Trends in industrial, technological, and biomedical design have converged in recent years to create new interest in high-precision machining – to produce the highly accurate components that realize those designs. And this direction in new product design has enlivened interest in a long established production process, Swiss machining.
Swiss machines, or Swiss lathes, achieve precision for exceptionally small parts by minimizing various forces generated by turning or grinding, as a workpiece passes through a sliding headstock and a guide bushing.
Now the developers at Tschudin AG are introducing a design element that will improve the accuracy of their machines even further. The Tschudin Cube 350 reportedly is the world’s first grinding machine with perfect heat transfer.
"We have been working consistently for three decades to reduce the heat transfer of our machines to a minimum,” explained Urs Tschudin. “With the completely new grinding and regulating spindles made of carbon, we have now put the final piece of the puzzle in place.
"With this spindle concept, we are underpinning our status as an innovator and offering our customers a new dimension of accuracy and removal rate," he added. By minimizing the heat cycle of the grinding sequence, production with consistently high accuracy is guaranteed, the developer claimed.
"Even if the machine stands still for a weekend, it can produce immediately within a maximum dimensional deviation of 1 µm," according to Mr. Tschudin. And in those conditions, every part can be produced to exact dimensions, even with multi-track grinding - the grinding wheel and regulating wheel remain parallel because thermal displacement is prevented.
To emphasize, this means that the new Cube 350 will work reliably and unattended for very long sequences, even unmanned shifts.
"The high grinding quality with full grinding gap coverage was already a quality feature of our machines. With the carbon spindles, we are further optimizing this aspect and pushing it to the maximum," Tschudin stressed.
Decades of development
The Swiss executive claimed that the introduction of carbon-fiber spindles fulfills a decades-long development. Tschudin machines have used linear motors for 30 years. More than 25 years ago, machine beds made of solid natural granite were adopted; those beds retain very little heat due to their dimensions and inertia.
Later, the grinding spindle slides were designed as granite blocks, and the vertical stop surface for the spindles further reduced heat transfer.
The carbon-fiber spindles for which Tschudin is now seeking a patent reduce the heat transfer “to an absolute minimum,” the Swiss machine builder announced. The new spindles were developed in collaboration with Carbon-Drive GmbH, and have been tested and adapted for more than six months – “with promising results.”
"How materials react to heat has a major influence on precision manufacturing. The temperature resistance of carbon-fiber is particularly high,” explained Nikolas Ernst, who is the design leader at Tschudin AG.
“Carbon spindles therefore prevent thermal expansion in the machine,” Ernst continued. “They are more dimensionally stable and have a higher bending stiffness, which means they can run at higher in-feeds, which in turn means higher cutting performance. In a series of tests, the carbon spindles have proven to be between ten to twenty percent more effective than steel spindles."
Carbon-Drive GmbH, Weiterstadt, Germany, is Tschudin's exclusive development and design partner for carbon-fiber spindles in the centerless grinding sector. The German company was founded on the strength of research conducted at the Technical University of Darmstadt.
"Spindles made of carbon fiber have various advantages, first and foremost minimal thermal expansion,” detailed co-founder and managing director Dr.-Ing. Martin Klimach. “Depending on the type of fiber and fiber orientation, we can produce carbon-fiber spindles with different properties and thus respond to a customers' process requirements."
Urs Tschudin and Martin Klimach met in 2019, when Carbon-Drive GmbH was working on milling spindles made from carbon fiber. The idea to adopt carbon-fiber spindles for grinding was a mutual goal, and the prototype spindle was ready at the end of 2023.
Better than steel
"Every development process is complex. The established manufacturers know steel (spindles) inside out; all processes are designed for steel,” Ernst observed. “However, we are convinced that carbon-fiber spindles offer essential added value due to their physical properties and will also be attractively priced."
According to Urs Tschudin, the Cube 350 grinding system equipped with carbon-fiber spindles should appeal to manufacturers who have the highest demands in terms of quality and precision. "The more precisely parts have to be manufactured, the more interesting the grinding machine with optimal heat transfer becomes. This is because we can offer real added value here thanks to the greater dimensional stability and higher drive power," Tschudin elaborated.
The Tschudin Cube 350 is a centerless grinding machine designed to produce parts up to 20 mm in diameter and to plunge grind parts up to 150 mm long. It also excels at thorough-feed grinding of parts. It can be equipped with various automatic loading options and pre and/or post process gauging.
The Cube 350 compact centerless grinding machine also offers manufacturers high-precision machining a small footprint, with a base of just 2.60 x 1.70 meters. In production, the machine is capable of high productivity thanks to exceptionally short changeover times: replacing the grinding and regulating wheels can be done in just six minutes, according to the developers.
Its ergonomic design is appealing too, as the machine can be operated from both the left and the right sides.
The standard version of the Cube 350 will continue to be equipped with steel spindles, according to Tschudin AG, with the carbon spindles now available as an option.