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Water-miscible cooling lubricants are used in approx. 90% of metalworking processes mainly for lubrication and cooling of the contact zone between tool and workpiece. The base oils of the widely used water-miscible emulsions are often of mineral origin and represent a significant share of the CO2-fingerprint in production systems in terms of their extraction, processing and the possibility of recycling. Cooling lubricants are furthermore negatively discussed regarding to their health compatibility. Those disadvantages of conventional cooling lubricants drive the research for replacing mineral base oils with vegetable base oils, which contribute to a safer work environment and greener production. In this work, both conventional cooling lubricants and several water-miscible emulsions with various edible and non-edible vegetable-based oils were prepared and characterized regarding their suitability as cooling lubricants for the milling of aircraft stainless steels. Comprehensive experimental investigations were carried out to determine the process forces and the resulting tool wear as technical performance indicators for the test evaluation.

In machining, tool wear is one of the main influence factors for the resulting quality of the product. Several wear mechanisms have to be addressed to prevent unwanted deterioration of the tool integrity. For aluminium alloys, adhesion of the workpiece material on the cutting tool is one of the most challenging wear mechanisms. Engineering surface microtopographies has been proved as a convenient strategy to tackle this issue. Particularly, the direct laser interference patterning (DLIP) technique enables the integration of periodic structures on the micrometer or sub-micrometer scale. In this study the structuring of tungsten carbide with different cobalt content is presented. The interference of two laser beams leads to periodic line-like structures with a spatial period of 5.5 µm. A maximum structure depth of 2.2 µm is reached by controlling the processing parameters. Moreover, the wettability of the structured samples was analyzed by contact angle measurements with selected cooling lubricants, revealing a hydrophilic behavior with a decreased contact angle of 10°. This work gives an insight into the possibilities of structuring tungsten carbide materials with a picosecond laser source in combination with an innovative beam shaping setup from the point of view of an analysis to explore the formation of structured surfaces and their wetting behavior with cooling lubricants.

Cellular metals are highly porous materials with very distinctive properties. Although it is possible to manufacture near-net-shape parts of these materials with some manufacturing processes, additional machining operations are usually required. However, as conventional machining causes surface damage and poor precision, finishing operations are often performed using alternative, cost-intensive methods. In the present work, a mesoscopic finite element model was used to analyze the influence of cutting conditions and tool geometry in the orthogonal cutting process of cellular metals. The study considered the variability of the mesostructure, as the behavior of multiple cell arrangements under cutting conditions was evaluated. The influence of cutting speed, depth of cut, and tool rake angle on chip formation and surface damage was explored. Chip formation at higher cutting speed was different, as chip fragmentation was visible. Tools with a positive rake angle and a higher cutting speed led to a decrease in subsurface damage. Nevertheless, surface quality is markedly dependent on the stochastic nature of the mesostructure, as material separation is defined by the response of the cell array. Hence, a set of cutting parameters for optimal surface quality could not be identified.

Conventional machining of high-tech parts and components is often associated with complex processes, long lead times and small to medium batch sizes. Obviously, there is great interest to shorten process development periods and increase process reliability. The transformation of conventional machines into cyber-physical production systems (CPPS) promises significant improvements here. In fact, CPPS allows real-time data acquisition and processing, enabling to target integrated process improvement and quality assurance. In the present work, a methodical procedure for structured data aggregation is introduced for a Cyber-physical enhanced machining process while being explained from a high-tech application point of view. This includes data generation, extraction, transfer and storage, data-consolidation, linkage, visualization and interpretation. Finally, the paper illustrates these aspects in terms of the effects on the “digital product requirements” in order to achieve the presented “analytics-ready” data model using the example of a high-tech application.

Background: The aim is to evaluate methods to quantify the interstitial splitting force and thermal load input of self-tapping and self-drilling osteosynthesis screws. Methods: A specialized modular test bench was developed to measure the induced splitting force of self-drilling and self-tapping osteosynthesis screws using porcine mandibular bone. In addition, a fundamentally new approach to measure the temperature near the contact zone of osteosynthesis screws (fiber-optic sensor in the axis of the screw) was established. Results: The self-drilling screw type induces a splitting force of about 200 N in the surrounding tissue, so that microdamage of the bone and increased resorption can be assumed. Even pre-drilling induces a short-time force into the tissue, which is comparable to the splitting force of the self-tapping screw. The temperature increase in the screw is clearly higher compared to the temperature increase in the surrounding tissue, but no significant difference in temperature between the two screw types could be measured. Based on the measured temperatures of both screw types, the temperature increase in the contact zone is considered critical. Complications during the screwing process caused by the manual tool guidance resulted in numerous breakages of the fiber-optic sensors. Conclusions: The developed methods provide additional insight regarding the thermomechanical load input of self-drilling and self-tapping screws. However, based upon the optical fiber breakages, additional refinement of this technique may still be required.

Purpose The aim of this study is to evaluate a developed experimental set-up to measure the coefficient of friction between fresh mandibular bone and biomaterials used in oral and maxillofacial surgery including a standardized routine for specimen preparation. Material and methods For this purpose, we developed a specialized routine for harvesting and preparation of cortical bone specimen from cadaveric porcine mandibles and modified a ball-plate tribometer. These harvested bone specimen were kept moist all the time. A total of 24 bone cylinders with 8 repetitions per material were examined for their coefficient of friction against stainless steel (1.4404), a titanium alloy (Ti6Al4V) and a cobalt chromium molybdenum alloy (Biosil F®) and subsequently analyzed by laser-scanning and scanning electron microscopy. Results The lowest coefficients of friction between vital cortical bone and the investigated implant materials were found for Biosil F®, while the highest coefficients of friction were found for the titanium alloy Ti6Al4V. Significant differences for the initial coefficient of friction with p < 0.05 have been proven. Stick-slip effects occurred during the measurement and a layer of debris formed on the metallic samples. EDX analysis of the abrasion marks revealed that this layer consisted of elements contained in hydroxyapatites and carbon. Conclusion The experimental set-up is suitable to perform reproducible comparative measurements of the coefficient of friction of different material combinations. A significant advantage of the methodology is the flexibility and scalability of harvesting and preparation of the bone specimen, which allows the simulation of realistic situations while measuring the coefficient of friction.

Thin sheets and thin-walled structures are of great economic importance in the aerospace industry due to the enormous efforts being made in lightweight construction. The challenge in machining is to use a reliable clamping device to take account of the sheet metal or component structure as well as to work productively and reliably. For this purpose, a hybrid clamping system has been developed that functions on the basis of vacuum and the adhesive properties of a carrier medium in order to form a complex joining. This method was verified by material tests and then developed to make it usable for the HSC and HPC milling of aluminum sheets. For this purpose, demonstrator parts were manufactured in order to test the critical loads of this clamping system on the one hand and to produce structures that cannot be realized economically with other machining methods on the other hand.

Cleft lip and palate belong to the most frequent craniofacial anomalies. Secondary osteoplasty is usually performed between 7 and 11 years with the closure of the osseus defect by autologous bone. Due to widespread occurrence of the defect in conjunction with its social significance due to possible esthetic impairments, the outcome of treatment is of substantial interest. The success of the treatment is determined by the precise rebuilding of the dental arch using autologous bone from the iliac crest. A detailed analysis of retrospective data disclosed a lack of essential and structured information to identify success factors for fast regeneration and specify the treatment. Moreover, according to the current status, no comparable process monitoring is possible during osteoplasty due to the lack of sensory systems. Therefore, a holistic approach was developed to determine the parameters for a successful treatment via the incorporation of patient data, the treatment sequences and sensor data gained by an attachable sensor module into a developed Dental Tech Space (DTS). This approach enables heterogeneous data sets to be linked inside of DTS, archiving and analysis, and is also for future considerations of respective patient-specific treatment plans.

High-speed plunge-cut centreless grinding opens up enormous potential for the manufacturing of difficult-to-machine materials and to improve the surface quality while reducing the grinding forces. For this investigation, a new grinding wheel base body of carbon fibre-reinforced plastic (CFRP) was developed to achieve grinding wheel speeds up to 150 m/s in plunge-cut centreless grinding of hardened shafts. For evaluation of the performance characteristics, the grinding forces and the surface quality of different grinding tools were detected. These experiments were conducted using a newly developed measuring system to analyse the grinding forces in the workrest blade. The experimental results are described and discussed in this article.

Additive manufacturing (AM), often referred to as 3D printing, is a generic term describing the layered build-up of material in near net shape frequently attributed with a freedom of design that cannot be achieved otherwise. AM focuses basically on the fabrication of parts for different fields in complex high-tech applications. Examples include components for jet engines, turbines blades, and implants in the medical sector. This is often justified with tool cost savings, shorter lead-time, and overcoming the “design for manufacture” paradigm. On the other hand, a machining allowance is frequently required to counteract the inherent surface roughness and the widespread challenge of part distortion due to residual stresses. At this point, geometrical complexity and small batch sizes transform into strong cost drivers compared to conventional subtractive processing. In fact, these parts are simply hard-to-clamp and hard-to-probe. Moreover, iterative processing is frequently required due to remaining residual stresses in order to reach the target geometry; even the part envelope changes unintentionally. The current paper explores the novel approach of semiautonomous postprocessing of AM parts and components based on flexible clamping, geometry acquisition in the as-clamped position using cooperating laser profile sensors, and an adaptive milling path planning strategy to counteract unforeseen change of the part envelope.

The surface topography of carbon fiber reinforced plastic composites after machining processes like milling or grinding has a complex character due to the inhomogeneous material structure. The usual procedure to evaluate the surface topography is given with the usage of parameters that describe one or more specific features of the surface. In mechanical engineering, for example, the roughness parameters Ra, Rz, Rmax and Rt have been established with tactile-based roughness measurement devices. However, the applicability of several parameters is not always suitable for composites. In this work the influence of the measurement positions, the distribution of the measured values and the behavior of these values in respect to the machined surface structure are analyzed by means of optical as well as tactile surface measurements. This work results in recommendations for the measurability of machined surfaces of carbon fiber reinforced plastics by using tactile profile methods and an assessment of the derived roughness parameters.

Manufacturing technologies in the semiconductor industry put high demands on accuracy, especially for the initial steps of wafering. ID grinding has established itself as a cost-effective manufacturing method for the production of wafers with a diameter of up to 150 mm. Methods for improving the quality parameters of the wafer, resulted in the integration of a magnetic position control for the ID grinding wheel to control its axial position. For this, a new conditioning strategy had to be developed in consideration of tool life of the grinding wheel, process automation and wafer quality.

Milling structural components from aluminum under enormous requirements of productivity and quality from the aerospace perspective is still the subject of extensive research. The assessment strategies of the surface quality are a big challenge for the surface measurement technique, since only a fraction of the manifesting surface topography can be described with the help of two-dimensional measured variables. The aim of this experimental investigation is a description of several influences on the parameter of the surface roughness Ra and to analyze the prediction of these values. As a result, it can be shown that a more in-depth analysis is necessary to describe the surface quality and topography, which goes beyond the simple specification of roughness parameters.

Purpose The aim of the present study was to evaluate the biomechanical stability of osteosynthesis in mandibular condyle fractures using a newly designed rhombic 3-dimensional (3D) condylar fracture plate and compare it with that using standard two 4-hole miniplates and with that in nonfractured condyles. Materials and Methods Using 200 porcine mandibles, 3 different monocortical plating techniques were evaluated. The condyles were fractured along a defined line tangentially through the sigmoid notch and perpendicular to the posterior border. After anatomic reduction, osteosynthesis was performed using either standard rhombic 3D condylar fracture plates and standard screws (group A) or locking rhombic 3D condylar fracture plates, which were fixed either with standard screws (group B) or locking screws (group C). For comparison, nonfractured condyles (group D) and condyles fixed with standard two 4-hole miniplates and 8 screws (group E) were included. Using a universal mechanical testing machine (TIRA Test 2720; TIRA GmbH Schalkau, Germany), each group was subjected to linear loading from laterally to medially, medially to laterally, anteriorly to posteriorly, and posteriorly to anteriorly. The maximum axial force and displacement at the maximum force were measured. The mean values were compared for statistical significance using analysis of variance with Bonferroni's correction (statistical significance set at P Results The main mode of failure in the plating techniques investigated was the pull out of screws from the proximal fragment. We found no statistically significant differences in the stability of osteosynthesis between the two 4-hole miniplates and the rhombic 3D condylar fracture plate when loading from posteriorly to anteriorly, laterally to medially, and medially to laterally. However, when loading from anteriorly to posteriorly, a statistically significant difference between the standard and locking system and the two 4-hole miniplate system was observed, with the latter proving more stable. Conclusions The results of the present biomechanical study suggest that the rhombic 3D condylar fracture plates are suitable for the treatment of condylar neck fractures. Both types of the plate are able to resist physiologic strains comparable to the two 4-hole miniplates.

Cellular metals and metal foams belong to a young material group. Although it is desired to manufacture near-net-shape parts of cellular metals by primary shaping processes, additional secondary machining operations are often unavoidable to obtain the required geometries and quality demands. Nevertheless, conventional machining of cellular metals leads to undesirable surface damage and poor precision. Furthermore, the chip formation and the mechanism description of the surface damage are still unclear. A mesoscopic finite element model was developed to simulate the chip formation process in machining cellular metals. Experimental data of orthogonal machining tests were used to validate the finite element model. The cutting and thrust forces, as well as the images of the chip formation process of both experiments and simulations were compared and analysed. The model enabled the analysis of the chip formation and the surface defect mechanisms. The rake angle and cutting conditions affected the chip formation process, but the cell arrangement was detected as a decisive factor in the chip formation and the resulting surface damage.

The machining operation drilling is part of the standard repertoire for medical applications. This machining cycle, which is usually a multi-stage process, generates the geometric element for the subsequent integration of implants, which are screwed into the bone in subsequent processes. In addition to the form, shape and position of the generated drill hole, it is also necessary to use a technology that ensures an operation with minimal damage. A surface damaged by excessive mechanical and thermal energy input shows a deterioration in the healing capacity of implants and represents a structure with complications for inflammatory reactions. The resulting loads are influenced by the material properties of the bone, the used technology and the tool properties. An important aspect of the process analysis is the fact that machining of bone is in most of the cases a manual process that depends mainly on the skills of the operator. This includes, among other things, the machining time for the production of a dr...

The selection of an adequate friction model is an important aspect inthe finite element modeling of machining. Previously, different friction modelshave been compared, but the influence of the constitutive model or theworkpiece material have not been considered. This article focuses on theinfluence of the material and the constitutive model on the evaluation of thefriction model in machining. Numerical experiments are performed on threedifferent materials using different constitutive models. For every combinationof material and constitutive model, several simulations using different Coulombcoefficients, but the same cutting parameters, are performed. Several variablesare evaluated: cutting force, shear plane angle, chip-tool contact length,maximum temperature and maximum stress. The results reveal that the workpiecematerial plays an important role in the evaluation of the friction model. Theyalso show that there is significant influence from the constitutive models oncontact length, curvature ratio and chip thickness.

Due to the inhomogeneous material structure, micromachining of fibre reinforced plastics places high requirements on machining processes. Using the hole drilling machining of carbon fibre reinforced plastics as an example, experiments on electro discharge machinability were carried out by means of solid carbide electrodes. Basing on the variation of technological process parameters, the tests were conducted with regard to both workpiece-related and tool-related parameters. The results accentuate the complexity of the influencing parameters affecting surface quality and thermal damage of the mater ial as well as tool wear. However, evidence of a low damage production of small drill holes could be provided.

For their unique properties, titanium alloys have found wide application in high-tech engineering. But these alloys are difficult to machine and to grind for their high chemical reactivity and poor thermal properties, which aggravate the grinding zone temperature and its detrimental effects. The objective of this article is a comparison of the grindability of Ti-6Al-4V regarding cubic boron nitride (CBN) and diamond brazed type monolayered grinding wheels under the influence of different environments. In grinding this alloy, cryogenic cooling did not help visibly for both CBN and diamond, but the application of oil and also of alkaline coolant significantly gave the best results.

The extension of technical capabilities of machine centres for complete machining of components can improve their performance. In the field of sheet metal machining, the objective beside the classic milling operation was a generation of functional surfaces by face brushing. The experimental studies have probed the influence of tools and technological parameters on the surface quality. In addition to an analysis of the relevant roughness parameters the formation of the surface topography was analysed by several measurement methods. By the application of force measurement, the results of the surface quality can be interpreted additionally. It could be shown that the feed rate in contrast to the cutting speed has the main influence on the surface roughness. A peculiarity is given by the parameter-based width of cut that should be known for reliable process control. The acquired data can be applied in the form of process characteristic fields for further processing with simulation and modelling methods.

This paper deals with an investigation of the grindability of Titanium alloy Ti–6Al–4V with monolayered brazed type superabrasive grinding wheels. The experiments, conducted under different grinding environments, showed the performance of the grinding fluids based on an evaluation of grinding forces, chip formation and tool condition. It could be found that conventional grinding fluids like oil or alkaline soap are preferable compared to dry or cryogenic conditions or with MoS 2 coated wheels.

The application of cellular metals and metal foams is still at the beginning of its development. The evaluation of the surface quality of these materials after machining processes is thus important for implementation in the field of construction. The existing tactile measurements are only capable of indicating both the structure of the material and the influences of machining processes to a limited degree. It is therefore necessary to analyse the structure of materials and to simulate surface parameters analogously to the known parameters of the measuring technology, before a measurement system can be applied. This work presents a method with which to analyse cross-sectional images acquired from computer tomography data as well as specially prepared cellular metal structures. Specialised software enables analysis of these cross-sections and makes statements about the material structures and the influence that mechanical processing has on them. It also facilitates the generation of virtual surface profiles which are essential in comparative studies of the measured surface profiles of machined material. The study will also reveal further analysis options made possible by the software. This includes the possibility of determining the density of analysed material by means of the cross-sections – in other words, a homogeneity analysis of the material structure.