In order to lower inertia, to relieve the feed drive systems, to enhance the feed motion dynamics and path accuracy, and to improve the energy efficiency, lightweight design provides a high potential in the machine tool sector. Lightweight design comprises either a structural optimization in terms of the topology and wall thicknesses of structural components or the application of lightweight materials such as CFRP, GFRP and composites, or even a combination of both approaches. A comprehensive overview of the state of the art regarding the application of materials and structural optimization for machine tools is given in [
2,
3]. Besides the lower density and higher specific stiffness of CFRP compared to cast iron and steel, higher material damping properties and thermal expansion coefficients close to zero can be exploited in machine component design [
4]. As a consequence of the buildup and internal structure of composite parts, including fibers and matrix, by exploiting the design degrees of freedom regarding the types of fibers, fiber orientation and layer composition, quasi-isotropic or targeted anisotropic mechanical and thermal characteristics can be created. In order to gain the full potential of these properties, sophisticated design, layout and optimization methods as well as modelling and simulation techniques are required [
3]. Against the background of the broad range of commercially available fiber materials and their mechanical and thermal properties, the related cost have to be considered as an additional optimization parameter.
Jung et al. investigated the design of a hybrid composite-aluminum beam structure with high modulus (HM) carbon/epoxy composites with respect to the design of a LCD glass panel inspection machine [
5]. The layout was optimized in terms of the cross section shape of the beam, the stacking sequence and the thickness of the composite reinforcement with respect to the fundamental natural frequency and bending deformation. The beneficial dynamic properties of composites were exploited by Lee et al. with respect to the design of a guiding arm of an electrical discharge wire cutting machine [
6]. With the support of Finite Element (FE) simulations, the detailed design regarding bonding length and number of reinforcing plies was conducted. Compared to the conventional arm, the mass was reduced to less than 50%, the static stiffness was maintained and the fundamental natural frequency as well as the damping ratio were significantly improved.
With respect to the design of machine tools for material removal operations, various investigations were carried out and prototypes were built in order to achieve the best compromise between mass reduction, static stiffness, fundamental natural frequencies, damping ratios as well as thermal stability. Besides more or less pure composite structures, the majority of approaches considers hybrid approaches in which different materials are combined. A hybrid steel-composite headstock for high-precision grinding machines was analyzed by Chang et al. [
7]. The composite reinforcement led to an improvement of the dynamic stiffness and damping in the higher frequency range of 100–500 Hz. Suh and Lee presented the design of a hybrid material slide structure with composite reinforcements [
8,
9]. The first natural frequency was increased from 64 to 92 Hz and the damping factors for the first 5 modes were enhanced by up to more than 100%. The strength of the adhesively bonded sandwich structure of the horizontal moving body was analyzed in [
10]. Furthermore, the thermal properties of the composite sandwich were investigated. In [
11], carbon/epoxy composite-aluminum hybrid structures with friction layers were applied with the aim to achieve a high structural damping. The static deflection and first natural frequency were analyzed regarding the stacking angle and thickness of the composite. Between the aluminum and composite interface, a friction damping layer was inserted. Composite reinforcements, the use of composite sandwich materials and composite-foam-resin concrete sandwich structures were analyzed in [
12‐
14], respectively. Kulisek et al. performed case studies on rams with, on the one hand, a thick-walled composite body and minimal amount of steel as well as, on the other hand, a hybrid structure with fiber composites and cork layers [
15]. Fleischer, et al. and Koch et al. filled a composite machine slide with different amounts of fluids in order to control the structural dynamics during machine utilization [
16,
17]. A serious aspect especially for hybrid combinations of materials with different thermal expansion coefficient concerns thermally induced mechanical stresses in the interfaces and joints which can lead to de-bonding and a loss of structural stiffness. Residual stresses in material interfaces can already occur during the curing of the composite parts [
18‐
22]. The characteristics of composite structures are influenced by the joints, e.g. towards metal parts as interfaces for guides, drives or machine components. The layout of mechanically fastened joints has to be carried out carefully in order to avoid structural damage of the composite elements [
23]. Composite material structures are suitable for inherent sensor and actuator integration. On the one hand, integrated sensors can be used for structural health monitoring [
24]. Integrated sensors also provide relevant information for machine and process state monitoring. Meo et al. integrated fiber optic Bragg strain sensors into a ram of a vertical milling center in order to gather bending deformations and tool displacements during the process [
25]. In [
26,
27], piezo ceramic sensors are embedded in composite machine components. A printed circuit is integrated in [
26] in order to realize the wiring of distributed sensors within the analyzed test specimen. Brecher et al. exploit the thermal stability of CFRP rods for a direct integrated measuring device for thermal state monitoring and compensation of thermally induced machine deflections [
28]. The application of piezo sensor integrated CFRP structures in a workpiece clamping intelligent chuck system is introduced in [
29]. The sensory piezo patch transducers are embedded in CFRP fingers which are pre-stressed against the workpiece during the clamping setup. Due to their high sensitivity, the sensors are capable to measure workpiece vibrations during the milling operations. By this, process monitoring regarding chatter occurrence becomes possible as well as an adaptive control of countermeasures.
As a summary, the advantageous material properties of CFRP have been analyzed with respect to machine tool applications already in the past. However, the comprehensive design, realization and analysis up to machining tests, as well as a comparison of variants of new lightweight machine slide components as conducted here cannot be found in literature. Considering that lightweight design approaches can either be used to reduce the mass of a component maintaining its stiffness or to improve the stiffness maintaining the mass, the investigation of different layouts of the same component reveals the range in which a technical optimization can be implemented. Furthermore, in contrast to previous studies, the work presented here includes the optimization of both mechanical and thermal properties of the exemplary component and also takes manufacturing costs into account. Integrated sensory elements show their sensitivity to mechanical loads acting on the slide component. In addition, with respect to the application in industrial machine tools, influences of chips and coolant lubricant on the performance of the machine component are studied herein. Finally, an analysis of machining results is presented that allows a comparison with the conventional casted machine slide.