managing Director Simon Eickholt has joy written all over his face regarding the new innovation. Nevertheless, he explains matter-of-factly: 'The Fortis HD is not only visually very close to our Micro HD. It also served as a template for our developers in technical terms and in terms of usability, and thus has many similarities.' He then adds emotionally: 'That we have succeeded in transferring the unmatched precision to travel paths and components that are about twice as large still seems incredible to me.'
Because it is not the case that we simply take the Kern Micro HD and double it. The Kern Fortis operates according to the same principles, but ultimately it is a completely new machine.'
Kern accuracy despite new dimensions
To give a face to the terms component size, travel paths, and 'unmatched precision': Blanks for the Fortis HD may have a diameter of up to 565 mm and a height of 350 mm (Micro HD: D = 350 mm, H = 200 mm). The travel paths are: X = 780 mm, Y = 420 mm, and Z = 450 mm (Micro HD: 350, 220, 250 mm). The machine requires a footprint of 4.07 m x 3.05 m and has a height of 3.48 m (Micro HD: 2.65 m x 1.7 m and H = 2.65 m).
Regarding component accuracy, the Fortis HD proves to achieve the same results as the Micro HD despite being nearly twice the size. The basis for this lies, among other things, in the positional accuracy of the linear axes. Various measurements have shown that the values of the two machines are almost identical. Circularity tests confirmed the Fortis with accuracies under 1 µm at the same travel path – and that even in series. According to the Kern team, no other 5-axis machine of this size has been able to achieve this so far.
Important for practical application is that the Kern Fortis HD not only achieves the highest accuracy but also large material removal volumes of up to 1 l/min in steel. Crucial for this: In addition to an HSK 40 tool spindle, an HSK 63 version is also available, which can accommodate tools with diameters of up to 200 mm and lengths of 390 mm.
Both are designed by the Kern development partner Fischer as CSC spindles (Compact Shaft Cooling). This means: The integrated shaft cooling ensures that otherwise necessary run-in times can be largely avoided. Additionally, the spindle remains thermally stable even at maximum speed and highest load, which is important for tool holders and tools. This allows users to consistently achieve stable milling processes with high material removal rates during roughing and with mirror-smooth surfaces during finishing.
Highlights: Micro-gap hydrostatics and temperature management
However, several other technical highlights are crucial for high performance and precision, which have been transferred and further developed from the Micro HD to the Fortis. For example, the developers around project manager Christian Maier have equipped all linear axes with direct drives and the patented micro-gap hydrostatics from Kern, similar to HD-like. The engineer explains: 'The small gap achieves optimal stiffness and damping properties, which ensures the highest surface quality and accuracy on the workpiece.' At the same time, the integral design in combination with linear motors makes the drives particularly robust and reduces energy consumption compared to conventional hydrostatic systems by about 80 percent.
Equally significant for the consistently achievable precision is the temperature management. According to studies, temperature influences are responsible for around 70 percent of all accuracy errors in the high-precision range. 'Since we have a significantly larger machining area, more moving masses, and more power in the machine with the Fortis HD than with the Micro HD, it is even more important to dissipate the heat directly at the points where it is generated,' explains Maier, emphasizing that the implementation posed a particular challenge but ultimately succeeded perfectly.
This means: The temperature management of the Fortis HD perfectly compensates for the higher heat output of the individual components. Similar to the Micro HD, the linear motors are temperature-controlled and integrated into the hydrostatic linear axis system. This measure already minimizes the heat input. Additionally, structures such as the swivel axis, linear axes, and spindle are also temperature-controlled by an extremely precisely regulated temperature management system with a flow rate of up to 260 l/min.
Christian Maier on this: 'This allows us to keep temperature fluctuations in the Fortis to just +/- 0.05 Kelvin.'
The accommodation of the unit necessary for the hydrostatic axes and temperature management is also particularly elegantly solved. The developers have integrated it directly into the housing of the Fortis HD, so it does not require additional floor space.
Highest productivity and machining performance
In addition to the demanding adjustments to the changed dimensions, project manager Maier and his team have also implemented some completely new approaches. For example, two measures take into account the higher chip volume of the new machining center. On the one hand, the axes are completely enclosed and thus optimally protected. On the other hand, scraper belt conveyors and a band filter system are used after the chips have been reliably transported away due to a new design of the machine room.
Particularly interesting for the operator: The Fortis HD now features a two-part access door that can be pushed open to the left and right. This makes it easier for the operator to load and set up the machine and also provides optimal accessibility and clarity.
As with the Kern Micro HD introduced this year, the Fortis HD will also be delivered with the new TNC7 control from Heidenhain. This ensures both the highest technical stability and user-friendliness. The program structure corresponds to the familiar layout, and existing programs can usually be transferred easily with minor adjustments.
In testing for years
That the new developments of the Kern Fortis HD not only sound good in theory but also work in practice has been demonstrated by Kern in elaborate tests and trial operations for several customers. Managing director Simon Eickholt is pleased to note: 'We received feedback multiple times that with our Fortis, we achieve better results after short run-in phases than our customers do with their most precise existing machines, even though these had already undergone months of optimization.' Feedback that suggests high demand and confirms the Kern CEO's fundamental attitude, because: 'We are always very close to the market and orient ourselves to the development wishes of our customers. What is technologically possible, we implement.'
Info: The Kern Fortis HD coming soon
- Installation area: L x W x H: 4.07 m x 3.05 m x 3.48 m.
- Axis travel paths: X = 780 mm, Y = 420 mm, Z = 450 mm
- Machinable component size: 565 mm diameter, 350 mm height
- CSC tool spindle (Compact Shaft Cooling): HSK E40 for tools with up to 70 mm diameter and 245 mm length or HSK A63 for tools with up to 190 mm diameter and 390 mm length.
- X, Y, and Z axes: Direct drives with micro-gap hydrostatics
- B and C axes: Torque drives with rolling bearing
Enhanced active temperature management in all linear axes, rotary/tilting axes, the axis drive, machine stand, and spindle.
Heidenhain control TNC 7
Contact:
