"Get that water on! UHPC in mechanical engineering is now resistant to cooling lubricants containing water!". That is the striking statement that durcrete GmbH has released ahead of EMO Hannover 2017 to drum up attention. Modern Ultra High Performance Concrete (UHPC) has become a favorite material in mechanical engineering. Indeed, cement-bound UHCP can dampen vibrations considerably and exhibits excellent thermal inertia. Numerous applications have already demonstrated the material's suitability for use in machine beds, not to mention its very attractive price-performance ratio. However, because it is well-known that concrete tends to swell when exposed to moisture, many manufacturers of milling and grinding machines are still reluctant to mount linear guide rails directly onto ground but unprotected concrete surfaces. durcrete GmbH set out to change attitudes by joining forces with other companies to carry out a series of tests. The results showed that exposing precision-ground concrete surfaces to water does not affect the precision of machine tools.
Four companies combined their expertise to scrutinize the issue of swelling and its consequences once and for all - durcrete GmbH, the market and technology leader for UHPC in mechanical engineering, Dyckerhoff GmbH, the supplier of high-performance binding agent Dyckerhoff Nanodur, machine frame manufacturer Sudholt-Wasemann GmbH and Swiss company MDC Max Daetwyler AG, which runs a precision grinding facility. The partners developed and manufactured a suitable test piece fitted with guide rails mounted on precision-ground guide tracks. Deformation in the surface of the concrete and on the linear guide rails was measured under both dry and wet conditions, and the results were surprising. The evenness of the linear guides, whether measured over individual rails or several rails, is not affected in any way by exposure to water, only minimal absolute height changes occur. However, the surface of the concrete does show a clear response when exposed to water, exhibiting deformation and variations in evenness. durcrete GmbH explains the results as follows: On the one hand, the preload between the linear guide and the concrete stops water penetrating into the gap between the two. On the other hand, this preload counteracts pressure caused by swelling and stops the linear guide from being pushed up. What’s more, the preload and the rigidity of the rails are so high that any differential areas of swelling in the surface of the concrete have no impact on the evenness as measured over the surface of the rails. As a result of the collaborative testing, durcrete GmbH was able to draw the conclusion that exposure to water, due to the use of cooling lubricants for example, has no tangible influence on the precision of machinery mounted on frames made from NANODUR concrete.